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Sample records for zora dft investigations

  1. Care Robot ZORA in Dutch Nursing Homes; An Evaluation Study.

    Science.gov (United States)

    Kort, Helianthe; Huisman, Chantal

    2017-01-01

    From May 2016 - November 2016 the use of the ZORA robot was investigated in 15 long-term care facilities for older people. The ZORA robot is built as a social robot and used for pleasure and entertainment or to stimulate physical activities of the residents.

  2. Ab-initio ZORA calculations

    NARCIS (Netherlands)

    Faas, S.; Snijders, Jaap; van Lenthe, J.H.; HernandezLaguna, A; Maruani, J; McWeeny, R; Wilson, S

    2000-01-01

    In this paper we present the first application of the ZORA (Zeroth Order Regular Approximation of the Dirac Fock equation) formalism in Ab Initio electronic structure calculations. The ZORA method, which has been tested previously in the context of Density Functional Theory, has been implemented in

  3. Investigating actinide compounds within a hybrid MCSCF-DFT model

    International Nuclear Information System (INIS)

    Fromager, E.; Jensen, H.J.A.; Wahlin, P.; Real, F.; Wahlgren, U.

    2007-01-01

    Complete text of publication follows: Investigations of actinide chemistry with quantum chemical methods still remain a complicated task since it requires an accurate and efficient treatment of the environment (crystal or solvent) as well as relativistic and electron correlation effects. Concerning the latter, the current correlated methods, based on either Density-Functional Theory (DFT) or Wave-Function Theory (WFT), have their advantages and drawbacks. On the one hand, Kohn-Sham DFT (KS-DFT) calculates the dynamic correlation quite accurately and at a fairly low computational cost. However, it does not treat adequately the static correlation, which is significant in some actinide compounds because of the near-degeneracy of the 5f orbitals: a first example is the bent geometry obtained in KS-DFT(B3LYP) for the neptunyl ion NpO 2 3+ , which is found to be linear within a Multi-Configurational Self-Consistent Field (MCSCF) model [1]. A second one is the stable and bent geometry obtained in KS-DFT(B3LYP) for the plutonyl ion PuO 2 4+ , which disintegrates at the MCSCF level [1]. On the other hand, WFT can describe the static correlation, using for example a MCSCF model, but then an important part of the dynamic correlation has to be neglected. This can be recovered with perturbation-theory based methods like for example CASPT2 or NEVPT2, but their computational complexity prevents large scale calculations. It is therefore of great interest to develop a hybrid MCSCF-DFT model which combines the best of both WFT and DFT approaches. The merge of WFT and DFT can be achieved by splitting the two-electron interaction into long-range and short-range parts [2]. The long-range part is then treated by WFT and the short-range part by DFT. We use the so-called 'erf' long-range interaction erf(μr 12 )/r 12 , which is based on the standard error function, and where μ is a free parameter which controls the long/short-range decomposition. The newly proposed recipe for the

  4. Palladium(0) alkyne complexes as active species: A DFT-investigation

    DEFF Research Database (Denmark)

    Ahlquist, Mårten Sten Gösta; Fabrizi, Giancarlo; Cacchi, Sandro

    2005-01-01

    Alkynes have been found to be excellent ligands for Pd(0); the stability of a range of alkyne-Pd(0) complexes, and their reactivity in oxidative addition, have been investigated by DFT methods.......Alkynes have been found to be excellent ligands for Pd(0); the stability of a range of alkyne-Pd(0) complexes, and their reactivity in oxidative addition, have been investigated by DFT methods....

  5. Electrocatalytic aerobic epoxidation of alkenes: Experimental and DFT investigation

    International Nuclear Information System (INIS)

    Magdesieva, Tatiana V.; Borisova, Nataliya E.; Dolganov, Alexander V.; Ustynyuk, Yuri A.

    2012-01-01

    A new method for electrocatalytic aerobic epoxidation of alkenes catalyzed by binuclear Cu(II) complexes with azomethine ligands based on 2,6-diformyl-4-tert-butylphenol is described. In acetonitrile–water (5%), at the potential of Cu II /Cu I redox couple (–0.8 V vs. Ag/AgCl/KCl) at room temperature the epoxide is obtained in an average yield of around 50%. Contrary to the majority of known epoxidations, no strong oxidants are involved and no free hydrogen peroxide is formed in the reaction, thus making it ecologically friendly. The DFT quantum-chemical modeling of the reaction mechanism revealed that a copper hydroperoxo-complex rather than hydrogen peroxide or a copper oxo-complex oxidizes alkene. The process is very selective since neither products of hydroxylation of benzene ring in styrene nor of allylic oxidation of cyclohexene were detected.

  6. Understanding Zora Neale Hurston's Their Eyes Were Watching God

    Directory of Open Access Journals (Sweden)

    Tatjana Vukelić

    2007-12-01

    Full Text Available The work of Zora Neale Hurston, in particular, the novel Their Eyes Were Watching God, has been the object of more than a decade of critical attention. But, in addition to the critical consideration of Hurston's writings, her work has received the level of institutional support necessary for Hurston to enter the American literary mainstream. The article addresses the issue of black women literary tradition and the search for freedom and identity in the white American social and cultural environment.

  7. Robot ZORA in rehabilitation and special education for children with severe physical disabilities: a pilot study.

    Science.gov (United States)

    van den Heuvel, Renée J F; Lexis, Monique A S; de Witte, Luc P

    2017-12-01

    The aim of this study was to explore the potential of ZORA robot-based interventions in rehabilitation and special education for children with severe physical disabilities. A two-centre explorative pilot study was carried out over a 2.5-month period involving children with severe physical disabilities with a developmental age ranging from 2 to 8 years. Children participated in six sessions with the ZORA robot in individual or in group sessions. Qualitative and quantitative methods were used to collect data on aspects of feasibility, usability, barriers and facilitators for the child as well as for the therapist and to obtain an indication of the effects on playfulness and the achievement of goals. In total, 17 children and seven professionals participated in the study. The results of this study show a positive contribution of ZORA in achieving therapy and educational goals. Moreover, sessions with ZORA were indicated as playful. Three main domains were indicated to be the most promising for the application of ZORA: movement skills, communication skills and cognitive skills. Furthermore, ZORA can contribute towards eliciting motivation, concentration, taking initiative and improving attention span of the children. On the basis of the results of the study, it can be concluded that ZORA has potential in therapy and education for children with severe physical disabilities. More research is needed to gain insight into how ZORA can be applied best in rehabilitation and special education.

  8. Novel Trolox derivatives as antioxidant: A DFT investigation

    Directory of Open Access Journals (Sweden)

    Farmanzadeh Dvood

    2016-01-01

    Full Text Available In this paper the antioxidant activity of Trolox derivatives were investigated by density function theory and polarization continuum model as solvent model in order to propose the novel derivatives with higher antioxidant activity from a theoretical viewpoint. The effects of various ortho and meta substituents on the reaction enthalpies of antioxidant mechanisms of Trolox were investigated. Also the effect of reducing the number of atoms in the heterocyclic ring and effect of replacing the oxygen heteroatom of Trolox with other heteroatoms on the antioxidant activity of Trolox were evaluated. Results show that the NH2, OH and NHMe substituents in meta and ortho positions decrease the BDE and IP values and also increase the antioxidant activity of Trolox from the theoretical viewpoint. The derivatives e, c and d with NH, S and Se instead of O have higher antioxidant activity from the theoretical viewpoint. Obtained results show that reducing the number of atom in the heterocyclic ring (derivatives a and b decrease the BDE and IP values and also increase the antioxidant activity of Trolox from the theoretical viewpoint. The linear dependencies between BDE of OH bond and IP values of studied Trolox derivatives and corresponding EHOMO and R(O-H values can be useful to propose novel derivatives with higher antioxidant activity from the theoretical viewpoint.

  9. Spectroscopic Investigations and DFT Calculations on 3-(Diacetylamino-2-ethyl-3H-quinazolin-4-one

    Directory of Open Access Journals (Sweden)

    Yusuf Sert

    2016-01-01

    Full Text Available The theoretical and experimental vibrational frequencies of 3-(diacetylamino-2-ethyl-3H-quinazolin-4-one (2 were investigated. The experimental Laser-Raman spectrum (4000–100 cm−1 and FT-IR spectrum (4000–400 cm−1 of the newly synthesized compound were recorded in the solid phase. Both the theoretical vibrational frequencies and the optimized geometric parameters such as bond lengths and bond angles have for the first time been calculated using density functional theory (DFT/B3LYP and DFT/M06-2X quantum chemical methods with the 6-311++G(d,p basis set using Gaussian 03 software. The vibrational frequencies were assigned with the help of potential energy distribution (PED analysis using VEDA 4 software. The calculated vibrational frequencies and the optimized geometric parameters were found to be in good agreement with the corresponding reported experimental data. Also, the energies of the lowest unoccupied molecular orbital (LUMO, highest occupied molecular orbital (HOMO, and other related molecular energies for 3-(diacetylamino-2-ethyl-3H-quinazolin-4-one (2 have been investigated using the same computational methods.

  10. Atelje Zore Petrović / Zora Petrovic’s studio

    Directory of Open Access Journals (Sweden)

    Jasmina Čubrilo

    2012-12-01

    Full Text Available The big oil on canvas in the studio from 1941, and small, undated, double-sided tempera on the paper of the same name are complex images that define the horizon of Zora Petrović’s art world – different social, art, ideological discourses intertwine on its surfaces. These images reflect overlapping the private and public sphere, different power positions inside this overlapping and within the local art world of that time such as female artist vs. male art collector; female artist vs. male artist, female artist vs. male artist; female artist vs. female model, female artist/worker vs. female (upper middle class possible amateur. Broad strokes and colour, which, in the sense of matter that Petrović used to cover her canvases, to (almost all critics manifest the quality of wild expression mostly seen as a “masculine approach” and manly strength, actually, possess the quality of untamed fluidity that breaks down the psychic barriers between the inner and the outer being, as well as the barriers between the self and the other. It would appear that all these critics, by reading this manly method into her work, actually projected their fear of the abject, of the horror of the impure, unsymbolised, as if they to present that surplus in language, to present its inexpressibility, in language after all, and thus make it an integral part of the symbolic network. Also, probably for the same reason, critics found it necessary to describe and rationalise her disorderly studio, the brushes that she did not wash with water, the palettes underneath the layers of dried paint, as a consequence of her total dedication to her sublime task of creating uniquely valuable objects, which prevented her from dealing with such trifling, feminine tasks as keeping her working area orderly and clean. In that way the new signifying network was produced, the one that recognizes Zora’s studio in the metonymic series: studio, the surface of painting, female nude and her

  11. Substituent effects on geometric and electronic properties of iron tetraphenylporphyrin: a DFT investigation.

    Science.gov (United States)

    Wei, Lu; She, Yuanbin; Yu, Yanmin; Yao, Xiaoqian; Zhang, Suojiang

    2012-06-01

    To investigate the effects of the substituents, substituent positions and axial chloride ligand on the geometric and electronic properties of the iron tetraphenylporphyrin (FeTPP), a series of the substituented iron tetraphenylporphyrins and their chlorides, FeT(o/p-R)PP and FeT(o/p-R)PPCl (R = -H, -Cl, -NO(2), -OH, -OCH(3)), were systematically calculated without any symmetry constraint by using DFT method. For geometric structure, the substituent position and axial Cl ligand change the configuration of the iron porphyrin obviously. The ortho-substituents prefer making the phenyls perpendicular to the porphyrin ring; the axial chloride draws the central Fe ion ~0.500 Å out of the porphyrin plane toward the ligand. With regard to electronic properties, it is found that E(LUMO) could be related to the catalytic activity. The electron-withdrawing group always lowers the energies of both frontier orbitals, while the electron-donating one heightens them simultaneously, but they affect the E(HOMO) and E(LUMO) in the same sequence, -NO(2) < -Cl < -H < -OH < -OCH(3). The substituent effects on the central Fe ion were explored by calculating NBO charge distribution, spin density and natural electron configuration.

  12. Folklore in Zora Neale Hurston's "Their Eyes Were Watching God." [Lesson Plan].

    Science.gov (United States)

    2002

    Zora Neale Hurston's work is lively, lyrical, funny, and poignant, but this consummate literary craftsperson was also a first-rate ethnographer, conducting field work for Franz Boas and for the Works Progress Administration (WPA). "Their Eyes Were Watching God," often acclaimed as Hurston's masterpiece, is perhaps the richest beneficiary…

  13. Water at silica/liquid water interfaces investigated by DFT-MD simulations

    Science.gov (United States)

    Gaigeot, Marie-Pierre

    This talk is dedicated to probing the microscopic structural organization of water at silica/liquid water interfaces including electrolytes by first principles DFT-based molecular dynamics simulations (DFT-MD). We will present our very recent DFT-MD simulations of electrolytic (KCl, NaCl, NaI) silica/liquid water interfaces in order to unravel the intertwined structural properties of water and electrolytes at the crystalline quartz/liquid water and amorphous silica/liquid water interfaces. DFT-MD simulations provide direct knowledge of the structural organization of water and the H-Bond network formed between the water molecules within the different water layers above the silica surface. One can furthermore extract vibrational signatures of the water molecules within the interfacial layers from the DFT-MD simulations, especially non-linear SFG (Sum Frequency generation) signatures that are active at solid/liquid interfaces. The strength of the simulated spectra is that a detailed analysis of the signatures in terms of the water/water H-Bond networks formed within the interfacial water layers and in terms of the water/silica or water/electrolytes H-Bond networks can be given. Comparisons of SFG spectra between quartz/water/electrolytes and amorphous silica/water/electrolytes interfaces allow us to definitely conclude on how the structural arrangements of liquid water at these electrolytic interfaces modulate the final spectroscopic signatures. Invited speaker.

  14. Theoretical investigation of lead vapor adsorption on kaolinite surfaces with DFT calculations

    Energy Technology Data Exchange (ETDEWEB)

    Wang, Xinye [Key Laboratory of Energy Thermal Conversion and Control of Ministry of Education, School of Energy and Environment, Southeast University, Nanjing 210096 (China); Huang, Yaji, E-mail: heyyj@seu.edu.cn [Key Laboratory of Energy Thermal Conversion and Control of Ministry of Education, School of Energy and Environment, Southeast University, Nanjing 210096 (China); Pan, Zhigang [College of Materials Science and Engineering, Nanjing Tech University, Nanjing 210009 (China); Wang, Yongxing; Liu, Changqi [Key Laboratory of Energy Thermal Conversion and Control of Ministry of Education, School of Energy and Environment, Southeast University, Nanjing 210096 (China)

    2015-09-15

    Highlights: • Al surface after dehydroxylation is active while Si surface is inert. • The active sites are the unsaturated Al atoms and O atoms losing H atom. • PbO is the most suitable species for adsorption. • Increasing the activities of Al atoms can enhance the performance of kaolinite. • Produce of amorphous silica is a potential path to enhance the performance of kaolinite. - Abstract: Kaolinite can be used as the in-furnace sorbent/additive to adsorb lead (Pb) vapor at high temperature. In this paper, the adsorptions of Pb atom, PbO molecule and PbCl{sub 2} molecule on kaolinie surfaces were investigated by density functional theory (DFT) calculation. Si surface is inert to Pb vapor adsorption while Al surfaces with dehydroxylation are active for the unsaturated Al atoms and the O atoms losing H atoms. The adsorption energy of PbO is much higher than that of Pb atom and PbCl{sub 2}. Considering the energy barriers, it is easy for PbO and PbCl{sub 2} to adsorb on Al surfaces but difficult to escape. The high energy barriers of de–HCl process cause the difficulties of PbCl{sub 2} to form PbO·Al{sub 2}O{sub 3}·2SiO{sub 2} with kaolinite. Considering the inertia of Si atoms and the activity of Al atoms after dehydroxylation, calcination, acid/alkali treatment and some other treatment aiming at amorphous silica producing and Al activity enhancement can be used as the modification measures to improve the performance of kaolinite as the in-furnace metal capture sorbent.

  15. The solvent effects on dimethyl phthalate investigated by FTIR characterization, solvent parameter correlation and DFT computation

    Science.gov (United States)

    Chen, Yi; Zhang, Hui; Zhou, Wenzhao; Deng, Chao; Liao, Jian

    2018-06-01

    This study set out with the aim of investigating the solvent effects on dimethyl phthalate (DMP) using FTIR characterization, solvent parameter correlation and DFT calculation. DMP exposed to 17 organic solvents manifested varying shift in the carbonyl stretching vibration frequency (νCdbnd O). Non-alkanols induced Band I and alkanols produced Band I and Band II. Through correlating the νCdbnd O with the empirical solvent scales including acceptor parameter (AN), Schleyer's linear free energy parameter (G), and linear free salvation energy relationships (LSER), Band I was mainly ascribed to non-specific effects from either non-alkanols or alkanol polymers ((alkanol)n). νCdbnd O of the latter indicated minor red shift and less variability compared to the former. An assumption was made and validated about the sequestering of hydroxyl group by the bulky hydrophobic chain in (alkanol)n, creating what we refer to as "screening effects". Ab initio calculation, on the other hand, provided insights for possible hydrogen binding between DMP and (ethanol)n or between ethanol monomers. The two components of Band I observed in inert solvents were assigned to the two Cdbnd O groups adopting differentiated conformations. This in turn prompted our consideration that hydrogen binding was highly selective in favor of lowly associated (alkanol)n and the particular Cdbnd O group having relatively less steric hindrance and stronger electron-donating capacity. Band II was therefore believed to derive from hydrogen-bond interactions mainly in manner of 1:1 and 1:2 DMP-(alkanol)n complexes.

  16. Combined DFT and XPS investigation of iodine anions adsorption on the sulfur terminated (001) chalcopyrite surface

    Energy Technology Data Exchange (ETDEWEB)

    Li, Kui, E-mail: likui9606@stu.xjtu.edu.cn [School of Nuclear Science and Technology, Xi’an Jiaotong University, Xi’an 710049 (China); Zhao, Yaolin, E-mail: zhaoyaolin@mail.xjtu.edu.cn [School of Nuclear Science and Technology, Xi’an Jiaotong University, Xi’an 710049 (China); Zhang, Peng, E-mail: zp32@qq.com [Sino Shaanxi Nuclear Industry Group, Xi’an 710100 (China); He, Chaohui, E-mail: hechaohui@mail.xjtu.edu.cn [School of Nuclear Science and Technology, Xi’an Jiaotong University, Xi’an 710049 (China); Deng, Jia, E-mail: djkokocase@stu.xjtu.edu.cn [School of Nuclear Science and Technology, Xi’an Jiaotong University, Xi’an 710049 (China); Ding, Shujiang, E-mail: dingsj@mail.xjtu.edu.cn [Department of Applied Chemistry, School of Science, Xi’an Jiaotong University, Xi’an 710049 (China); Shi, Weiqun, E-mail: shiwq@ihep.ac.cn [Key Laboratory of Nuclear Radiation and Nuclear Energy Technology and Key Laboratory for Biomedical Effects of Nanomaterials and Nanosafety, Institute of High Energy Physics, Chinese Academy of Sciences, Beijing 100049 (China)

    2016-12-30

    Highlights: • Metal surface sites of (001)-S surface of chalcopyrite show significant chemical affinity to iodide and iodate. • The energetically favorable active site is copper for iodide adsorption and iron for iodate adsorption, respectively. • Iodate undergoes a dissociative adsorption on the copper site of chalcopyrite surface. - Abstract: The adsorption of iodine anions (iodide and iodate) on the sulfur terminated (001) chalcopyrite surface has been systematically investigated combining first-principles calculations based on density functional theory (DFT) with X-ray photoelectron spectroscopy (XPS) measurements. Based on the total energy calculations and geometric optimization, the thermodynamically preferred site was copper atom for iodide adsorption and iron atom for iodate adsorption, respectively. In the case of Cu site mode, the iodate underwent a dissociative adsorption, where one I−O bond of iodate ion was broken and the dissociative oxygen atom adsorbed on the adjacent sulphur site. Projected density of states (PDOS) analysis further clarified the interaction mechanism between active sites of chalcopyrite surface and adsorbates. In addition, full-range XPS spectra qualitatively revealed the presence of iodine on chalcopyrite surface. High resolution XPS spectra of the I 3d peaks after adsorption verified the chemical environment of iodine. The binding energies of 618.8 eV and 623.5 eV for I 3d{sub 5/2} peaks unveiled that the adsorption of iodide and iodate ions on copper-iron sulfide minerals was the result of formation of low solubility metal iodides precipitate. Also two I 3d peaks with low intensity around 618 eV and 630 eV might be related to the inorganic reduction of iodate to iodide by reducing S{sup 2−} ion of chalcopyrite.

  17. DFT theoretical investigations of π-conjugated molecules based on thienopyrazine and different acceptor moieties for organic photovoltaic cells

    Directory of Open Access Journals (Sweden)

    Mohammed Bourass

    2016-09-01

    Full Text Available In this work, theoretical study by using the DFT method on eleven conjugated compounds based on thienopyrazine is reported. Different electron side groups were introduced to investigate their effects on the electronic structure; The HOMO, LUMO and Gap energy of these compounds have been calculated and reported in this paper. A systematic theoretical study of such compound has not been reported as we know. Thus, our aim is first, to explore their electronic and spectroscopic properties on the basis of the DFT quantum chemical calculations. Second, we are interested to elucidate the parameters that influence the photovoltaic efficiency toward better understanding of the structure–property relationships. The study of structural, electronic and optical properties for these compounds could help to design more efficient functional photovoltaic organic materials.

  18. Interaction of water with (silico)aluminophosphate zeotypes: a comparative investigation using dispersion-corrected DFT.

    Science.gov (United States)

    Fischer, Michael

    2016-06-21

    Porous aluminophosphates (AlPOs) and silicoaluminophosphates (SAPOs) with zeolite-like structures have received considerable attention as potential adsorbents for heat transformation applications using water adsorption/desorption cycles. Since a detailed experimental characterisation of the water adsorption properties has only been performed for some of these materials, such as AlPO-18 (AEI topology) and SAPO-34 (CHA topology), more systematic insights regarding the influence of the pore topology and (for SAPOs) the arrangement of the framework protons on the affinity towards water are lacking. To study the relationships between structure and properties in more detail, the interaction of water with six structurally different AlPOs (with AEI, AFX, CHA, ERI, GIS, RHO topologies) and their SAPO analogues was investigated using dispersion-corrected density-functional theory (DFT-D) calculations. Different possible locations of silicon atoms and charge-balancing protons were considered for the SAPO systems. The calculations for SAPOs at low water loadings (one H2O molecule per framework proton) revealed that the interaction energies exhibit a considerable variation, ranging from -75 to -100 kJ mol(-1) (per water molecule). The differences in interaction energy were rationalised with the different structural environment of the framework protons at which the water molecules are adsorbed. At high water uptakes (near saturation), interaction energies in the range of -65 kJ mol(-1) were obtained for all AlPOs, and there was no evidence for a marked influence of pore size and/or topology on the interaction strength. The interaction of water with SAPOs was found to be approximately 5 kJ mol(-1) stronger than for AlPOs due to an increased contribution of electrostatic interactions. An analysis of the structural changes upon water adsorption revealed striking differences between the distinct topologies, with the materials with GIS and RHO topologies being distorted much more

  19. Critical difference between optoelectronic properties of α- and β-SnWO4semiconductors: A DFT/HSE06 and experimental investigation

    KAUST Repository

    Harb, Moussab; Ziani, Ahmed; Takanabe, Kazuhiro

    2016-01-01

    The optoelectronic properties of β-SnWO4 are investigated in details using experiments on thin film generated by rapid quenching and the first-principles quantum calculations based on the density functional theory (DFT, including the perturbation

  20. DFT investigation of the interaction of gold nanoclusters with poly(amidoamine) PAMAM G0 dendrimer

    Science.gov (United States)

    Camarada, M. B.

    2016-06-01

    The interaction between PAMAM G0 and gold nanoclusters Aun (n = 2, 4, 6, and 8) was studied theoretically at DFT level. Different coordination sites were explored, including internal and superficial coordination. All stable complexes exhibited external interaction with the amine or carbonyl site, while the core site coordination was not favored. The more stable binding of Aun was registered with the terminal amine group, while the binding at the amide site was relatively weaker. The vertical first ionization potential, electron affinity, Fermi level, and the HOMO-LUMO gap of PAMAM and Aun-PAMAM G0 complexes were also analyzed.

  1. DFT investigation on the adsorption behavior of dimethyl and trimethyl amine molecules on borophene nanotube

    Science.gov (United States)

    Bhuvaneswari, R.; Chandiramouli, R.

    2018-06-01

    The electronic properties of borophene nanotube (BNT) are witnessed and the adsorption properties of dimethyl amine (DMA) and trimethyl amine (TMA) molecules on borophene nanotube are explored through non-equilibrium Green's function (NEGF) and density functional theory (DFT) method. The device density of states spectrum interprets the change in peak maxima, thus indicating the electron transition between DMA, TMA molecules and BNT base material. I-V characteristics strengthen the adsorption property of DMA and TMA on BNT by pointing out the variation in the current. The present work assures that borophene nanotube (BNT) can be employed as DMA and TMA sensor.

  2. Adsorption of beryllium atoms and clusters both on graphene and in a bilayer of graphite investigated by DFT.

    Science.gov (United States)

    Ferro, Yves; Fernandez, Nicolas; Allouche, Alain; Linsmeier, Christian

    2013-01-09

    We herein investigate the interaction of beryllium with a graphene sheet and in a bilayer of graphite by means of periodic DFT calculations. In all cases, we find the beryllium atoms to be more weakly bonded on graphene than in the bilayer. Be(2) forms both magnetic and non-magnetic structures on graphene depending on the geometrical configuration of adsorption. We find that the stability of the Be/bilayer system increases with the size of the beryllium clusters inserted into the bilayer of graphite. We also find a charge transfer from beryllium to the graphite layers. All these results are analysed in terms of electronic structure.

  3. Probing the (110)-Oriented plane of rutile ZnF2: A DFT investigation

    Science.gov (United States)

    Tamijani, Ali Abbaspour; Ebrahimiaqda, Elham

    2017-12-01

    For many years, rutile-like crystals have given rise to pronounced enthusiasm amongst mineralogists. In this context, rutile-type ZnF2 has found numerous applications across a variety of disciplines, ranging from material sciences to optoelectronics. Surprisingly, very limited literature is concerned with the molecular adsorption on ZnF2 surfaces and related energetics. Additionally, surface probing with small particles is a well-entrenched technique to analyze the interfacial properties. In this regard, small organic species are valuable picks. In the present work, we have employed electronic structure calculations to simulate the adsorption of methane, chloroform, pyrrole, benzene, naphthalene, anthracene, tetracene and pentacene at the (110) plane of rutile ZnF2. Dispersion-corrected DFT method was chosen to predict the binding energies and structures of molecule-adsorbed surfaces. Interestingly, a linear proportionality relationship was found between the binding energies of aromatic adsorbates and their respective molecular lengths. By applying this relationship, we were able to predict the adsorption energy of pentacene on ZnF2 to within 2% of our DFT-based result.

  4. Spectroscopic analysis of 8-hydroxyquinoline derivatives and investigation of its reactive properties by DFT and molecular dynamics simulations

    Science.gov (United States)

    Sureshkumar, B.; Mary, Y. Sheena; Resmi, K. S.; Panicker, C. Yohannan; Armaković, Stevan; Armaković, Sanja J.; Van Alsenoy, C.; Narayana, B.; Suma, S.

    2018-03-01

    Two 8-hydroxyquinoline derivatives, 5,7-dichloro-8-hydroxyquinoline (57DC8HQ) and 5-chloro-7-iodo-8-hydroxy quinoline (5CL7I8HQ) have been investigated in details by means of spectroscopic characterization and computational molecular modelling techniques. FT-IR and FT-Raman experimental spectroscopic approaches have been utilized in order to obtain detailed spectroscopic signatures of title compounds, while DFT calculations have been used in order to visualize and assign vibrations. The computed values of dipole moment, polarizability and hyperpolarizability indicate that the title molecules exhibit NLO properties. The evaluated HOMO and LUMO energies demonstrate the chemical stability of the molecules. NBO analysis is made to study the stability of the molecules arising from hyperconjugative interactions and charge delocalization. DFT calculations have been also used jointly with MD simulations in order to investigate in details global and local reactivity properties of title compounds. Also, molecular docking has been also used in order to investigate affinity of title compounds against decarboxylase inhibitor and quinoline derivatives can be a lead compounds for developing new antiparkinsonian drug.

  5. A DFT investigation on interactions between asymmetric derivatives of cisplatin and nucleobase guanine

    Science.gov (United States)

    Tai, Truong Ba; Nhat, Pham Vu

    2017-07-01

    The interactions of hydrolysis products of cisplatin and its asymmetric derivatives cis- and trans-[PtCl2(iPram)(Mepz)] with guanine were studied using DFT methods. These interactions are dominated by electrostatic effects, namely hydrogen bond contributions and there exists a charge flow from H-atoms of ligands to the O-atoms of guanine. The replacement of NH3 moieties by larger functional groups accompanies with a moderate reaction between PtII and guanine molecule, diminishing the cytotoxicity of the drug. The asymmetric and symmetric NH2 stretching modes of complexes having strong hydrogen bond interactions are red shifted importantly as compared to complexes without presence of hydrogen bond interactions.

  6. Structural, vibrational and nuclear magnetic resonance investigations of 4-bromoisoquinoline by experimental and theoretical DFT methods.

    Science.gov (United States)

    Arjunan, V; Thillai Govindaraja, S; Jayapraksh, A; Mohan, S

    2013-04-15

    Quantum chemical calculations of energy, structural parameters and vibrational wavenumbers of 4-bromoisoquinoline (4BIQ) were carried out by using B3LYP method using 6-311++G(**), cc-pVTZ and LANL2DZ basis sets. The optimised geometrical parameters obtained by DFT calculations are in good agreement with electron diffraction data. Interpretations of the experimental FTIR and FT-Raman spectra have been reported with the aid of the theoretical wavenumbers. The differences between the observed and scaled wavenumber values of most of the fundamentals are very small. The thermodynamic parameters have also been computed. Electronic properties of the molecule were discussed through the molecular electrostatic potential surface, HOMO-LUMO energy gap and NBO analysis. To provide precise assignments of (1)H and (13)CNMR spectra, isotropic shielding and chemical shifts were calculated with the Gauge-Invariant Atomic Orbital (GIAO) method. Copyright © 2013 Elsevier B.V. All rights reserved.

  7. DFT simulation, quantum chemical electronic structure, spectroscopic and structure-activity investigations of 2-benzothiazole acetonitrile.

    Science.gov (United States)

    Arjunan, V; Thillai Govindaraja, S; Jose, Sujin P; Mohan, S

    2014-07-15

    The Fourier transform infrared and FT-Raman spectra of 2-benzothiazole acetonitrile (BTAN) have been recorded in the range 4000-450 and 4000-100 cm(-1) respectively. The conformational analysis of the compound has been carried out to obtain the stable geometry of the compound. The complete vibrational assignment and analysis of the fundamental modes of the compound are carried out using the experimental FTIR and FT-Raman data and quantum chemical studies. The experimental vibrational frequencies are compared with the wavenumbers derived theoretically by B3LYP gradient calculations employing the standard 6-31G(**), high level 6-311++G(**) and cc-pVTZ basis sets. The structural parameters, thermodynamic properties and vibrational frequencies of the normal modes obtained from the B3LYP methods are in good agreement with the experimental data. The (1)H (400 MHz; CDCl3) and (13)C (100 MHz;CDCl3) nuclear magnetic resonance (NMR) spectra are also recorded. The electronic properties, the energies of the highest occupied and lowest unoccupied molecular orbitals are measured by DFT approach. The kinetic stability of the molecule has been determined from the frontier molecular orbital energy gap. The charges of the atoms and the structure-chemical reactivity relations of the compound are determined by its chemical potential, global hardness, global softness, electronegativity, electrophilicity and local reactivity descriptors by conceptual DFT methods. The non-linear optical properties of the compound have been discussed by measuring the polarisability and hyperpolarisability tensors. Copyright © 2014 Elsevier B.V. All rights reserved.

  8. Mechanical and magneto-opto-electronic investigation of transition metal based fluoro-perovskites: An ab-initio DFT study

    Science.gov (United States)

    Erum, Nazia; Azhar Iqbal, Muhammad

    2017-09-01

    Detailed ab-initio calculations are performed to investigate structural, elastic, mechanical, magneto-electronic and optical properties of the KXF3 (X = V, Fe, Co, Ni) fluoro-perovskites using Full Potential Linearized Augmented Plane Wave (FP-LAPW) method within the framework of density functional theory (DFT). The calculated structural parameters by DFT and analytical methods are found consistent with the experimental results. From the elastic and mechanical properties, it can be inferred that these compounds are elastically stable and anisotropic while KCoF3 is harder than rest of the compounds. Furthermore, thermal behavior of these compounds is analyzed by calculating Debye temperature (θD). The calculated spin dependent magneto-electronic properties in these compounds reveal that exchange splitting is dominated by N-3d orbital. The stable magnetic phase optimizations verify the experimental observations at low temperature. Type of chemical bonding is analyzed with the help of variations in electron density difference distribution that is induced due to changes of the second cation. The linear optical properties are also discussed in terms of optical spectra. The present methodology represents an influential approach to calculate the whole set of mechanical and magneto-opto-electronic parameters, which would support to understand various physical phenomena and empower device engineers for implementing these materials in spintronic applications.

  9. Spectroscopic analysis and molecular docking of imidazole derivatives and investigation of its reactive properties by DFT and molecular dynamics simulations

    Science.gov (United States)

    Thomas, Renjith; Hossain, Mossaraf; Mary, Y. Sheena; Resmi, K. S.; Armaković, Stevan; Armaković, Sanja J.; Nanda, Ashis Kumar; Ranjan, Vivek Kumar; Vijayakumar, G.; Van Alsenoy, C.

    2018-04-01

    Solvent-free synthesis pathway for obtaining two imidazole derivatives (2-chloro-1-(4-methoxyphenyl)-4,5-dimethyl-1H-imidazole (CLMPDI) and 1-(4-bromophenyl)-2-chloro-4,5-dimethyl-1H-imidazole (BPCLDI) has been reported in this work, followed by detailed experimental and computational spectroscopic characterization and reactivity study. Spectroscopic methods encompassed IR, FT-Raman and NMR techniques, with the mutual comparison of experimentally and computationally obtained results at DFT/B3LYP level of theory. Reactivity study based on DFT calculations encompassed molecular orbitals analysis, followed by calculations of molecular electrostatic potential (MEP) and average local ionization energy (ALIE) values, Fukui functions and bond dissociation energies (BDE). Additionally, the stability of title molecules in water has been investigated via molecular dynamics (MD) simulations, while interactivity with aspulvinonedimethylallyl transferase protein has been evaluated by molecular docking procedure. CLMPDI compound showed antimicrobial activity against all four bacterial strain in both gram positive and gram negative bacteria while, BPCLDI showed only in gram positive bacteria, Staphylococcus Aureus (MTCC1144). The first order hyperpolarizability of CLMPDI and BPCLDI are 20.15 and 6.10 times that of the standard NLO material urea.

  10. Complexation of rhodium(II) tetracarboxylates with aliphatic diamines in solution: 1H and 13C NMR and DFT investigations.

    Science.gov (United States)

    Jaźwiński, Jarosław; Sadlej, Agnieszka

    2013-10-01

    The complexation of rhodium(II) tetraacetate, tetrakistrifluoroaceate and tetrakisoctanoate with a set of diamines (ethane-1,diamine, propane-1,3-diamine and nonane-1,9-diamine) and their N,N'-dimethyl and N,N,N',N'-tetramethyl derivatives in chloroform solution has been investigated by (1) H and (13) C NMR spectroscopy and density functional theory (DFT) modelling. A combination of two bifunctional reagents, diamines and rhodium(II) tetracarboxylates, yielded insoluble coordination polymers as main products of complexation and various adducts in the solution, being in equilibrium with insoluble material. All diamines initially formed the 2 : 1 (blue), (1 : 1)n oligomeric (red) and 1 : 2 (red) axial adducts in solution, depending on the reagents' molar ratio. Adducts of primary and secondary diamines decomposed in the presence of ligand excess, the former via unstable equatorial complexes. The complexation of secondary diamines slowed down the inversion at nitrogen atoms in NH(CH3 ) functional groups and resulted in the formation of nitrogenous stereogenic centres, detectable by NMR. Axial adducts of tertiary diamines appeared to be relatively stable. The presence of long aliphatic chains in molecules (adducts of nonane-1,9-diamines or rhodium(II) tetrakisoctanoate) increased adduct solubility. Hypothetical structures of the equatorial adduct of rhodium(II) tetraacetate with ethane-1,2-diamine and their NMR parameters were explored by means of DFT calculations. Copyright © 2013 John Wiley & Sons, Ltd.

  11. Synthesis, structural, photoluminescence, vibrational and DFT investigation of the bis (4-aminopyridinium) tetrachloridocuprate(II) monohydrate

    International Nuclear Information System (INIS)

    Kessentini, A.; Belhouchet, M.; Suñol, J.J.; Abid, Y.; Mhiri, T.

    2014-01-01

    The crystals of the family of alkylammonuim tetrachloridocuprate (II), (C 5 H 7 N 2 ) 2 CuCl 4 H 2 O, have been grown, structurally characterized and their vibrational as well as optical properties been studied. A preliminary single crystal X-ray diffraction structural analysis has revealed that the title compound belongs to the monoclinic system with space group C2/c. Its unit cell dimensions are: a=8.454 (2) Å, b=14.279 (2) Å, c=14.363 (3) Å, β=95.813 (4)°, with Z=4 and its crystal structure was determined and refined down to R 1 =0.029 and wR 2 =0.080. The crystal lattice is composed of discrete [CuCl 4 ] 2− tetrahedra surrounded by 4-aminopyridinium cations and water molecules which are interconnected by means of hydrogen bonding contacts [N–H…Cl, O–H…Cl and N–H…O]. Furthermore, the room temperature IR and Raman spectra of the title compound were recorded and analyzed. The optimized molecular structure and the vibrational spectra were calculated by the density functional theory (DFT) method using the B3LYP function. The organic–inorganic hybrid crystal thin film can be easily prepared by spin-coating method from the ethanol solution of the (C 5 H 7 N 2 ) 2 CuCl 4 H 2 O perovskite and it showed characteristic absorptions of CuCl-based layered perovskite centered at 288 and 400 nm, as well as the photoluminescence peak at around 443 nm. The unaided-eye-detectable blue luminescence emission comes from the excitonic transition in the CuCl 4 anions. - Highlights: • A new hybrid compound (C 5 H 7 N 2 ) 2 CuCl 4 H 2 O was synthesized. • Vibrational properties were studied by IR and Raman spectroscopy and examined theoretically using the DFT/B3LYP/LanL2DZ level of theory. • The UV–vis spectrum shows two absorption peaks at 288 and at 400 nm. • This compound show a strong blue emission at 443 nm

  12. Synthesis, structural, photoluminescence, vibrational and DFT investigation of the bis (4-aminopyridinium) tetrachloridocuprate(II) monohydrate

    Energy Technology Data Exchange (ETDEWEB)

    Kessentini, A., E-mail: kessentiniabir@gmail.com [Laboratoire Physico-Chimie de l’Etat Solide, Département de Chimie, Faculté des Sciences de Sfax, Université de Sfax, B. P. 1171, 3000 Sfax (Tunisia); Belhouchet, M. [Laboratoire Physico-Chimie de l’Etat Solide, Département de Chimie, Faculté des Sciences de Sfax, Université de Sfax, B. P. 1171, 3000 Sfax (Tunisia); Suñol, J.J. [Departamento De Fisica, Universita de Girona, Compus Montilivi, Girona 17071 (Spain); Abid, Y. [Laboratoire de Physique appliquée, Faculté des Sciences de Sfax, Université de Sfax, B. P. 1171, 3000 Sfax (Tunisia); Mhiri, T. [Laboratoire Physico-Chimie de l’Etat Solide, Département de Chimie, Faculté des Sciences de Sfax, Université de Sfax, B. P. 1171, 3000 Sfax (Tunisia)

    2014-05-01

    The crystals of the family of alkylammonuim tetrachloridocuprate (II), (C{sub 5}H{sub 7}N{sub 2}){sub 2}CuCl{sub 4}H{sub 2}O, have been grown, structurally characterized and their vibrational as well as optical properties been studied. A preliminary single crystal X-ray diffraction structural analysis has revealed that the title compound belongs to the monoclinic system with space group C2/c. Its unit cell dimensions are: a=8.454 (2) Å, b=14.279 (2) Å, c=14.363 (3) Å, β=95.813 (4)°, with Z=4 and its crystal structure was determined and refined down to R{sub 1}=0.029 and wR{sub 2}=0.080. The crystal lattice is composed of discrete [CuCl{sub 4}]{sup 2−} tetrahedra surrounded by 4-aminopyridinium cations and water molecules which are interconnected by means of hydrogen bonding contacts [N–H…Cl, O–H…Cl and N–H…O]. Furthermore, the room temperature IR and Raman spectra of the title compound were recorded and analyzed. The optimized molecular structure and the vibrational spectra were calculated by the density functional theory (DFT) method using the B3LYP function. The organic–inorganic hybrid crystal thin film can be easily prepared by spin-coating method from the ethanol solution of the (C{sub 5}H{sub 7}N{sub 2}){sub 2}CuCl{sub 4}H{sub 2}O perovskite and it showed characteristic absorptions of CuCl-based layered perovskite centered at 288 and 400 nm, as well as the photoluminescence peak at around 443 nm. The unaided-eye-detectable blue luminescence emission comes from the excitonic transition in the CuCl{sub 4} anions. - Highlights: • A new hybrid compound (C{sub 5}H{sub 7}N{sub 2}){sub 2}CuCl{sub 4}H{sub 2}O was synthesized. • Vibrational properties were studied by IR and Raman spectroscopy and examined theoretically using the DFT/B3LYP/LanL2DZ level of theory. • The UV–vis spectrum shows two absorption peaks at 288 and at 400 nm. • This compound show a strong blue emission at 443 nm.

  13. Domestic Violence in Zora Neale Hurston's Their Eyes Were Watching God: A Feminist Reading

    Directory of Open Access Journals (Sweden)

    Parmis Tasharofi

    2014-07-01

    Full Text Available Zora Neale Hurston's Their Eyes Were Watching God is one of the acclaimed boldly feminist novels of the 20th century. In general, this article draws on feminism and what looms large in feminism which is called sexism. In particular it focuses on domestic violence as a major sexist oppression. Domestic violence aroused by jealousy, anger, coercion, humiliation, threatening is manifest in verbal and physical abusing of women. Hurston skillfully depicts her heroine's undergoing of domestic violence by her husbands, each in different ways. This article aims to show that how the black heroine's battling with this violence purports to feminism and self-discovery of women.

  14. Magnetic and electronic properties of Neptunium chalcogenides from GGA + U + SOC and DFT investigations

    Energy Technology Data Exchange (ETDEWEB)

    Khan, Wilayat [New Technologies – Research Center, University of West Bohemia, Univerzitni 8, 306 14 Pilsen (Czech Republic); Goumri-Said, Souraya, E-mail: sosaid@alfaisal.edu [College of Science, Physics Department, Alfaisal University, Riyadh 11533 (Saudi Arabia)

    2017-06-15

    Highlights: • Electronic and magnetic properties of Neptunium chalcogenides were explored theoretically using DFT approach. • Spin orbit coupling and GGA + U approach described successfully the f–f coupling. • Np{sub 2}X{sub 5} ate metallic with high magnetic character due to the Neptunium. • Fermi surfaces of Np{sub 2}Te{sub 5} have shown a greater electrical conductivity compared to Np{sub 2}Se{sub 5} and Np{sub 2}S{sub 5}. - Abstract: First-principles calculations techniques were employed to explore the structural, electronic and magnetic properties of Neptunium chalcogenides (Np{sub 2}X{sub 5}, X = S, Se and Te). No experimental or theoretical studies of their physical properties have been previously reported in the literature. The presence of highly localized f states has requested the employment of the spin orbit coupling and GGA + U approach in order to describe correctly the f–f coupling. Np{sub 2}X{sub 5} was found metallic with high magnetic character due to the Neptunium presence. Fermi surfaces of Np{sub 2}Te{sub 5} have shown a greater electrical conductivity compared to Np{sub 2}Se{sub 5} and Np{sub 2}S{sub 5}. The magnetic moment was found to be between 13.24 and 13.92μ{sub B}, principally induced by Np f and d-orbitals as well as the spin-polarization of the chalcogenes (Te, Se, S) induced by Np. Neptunium chalcogenides have shown interesting magnetic properties and should be manipulated with precaution due to their radioactive properties.

  15. Relativistic DFT calculations of hyperfine coupling constants in the 5d hexafluorido complexes

    DEFF Research Database (Denmark)

    Haase, Pi Ariane Bresling; Repisky, Michal; Komorovsky, Stanislav

    2018-01-01

    We have investigated the performance of the most popular relativistic density functional theory methods, zeroth order regular approximation (ZORA) and 4-component Dirac-Kohn-Sham (DKS), in the calculation of the recently measured hyperfine coupling constants of ReIV and IrIV in their hexafluorido...

  16. "Different by Degree": Ella Cara Deloria, Zora Neale Hurston, and Franz Boas Contend with Race and Ethnicity.

    Science.gov (United States)

    Hoefel, Roseanne

    2001-01-01

    American Indian ethnographer and linguist Ella Cara Deloria and African American folklorist and writer Zora Neale Hurston did fieldwork for Franz Boas, the father of modern anthropology. Both were shocked by how American racism empowered white people's historical actions. By correcting stereotypes through their work, they reasserted the role of…

  17. Zora D. by Isidora Žebeljan: Towards the new opera

    Directory of Open Access Journals (Sweden)

    Čičovački Borislav

    2004-01-01

    Full Text Available Opera Zora D., composed by Isidora Žebeljan during 2002 and 2003, and which was premiered in Amsterdam in June 2003, is the first Serbian opera that had a world premiere abroad. It is also the first Serbian opera that has been staged outside Serbia since 1935, after being acclaimed at a competition organized by the Genesis Foundation from London. Isidora Žebeljan was commissioned (granted financial backing to compose a complete opera with a secured stage realization. The Dutch Chamber Opera (Opera studio Nederland and the Viennese Chamber Opera (Wiener Kammeroper were the co-producers of the first production. The opera was directed by David Pountney, the renowned opera director, while an international team of young singers and celebrated artists assisted the co-production. The opera was played three times in Amsterdam. Winfried Maczewski conducted the Amsterdam Nieuw Ensemble whereas Daniel Hoyem Cavazza conducted the Wiener Kammeroper on twelve performances. The Viennese premier of Zora D. opened the season of celebrations, thus marking the 50th anniversary of the Wiener Kammeroper. The libretto, based on the script for a TV film by Dušan Ristić, was co-written by Isidora Žebeljan, Milica Žebeljan and Borislav Čičovački. Speaking of genre, the libretto represents a mélange of thriller, melodrama and mystery, with elements of fiction. The opera consists of the prologue and seven scenes. The story, set in the present-day Belgrade, also goes back to the 1930’s and the periods interweave. The opera was written for four vocalists: the soprano, the baritone, and two mezzo-sopranos. The chamber orchestra has fifteen musicians. The story: One summer day in 1935, Belgrade poetess Zora Dulijan mysteriously disappears. Sixty years later, Mina, an ordinary girl from Belgrade, quite unexpectedly becomes part of an incredible story, which gradually unravels as time goes by. Led by a dream (recurring night after night, with some vague verses about

  18. Water Adsorption and Dissociation on Ceria-Supported Single-Atom Catalysts: A First-Principles DFT+U Investigation.

    Science.gov (United States)

    Han, Zhong-Kang; Gao, Yi

    2016-02-01

    Single-atom catalysts have attracted wide attention owing to their extremely high atom efficiency and activities. In this paper, we applied density functional theory with the inclusion of the on-site Coulomb interaction (DFT+U) to investigate water adsorption and dissociation on clean CeO 2 (111) surfaces and single transition metal atoms (STMAs) adsorbed on the CeO 2 (111) surface. It is found that the most stable water configuration is molecular adsorption on the clean CeO 2 (111) surface and dissociative adsorption on STMA/CeO 2 (111) surfaces, respectively. In addition, our results indicate that the more the electrons that transfer from STMA to the ceria substrate, the stronger the binding energies between the STMA and ceria surfaces. A linear relationship is identified between the water dissociation barriers and the d band centers of STMA, known as the generalized Brønsted-Evans-Polanyi principle. By combining the oxygen spillovers, single-atom dispersion stabilities, and water dissociation barriers, Zn, Cr, and V are identified as potential candidates for the future design of ceria-supported single-atom catalysts for reactions in which the dissociation of water plays an important role, such as the water-gas shift reaction. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  19. Investigation of the interaction of carbon dioxide fluid with internal and external single-wall carbon nanotubes by DFT

    Directory of Open Access Journals (Sweden)

    M. Oftadeh

    2011-07-01

    Full Text Available The effective parameters of (5, 0 and (5, 5 single-wall carbon nanotubes during the interaction with carbon dioxide as sensors are determined. The interaction of carbon dioxide  molecules with internal and external walls of the nanotubes is studied using Gaussian 03 coding by density functional theory (DFT at the B3LYP/6-311G level of theory. CO2 rotation around tube axles vertically and parallel to the internal and external walls has been investigated. The carbon dioxide molecule is predicted to bind only weakly to nanotubes, and the tube-molecule interactions can be identified as physisorption. CO2 adsorption is stronger on external wallsthan on internal walls, and adsorption on the external wall of (5, 0 is stronger than on the external wall of (5, 5; the adsorption energies are exothermic and equal to -0.8884 and -0.0528 kcal/mol, respectively. The rotation energy barrier for (5, 5 is lower than that for (5, 0 in all rotations, therefore in these interactions (5, 5 is more active. The energy gap significantly changes in the presence of  carbon  dioxide molecules on the inside surface of (5, 0 and the electric conductivity is affected, but no remarkable change is observed in the electronic structure of (5, 5.

  20. Spectroscopic analysis of 8-hydroxyquinoline-5-sulphonic acid and investigation of its reactive properties by DFT and molecular dynamics simulations

    Science.gov (United States)

    Sureshkumar, B.; Sheena Mary, Y.; Panicker, C. Yohannan; Resmi, K. S.; Suma, S.; Armaković, Stevan; Armaković, Sanja J.; Van Alsenoy, C.

    2017-12-01

    A detailed interpretation of the FT-IR and FT-Raman spectra has been performed on the basis of the observed and calculated infrared and Raman spectra as well as calculated potential energy distribution values. Comparison of Raman and SERS spectra suggests a tilted orientation of the rings on the metal surface. The dipole moment, polarizability and first and second order hyperpolarizability values of the molecule were calculated. Global reactivity parameters were predicted. The relative reactivities towards electrophilic and nucleophilic attack are predicted using molecular electrostatic potential map. Average local ionization energy (ALIE) and Fukui functions have been inspected in order to investigate local reactivity properties of title molecule. The importance of autoxidation and hydrolysis mechanisms for the title molecule has been assessed by DFT calculations of bond dissociation energies (BDE) and by calculations of radial distribution functions (RDFs) after molecular dynamics (MD) simulations. Molecular docking studies suggest that the title compound can be a lead compound for developing new anti-cancerous drug.

  1. Combined DFT and DEMS investigation of the effect of dopants in secondary zinc‐air batteries

    DEFF Research Database (Denmark)

    Lysgaard, Steen; Christensen, Mathias K.; Hansen, Heine A.

    2018-01-01

    Zinc‐air batteries offer the potential of low cost energy storage with high energy density, but at present secondary batteries suffer from poor cyclability. To develop secondary Zn‐air batteries, several challenges need to be overcome: choking of the cathode, catalyzing the oxygen evolution...... and reduction reactions, limiting dendrite formation and the hydrogen evolution reaction (HER). Understanding and alleviating HER at the anode is a challenge, where it is necessary to involve computational as well as experimental research. Here, we combine Differential Electrochemical Mass Spectrometry (DEMS......) and density functional theory calculations to investigate the fundamental role and stability over cycling of possible additives such as In, Bi and Ag. We show that both In and Bi have the desired property for a secondary battery that upon recharging, they will remain in the surface, thereby retaining...

  2. UPS and DFT investigation of the electronic structure of gas-phase trimesic acid

    Energy Technology Data Exchange (ETDEWEB)

    Reisberg, L., E-mail: rebban@ut.ee [Institute of Physics, University of Tartu, W. Oswaldi 1, EE-50411 Tartu (Estonia); Pärna, R. [Institute of Physics, University of Tartu, W. Oswaldi 1, EE-50411 Tartu (Estonia); MAX IV Laboratory, Lund University, Fotongatan 2, 225 94 Lund (Sweden); Kikas, A.; Kuusik, I.; Kisand, V. [Institute of Physics, University of Tartu, W. Oswaldi 1, EE-50411 Tartu (Estonia); Hirsimäki, M.; Valden, M. [Surface Science Laboratory, Optoelectronics Research Centre, Tampere University of Technology, FIN-33101 Tampere (Finland); Nõmmiste, E. [Institute of Physics, University of Tartu, W. Oswaldi 1, EE-50411 Tartu (Estonia)

    2016-11-15

    Highlights: • In the current study outer valence band electronic structure of benzene-1,3,5-tricarboxylic acid was interpreted. • Experimental and calculated trimesic acid (TMA) spectrum were compared to ones of benzene and benzoic acid. • It is shown that similarities between MO energies and shapes for benzene and TMA exists. • Addition of carboxyl groups to the benzene ring clearly correlates with increasing binding energy of HOMO. - Abstract: Benzene-1,3,5-tricarboxylic acid (trimesic acid, TMA) molecules in gas-phase have been investigated by using valence band photoemission. The photoelectron spectrum in the binding energy region from 9 to 22 eV is interpreted by using density functional theory calculations. The electronic structure of TMA is compared with benzene and benzoic acid in order to demonstrate changes in molecular orbital energies induced by addition of carboxyl groups to benzene ring.

  3. The DFT investigations of the electron injection in hydrazone-based sensitizers

    KAUST Repository

    Al-Sehemi, Abdullah G.

    2012-03-01

    Quantum chemical calculations were carried out by using density functional theory and time-dependant density functional theory at B3LYP/6-31G(d) and TD-B3LYP/6-31G(d) level of theories. The absorption spectra have been computed with and without solvent. The calculated absorption spectra in ethanol, acetonitrile, and methanol are in good agreement with experimental evidences. The absorption spectra are red shifted compared to System1. On the basis of electron injection and electronic coupling constant, we have shed light on the nature of different sensitizers. The coplanarity between the benzene near anchoring group having LUMO and the bridge (N-N) is broken in System6 and System7 that would hamper the recombination process. The electron injection of System2-System10 is superior to System1. The highest electronic coupling constant has been observed for System6 that followed the System7 and System8. The light-harvesting efficiency of all the sensitizers enlarged in acetonitrile and ethanol. The long-range-corrected functional (LC-BLYP), Coulomb-attenuating method (CAM-B3LYP), and BH and HLYP functional underestimate the excitation energies while B3LYP is good to reproduce the experimental data. Moreover, we have investigated the effect of cyanoacetic acid as anchoring group on the electron injection. © 2012 Springer-Verlag.

  4. DFT and time-resolved IR investigation of electron transfer between photogenerated 17- and 19-electron organometallic radicals

    Energy Technology Data Exchange (ETDEWEB)

    Cahoon, James B.; Kling, Matthias F.; Sawyer, Karma R.; Andersen, Lars K.; Harris, Charles B.

    2008-04-30

    The photochemical disproportionation mechanism of [CpW(CO){sub 3}]{sub 2} in the presence of Lewis bases PR{sub 3} was investigated on the nano- and microsecond time-scales with Step-Scan FTIR time-resolved infrared spectroscopy. 532 nm laser excitation was used to homolytically cleave the W-W bond, forming the 17-electron radicals CpW(CO){sub 3} and initiating the reaction. With the Lewis base PPh{sub 3}, disproportionation to form the ionic products CpW(CO){sub 3}PPh{sub 3}{sup +} and CpW(CO){sub 3}{sup -} was directly monitored on the microsecond time-scale. Detailed examination of the kinetics and concentration dependence of this reaction indicates that disproportionation proceeds by electron transfer from the 19-electron species CpW(CO){sub 3}PPh{sub 3} to the 17-electron species CpW(CO){sub 3}. This result is contrary to the currently accepted disproportionation mechanism which predicts electron transfer from the 19-electron species to the dimer [CpW(CO){sub 3}]{sub 2}. With the Lewis base P(OMe){sub 3} on the other hand, ligand substitution to form the product [CpW(CO){sub 2}P(OMe){sub 3}]{sub 2} is the primary reaction on the microsecond time-scale. Density Functional Theory (DFT) calculations support the experimental results and suggest that the differences in the reactivity between P(OMe){sub 3} and PPh{sub 3} are due to steric effects. The results indicate that radical-to-radical electron transfer is a previously unknown but important process for the formation of ionic products with the organometallic dimer [CpW(CO){sub 3}]{sub 2} and may also be applicable to the entire class of organometallic dimers containing a single metal-metal bond.

  5. DFT and experimental studies on structure and spectroscopic parameters of 3,6-diiodo-9-ethyl-9H-carbazole

    DEFF Research Database (Denmark)

    Radula-Janik, Klaudia; Kupka, Teobald; Ejsmont, Krzysztof

    2016-01-01

    The first report on crystal and molecular structure of 3,6-diiodo-9-ethyl-9H-carbazole is presented. Experimental room-temperature X-ray and 13C chemical shift studies were supported by advanced theoretical calculations using density functional theory (DFT). The 13C nuclear magnetic shieldings were...... predicted at the non-relativistic and relativistic level of theory using the zeroth-order regular approximation (ZORA). Theoretical relativistic calculations of chemical shifts of carbons C3 and C6, directly bonded to iodine atoms, produced a reasonable agreement with experiment (initial deviation from...

  6. Direct Production of Propene from the Thermolysis of Poly(β-hydroxybutyrate) (PHB). An Experimental and DFT Investigation.

    Science.gov (United States)

    Clark, Jared M; Pilath, Heidi M; Mittal, Ashutosh; Michener, William E; Robichaud, David J; Johnson, David K

    2016-01-28

    We demonstrate a synthetic route toward the production of propene directly from poly(β-hydroxybutyrate) (PHB), the most common of a wide range of high-molecular-mass microbial polyhydroxyalkanoates. Propene, a major commercial hydrocarbon, was obtained from the depolymerization of PHB and subsequent decarboxylation of the crotonic acid monomer in good yields (up to 75 mol %). The energetics of PHB depolymerization and the gas-phase decarboxylation of crotonic acid were also studied using density functional theory (DFT). The average activation energy for the cleavage of the R'C(O)O-R linkage is calculated to be 163.9 ± 7.0 kJ mol(-1). Intramolecular, autoacceleration effects regarding the depolymerization of PHB, as suggested in some literature accounts, arising from the formation of crotonyl and carboxyl functional groups in the products could not be confirmed by the results of DFT and microkinetic modeling. DFT results, however, suggest that intermolecular catalysis involving terminal carboxyl groups may accelerate PHB depolymerization. Activation energies for this process were estimated to be about 20 kJ mol(-1) lower than that for the noncatalyzed ester cleavage, 144.3 ± 6.4 kJ mol(-1). DFT calculations predict the decarboxylation of crotonic acid to follow second-order kinetics with an activation energy of 147.5 ± 6.3 kJ mol(-1), consistent with that measured experimentally, 146.9 kJ mol(-1). Microkinetic modeling of the PHB to propene overall reaction predicts decarboxylation of crotonic acid to be the rate-limiting step, consistent with experimental observations. The results also indicate that improvements made to enhance the isomerization of crotonic acid to vinylacetic acid will improve the direct conversion of PHB to propene.

  7. Optimalizace manipulační techniky v podniku Nestlé Česko s.r.o., závod ZORA Olomouc

    OpenAIRE

    Kovář, Jiří

    2015-01-01

    This thesis discusses the optimal way of material-handling equipment replacement at Nestlé Česko s.r.o., plant ZORA Olomouc. The theoretical part describes the issue of warehousing in general and focuses on the material-handling equipment and vehicles. The following analytical part focuses specifically on the company Nestlé Česko s.r.o., particularly the plant ZORA Olomouc with the foremost aim of analysing and optimising the current material-handling equipment.

  8. Spectroscopic investigation on structure (monomer and dimer), molecular characteristics and comparative study on vibrational analysis of picolinic and isonicotinic acids using experimental and theoretical (DFT & IVP) methods

    Science.gov (United States)

    Ramesh, Gaddam; Reddy, Byru Venkatram

    2018-05-01

    In this investigation, the monomeric structure is determined for picolinic and isonicotinic acids based on geometry optimization for one of the four possible conformers and intramolecular hydrogen bond of Osbnd H⋯O using density functional theory (DFT) employing B3LYP functional supplemented with 6-311++G(d,p) basis set. Using this optimized monomeric form, the dimer structure is determined based on minimum energy and length of hydrogen bonds obtained for two possible dimeric forms yielded due to head-to-tail intermolecular Osbnd H⋯N hydrogen bond (dimer 1) linkage and tail-to -tail intermolecular Osbnd H⋯O hydrogen bond (dimer 2) linkage between pyridine ring and carboxyl group. The structure parameters obtained for monomer and dimer forms are in good agreement with the experimental literature values. The vibrational assignments have been made unambiguously for all the vibrations from FTIR and FT-Raman spectra based on the potential energy distribution (PED) and eigen vectors obtained in DFT and inverse vibrational problem (IVP) computations. The rms error between the observed and scaled frequencies is 7.7 and 9.4 cm-1 for PIA and INA, respectively. A 74-element modified valence force field is derived by Wilson's GF matrix method using 58 experimental frequencies of the two molecules in overlay least-squares technique. The average error between observed and computed frequencies by this method is calculated to be 10.39 cm-1. The results of both DFT and IVP computations yielded good agreement between observed and calculated frequencies. The NLO behaviour using hyperpolarizability values; and HOMO and LUMO energies; of the two molecules are investigated by DFT. Charge density distribution and site of chemical reactivity of the molecules are studied by molecular electrostatic surface potential (MESP). Stability of the molecules arising from hyper conjugative interactions and charge delocalization has been analyzed using natural bond orbital (NBO

  9. DFT + U investigation on the adsorption and initial decomposition of methylamine by a Pt single-atom catalyst supported on rutile (110) TiO{sub 2}

    Energy Technology Data Exchange (ETDEWEB)

    Lv, Cun-Qin [College of Chemistry and Environmental Engineering, Shanxi Datong University, Datong 037009, Shanxi Province (China); Key Laboratory of Advanced Energy Materials Chemistry (Ministry of Education), Nankai University, Tianjin 300071 (China); Liu, Jian-Hong, E-mail: ljh173@126.com [College of Chemistry and Environmental Engineering, Shanxi Datong University, Datong 037009, Shanxi Province (China); Guo, Yong; Li, Xue-Mei [College of Chemistry and Environmental Engineering, Shanxi Datong University, Datong 037009, Shanxi Province (China); Wang, Gui-Chang, E-mail: wangguichang@nankai.edu.cn [Department of Chemistry, Tianjin Key Lab. of Metal and Molecule-Based Material Chemistry, Nankai University, Tianjin 300071 (China)

    2016-12-15

    Highlights: • DFT + U is used to investigate the initial decomposition of methylamine. • The adsorption characteristics of possible intermediates involved in methylamine initial decomposition are discussed. • The energy barriers of the possible elementary reactions involved are obtained. • C−H bond scission is the most favored among the C−H, N−H and C−N bond breakings in methylamine. - Abstract: The adsorption and initial decomposition for methylamine catalyzed by a single Pt atom supported on rutile (110) titania (namely, Pt{sub 1}/TiO{sub 2}–R(110)) surface have been investigated by the density functional theory slab calculations with Hubbard corrections (DFT + U). The main purpose of the work is to better understand the role of dispersed platinum metal on the surface of rutile (110) titania in the initial decomposition of methylamine. Our calculated results show that the barriers increased with the order of C−H < N−H < C−N, which indicates that the C−H bond is the easiest to decompose and the C−N bond is the most difficult to break.

  10. Investigation of synthesized new vanadium(III) complexes of ditolyldithiophosphate ligands by spectroscopic, cyclic voltammetric, DFT, antimicrobial and cytotoxic studies

    Science.gov (United States)

    Kumar, Sandeep; Syed, Atiya; Andotra, Savit; Kaur, Ramanpreet; Vikas; Pandey, Sushil K.

    2018-02-01

    Vanadium(III) complexes with sulfur donor dithiophosphate ligands corresponding to [{(ArO)2PS2}3V] and [{(ArO)2PS2}2VCl.L] (Ar = o-, m-, p-CH3C6H4 and p-Cl-m-CH3C6H3; L = NC5H5, P(C6H5)3, have been synthesized and characterized by various physico-chemical techniques like elemental analyses, magnetic studies, ESI-Mass, IR, UV and heteronuclear NMR (1H, 13C and 31P) spectral studies. These analyses have contributed to the prediction of structure: by exhibiting significant v(P-S) and v(Pdbnd S) band shifting in comparative IR spectra; shifting of resonance signal in comparative 31P NMR spectra of ligands and complexes and stability of V(III) ion in the complexed state is confirmed by magnetic and UV studies. Therefore, the six coordinated geometry stabilizing the trivalent vanadium atom in the complexes and adducts, respectively has been confirmed. The cyclic voltammetric analyses presented the redox aptitude of the complex under analysis which can be utilized as catalyst in organic synthesis. The geometry of ligands and complexes has been optimized using density functional theory (DFT). The structural parameters, vibrational bands and energy gaps of frontier orbitals (HOMO-LUMO) have also been calculated. The calculated geometric and spectral results reproduced the experimental data with well agreement. The DFT computed frontier molecular orbitals (HOMO-LUMO) and their energies suggest charge transfer occurs within the complexes. Antimicrobial screening of the complexes against two bacterial strains: Gram-positive, Enterrococcus faecalis and Gram-negative, Eischerichia coli and fungus Fusarium oxysporum have shown potential bioactivity. A preliminary cytotoxic analysis has been carried out using the cultivated human cell lines: lung adeno carcinoma cell line A-549, leukemia cell line THP-1, prostate cancer cell line PC3 and colorectal cancer cell line HCT-116.

  11. NSAIDs as potential treatment option for preventing amyloid β toxicity in Alzheimer's disease: an investigation by docking, molecular dynamics, and DFT studies.

    Science.gov (United States)

    Azam, Faizul; Alabdullah, Nada Hussin; Ehmedat, Hadeel Mohammed; Abulifa, Abdullah Ramadan; Taban, Ismail; Upadhyayula, Sreedevi

    2018-06-01

    Aggregation of amyloid beta (Aβ) protein considered as one of contributors in development of Alzheimer's disease (AD). Several investigations have identified the importance of non-steroidal anti-inflammatory drugs (NSAIDs) as Aβ aggregation inhibitors. Here, we have examined the binding interactions of 24 NSAIDs belonging to eight different classes, with Aβ fibrils by exploiting docking and molecular dynamics studies. Minimum energy conformation of the docked NSAIDs were further optimized by density functional theory (DFT) employing Becke's three-parameter hybrid model, Lee-Yang-Parr (B3LYP) correlation functional method. DFT-based global reactivity descriptors, such as electron affinity, hardness, softness, chemical potential, electronegativity, and electrophilicity index were calculated to inspect the expediency of these descriptors for understanding the reactive nature and sites of the molecules. Few selected NSAID-Aβ fibrils complexes were subjected to molecular dynamics simulation to illustrate the stability of these complexes and the most prominent interactions during the simulated trajectory. All of the NSAIDs exhibited potential activity against Aβ fibrils in terms of predicted binding affinity. Sulindac was found to be the most active compound underscoring the contribution of indene methylene substitution, whereas acetaminophen was observed as least active NSAID. General structural requirements for interaction of NSAIDs with Aβ fibril include: aryl/heteroaryl aromatic moiety connected through a linker of 1-2 atoms to a distal aromatic group. Considering these structural requirements and electronic features, new potent agents can be designed and developed as potential Aβ fibril inhibitors for the treatment of AD.

  12. Redox properties of biscyclopentadienyl uranium(V) imido-halide complexes: a relativistic DFT study.

    Science.gov (United States)

    Elkechai, Aziz; Kias, Farida; Talbi, Fazia; Boucekkine, Abdou

    2014-06-01

    Calculations of ionization energies (IE) and electron affinities (EA) of a series of biscyclopentadienyl imido-halide uranium(V) complexes Cp*2U(=N-2,6-(i)Pr2-C6H3)(X) with X =  F, Cl, Br, and I, related to the U(IV)/U(V) and U(V)/U(VI) redox systems, were carried out, for the first time, using density functional theory (DFT) in the framework of the relativistic zeroth order regular approximation (ZORA) coupled with the conductor-like screening model (COSMO) solvation approach. A very good linear correlation (R(2) =  0.993) was obtained, between calculated ionization energies at the ZORA/BP86/TZP level, and the experimental half-wave oxidation potentials E1/2. A similar linear correlation between the computed electron affinities and the electrochemical reduction U(IV)/U(III) potentials (R(2) =  0.996) is obtained. The importance of solvent effects and of spin-orbit coupling is definitively confirmed. The molecular orbital analysis underlines the crucial role played by the 5f orbitals of the central metal whereas the Nalewajski-Mrozek (N-M) bond indices explain well the bond distances variations following the redox processes. The IE variation of the complexes, i.e., IE(F) uranium charges and E1/2 in the reduction process of the U(V) species.

  13. Ba-DOPED ZnO MATERIALS: A DFT SIMULATION TO INVESTIGATE THE DOPING EFFECT ON FERROELECTRICITY

    Directory of Open Access Journals (Sweden)

    Luis H. da S. Lacerda

    2016-04-01

    Full Text Available ZnO is a semiconductor material largely employed in the development of several electronic and optical devices due to its unique electronic, optical, piezo-, ferroelectric and structural properties. This study evaluates the properties of Ba-doped wurtzite-ZnO using quantum mechanical simulations based on the Density Functional Theory (DFT allied to hybrid functional B3LYP. The Ba-doping caused increase in lattice parameters and slight distortions at the unit cell angle in a wurtzite structure. In addition, the doping process presented decrease in the band-gap (Eg at low percentages suggesting band-gap engineering. For low doping amounts, the wavelength characteristic was observed in the visible range; whereas, for middle and high doping amounts, the wavelength belongs to the Ultraviolet range. The Ba atoms also influence the ferroelectric property, which is improved linearly with the doping amount, except for doping at 100% or wurtzite-BaO. The ferroelectric results indicate the ZnO:Ba is an strong option to replace perovskite materials in ferroelectric and flash-type memory devices.

  14. DFT investigations of phosphotriesters hydrolysis in aqueous solution: a model for DNA single strand scission induced by N-nitrosoureas.

    Science.gov (United States)

    Liu, Tingting; Zhao, Lijiao; Zhong, Rugang

    2013-02-01

    DNA phosphotriester adducts are common alkylation products of DNA phosphodiester moiety induced by N-nitrosoureas. The 2-hydroxyethyl phosphotriester was reported to hydrolyze more rapidly than other alkyl phosphotriesters both in neutral and in alkaline conditions, which can cause DNA single strand scission. In this work, DFT calculations have been employed to map out the four lowest activation free-energy profiles for neutral and alkaline hydrolysis of triethyl phosphate (TEP) and diethyl 2-hydroxyethyl phosphate (DEHEP). All the hydrolysis pathways were illuminated to be stepwise involving an acyclic or cyclic phosphorane intermediate for TEP or DEHEP, respectively. The rate-limiting step for all the hydrolysis reactions was found to be the formation of phosphorane intermediate, with the exception of DEHEP hydrolysis in alkaline conditions that the decomposition process turned out to be the rate-limiting step, owing to the extraordinary low formation barrier of cyclic phosphorane intermediate catalyzed by hydroxide. The rate-limiting barriers obtained for the four reactions are all consistent with the available experimental information concerning the corresponding hydrolysis reactions of phosphotriesters. Our calculations performed on the phosphate triesters hydrolysis predict that the lower formation barriers of cyclic phosphorane intermediates compared to its acyclic counter-part should be the dominant factor governing the hydrolysis rate enhancement of DEHEP relative to TEP both in neutral and in alkaline conditions.

  15. Europium, uranyl, and thorium-phenanthroline amide complexes in acetonitrile solution: an ESI-MS and DFT combined investigation.

    Science.gov (United States)

    Xiao, Cheng-Liang; Wang, Cong-Zhi; Mei, Lei; Zhang, Xin-Rui; Wall, Nathalie; Zhao, Yu-Liang; Chai, Zhi-Fang; Shi, Wei-Qun

    2015-08-28

    The tetradentate N,N'-diethyl-N,N'-ditolyl-2,9-diamide-1,10-phenanthroline (Et-Tol-DAPhen) ligand with hard-soft donor atoms has been demonstrated to be promising for the group separation of actinides from highly acidic nuclear wastes. To identify the formed complexes of this ligand with actinides and lanthanides, electrospray ionization mass spectrometry (ESI-MS) combined with density functional theory (DFT) calculations was used to probe the possible complexation processes. The 1 : 2 Eu-L species ([EuL2(NO3)](2+)) can be observed in ESI-MS at low metal-to-ligand ([M]/[L]) ratios, whereas the 1 : 1 Eu-L species ([EuL(NO3)2](+)) can be observed when the [M]/[L] ratio is higher than 1.0. However, ([UO2L(NO3)](+)) is the only detected species for the uranyl complexes. The [ThL2(NO3)2](2+) species can be observed at low [M]/[L] ratios; the 1 : 2 species ([ThL2(NO3)](3+)) and a new 1 : 1 species ([ThL(NO3)3](+)) can be detected at high [M]/[L] ratios. Collision-induced dissociation (CID) results showed that Et-Tol-DAPhen ligands can coordinate strongly with metal ions, and the coordination moieties remain intact under CID conditions. Natural bond orbital (NBO), molecular electrostatic potential (MEP), electron localization function (ELF), atoms in molecules (AIM) and molecular orbital (MO) analyses indicated that the metal-ligand bonds of the actinide complexes exhibited more covalent character than those of the lanthanide complexes. In addition, according to thermodynamic analysis, the stable cationic M-L complexes in acetonitrile are found to be in good agreement with the ESI-MS results.

  16. Major difference in visible-light photocatalytic features between perfect and self-defective Ta3N5 materials: A screened coulomb hybrid dft investigation

    KAUST Repository

    Harb, Moussab; Cavallo, Luigi; Basset, Jean-Marie

    2014-01-01

    theory (DFT, including the perturbation theory DFPT) within the screened coulomb hybrid (HSE06) exchange-correlation formalism. Among the various explored self-defective structures, a strong stabilization is obtained for the configuration displaying a

  17. Supramolecular architecture of 5-bromo-7-methoxy-1-methyl-1H-benzoimidazole.3H2O: Synthesis, spectroscopic investigations, DFT computation, MD simulations and docking studies

    Science.gov (United States)

    Murthy, P. Krishna; Smitha, M.; Sheena Mary, Y.; Armaković, Stevan; Armaković, Sanja J.; Rao, R. Sreenivasa; Suchetan, P. A.; Giri, L.; Pavithran, Rani; Van Alsenoy, C.

    2017-12-01

    Crystal and molecular structure of newly synthesized compound 5-bromo-7-methoxy-1-methyl-1H-benzoimidazole (BMMBI) has been authenticated by single crystal X-ray diffraction, FT-IR, FT-Raman, 1H NMR, 13C NMR and UV-Visible spectroscopic techniques; compile both experimental and theoretical results which are performed by DFT/B3LYP/6-311++G(d,p) method at ground state in gas phase. Visualize nature and type of intermolecular interactions and crucial role of these interactions in supra-molecular architecture has been investigated by use of a set of graphical tools 3D-Hirshfeld surfaces and 2D-fingerprint plots analysis. The title compound stabilized by strong intermolecular hydrogen bonds N⋯Hsbnd O and O⋯Hsbnd O, which are envisaged by dark red spots on dnorm mapped surfaces and weak Br⋯Br contacts envisaged by red spot on dnorm mapped surface. The detailed fundamental vibrational assignments of wavenumbers were aid by with help of Potential Energy distribution (PED) analysis by using GAR2PED program and shows good agreement with experimental values. Besides frontier orbitals analysis, global reactivity descriptors, natural bond orbitals and Mullikan charges analysis were performed by same basic set at ground state in gas phase. Potential reactive sites of the title compound have been identified by ALIE, Fukui functions and MEP, which are mapped to the electron density surfaces. Stability of BMMBI have been investigated from autoxidation process and pronounced interaction with water (hydrolysis) by using bond dissociation energies (BDE) and radial distribution functions (RDF), respectively after MD simulations. In order to identify molecule's most important reactive spots we have used a combination of DFT calculations and MD simulations. Reactivity study encompassed calculations of a set of quantities such as: HOMO-LUMO gap, MEP and ALIE surfaces, Fukui functions, bond dissociation energies and radial distribution functions. To confirm the potential

  18. Investigation on the electronic structures and photophysical properties of a series of cyclometalated iridium(III) complexes based on DFT/TDDFT calculations

    Energy Technology Data Exchange (ETDEWEB)

    Shang, Chunyu, E-mail: shang.chun.yu@163.com; Xu, Jie; Du, Yanqiu; Zhao, Jie

    2016-07-15

    The electronic structures and photophysical properties of a series of cyclometalated iridium (III) complexes Ir(C{sup ∧}N){sub 2}(H{sub 2}NNHCOO), including 1 [C{sup ∧}N=2-phenyl-pyridine], 2 [C{sup ∧}N=5-fluoro-2-phenylpyridine], 3 [C{sup ∧}N=2-phenyl-5-trifluoromethylpyridine], 4 [C{sup ∧}N=6-phenyl-[2, 3] bipyridinyl], 5 [C{sup ∧}N=7-phenyl-cyclopenta [4] dipyridine] and 6 [C{sup ∧}N=8-phenyl-[1, 9] phenanthroline], have been theoretically investigated based on density functional theory (DFT) and time-dependent DFT. The characteristics in phosphorescent performances have been outlined for each of the complexes in the applications in OLED. On the basis of the two simplifications presented in this paper and the available experimental data, the magnitudes of phosphorescent radiative rates for complexes 1–6 were approximately calculated to be: 5.56×10{sup 5} s{sup −1}, 2.68×10{sup 5} s{sup −1}, 1.17×10{sup 6} s{sup −1}, 9.78×10{sup 4} s{sup −1}, 5.30×10{sup 6} s{sup −1} and 6.71×10{sup 6} s{sup −1}, respectively. Meanwhile, the sequence of phosphorescent quantum efficiencies was obtained to be: Φ{sub PL}(4)<Φ{sub PL}(2)<Φ{sub PL}(1)<Φ{sub PL}(3)<Φ{sub PL}(5)<Φ{sub PL}(6), in which Φ{sub PL}(4) is by far the lowest, Φ{sub PL}(5) is much larger and Φ{sub PL}(6) is by far the largest. In contrast to complex 1, the emission wavelengths are slightly red-shifted for 2 and 3 and significantly red-shifted for 4 and 5, while the emission wavelength of 6 is slightly blue-shifted. In comparison, complexes 6 and 5 may be singled out to be the most efficient phosphorescence emitters for the applications in OLED.

  19. Critical difference between optoelectronic properties of α- and β-SnWO4semiconductors: A DFT/HSE06 and experimental investigation

    KAUST Repository

    Harb, Moussab

    2016-02-03

    The optoelectronic properties of β-SnWO4 are investigated in details using experiments on thin film generated by rapid quenching and the first-principles quantum calculations based on the density functional theory (DFT, including the perturbation approach DFPT) and employing the PBE and the range-separated hybrid exchange-correlation HSE06 functionals. The obtained bandgap, optical absorption coefficient, dielectric constant, and charge-carrier effective masses for β-SnWO4 exhibit data irreconcilable with the reported values: e.g., a large and direct bandgap of 4.30eV (UV-responsive), inconsistent with the values in the literature (visible-responsive). These properties obtained for β-SnWO4 are distinctive from those for α-SnWO4: an indirect bandgap of 1.52eV with higher charge mobilities. These data of intrinsic stoichiometric materials suggest that the literature reported nonstoichiometric materials where defects significantly influence the optoelectronic properties. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  20. Synthesis, structural and vibrational investigation on 2-phenyl-N-(pyrazin-2-yl)acetamide combining XRD diffraction, FT-IR and NMR spectroscopies with DFT calculations.

    Science.gov (United States)

    Lukose, Jilu; Yohannan Panicker, C; Nayak, Prakash S; Narayana, B; Sarojini, B K; Van Alsenoy, C; Al-Saadi, Abdulaziz A

    2015-01-25

    The optimized molecular structure, vibrational frequencies, corresponding vibrational assignments of 2-phenyl-N-(pyrazin-2-yl)acetamide have been investigated experimentally and theoretically using Gaussian09 software package. The title compound was optimized by using the HF/6-31G(6D,7F) and B3LYP/6-31G(6D,7F) calculations. The geometrical parameters are in agreement with the XRD data. The stability of the molecule arising from hyper-conjugative interaction and charge delocalization has been analyzed using NBO analysis. Gauge-including atomic orbital (1)H-NMR chemical shifts calculations were carried out and compared with experimental data. The HOMO and LUMO analysis is used to determine the charge transfer within the molecule. Molecular electrostatic potential was performed by the DFT method. First hyperpolarizability is calculated in order to find its role in non linear optics. From the XRD data, in the crystal, molecules are held together by strong C-H⋯O and N-H⋯O intermolecular interactions. Copyright © 2014 Elsevier B.V. All rights reserved.

  1. Synthesis, molecular structure, FT-IR and XRD investigations of 2-(4-chlorophenyl)-2-oxoethyl 2-chlorobenzoate: a comparative DFT study.

    Science.gov (United States)

    Chidan Kumar, C S; Fun, Hoong Kun; Tursun, Mahir; Ooi, Chin Wei; Chandraju, Siddegowda; Quah, Ching Kheng; Parlak, Cemal

    2014-04-24

    2-(4-Chlorophenyl)-2-oxoethyl 2-chlorobenzoate has been synthesized, its structural and vibrational properties have been reported using FT-IR and single-crystal X-ray diffraction (XRD) studies. The conformational analysis, optimized geometric parameters, normal mode frequencies and corresponding vibrational assignments of the synthesized compound (C15H10Cl2O3) have been examined by means of Becke-3-Lee-Yang-Parr (B3LYP) density functional theory (DFT) method together with 6-31++G(d,p) basis set. Furthermore, reliable conformational investigation and vibrational assignments have been made by the potential energy surface (PES) and potential energy distribution (PED) analyses, respectively. Calculations are performed with two possible conformations. The title compound crystallizes in orthorhombic space group Pbca with the unit cell dimensions a=12.312(5) Å, b=8.103(3) Å, c=27.565(11) Å, V=2750.0(19) Å(3). B3LYP method provides satisfactory evidence for the prediction of vibrational wavenumbers and structural parameters. Copyright © 2014 Elsevier B.V. All rights reserved.

  2. Molecular vibrational investigation [FT-IR, FT-Raman, UV-Visible and NMR] on Bis(thiourea) Nickel chloride using HF and DFT calculations

    Science.gov (United States)

    Anand, S.; Sundararajan, R. S.; Ramachandraraja, C.; Ramalingam, S.; Durga, R.

    2015-03-01

    In the present research work, the FT-IR, FT-Raman spectra of the Bis(thiourea) Nickel chloride (BTNC) were recorded and analyzed. The observed fundamental frequencies in finger print and functional group regions were assigned according to their uniqueness region. The computational calculations were carried out by HF and DFT (B3LYP and B3PW91) methods with 6-31++G(d,p) and 6-311++G(d,p) basis sets and the corresponding results were tabulated. The present organo-metallic compound was made up of covalent and coordination covalent bonds. The modified vibrational pattern of the complex molecule associated with ligand group was analyzed. Furthermore, the 13C NMR and 1H NMR spectral data were calculated by using the gauge independent atomic orbital (GIAO) method with B3LYP/6-311++G(d,p) basis set and their spectra were simulated and the chemical shifts linked to TMS were compared. A investigation on the electronic and optical properties; absorption wavelengths, excitation energy, dipole moment and frontier molecular orbital energies were carried out. The kubo gap of the present compound was calculated related to HOMO and LUMO energies which confirm the occurring of charge transformation between the base and ligand. Besides frontier molecular orbitals (FMO), molecular electrostatic potential (MEP) was performed. The NLO properties related to Polarizability and hyperpolarizability based on the finite-field approach were also discussed.

  3. Molecular vibrational investigation [FT-IR, FT-Raman, UV-Visible and NMR] on Bis(thiourea) Nickel chloride using HF and DFT calculations.

    Science.gov (United States)

    Anand, S; Sundararajan, R S; Ramachandraraja, C; Ramalingam, S; Durga, R

    2015-03-05

    In the present research work, the FT-IR, FT-Raman spectra of the Bis(thiourea) Nickel chloride (BTNC) were recorded and analyzed. The observed fundamental frequencies in finger print and functional group regions were assigned according to their uniqueness region. The computational calculations were carried out by HF and DFT (B3LYP and B3PW91) methods with 6-31++G(d,p) and 6-311++G(d,p) basis sets and the corresponding results were tabulated. The present organo-metallic compound was made up of covalent and coordination covalent bonds. The modified vibrational pattern of the complex molecule associated with ligand group was analyzed. Furthermore, the (13)C NMR and (1)H NMR spectral data were calculated by using the gauge independent atomic orbital (GIAO) method with B3LYP/6-311++G(d,p) basis set and their spectra were simulated and the chemical shifts linked to TMS were compared. A investigation on the electronic and optical properties; absorption wavelengths, excitation energy, dipole moment and frontier molecular orbital energies were carried out. The kubo gap of the present compound was calculated related to HOMO and LUMO energies which confirm the occurring of charge transformation between the base and ligand. Besides frontier molecular orbitals (FMO), molecular electrostatic potential (MEP) was performed. The NLO properties related to Polarizability and hyperpolarizability based on the finite-field approach were also discussed. Crown Copyright © 2014. Published by Elsevier B.V. All rights reserved.

  4. H{sub 2} dissociation on γ-Al{sub 2}O{sub 3} supported Cu/Pd atoms: A DFT investigation

    Energy Technology Data Exchange (ETDEWEB)

    Wang, Hongtao [College of Environmental Science and Engineering, Taiyuan University of Technology, Taiyuan 030024, Shanxi (China); Key Laboratory of Coal Science and Technology of Shanxi Province and Ministry of Education, Taiyuan University of Technology, Taiyuan 030024, Shanxi (China); Chen, Lijuan [Key Laboratory of Coal Science and Technology of Shanxi Province and Ministry of Education, Taiyuan University of Technology, Taiyuan 030024, Shanxi (China); Lv, Yongkang, E-mail: lykang@tyut.edu.cn [Key Laboratory of Coal Science and Technology of Shanxi Province and Ministry of Education, Taiyuan University of Technology, Taiyuan 030024, Shanxi (China); Ren, Ruipeng, E-mail: s2003wht@126.com [Key Laboratory of Coal Science and Technology of Shanxi Province and Ministry of Education, Taiyuan University of Technology, Taiyuan 030024, Shanxi (China)

    2014-01-30

    The density functional theory (DFT) was applied to investigate the promotion effects of single Cu and Pd atoms deposition on γ-Al{sub 2}O{sub 3} surface for the adsorption and dissociation of H{sub 2} molecule, which is of importance for many catalysis reactions. Due to its strong Lewis acidity, the tri-coordinated surface Al site was identified to be the most preferable site for both Cu and Pd location. The inner surface electrons rearrangement from O to Al of alumina was found to be a key factor to stabilize the Cu/Pd adsorption configurations, rather than the total electrons transfer between Cu/Pd and the surface. It was found that the supported Cu and Pd atoms are more active for H{sub 2} dissociation than the clean γ-Al{sub 2}O{sub 3} surface. The supported Pd is more active than Cu for H{sub 2} dissociation. In addition, the metal–support interaction of the γ-Al{sub 2}O{sub 3} supported Cu/Pd atoms are more favored than the metal–metal interaction of the metal clusters for the H{sub 2} dissociated adsorption.

  5. New Pyrazole-Hydrazone Derivatives: X-ray Analysis, Molecular Structure Investigation via Density Functional Theory (DFT) and Their High In-Situ Catecholase Activity.

    Science.gov (United States)

    Karrouchi, Khalid; Yousfi, El Bekkaye; Sebbar, Nada Kheira; Ramli, Youssef; Taoufik, Jamal; Ouzidan, Younes; Ansar, M'hammed; Mabkhot, Yahia N; Ghabbour, Hazem A; Radi, Smaail

    2017-10-25

    The development of low-cost catalytic systems that mimic the activity of tyrosinase enzymes (Catechol oxidase) is of great promise for future biochemistry technologic demands. Herein, we report the synthesis of new biomolecules systems based on hydrazone derivatives containing a pyrazole moiety ( L1 - L6 ) with superior catecholase activity. Crystal structures of L1 and L2 biomolecules were determined by X-ray single crystal diffraction (XRD). Optimized geometrical parameters were calculated by density functional theory (DFT) at B3LYP/6-31G (d, p) level and were found to be in good agreement with single crystal XRD data. Copper (II) complexes of the compounds ( L1 - L6 ), generated in-situ, were investigated for their catalytic activities towards the oxidation reaction of catechol to ortho -quinone with the atmospheric dioxygen, in an attempt to model the activity of the copper containing enzyme tyrosinase. The studies showed that the activities depend on four parameters: the nature of the ligand, the nature of counter anion, the nature of solvent and the concentration of ligand. The Cu(II)-ligands, given here, present the highest catalytic activity (72.920 μmol·L -1 ·min -1 ) among the catalysts recently reported in the existing literature.

  6. A DFT investigation on group 8B transition metal-doped silicon carbide nanotubes for hydrogen storage application

    Science.gov (United States)

    Tabtimsai, Chanukorn; Ruangpornvisuti, Vithaya; Tontapha, Sarawut; Wanno, Banchob

    2018-05-01

    The binding of group 8B transition metal (TMs) on silicon carbide nanotubes (SiCNT) hydrogenated edges and the adsorption of hydrogen molecule on the pristine and TM-doped SiCNTs were investigated using the density functional theory method. The B3LYP/LanL2DZ method was employed in all calculations for the considered structural, adsorption, and electronic properties. The Os atom doping on the SiCNT is found to be the strongest binding. The hydrogen molecule displays a weak interaction with pristine SiCNT, whereas it has a strong interaction with TM-doped SiCNTs in which the Os-doped SiCNT shows the strongest interaction with the hydrogen molecule. The improvement in the adsorption abilities of hydrogen molecule onto TM-doped SiCNTs is due to the protruding structure and the induced charge transfer between TM-doped SiCNT and hydrogen molecule. These observations point out that TM-doped SiCNTs are highly sensitive toward hydrogen molecule. Moreover, the adsorptions of 2-5 hydrogen molecules on TM-doped SiCNT were also investigated. The maximum storage number of hydrogen molecules adsorbed on the first layer of TM-doped SiCNTs is 3 hydrogen molecules. Therefore, TM-doped SiCNTs are suitable to be sensing and storage materials for hydrogen gas.

  7. Molecular reorganization of selected quinoline derivatives in the ground and excited states—Investigations via static DFT

    Science.gov (United States)

    Błaziak, Kacper; Panek, Jarosław J.; Jezierska, Aneta

    2015-07-01

    Quinoline derivatives are interesting objects to study internal reorganizations due to the observed excited-state-induced intramolecular proton transfer (ESIPT). Here, we report on computations for selected 12 quinoline derivatives possessing three kinds of intramolecular hydrogen bonds. Density functional theory was employed for the current investigations. The metric and electronic structure simulations were performed for the ground state and first excited singlet and triplet states. The computed potential energy profiles do not show a spontaneous proton transfer in the ground state, whereas excited states exhibit this phenomenon. Atoms in Molecules (AIM) theory was applied to study the nature of hydrogen bonding, whereas Harmonic Oscillator Model of aromaticity index (HOMA) provided data of aromaticity evolution as a derivative of the bridge proton position. The AIM-based topological analysis confirmed the presence of the intramolecular hydrogen bonding. In addition, using the theory, we were able to provide a quantitative illustration of bonding transformation: from covalent to the hydrogen. On the basis of HOMA analysis, we showed that the aromaticity of both rings is dependent on the location of the bridge proton. Further, the computed results were compared with experimental data available. Finally, ESIPT occurrence was compared for the three investigated kinds of hydrogen bridges, and competition between two bridges in one molecule was studied.

  8. Molecular reorganization of selected quinoline derivatives in the ground and excited states—Investigations via static DFT

    International Nuclear Information System (INIS)

    Błaziak, Kacper; Panek, Jarosław J.; Jezierska, Aneta

    2015-01-01

    Quinoline derivatives are interesting objects to study internal reorganizations due to the observed excited-state-induced intramolecular proton transfer (ESIPT). Here, we report on computations for selected 12 quinoline derivatives possessing three kinds of intramolecular hydrogen bonds. Density functional theory was employed for the current investigations. The metric and electronic structure simulations were performed for the ground state and first excited singlet and triplet states. The computed potential energy profiles do not show a spontaneous proton transfer in the ground state, whereas excited states exhibit this phenomenon. Atoms in Molecules (AIM) theory was applied to study the nature of hydrogen bonding, whereas Harmonic Oscillator Model of aromaticity index (HOMA) provided data of aromaticity evolution as a derivative of the bridge proton position. The AIM-based topological analysis confirmed the presence of the intramolecular hydrogen bonding. In addition, using the theory, we were able to provide a quantitative illustration of bonding transformation: from covalent to the hydrogen. On the basis of HOMA analysis, we showed that the aromaticity of both rings is dependent on the location of the bridge proton. Further, the computed results were compared with experimental data available. Finally, ESIPT occurrence was compared for the three investigated kinds of hydrogen bridges, and competition between two bridges in one molecule was studied

  9. Hydrogen-Induced Adsorption of Carbon Monoxide on the Gold Dimer Cation: A Joint Experimental and DFT Investigation.

    Science.gov (United States)

    Vojkovic, Marin; Rayane, Driss; Antoine, Rodolphe; Broyer, Michel; Allouche, Abdul-Rahman; Mignon, Pierre; Dugourd, Philippe

    2017-06-15

    It is demonstrated, using tandem mass spectrometry and radio frequency ion trap, that the adsorption of a H atom on the gold dimer cation, Au 2 H + , prevents its dissociation and allows for adsorption of CO. Reaction kinetics are measured by employing a radio frequency ion trap, where Au 2 + and CO interact for a given reaction time. The effect of a hydrogen atom is evaluated by comparing reaction rate constants measured for Au 2 + and Au 2 H + . The theoretical results for the adsorption of CO molecules and their reaction characteristics with Au 2 + and Au 2 H + are found to agree with the experimental findings. The joint investigations provide insights into hydrogen atom adsorption effects and consequent reaction mechanisms.

  10. Antioxidant activity of omega-3 derivatives and their delivery via nanocages and nanocones: DFT and experimental in vivo investigation.

    Science.gov (United States)

    Najafi, Houshang; Changizi-Ashtiyani, Saeed; Najafi, Meysam

    2017-10-28

    The antioxidant properties of omega-3 were investigated via experimental in vivo and theoretical methods. For experimental evaluation, oxidative stress was induced by 30 min bilateral renal ischemia and 24 h of reperfusion in male Sprague Dawley rats. The oxidative stress was evaluated through measuring malondialdehyde (MDA) and ferric reducing/antioxidant power (FRAP) levels in renal tissue. In theoretical methods, the reaction enthalpies of antioxidant mechanisms of omega-3 were calculated and the effects of NHMe, OMe, OH, Cl, and Me substituents on its antioxidant activity were investigated. Moreover, the omega-3 delivery potential by carbon and boron nitride nanocages and naocones were evaluated. The experimental results showed that omega-3 administration decreases MDA and increases FRAP levels after their changes by ischemia/reperfusion. Theoretical results indicated that NHMe and OMe substituents can significantly improve the antioxidant activity of omega-3. Also, boron nitride nanocone (BNNC) has higher |∆E ad | values, so it has higher potential for omega-3 delivery. Taken together, the new findings presented here indicate that omega-3 has anti-oxidative properties and NHMe and OMe substituents can improve its antioxidant activity. Moreover, adsorption of omega-3 on the surface of the studied nanostructures was exothermic, and BNNC with higher |∆Ead| values has higher potential for omega-3 delivery. Graphical abstract The interaction and adsorption of BNNC with omega-3 is exothermic and experimentally possible from the energetic viewpoint, so the BNNC with higher |∆E ad | and |∆G ad | values has higher potential for omega-3 delivery.

  11. Structural and vibrational spectral investigations of melaminium glutarate monohydrate by FTIR, FT-Raman and DFT methods

    Science.gov (United States)

    Arjunan, V.; Marchewka, M. K.; Raj, Arushma; Yang, Haifeng; Mohan, S.

    2015-01-01

    Melaminium glutarate monohydrate has been synthesised and FTIR and FT-Raman spectral investigations are carried out. The molecular geometry and vibrational frequencies of melaminium glutarate monohydrate in the ground state have been determined by using B3LYP method with 6-31++G**, 6-31++G and cc-pVDZ basis sets. The stability of the system, inter molecular hydrogen bonding and the electron donor-acceptor interactions of the complex have been investigated by using natural bonding orbital analysis. It reveals that the Nsbnd H⋯O and Osbnd H⋯O intermolecular interactions significantly influence crystal packing of this molecular complex. The glutarate anion forms hydrogen bonds to the melaminium cation as the proton donor of the type Nsbnd H⋯O with a distance (N⋯O) = 2.51 Å. It is also linked by other hydrogen bonds to the water molecule of the type Osbnd H⋯O with (O⋯O) = 2.82 Å and to the amino (sbnd NH2) group of melaminium cation of the type Nsbnd H⋯O with (N⋯O) = 2.82 Å as the proton acceptor. The electrostatic potential of the complex is in the range +1.892e × 10-2 to -1.892e × 10-2. The limits of total electron density of the complex is +6.679e × 10-2 to -6.679e × 10-2.

  12. Structural and vibrational spectral investigations of melaminium glutarate monohydrate by FTIR, FT-Raman and DFT methods.

    Science.gov (United States)

    Arjunan, V; Marchewka, M K; Raj, Arushma; Yang, Haifeng; Mohan, S

    2015-01-25

    Melaminium glutarate monohydrate has been synthesised and FTIR and FT-Raman spectral investigations are carried out. The molecular geometry and vibrational frequencies of melaminium glutarate monohydrate in the ground state have been determined by using B3LYP method with 6-31++G(**), 6-31++G and cc-pVDZ basis sets. The stability of the system, inter molecular hydrogen bonding and the electron donor-acceptor interactions of the complex have been investigated by using natural bonding orbital analysis. It reveals that the N-H⋯O and O-H⋯O intermolecular interactions significantly influence crystal packing of this molecular complex. The glutarate anion forms hydrogen bonds to the melaminium cation as the proton donor of the type N-H⋯O with a distance (N⋯O)=2.51 Å. It is also linked by other hydrogen bonds to the water molecule of the type O-H⋯O with (O⋯O)=2.82 Å and to the amino (NH2) group of melaminium cation of the type N-H⋯O with (N⋯O)=2.82 Å as the proton acceptor. The electrostatic potential of the complex is in the range +1.892e×10(-2) to -1.892e×10(-2). The limits of total electron density of the complex is +6.679e×10(-2) to -6.679e×10(-2). Copyright © 2014 Elsevier B.V. All rights reserved.

  13. TD-DFT investigation of the magnetic circular dichroism spectra of some purine and pyrimidine bases of nucleic acids.

    Science.gov (United States)

    Fahleson, Tobias; Kauczor, Joanna; Norman, Patrick; Santoro, Fabrizio; Improta, Roberto; Coriani, Sonia

    2015-05-28

    We present a computational study of the magnetic circular dichroism (MCD) spectra in the 200-300 nm wavelength region of purine and its derivative hypoxanthine, as well as of the pyrimidine bases of nucleic acids uracil, thymine, and cytosine, using the B3LYP and CAM-B3LYP functionals. Solvent effects are investigated within the polarizable continuum model and by inclusion of explicit water molecules. In general, the computed spectra are found to be in good agreement with the experimental ones, apart from some overall blue shifts. Both the pseudo-A term shape of the MCD spectra of the purines and the B term shape of the spectra of pyrimidine bases are reproduced. Our calculations also correctly reproduce the reversed phase of the MCD bands in purine compared to that of its derivatives present in nucleic acids. Solvent effects are sizable and system specific, but they do not in general alter the qualitative shape of the spectra. The bands are dominated by the bright π → π* transitions, and our calculations in solution nicely reproduce their energy differences, improving the estimates obtained in the gas phase. Shoulders are predicted for purine and uracil due to n → π* excitations, but they are too weak to be observed in the experiment.

  14. “Not a Thing of the Past”, Zora Neale Hurston and the Living Legacy of Folklore « Not a Thing of the Past », Zora Neale Hurston et le legs vivant du folklore

    Directory of Open Access Journals (Sweden)

    Margaret Gillespie

    2009-11-01

    Full Text Available Auteur important bien qu’atypique de la Renaissance de Harlem et premier anthropologue afro-américain à avoir étudié sa propre culture, Zora Neale Hurston est, à de nombreux titres, un écrivain d’exception. Contrairement à d’autres, dont Robert Wright et Alain Locke, Hurston ne renie nullement le legs culturel que représente le folklore noir qu’elle apprécie selon ses propres critères, folklore qui influencera tant la forme que le fond de son art. Anthropologue de formation, Hurston appréhende néanmoins la culture noire américaine du sud non pas comme un vestige du passé qu’il conviendrait de conserver précieusement intact, mais comme une partie intégrante du vécu actuel. À travers les stratégies discursives orales vernaculaires qu’elle adopte et adapte de la tradition folklorique afro-américaine, Hurston, en pionnière, ouvre une voie et donne une voix aux écrivains Noirs à venir.

  15. DFT investigation of NH_3, PH_3, and AsH_3 adsorptions on Sc-, Ti-, V-, and Cr-doped single-walled carbon nanotubes

    International Nuclear Information System (INIS)

    Buasaeng, Prayut; Rakrai, Wandee; Wanno, Banchob; Tabtimsai, Chanukorn

    2017-01-01

    Highlights: • Transition metal-doped single wall carbon nanotubes and their adsorption with NH_3, PH_3 and AsH_3 molecules were investigated using a DFT method. • Adsorptions of NH_3, PH_3 and AsH_3 molecules on pristine single wall carbon nanotubeswere improved by transition metal doping. • Structural and electronic properties of single wall carbon nanotubes were significantly changed by transition metal doping and gas adsorptions. - Abstract: The adsorption properties of ammonia (NH_3), phosphine (PH_3), and arsine (AsH_3) on pristine and transition metal- (TM = Sc, Ti, V, and Cr) doped (5,5) armchair single-walled carbon nanotubes (SWCNTs) were theoretically investigated. The geometric and electronic properties and adsorption abilities for the most stable configuration of NH_3, PH_3, and AsH_3 adsorptions on pristine and TM-doped SWCNTs were calculated. It was found that the binding abilities of TMs to the SWCNT were in the order: Cr > V > Sc > Ti. However, the adsorption energy showed that the pristine SWCNT weakly adsorbed gas molecules and its electronic properties were also insensitive to gas molecules. By replacing a C atom with TM atoms, all doping can significantly enhance the adsorption energy of gas/SWCNT complexes and their adsorption ability was in the same order: NH_3 > PH_3 > AsH_3. A remarkable increase in adsorption energy and charge transfer of these systems was expected to induce significant changes in the electrical conductivity of the TM-doped SWCNTs. This work revealed that the sensitivity of SWCNT-based chemical gas adsorptions and sensors can be greatly improved by introducing an appropriate TM dopant. Accordingly, TM-doped SWCNTs are more suitable for gas molecule adsorptions and detections than the pristine SWCNT.

  16. Solid state structural investigations of the bis(chalcone) compound with single crystal X-ray crystallography, DFT, gamma-ray spectroscopy and chemical spectroscopy methods

    Science.gov (United States)

    Yakalı, Gül; Biçer, Abdullah; Eke, Canel; Cin, Günseli Turgut

    2018-04-01

    A bis(chalcone), (2E,6E)-2,6-bis((E)-3phenylallidene)cyclohexanone, was characterized by 1H NMR, 13C NMR, FTIR, UV-Vis spectroscopy, gamma-ray spectroscopy and single crystal X- ray structural analysis. The optimized molecular structure of the compound is calculated using DFT/B3LYP with 6-31G (d,p) level. The calculated geometrical parameters are in good agreement with the experimental data obtained from our reported X-ray structure. The powder and single crystal compounds were gama-irradiated using clinical electron linear accelerator and 60Co gamma-ray source, respectively. Spectral studies (1H NMR, 13C NMR, FTIR and UV-Vis) of powder chalcone compound were also investigated before and after irradiation. Depending on the irradiation notable changes were observed in spectral features powder sample. Single crystal X-ray diffraction investigation shows that both unirradiated and irradiated single crystal samples crystallizes in a orthorhombic crystal system in the centrosymmetric space group Pbcn and exhibits an C-H..O intramolecular and intermolecular hydrogen bonds. The crystal packing is stabilised by strong intermolecular bifurcate C-H..O hydrogen bonds and π…π stacking interactions. The asymmetric unit of the title compound contains one-half of a molecule. The other half of the molecule is generated with (1-x,y,-3/2-z) symmetry operator. The molecule is almost planar due to having π conjugated system of chalcones. However, irradiated single crystal compound showed significant changes lattice parameters, crystal volume and density. According to results of gamma-ray spectroscopy, radioactive elements of powder compound which are 123Sb(n,g),124Sb,57Fe(g,p),56Mn, 55Mn(g,n), and 54Mn were determined using photoactivation analysis. However, the most intensive gamma-ray energy signals are 124Sb.

  17. Major difference in visible-light photocatalytic features between perfect and self-defective Ta3N5 materials: A screened coulomb hybrid dft investigation

    KAUST Repository

    Harb, Moussab

    2014-09-11

    Relevant properties to visible-light overall water splitting reactions of perfect and self-defective bulk Ta3N5 semiconductor photocatalysts are investigated using accurate first-principles quantum calculations on the basis of density functional theory (DFT, including the perturbation theory DFPT) within the screened coulomb hybrid (HSE06) exchange-correlation formalism. Among the various explored self-defective structures, a strong stabilization is obtained for the configuration displaying a direct interaction between the created N- and Ta-vacancies. In the lowest-energy structure, each of the three created Ta-vacancies and the five created N-vacancies is found to be in aggregated disposition, leading to the formation of cages into the lattice. Although the calculated structural, electronic, and optical properties of the two materials are found to be very similar and in good agreement with available experimental works, their photocatalytic features for visible-light overall water splitting reactions show completely different behaviors. On the basis of calculated band edge positions relative to water redox potentials, the perfect Ta3N5 (calculated band gap of 2.2 eV) is predicted by HSE06 to be a good candidate only for H+ reduction while the self-defective Ta3N5 (calculated band gap of 2.0 eV) reveals suitable band positions for both water oxidation and H+ reduction similar to the experimental data reported on Ta3N5 powders. Its ability to reduce H+ is predicted to be lower than the perfect one. However, the strongly localized electronic characters of the valence band (VB) and conduction band (CB) edge states of the self-defective material only on the N 2p and Ta 5d orbitals surrounding the aggregated N- and Ta-vacancies are expected to strongly limit the probability of photogenerated carrier mobility through its crystal structure.

  18. The plane-wave DFT investigations into the structure and the 11B solid-state NMR parameters of lithium fluorooxoborates

    Czech Academy of Sciences Publication Activity Database

    Czernek, Jiří; Brus, Jiří

    2016-01-01

    Roč. 666, 1 December (2016), s. 22-27 ISSN 0009-2614 R&D Projects: GA MŠk(CZ) LO1507 Institutional support: RVO:61389013 Keywords : NMR * DFT * fluorooxoborates Subject RIV: CD - Macromolecular Chemistry Impact factor: 1.815, year: 2016

  19. γ‐ and δ-Lactams through Palladium-Catalyzed Intramolecular Allylic Alkylation: Enantioselective Synthesis, NMR Investigation, and DFT Rationalization

    DEFF Research Database (Denmark)

    Bantreil, Xavier; Prestat, Guillaume; Moreno, Aitor

    2011-01-01

    the cyclization reactions to take place in up to 94:6 enantiomeric ratio. A model Pd-allyl complex has been prepared and studied through NMR spectroscopic analysis, which provided insight into the processes responsible for the observed enantiomeric ratios. DFT studies were used to characterize the diastereomeric...

  20. Investigation of the adsorption of ozone molecules on TiO2/WSe2 nanocomposites by DFT computations: Applications to gas sensor devices

    Science.gov (United States)

    Abbasi, Amirali; Sardroodi, Jaber Jahanbin

    2018-04-01

    The adsorption of O3 molecule on the undoped and N-doped TiO2/WSe2 nanocomposites was studied using first principles density functional theory calculations. O3 interaction with TiO2/WSe2 nanocomposites is considered so as to investigate WSe2 effects on the adsorption process. WSe2 favors the adsorption of O3 on TiO2 particles. In other words, WSe2 is conducive to the interaction of O3 molecule with fivefold coordinated titanium sites of TiO2. The effects of vdW interactions were taken into account in order to obtain equilibrium geometries of O3 molecules at TiO2/WSe2 interfaces. For all adsorption configurations, the binding site was positioned on the fivefold coordinated titanium atoms. The results show that the interactions between O3 and TiO2 in TiO2/WSe2 nanocomposites are stronger than those between O3 and bare TiO2, suggesting that WSe2 helps to strengthen the interaction of ozone molecule with TiO2 particles. The results also indicate that the adsorption of the O3 molecule on the N-doped TiO2/WSe2 nanocomposite is more energetically favorable than the adsorption of O3 on the pristine one, representing that the N-doped nanocomposites are more sensitive than the undoped ones. Our DFT results clearly show that the N-doped TiO2/WSe2 nanocomposite would be a promising O3 gas sensor. The electronic structure of the adsorption system was also investigated, including analysis of the total and projected density of states, and charge density differences of the TiO2/WSe2 with adsorbed O3 molecules. The charge density difference calculations indicate that the charges were accumulated over the adsorbed O3 molecule. Besides, the N-doped nanocomposites have better sensing response than the pristine ones. This work was devoted to provide the theory basis for the design and development of novel and advanced O3 sensors based on modified TiO2/WSe2 nanocomposites.

  1. DFT investigation of Ni(II) adsorption onto MA-DTPA/PVDF chelating membrane in the presence of coexistent cations and organic acids.

    Science.gov (United States)

    Song, Laizhou; Zhao, Xiaodan; Fu, Jie; Wang, Xiuli; Sheng, Yiping; Liu, Xiaowei

    2012-01-15

    Melamine-diethylenetriaminepentaacetic acid/polyvinylidene fluoride (MA-DTPA/PVDF) chelating membrane bearing polyaminecarboxylate groups was used to remove Ni(II) from nickel plating effluents. Adsorption experiments were conducted to study the adsorption of the membrane towards Ni(II) in Ni(II)-Ca(II), Ni(II)-NH(4)(+), Ni(II)-Fe(III) binary systems, and Ni(II)-lactic acid, Ni(II)-succinic acid and Ni(II)-citric acid complex systems. For the ternary nickel plating processes, the effects of 3d transition metals including Fe(II), Co(II), Cu(II) and Zn(II) on Ni(II) adsorption were evaluated. The influences of the aforementioned coexistent cations and organic acids were elucidated by the continuum solvation model (COSMO)-corrected density functional theory (DFT) method. Geometries and complexation energies were analyzed for metal-MA-DTPA and Ni(II)-organic acid complexes. DFT results accord with the experimental data, indicating that DFT is helpful to evaluate the complexation between the membrane and metal cations. The coexistent Ca(II) tends to form more stable complex with MA-DTPA ligand than NH(4)(+) and Fe(III), and can interfere with the formation of Ni(II)-MA-DTPA complex. The complexing sequence of 3d metals with MA-DTPA ligand is Zn(II)

  2. DFT/TDDFT investigation on the electronic structures and photophysical properties of phosphorescent iridium(III) complexes with 2-(pyridin-2-yl)-benzo[d]imidazole ligand

    Energy Technology Data Exchange (ETDEWEB)

    Shang, Xiaohong, E-mail: shangxiaohong58@aliyun.com [College of Chemistry and Life Science, Changchun University of Technology, Changchun 130012 (China); Han, Deming [School of Life Science and Technology, Changchun University of Science and Technology, Changchun 130022 (China); Li, Dongfeng [College of Chemistry and Life Science, Changchun University of Technology, Changchun 130012 (China); Zhang, Gang [State Key Laboratory of Theoretical and Computational Chemistry, Institute of Theoretical Chemistry, Jilin University, Changchun 130023 (China)

    2014-03-15

    We have reported a theoretical analysis of a series of heteroleptic iridium(III) complexes (mpmi){sub 2}Ir(pybi) [mpmi=1-(4-tolyl)-3-methyl-imidazole, pybi=2-(pyridin-2-yl)-benzo[d]imidazole] (1a), (fpmi){sub 2}Ir(pybi) [fpmi=1-(4-fluoro-phenyl)-3-methyl-imidazole] (1b), (tfpmi){sub 2}Ir(pybi) [tfpmi=1-methyl-3-(4-trifluoromethyl-phenyl)-imidazole] (1c), (pypmi){sub 2}Ir(pybi) [pypmi=3-(3-methyl-imidazol)-pyrazole] (2a), (phpymi){sub 2}Ir(pybi) [phpymi=3-(3-methyl-imidazol)-5-phenyl-pyrazole] (2b), and (inpymi){sub 2}Ir(pybi) [inpymi=3-(3-methyl-imidazol)-indeno[1,2-c]pyrazole] (2c) by using the density functional theory (DFT) method to investigate their electronic structures and photophysical properties and obtain further insights into the phosphorescent efficiency mechanism. By changing cyclometalated ligands, the conjugation length, and substituents of the cyclometalated ligands, one can tune the emission color from green (λ{sub em}=520 nm) to orange (λ{sub em}=592 nm). Complexes 1a, 1b, 2a, and 2b have the almost identical emission wavelength about 550 nm, while 592 nm for 1c and 520 nm for 2c are red shifted and blue shifted, respectively, relative to 1a. The calculated results indicate that, for 1b and 1c, the substituents of −F and −CF{sub 3} at the phenyl moiety cause a poor hole-injection ability compared with that of 1a. For all these complexes studied, the hole-transporting performances are better than the electron-transporting ones. The difference between reorganization energies for hole transport (λ{sub ih}) and reorganization energies for electron transport (λ{sub ie}) for complex 1c are relatively smaller, indicating that the hole and electron transfer balance could be achieved more easily in the emitting layer. The alteration of cyclometalated ligands with different conjugation lengths and substituents has an impact on the optoelectronic properties of these complexes. It is believed that the larger metal to ligand charge transfer (MLCT

  3. DFT investigations on mechanical stability, electronic structure and magnetism in Co2TaZ (Z = Al, Ga, In) heusler alloys

    Science.gov (United States)

    Khandy, Shakeel Ahmad; Gupta, Dinesh C.

    2017-12-01

    Ferromagnetic Heusler compounds have vast and imminent applications for novel devices, smart materials thanks to density functional theory (DFT) based simulations, which have scored out a new approach to study these materials. We forecast the structural stability of Co2TaZ alloys on the basis of total energy calculations and mechanical stability criteria. The elastic constants, robust spin-polarized ferromagnetism and electron densities in these half-metallic alloys are also discussed. The observed structural aspects calculated to predict the stability and equilibrium lattice parameters agree well with the experimental results. The elastic parameters like elastic constants, bulk, Young’s and shear moduli, poison’s and Pugh ratios, melting temperatures, etc have been put together to establish their mechanical properties. The elaborated electronic band structures along with indirect band gaps and spin polarization favour the application of these materials in spintronics and memory device technology.

  4. An ab initio and TD DFT

    Indian Academy of Sciences (India)

    The photophysical behaviour of N-(2-hydroxy benzylidene) aniline or most commonly known as salicylideneaniline (SA) has been investigated using the ab initio and DFT levels of theory. The quantum chemical calculations show that the optimized non planar enol (1) form of the SA molecule is the most stable conformer ...

  5. Investigation of different physical aspects such as structural, mechanical, optical properties and Debye temperature of Fe2ScM (M=P and As) semiconductors: A DFT-based first principles study

    Science.gov (United States)

    Ali, Md. Lokman; Rahaman, Md. Zahidur

    2018-04-01

    By using first principles calculation dependent on the density functional theory (DFT), we have investigated the mechanical, structural properties and the Debye temperature of Fe2ScM (M=P and As) compounds under various pressures up to 60 GPa. The optical properties have been investigated under zero pressure. Our calculated optimized structural parameters of both the materials are in good agreement with other theoretical predictions. The calculated elastic constants show that Fe2ScM (M=P and As) compounds are mechanically stable under external pressure below 60 GPa. From the elastic constants, the shear modulus G, the bulk modulus B, Young’s modulus E, anisotropy factor A and Poisson’s ratio ν are calculated by using the Voigt-Reuss-Hill approximation. The Debye temperature and average sound velocities are also investigated from the obtained elastic constants. The detailed analysis of all optical functions reveals that both compounds are good dielectric material.

  6. VLSI Architectures for Computing DFT's

    Science.gov (United States)

    Truong, T. K.; Chang, J. J.; Hsu, I. S.; Reed, I. S.; Pei, D. Y.

    1986-01-01

    Simplifications result from use of residue Fermat number systems. System of finite arithmetic over residue Fermat number systems enables calculation of discrete Fourier transform (DFT) of series of complex numbers with reduced number of multiplications. Computer architectures based on approach suitable for design of very-large-scale integrated (VLSI) circuits for computing DFT's. General approach not limited to DFT's; Applicable to decoding of error-correcting codes and other transform calculations. System readily implemented in VLSI.

  7. Vibrational, structural and electronic properties investigation by DFT calculations and molecular docking studies with DNA topoisomerase II of strychnobrasiline type alkaloids: A theoretical approach for potentially bioactive molecules

    Science.gov (United States)

    Costa, Renyer A.; Oliveira, Kelson M. T.; Costa, Emmanoel Vilaça; Pinheiro, Maria L. B.

    2017-10-01

    A combined experimental and theoretical DFT study of the structural, vibrational and electronic properties of strychnobrasiline and 12-hydroxy-10,11-dimethoxystrychnobrasiline is presented using the Becke three-parameter Lee-Yang-Parr function (B3LYP) and 6-311G(2d,p) basis set. The theoretical geometry optimization data were compared with the X-ray data for a similar structure in the associated literature, showing close values. The calculated HOMO-LUMO gap values showed that the presence of substituents in the benzene ring influences the quantum properties which are directly related to the reactive properties. Theoretical UV spectra agreed well with the measured experimental data, with bands assigned. In addition, Natural Bond Orbitals (NBOs), Mapped molecular electrostatic potential surface (MEPS) and NLO calculations were also performed at the same theory level. The theoretical vibrational analysis revealed several characteristic vibrations that may be used as a diagnostic tool for other strychnobrasiline type alkaloids, simplifying their identification and structural characterization. Molecular docking calculations with DNA Topoisomerase II-DNA complex showed binding free energies values of -8.0 and -9.5 kcal/mol for strychnobrasiline and 12-hydroxy-10,11-dimethoxystrychnobrasiline respectively, while for amsacrine, used for the treatment of leukemia, the binding free energy ΔG presented a value of -10.0 kcal/mol, suggesting that strychnobrasiline derivative alkaloids might exhibit an antineoplastic activity.

  8. One Pot Selective Arylation of 2-Bromo-5-Chloro Thiophene; Molecular Structure Investigation via Density Functional Theory (DFT), X-ray Analysis, and Their Biological Activities.

    Science.gov (United States)

    Rasool, Nasir; Kanwal, Aqsa; Rasheed, Tehmina; Ain, Quratulain; Mahmood, Tariq; Ayub, Khurshid; Zubair, Muhammad; Khan, Khalid Mohammed; Arshad, Muhammad Nadeem; M Asiri, Abdullah; Zia-Ul-Haq, Muhammad; Jaafar, Hawa Z E

    2016-06-28

    Synthesis of 2,5-bisarylthiophenes was accomplished by sequential Suzuki cross coupling reaction of 2-bromo-5-chloro thiophenes. Density functional theory (DFT) studies were carried out at the B3LYP/6-31G(d, p) level of theory to compare the geometric parameters of 2,5-bisarylthiophenes with those from X-ray diffraction results. The synthesized compounds are screened for in vitro bacteria scavenging abilities. At the concentration of 50 and 100 μg/mL, compounds 2b, 2c, 2d, 3c, and 3f with IC50-values of 51.4, 52.10, 58.0, 56.2, and 56.5 μg/mL respectively, were found most potent against E. coli. Among all the synthesized compounds 2a, 2d, 3c, and 3e with the least values of IC50 77, 76.26, 79.13 μg/mL respectively showed significant antioxidant activities. Almost all of the compounds showed good antibacterial activity against Escherichia coli, whereas 2-chloro-5-(4-methoxyphenyl) thiophene (2b) was found most active among all synthesized compound with an IC50 value of 51.4 μg/mL. All of the synthesized compounds were screened for nitric oxide scavenging activity as well. Frontier molecular orbitals (FMOs) and molecular electrostatic potentials of the target compounds were also studied theoretically to account for their relative reactivity.

  9. A study of vibrational spectra and investigations of charge transfer and chemical bonding features of 2-chloro benzimidazole based on DFT computations

    Science.gov (United States)

    Muthunatesan, S.; Ragavendran, V.

    2015-01-01

    Benzimidazoles are bicyclic heteroatomic molecules. Polycyclic heteroatomic molecules have extensive coupling of different modes leading to strong coupling of force constants associated with the various chemical bonds of the molecules. To carry out a detailed vibrational spectroscopic analysis of such a bicyclic heteroatomic molecule, FT-IR and FT-Raman spectra of 2-chloro benzimidazole (CBZ) have been recorded in the condensed phase. Density Functional Theory calculations in the B3LYP/6-31G* level have been carried out to determine the optimized geometry and vibrational frequencies. In order to obtain a close agreement between theoretical and observed frequencies and hence to perform a reliable assignment, the theoretical DFT force field was transformed from Cartesian to local symmetry co-ordinates and then scaled empirically using SQM methodology. The SQM treatment resulted in a RMS deviation of 9.4 cm-1. For visual comparison, the observed and calculated spectra are presented on a common wavenumber scale. From the NBO analysis, the electron density (ED) charge transfers in the σ* and π* antibonding orbitals and second order delocalization energies E(2) confirms the occurrence of intramolecular charge transfer (ICT) within the molecule. The calculated Homo and Lumo energies show that charge transfer occurs within the molecule. The results obtained from the vibrational, NBO and HOMO-LUMO analyses have been properly tabulated.

  10. Electronic structure investigations of 4-aminophthal hydrazide by UV-visible, NMR spectral studies and HOMO-LUMO analysis by ab initio and DFT calculations.

    Science.gov (United States)

    Sambathkumar, K; Jeyavijayan, S; Arivazhagan, M

    2015-08-05

    Combined experimental and theoretical studies were conducted on the molecular structure and vibrational spectra of 4-AminoPhthalhydrazide (APH). The FT-IR and FT-Raman spectra of APH were recorded in the solid phase. The molecular geometry and vibrational frequencies of APH in the ground state have been calculated by using the ab initio HF (Hartree-Fock) and density functional methods (B3LYP) invoking 6-311+G(d,p) basis set. The optimized geometric bond lengths and bond angles obtained by HF and B3LYP method show best agreement with the experimental values. Comparison of the observed fundamental vibrational frequencies of APH with calculated results by HF and density functional methods indicates that B3LYP is superior to the scaled Hartree-Fock approach for molecular vibrational problems. The difference between the observed and scaled wave number values of most of the fundamentals is very small. A detailed interpretation of the NMR spectra of APH was also reported. The theoretical spectrograms for infrared and Raman spectra of the title molecule have been constructed. UV-vis spectrum of the compound was recorded and the electronic properties, such as HOMO and LUMO energies, were performed by time dependent density functional theory (TD-DFT) approach. Finally the calculations results were applied to simulated infrared and Raman spectra of the title compound which show good agreement with observed spectra. And the temperature dependence of the thermodynamic properties of constant pressure (Cp), entropy (S) and enthalpy change (ΔH0→T) for APH were also determined. Copyright © 2015 Elsevier B.V. All rights reserved.

  11. DFT investigation of electronic structures and magnetic properties of halides family MeHal3 (Me=Ti, Mo,Zr,Nb, Ru, Hal=Cl,Br,I) one dimensional structures

    Science.gov (United States)

    Kuzubov, A. A.; Kovaleva, E. A.; Popova, M. I.; Kholtobina, A. S.; Mikhaleva, N. S.; Visotin, M. A.; Fedorov, A. S.

    2017-10-01

    Using DFT GGA calculations, electronic structure and magnetic properties of wide family of transition metal trihalides (TMHal3) (Zr, Ti and Nb iodides, Mo, Ru, Ti and Zr bromides and Ti or Zr chlorides) are investigated. These structures consist of transition metal atoms chains surrounded by halides atoms. Chains are connected to each other by weak interactions. All TMHal3 compounds were found to be conductive along chain axis except of MoBr3 which is indirect gap semiconductor. It was shown that NbI3 and MoBr3 have large magnetic moments on metal atoms (1.17 and 1.81 μB, respectively) but other TMHal3 materials have small or zero magnetic moments. For all structures ferromagnetic and anti-ferromagnetic phases have almost the same energies. The causes of these properties are debated.

  12. Generalized gravity from modified DFT

    International Nuclear Information System (INIS)

    Sakatani, Yuho; Uehara, Shozo; Yoshida, Kentaroh

    2017-01-01

    Recently, generalized equations of type IIB supergravity have been derived from the requirement of classical kappa-symmetry of type IIB superstring theory in the Green-Schwarz formulation. These equations are covariant under generalized T-duality transformations and hence one may expect a formulation similar to double field theory (DFT). In this paper, we consider a modification of the DFT equations of motion by relaxing a condition for the generalized covariant derivative with an extra generalized vector. In this modified double field theory (mDFT), we show that the flatness condition of the modified generalized Ricci tensor leads to the NS-NS part of the generalized equations of type IIB supergravity. In particular, the extra vector fields appearing in the generalized equations correspond to the extra generalized vector in mDFT. We also discuss duality symmetries and a modification of the string charge in mDFT.

  13. Generalized gravity from modified DFT

    Energy Technology Data Exchange (ETDEWEB)

    Sakatani, Yuho [Department of Physics, Kyoto Prefectural University of Medicine,Kyoto 606-0823 (Japan); Fields, Gravity and Strings, CTPU,Institute for Basic Sciences, Daejeon 34047 (Korea, Republic of); Uehara, Shozo [Department of Physics, Kyoto Prefectural University of Medicine,Kyoto 606-0823 (Japan); Yoshida, Kentaroh [Department of Physics, Kyoto University,Kitashirakawa Oiwake-cho, Kyoto 606-8502 (Japan)

    2017-04-20

    Recently, generalized equations of type IIB supergravity have been derived from the requirement of classical kappa-symmetry of type IIB superstring theory in the Green-Schwarz formulation. These equations are covariant under generalized T-duality transformations and hence one may expect a formulation similar to double field theory (DFT). In this paper, we consider a modification of the DFT equations of motion by relaxing a condition for the generalized covariant derivative with an extra generalized vector. In this modified double field theory (mDFT), we show that the flatness condition of the modified generalized Ricci tensor leads to the NS-NS part of the generalized equations of type IIB supergravity. In particular, the extra vector fields appearing in the generalized equations correspond to the extra generalized vector in mDFT. We also discuss duality symmetries and a modification of the string charge in mDFT.

  14. Screened coulomb hybrid DFT investigation of band gap and optical absorption predictions of CuVO3, CuNbO3 and Cu 5Ta11O30 materials

    KAUST Repository

    Harb, Moussab; Masih, Dilshad; Takanabe, Kazuhiro

    2014-01-01

    with high accuracy using advanced first-principles quantum methods based on DFT (including the perturbation theory approach DFPT) within the screened coulomb hybrid HSE06 exchange-correlation formalism. The calculated density of states are found

  15. Synthesis, spectroscopic investigations, DFT studies, molecular docking and antimicrobial potential of certain new indole-isatin molecular hybrids: Experimental and theoretical approaches

    Science.gov (United States)

    Almutairi, Maha S.; Zakaria, Azza S.; Ignasius, P. Primsa; Al-Wabli, Reem I.; Joe, Isaac Hubert; Attia, Mohamed I.

    2018-02-01

    Indole-isatin molecular hybrids 5a-i have been synthesized and characterized by different spectroscopic methods to be evaluated as new antimicrobial agents against a panel of Gram positive bacteria, Gram negative bacteria, and moulds. Compound 5h was selected as a representative example of the prepared compounds 5a-i to perform computational investigations. Its vibrational properties have been studied using FT-IR and FT-Raman with the aid of density functional theory approach. The natural bond orbital analysis as well as HOMO and LUMO molecular orbitals investigations of compound 5h were carried out to explore its possible intermolecular delocalization or hyperconjugation and its possible interactions with the target protein. Molecular docking of compound 5h predicted its binding mode with the fungal target protein.

  16. Mechanism of phosphorus passivation of near-interface oxide traps in 4H–SiC MOS devices investigated by CCDLTS and DFT calculation

    Science.gov (United States)

    Jayawardena, Asanka; Shen, X.; Mooney, P. M.; Dhar, Sarit

    2018-06-01

    Interfacial charge trapping in 4H–SiC MOS capacitors with P doped SiO2 or phospho-silicate glass (PSG) as a gate dielectric has been investigated with temperature dependent capacitance–voltage measurements and constant capacitance deep level transient spectroscopy (CCDLTS) measurements. The measurements indicate that P doping in the dielectric results in significant reduction of near-interface electron traps that have energy levels within 0.5 eV of the 4H–SiC conduction band edge. Extracted trap densities confirm that the phosphorus induced near-interface trap reduction is significantly more effective than interfacial nitridation, which is typically used for 4H–SiC MOSFET processing. The CCDLTS measurements reveal that the two broad near-interface trap peaks, named ‘O1’ and ‘O2’, with activation energies around 0.15 eV and 0.4 eV below the 4H–SiC conduction band that are typically observed in thermal oxides on 4H–SiC, are also present in PSG devices. Previous atomic scale ab initio calculations suggested these O1 and O2 traps to be carbon dimers substituted for oxygen dimers (CO=CO) and interstitial Si (Sii) in SiO2, respectively. Theoretical considerations in this work suggest that the presence of P in the near-interfacial region reduces the stability of the CO=CO defects and reduces the density of Sii defects through the network restructuring. Qualitative comparison of results in this work and reported work suggest that the O1 and O2 traps in SiO2/4H–SiC MOS system negatively impact channel mobility in 4H–SiC MOSFETs.

  17. DFT investigation on two-dimensional GeS/WS2 van der Waals heterostructure for direct Z-scheme photocatalytic overall water splitting

    Science.gov (United States)

    Ju, Lin; Dai, Ying; Wei, Wei; Li, Mengmeng; Huang, Baibiao

    2018-03-01

    Recently, extensive attention has been paid to the direct Z-scheme systems for photocatalytic water splitting where carriers migrate directly between the two semiconductors without a redox mediator. In the present work, the electronic structure and related properties of two-dimensional (2D) van de Waals (vdW) GeS/WX2 (X = O, S, Se, Te) heterojunction are systematically investigated by first-principles calculations. Our results demonstrate that, the GeS/WS2 heterojunction could form a direct Z-scheme system for photocatalytic water splitting, whereas the GeS/WX2 (X = O, Se, Te) can't, because of their respective unsuitable electronic structures. For the GeS/WS2 heterojunction, the GeS and WS2 monolayers serve as photocatalysts for the hydrogen evolution reactionand oxygen evolution reaction, respectively. The internal electric field induced by the electron transfer at the interface can promote the separation of photo-generated charge carriers and formation of the interface Z-scheme electron transfer. Remarkably, the designed GeS/WS2 heterojunction not only enhances the hydrogen production activity of GeS and the oxygen production ability of WS2 but also improves the light absorption of the two monolayers by reducing the band gaps. Moreover, it is found that narrowing the interlayer distance could enhance the internal electric field, improving the photocatalytic ability of the vdW heterojunction. This work provides fundamental insights for further design and preparation of emergent metal dichalcogenide catalysts, beneficial for the development in clean energy.

  18. DFT investigation on the selective complexation of Fe3+ and Al3+ with hydroxypyridinones used for treatment of the aluminium and iron overload diseases.

    Science.gov (United States)

    Kaviani, Sadegh; Izadyar, Mohammad; Housaindokht, Mohammad Reza

    2018-03-01

    The chelating agents for Al 3+ and Fe 3+ metal cations with therapeutic applications have been considered in the recent years. In designing of the hydroxypyridinones (HPOs) as the therapeutic chelating agents for iron and aluminium overload pathologies, quantum mechanical (QM) calculations are necessary for predicting the binding energies and thermodynamic parameters of the metal-HPO complexes. Three derivatives of the HPOs called 3-hydroxy-1,2-dimethylpyridin-4(1H)-one (DFP), 3-hydroxy-4(1H)-pyridinone (HOPO) and 5-hydroxy-2-(hydroxymethyl)pyridin-4(1H)-one (P1) were investigated for complexation with Fe 3+ and Al 3+ metal ions. Because of the maximum interaction between Fe 3+ and HPOs, all HPOs form stable complexes with Fe 3+ metal ion. Moreover, it was found that [Fe-P1] 2+ is a more stable complex than [Fe-DFP] 2+ and [Fe-3,4-HOPO] 2+ in the gas phase and water, confirming that P1 is the strongest selective iron chelator. The more stability of [Fe-P1] 2+ was attributed to an intramolecular hydrogen bond formation between the hydrogen atom of NH group and the oxygen atom of CH 2 OH chain. All complexes of the HPOs with Fe 3+ and Al 3+ were formed through the oxygen atoms of the CO and OH groups of the HPO. Natural bond orbital analysis showed that the interaction of the lone pair electrons of the oxygen atom of the chelator and antibonding orbitals of the Al 3+ and Fe 3+ are important in the complex formation. Topological parameters at the bond critical points confirmed the effective interaction between the Al 3+ and Fe 3+ metal ions and HPO as well as the nature of the metal-oxygen bonds. Copyright © 2018 Elsevier Inc. All rights reserved.

  19. DFT investigation of NH{sub 3}, PH{sub 3}, and AsH{sub 3} adsorptions on Sc-, Ti-, V-, and Cr-doped single-walled carbon nanotubes

    Energy Technology Data Exchange (ETDEWEB)

    Buasaeng, Prayut; Rakrai, Wandee [Computational Chemistry Center for Nanotechnology and Department of Chemistry, Faculty of Science and Technology, Rajabhat Maha Sarakham University, Maha Sarakham, 44000 (Thailand); Wanno, Banchob [Center of Excellence for Innovation in Chemistry and Supramolecular Chemistry Research Unit, Department of Chemistry, Faculty of Science, Mahasarakham University, Maha Sarakham, 44150 (Thailand); Tabtimsai, Chanukorn, E-mail: tabtimsai.c@gmail.com [Computational Chemistry Center for Nanotechnology and Department of Chemistry, Faculty of Science and Technology, Rajabhat Maha Sarakham University, Maha Sarakham, 44000 (Thailand)

    2017-04-01

    Highlights: • Transition metal-doped single wall carbon nanotubes and their adsorption with NH{sub 3}, PH{sub 3} and AsH{sub 3} molecules were investigated using a DFT method. • Adsorptions of NH{sub 3}, PH{sub 3} and AsH{sub 3} molecules on pristine single wall carbon nanotubeswere improved by transition metal doping. • Structural and electronic properties of single wall carbon nanotubes were significantly changed by transition metal doping and gas adsorptions. - Abstract: The adsorption properties of ammonia (NH{sub 3}), phosphine (PH{sub 3}), and arsine (AsH{sub 3}) on pristine and transition metal- (TM = Sc, Ti, V, and Cr) doped (5,5) armchair single-walled carbon nanotubes (SWCNTs) were theoretically investigated. The geometric and electronic properties and adsorption abilities for the most stable configuration of NH{sub 3}, PH{sub 3}, and AsH{sub 3} adsorptions on pristine and TM-doped SWCNTs were calculated. It was found that the binding abilities of TMs to the SWCNT were in the order: Cr > V > Sc > Ti. However, the adsorption energy showed that the pristine SWCNT weakly adsorbed gas molecules and its electronic properties were also insensitive to gas molecules. By replacing a C atom with TM atoms, all doping can significantly enhance the adsorption energy of gas/SWCNT complexes and their adsorption ability was in the same order: NH{sub 3} > PH{sub 3} > AsH{sub 3}. A remarkable increase in adsorption energy and charge transfer of these systems was expected to induce significant changes in the electrical conductivity of the TM-doped SWCNTs. This work revealed that the sensitivity of SWCNT-based chemical gas adsorptions and sensors can be greatly improved by introducing an appropriate TM dopant. Accordingly, TM-doped SWCNTs are more suitable for gas molecule adsorptions and detections than the pristine SWCNT.

  20. Screened coulomb hybrid DFT investigation of band gap and optical absorption predictions of CuVO3, CuNbO3 and Cu 5Ta11O30 materials

    KAUST Repository

    Harb, Moussab

    2014-01-01

    We present a joint theoretical and experimental investigation of the optoelectronic properties of CuVO3, CuNbO3 and Cu 5Ta11O30 materials for potential photocatalytic and solar cell applications. In addition to the experimental results obtained by powder X-ray diffraction and UV-Vis spectroscopy of the materials synthesized under flowing N2 gas at atmospheric pressure via solid-state reactions, the electronic structure and the UV-Vis optical absorption coefficient of these compounds are predicted with high accuracy using advanced first-principles quantum methods based on DFT (including the perturbation theory approach DFPT) within the screened coulomb hybrid HSE06 exchange-correlation formalism. The calculated density of states are found to be in agreement with the UV-Vis diffuse reflectance spectra, predicting a small indirect band gap of 1.4 eV for CuVO3, a direct band gap of 2.6 eV for CuNbO3, and an indirect (direct) band gap of 2.1 (2.6) eV for Cu5Ta 11O30. It is confirmed that the Cu(i)-based multi-metal oxides possess a strong contribution of filled Cu(i) states in the valence band and of empty d0 metal states in the conduction band. Interestingly, CuVO3 with its predicted small indirect band gap of 1.4 eV shows the highest absorption coefficient in the visible range with a broad absorption edge extending to 886 nm. This novel result offers a great opportunity for this material to be an excellent candidate for solar cell applications. © the Partner Organisations 2014.

  1. Combined spectroscopic, DFT, TD-DFT and MD study of newly synthesized thiourea derivative

    Science.gov (United States)

    Menon, Vidya V.; Sheena Mary, Y.; Shyma Mary, Y.; Panicker, C. Yohannan; Bielenica, Anna; Armaković, Stevan; Armaković, Sanja J.; Van Alsenoy, Christian

    2018-03-01

    A novel thiourea derivative, 1-(3-bromophenyl)-3-[3-(trifluoromethyl)phenyl]thiourea (ANF-22) is synthesized and characterized by FTIR, FT-Raman and NMR spectroscopy experimentally and theoretically. A detailed conformational analysis of the title molecule has been conducted in order to locate the lowest energy geometry, which was further subjected to the detailed investigation of spectroscopic, reactive, degradation and docking studies by density functional theory (DFT) calculations and molecular dynamics (MD) simulations. Time dependent DFT (TD-DFT) calculations have been used also in order to simulate UV spectra and investigate charge transfer within molecule. Natural bond orbital analysis has been performed analyzing the charge delocalization and using HOMO and LUMO energies the electronic properties are analyzed. Molecular electrostatic potential map is used for the quantitative measurement of active sites in the molecule. In order to determine the locations possibly prone to electrophilic attacks we have calculated average local ionization energies and mapped them to the electron density surface. Further insight into the local reactivity properties have been obtained by calculation of Fukui functions, also mapped to the electron density surface. Possible degradation properties by the autoxidation mechanism have been assessed by calculations of bond dissociation energies for hydrogen abstraction. Atoms of title molecule with significant interactions with water molecules have been determined by calculations of radial distribution functions. The title compound can be a lead compound for developing new analgesic drug.

  2. Growth, spectral, optical, laser damage threshold and DFT investigations on 2-amino 4-methyl pyridinium 4-methoxy benzoate (2A4MP4MB): A potential organic third order nonlinear optical material for optoelectronic applications

    Science.gov (United States)

    Krishnakumar, M.; Karthick, S.; Thirupugalmani, K.; Babu, B.; Vinitha, G.

    2018-05-01

    In present investigation, single crystals of organic charge transfer complex, 2-amino-4-methyl pyridinium-4-methoxy benzoate (2A4MP4MB) was grown by controlled slow evaporation solution growth technique using methanol as a solvent at room temperature. Single crystal XRD analysis confirmed the crystal system and lattice parameters of 2A4MP4MB. The crystalline nature, presence of various vibrational modes and other chemical bonds in the compound have been recognized and confirmed by powder X-ray diffraction, FT-IR and FT-Raman spectroscopic techniques respectively. The presence of various proton and carbon positions in title compound was confirmed using 1H NMR and 13C NMR spectral studies. The wide optical operating window and cut-off wavelength were identified and band gap value of the title compound was calculated using UV-vis-NIR study. The specific heat capacity (cp) values of the title compound, 1.712 J g-1·K-1 at 300 K and 13.6 J g-1 K-1 at 433 K (melting point) were measured using Modulated Differential Scanning Calorimetric studies (MDSC). From Z-scan study, nonlinear refractive index (n2), nonlinear absorption (β) and third order nonlinear susceptibility (χ(3)) values were determined. The self-defocusing effect and saturable absorption behavior of the material were utilized to exhibit the optical limiting action at λ = 532 nm by employing the same continuous wave (cw) Nd: YAG laser source. The laser damage threshold (LDT) study of title compound was carried out using Nd: YAG laser of 532 nm wavelength. The Vickers' micro hardness test was carried out at room temperature and obtained results were investigated using classical Meyer's law. In addition, DFT calculations were carried out for the first time for this compound. These characterization studies performed on the title compound planned to probe the valuable and safe region of optical, thermal and mechanical properties to improve efficacy of 2A4MP4MB single crystals in optoelectronic device

  3. Predictions of Physicochemical Properties of Ionic Liquids with DFT

    Directory of Open Access Journals (Sweden)

    Karl Karu

    2016-07-01

    Full Text Available Nowadays, density functional theory (DFT-based high-throughput computational approach is becoming more efficient and, thus, attractive for finding advanced materials for electrochemical applications. In this work, we illustrate how theoretical models, computational methods, and informatics techniques can be put together to form a simple DFT-based throughput computational workflow for predicting physicochemical properties of room-temperature ionic liquids. The developed workflow has been used for screening a set of 48 ionic pairs and for analyzing the gathered data. The predicted relative electrochemical stabilities, ionic charges and dynamic properties of the investigated ionic liquids are discussed in the light of their potential practical applications.

  4. Spectral investigations and DFT studies of 3,7-dihydro-1,3,7-trimethyl-1H-purine-2,6-dione (caffeine) interaction and recognition by single amino acid derived self-assembled nanostructures

    Science.gov (United States)

    Govindhan, R.; Karthikeyan, B.

    2018-03-01

    Recognition of xanthine alkaloid caffeine with 3,5-bis(trifluoromethyl)benzylamine derived peptide nanotubes (BTTPNTs) through chemical interaction have been achieved through the host-guest like interaction. DFT simulation is carried out for caffeine interacted with BTTPNTs system and also experimentally characterized by ultraviolet-visible (UV-vis) absorbance, confocal Raman spectra (CRS) with microscopic imaging (CRM), FT-Raman, surface enhanced Raman scattering (SERS), UV-diffuse reflectance spectra (UV-DRS), high resolution transmission electron microscopy (HR-TEM) and cyclic voltammetry (CV) studies. The results are used to examine the morphologies, size of the nanostructure and study of its interaction with the caffeine molecule. The results show that BTTPNTs is having potential for sensing the caffeine molecules through the binding occurred from the NH2 of tyrosine moiety of the BTTPNTs. This intermolecular association through face-to-face stacking of BTTPNTs is explained by detailed DFT calculations.

  5. A DFT Structural Investigation of New Bimetallic PtSnx Surface Alloys Formed on the Pt(110) Surface and Their Interaction with Carbon Monoxide

    DEFF Research Database (Denmark)

    Zheng, Jian; Busch, Michael; Artiglia, Luca

    2016-01-01

    desorbs from the PtSnx surfaces at about 415-425 K compared to 495 K on the clean Pt(110). The energetics and geometry of the CO chemisorption sites have been studied by DFT calculations, obtaining an adsorption energy of 0.7-0.86 eV on p(3 x 1) and 0.9-1.05 eV on p(6 x 1). Overall our theoretical...... spectroscopy. Based on the experimental results and density functional theory (DFT) calculations, we propose atomic models for these surface alloys, which both consist of a highly corrugated row structure with a very similar surface motif. CO temperature-programmed desorption (TPD) experiments indicate that CO...

  6. Synthesis, electronic structure investigation of 3-pentyl-2,6-di(furan-2-yl)piperidin-4-one by FT-IR, FT-Raman and UV-Visible spectral studies and ab initio/DFT calculations.

    Science.gov (United States)

    Arockia Doss, M; Savithiri, S; Rajarajan, G; Thanikachalam, V; Anbuselvan, C

    2015-12-05

    FT-IR and FT-Raman spectra of 3-pentyl-2,6-di(furan-2-yl) piperidin-4-one (3-PFPO) were recorded in the solid phase. The structural and spectroscopic analyses of 3-PFPO were made by using B3LYP/HF level with 6-311++G(d, p) basis set. The fundamental vibrations are assigned on the basis of the total energy distribution (TED) of the vibrational modes, calculated with scaled quantum mechanics (SQM) method and PQS program. Comparison of the observed fundamental vibrational frequencies of 3-PFPO with calculated results by HF and DFT methods indicates that B3LYP is superior to HF method for molecular vibrational problems. The electronic properties such as excitation energies, oscillator strength, wavelengths and HOMO-LUMO energies were obtained by time-dependent DFT (TD-DFT) approach. The polarizability and first order hyperpolarizability of the title molecule were calculated and interpreted. The hyperconjugative interaction energy (E((2))) and electron densities of donor (i) and acceptor (j) bonds were calculated using NBO analysis. In addition, MEP and atomic charges of carbon, nitrogen, oxygen and hydrogen were calculated using B3LYP/6-311++G(d, p) level theory. Moreover, thermodynamic properties (heat capacities, entropy and enthalpy) of the title compound at different temperatures were calculated in gas phase. Copyright © 2015 Elsevier B.V. All rights reserved.

  7. Ab initio and DFT studies of the structure and vibrational spectra of anhydrous caffeine

    Science.gov (United States)

    Srivastava, Santosh K.; Singh, Vipin B.

    2013-11-01

    Vibrational spectra and molecular structure of anhydrous caffeine have been systematically investigated by second order Moller-Plesset (MP2) perturbation theory and density functional theory (DFT) calculations. Vibrational assignments have been made and many previous ambiguous assignments in IR and Raman spectra are amended. The calculated DFT frequencies and intensities at B3LYP/6-311++G(2d,2p) level, were found to be in better agreement with the experimental values. It was found that DFT with B3LYP functional predicts harmonic vibrational wave numbers more close to experimentally observed value when it was performed on MP2 optimized geometry rather than DFT geometry. The calculated TD-DFT vertical excitation electronic energies of the valence excited states of anhydrous caffeine are found to be in consonance to the experimental absorption peaks.

  8. Quantum mechanical and spectroscopic (FT-IR, 13C, 1H NMR and UV) investigations of 2-(5-(4-Chlorophenyl)-3-(pyridin-2-yl)-4,5-dihydropyrazol-1-yl)benzo[d]thiazole by DFT method

    Science.gov (United States)

    Diwaker

    2014-07-01

    The electronic, NMR, vibrational, structural properties of a new pyrazoline derivative: 2-(5-(4-Chlorophenyl)-3-(pyridine-2-yl)-4,5-dihydropyrazol-1-yl)benzo[d]thiazole has been studied using Gaussian 09 software package. Using VEDA 4 program we have reported the PED potential energy distribution of normal mode of vibrations of the title compound. We have also reported the 1H and 13C NMR chemical shifts of the title compound using B3LYP level of theory with 6-311++G(2d,2p) basis set. Using time dependent (TD-DFT) approach electronic properties such as HOMO and LUMO energies, electronic spectrum of the title compound has been studied and reported. NBO analysis and MEP surface mapping has also been calculated and reported using ab initio methods.

  9. Electronic and Optical Properties of CuO Based on DFT+U and GW Approximation

    International Nuclear Information System (INIS)

    Ahmad, F; Agusta, M K; Dipojono, H K

    2016-01-01

    We report ab initio calculations of electronic structure and optical properties of monoclinic CuO based on DFT+U and GW approximation. CuO is an antiferromagnetic material with strong electron correlations. Our calculation shows that DFT+U and GW approximation sufficiently reliable to investigate the material properties of CuO. The calculated band gap of DFT+U for reasonable value of U slightly underestimates. The use of GW approximation requires adjustment of U value to get realistic result. Hybridization Cu 3dxz, 3dyz with O 2p plays an important role in the formation of band gap. The calculated optical properties based on DFT+U and GW corrections by solving Bethe-Salpeter are in good agreement with the calculated electronic properties and the experimental result. (paper)

  10. Redesign of the DFT/MRCI Hamiltonian

    Energy Technology Data Exchange (ETDEWEB)

    Lyskov, Igor; Kleinschmidt, Martin; Marian, Christel M., E-mail: Christel.Marian@hhu.de [Institute of Theoretical and Computational Chemistry, Heinrich-Heine-University Düsseldorf, Universitätsstraße 1, 40225 Düsseldorf (Germany)

    2016-01-21

    The combined density functional theory and multireference configuration interaction (DFT/MRCI) method of Grimme and Waletzke [J. Chem. Phys. 111, 5645 (1999)] is a well-established semi-empirical quantum chemical method for efficiently computing excited-state properties of organic molecules. As it turns out, the method fails to treat bi-chromophores owing to the strong dependence of the parameters on the excitation class. In this work, we present an alternative form of correcting the matrix elements of a MRCI Hamiltonian which is built from a Kohn-Sham set of orbitals. It is based on the idea of constructing individual energy shifts for each of the state functions of a configuration. The new parameterization is spin-invariant and incorporates less empirism compared to the original formulation. By utilizing damping techniques together with an algorithm of selecting important configurations for treating static electron correlation, the high computational efficiency has been preserved. The robustness of the original and redesigned Hamiltonians has been tested on experimentally known vertical excitation energies of organic molecules yielding similar statistics for the two parameterizations. Besides that, our new formulation is free from artificially low-lying doubly excited states, producing qualitatively correct and consistent results for excimers. The way of modifying matrix elements of the MRCI Hamiltonian presented here shall be considered as default choice when investigating photophysical processes of bi-chromophoric systems such as singlet fission or triplet-triplet upconversion.

  11. DFT-Assisted Polymorph Identification from Lattice Raman Fingerprinting.

    Science.gov (United States)

    Bedoya-Martínez, Natalia; Schrode, Benedikt; Jones, Andrew O F; Salzillo, Tommaso; Ruzié, Christian; Demitri, Nicola; Geerts, Yves H; Venuti, Elisabetta; Della Valle, Raffaele Guido; Zojer, Egbert; Resel, Roland

    2017-08-03

    A combined experimental and theoretical approach, consisting of lattice phonon Raman spectroscopy and density functional theory (DFT) calculations, is proposed as a tool for lattice dynamics characterization and polymorph phase identification. To illustrate the reliability of the method, the lattice phonon Raman spectra of two polymorphs of the molecule 2,7-dioctyloxy[1]benzothieno[3,2-b]benzothiophene are investigated. We show that DFT calculations of the lattice vibrations based on the known crystal structures, including many-body dispersion van der Waals (MBD-vdW) corrections, predict experimental data within an accuracy of ≪5 cm -1 (≪0.6 meV). Due to the high accuracy of the simulations, they can be used to unambiguously identify different polymorphs and to characterize the nature of the lattice vibrations and their relationship to the structural properties. More generally, this work implies that DFT-MBD-vdW is a promising method to describe also other physical properties that depend on lattice dynamics like charge transport.

  12. DFT and TD-DFT calculations of metallotetraphenylporphyrin and metallotetraphenylporphyrin fullerene complexes as potential dye sensitizers for solar cells

    Science.gov (United States)

    El Mahdy, A. M.; Halim, Shimaa Abdel; Taha, H. O.

    2018-05-01

    Density functional theory (DFT) and time-dependent DFT calculations have been employed to model metallotetraphenylporphyrin dyes and metallotetraphenylporphyrin -fullerene complexes in order to investigate the geometries, electronic structures, the density of states, non-linear optical properties (NLO), IR-vis spectra, molecular electrostatic potential contours, and electrophilicity. To calculate the excited states of the tetraphenyl porphyrin analogs, time-dependent density functional theory (TD-DFT) are used. Their UV-vis spectra were also obtained and a comparison with available experimental and theoretical results is included. The results reveal that the metal and the tertiary butyl groups of the dyes are electron donors, and the tetraphenylporphyrin rings are electron acceptors. The HOMOs of the dyes fall within the (TiO2)60 and Ti38O76 band gaps and support the issue of typical interfacial electron transfer reaction. The resulting potential drop of Mn-TPP-C60 increased by ca. 3.50% under the effect of the tertiary butyl groups. The increase in the potential drop indicates that the tertiary butyl complexes could be a better choice for the strong operation of the molecular rectifiers. The introduction of metal atom and tertiary butyl groups to the tetraphenyl porphyrin moiety leads to a stronger response to the external electric field and induces higher photo-to-current conversion efficiency. This also shifts the absorption in the dyes and makes them potential candidates for harvesting light in the entire visible and near IR region for photovoltaic applications.

  13. TD-DFT investigation of the potential energy surface for Excited-State Intramolecular Proton Transfer (ESIPT) reaction of 10-hydroxybenzo[h]quinoline: Topological (AIM) and population (NBO) analysis of the intramolecular hydrogen bonding interaction

    International Nuclear Information System (INIS)

    Paul, Bijan Kumar; Guchhait, Nikhil

    2011-01-01

    Here, we report a Density Functional Theoretical (DFT) study on the photophysics of a potent Excited-State Intramolecular Proton Transfer (ESIPT) molecular system, viz., 10-hydroxybenzo[h]quinoline (HBQ). Particular emphasis has been rendered on the assessment of the proton transfer reaction in HBQ in the ground and excited-states through elucidation and a careful perusal of the potential energy surfaces (PES). The non-viability of Ground-State Intramolecular Proton Transfer (GSIPT) process is dictated by a high-energy barrier coupled with no energy minimum for the proton transferred (K-form) form at the ground-state (S 0 ) PES. Remarkable reduction of the barrier along with thermodynamic stability inversion between the enol (E-form) and the keto forms (K-form) of HBQ upon photoexcitation from S 0 to the S 1 -state advocate for the operation of ESIPT process. These findings have been cross-validated on the lexicon of analysis of optimized geometry parameters, Mulliken's charge distribution on the heavy atoms, and molecular orbitals (MO) of the E- and the K-forms of HBQ. Our computational results also corroborate to experimental observations. From the modulations in optimized geometry parameters in course of the PT process a critical assessment has been endeavoured to delve into the movement of the proton during the process. Additional stress has been placed on the analysis of the intramolecular hydrogen bonding (IMHB) interaction in HBQ. The IMHB interaction has been explored by calculation of electron density ρ(r) and the Laplacian ∇ 2 ρ(r) at the bond critical point (BCP) using Atoms-In-Molecule (AIM) method and by calculation of interaction between σ* of OH with the lone pair of the nitrogen atom using Natural Bond Orbital (NBO) analysis. - Highlights: → Theoretical modelling of the photophysics of an ESIPT probe 10-hydroxybenzo[h]quinoline (HBQ). → Calculation of intramolecular hydrogen bond (IMHB) energy. → Role of hyperconjugative charge transfer

  14. A DFT + DMFT approach for nanosystems

    Energy Technology Data Exchange (ETDEWEB)

    Turkowski, Volodymyr; Kabir, Alamgir; Nayyar, Neha; Rahman, Talat S, E-mail: vturkows@mail.ucf.ed [Department of Physics, University of Central Florida, Orlando, FL 32816 (United States)

    2010-11-24

    We propose a combined density-functional-theory-dynamical-mean-field-theory (DFT + DMFT) approach for reliable inclusion of electron-electron correlation effects in nanosystems. Compared with the widely used DFT + U approach, this method has several advantages, the most important of which is that it takes into account dynamical correlation effects. The formalism is illustrated through different calculations of the magnetic properties of a set of small iron clusters (number of atoms 2 {<=} N {<=} 5). It is shown that the inclusion of dynamical effects leads to a reduction in the cluster magnetization (as compared to results from DFT + U) and that, even for such small clusters, the magnetization values agree well with experimental estimations. These results justify confidence in the ability of the method to accurately describe the magnetic properties of clusters of interest to nanoscience. (fast track communication)

  15. A DFT + DMFT approach for nanosystems

    International Nuclear Information System (INIS)

    Turkowski, Volodymyr; Kabir, Alamgir; Nayyar, Neha; Rahman, Talat S

    2010-01-01

    We propose a combined density-functional-theory-dynamical-mean-field-theory (DFT + DMFT) approach for reliable inclusion of electron-electron correlation effects in nanosystems. Compared with the widely used DFT + U approach, this method has several advantages, the most important of which is that it takes into account dynamical correlation effects. The formalism is illustrated through different calculations of the magnetic properties of a set of small iron clusters (number of atoms 2 ≤ N ≤ 5). It is shown that the inclusion of dynamical effects leads to a reduction in the cluster magnetization (as compared to results from DFT + U) and that, even for such small clusters, the magnetization values agree well with experimental estimations. These results justify confidence in the ability of the method to accurately describe the magnetic properties of clusters of interest to nanoscience. (fast track communication)

  16. Synthesis, Spectroscopic Properties and DFT Calculation of Novel ...

    Indian Academy of Sciences (India)

    density functional theory (DFT) calculations. Keywords. ... time-dependent density functional theory (TD-DFT) calcu- lations. .... reaction, the pH of the solution was adjusted to 7 .... ORTEP diagram for L1 showing 30% probability ellipsoids.

  17. Synthesis and DFT calculations of some 2-aminothiazoles

    Science.gov (United States)

    Rezania, Jafar; Behzadi, Hadi; Shockravi, Abbas; Ehsani, Morteza; Akbarzadeh, Elahe

    2018-04-01

    A series of 2-aminothiazole derivatives have been synthesized by the reaction of acetyl compounds with thiourea and iodine as catalyst under solvent-free condition, a green chemistry method. The quantum chemical calculations at the DFT/B3LYP level of theory in gas phase were carried out for starting acetyl derivatives. The highest occupied molecular orbital (HOMO) and lowest unoccupied molecular orbital (LUMO) and related reactivity descriptor of acetyl derivatives, as well as, enthalpy of reactions are calculated in order to investigate the reaction properties of acetyl compounds and yields of the reactions. The calculated reactivity descriptors are well correlated to activity of different acetyl derivatives.

  18. Trans-dinitroglycoluril isomers-A DFT treatment

    Directory of Open Access Journals (Sweden)

    Lemi Türker

    2017-02-01

    Full Text Available Isomers of trans-1,4-Dinitroglycoluril (trans-DINGU and their 1,3-tautomers are considered within the constraints of B3LYP/6-31++G (d,p and B3LYP/CC-PVTZ levels of DFT calculations. Additionally, the interactions of these isomers and proton in vacuum are investigated. The data have revealed that two of the three isomers undergo CH bond cleavage as the result of interaction with proton in vacuum. The total energies, some structural properties, the calculated IR and UV spectra are discussed.

  19. DFT-based offset-QAM OFDM for optical communications.

    Science.gov (United States)

    Zhao, Jian

    2014-01-13

    We experimentally demonstrate and numerically investigate a discrete-Fourier-transform (DFT) based offset quadrature-amplitude-modulation (offset-QAM) orthogonal frequency division multiplexing (OFDM) system. We investigate the scheme using a set of square-root-raised-cosine functions and a set of super-Gaussian functions as signal spectra. It is shown that offset-QAM OFDM exhibits negligible penalty for all investigated spectra, in contrast to rectangular-function based Nyquist FDM (N-FDM) and sinc-function based conventional OFDM (C-OFDM). The required guard interval (GI) length for dispersion compensation in offset-QAM OFDM is analyzed and shown to scale with twice the subcarrier spacing rather than the full OFDM bandwidth. Experimental results show that 38-Gb/s offset-16QAM OFDM supports 600-km fiber transmission with negligible penalty in the absence of GI while a GI length of eight is required in C-OFDM. Further numerical simulations show that by avoiding the GI, 112-Gb/s polarization multiplexed offset-4QAM OFDM can achieve 23% increase in net data rate over C-OFDM under the same transmission reach. We also discuss the design of the pulse-shaping filter in the DFT-based implementation and show that when compared to N-FDM, the required memory length of the filter for pulse shaping can be reduced from 60 to 2 in offset-QAM OFDM regardless of the fiber length.

  20. Analyzing the errors of DFT approximations for compressed water systems

    International Nuclear Information System (INIS)

    Alfè, D.; Bartók, A. P.; Csányi, G.; Gillan, M. J.

    2014-01-01

    We report an extensive study of the errors of density functional theory (DFT) approximations for compressed water systems. The approximations studied are based on the widely used PBE and BLYP exchange-correlation functionals, and we characterize their errors before and after correction for 1- and 2-body errors, the corrections being performed using the methods of Gaussian approximation potentials. The errors of the uncorrected and corrected approximations are investigated for two related types of water system: first, the compressed liquid at temperature 420 K and density 1.245 g/cm 3 where the experimental pressure is 15 kilobars; second, thermal samples of compressed water clusters from the trimer to the 27-mer. For the liquid, we report four first-principles molecular dynamics simulations, two generated with the uncorrected PBE and BLYP approximations and a further two with their 1- and 2-body corrected counterparts. The errors of the simulations are characterized by comparing with experimental data for the pressure, with neutron-diffraction data for the three radial distribution functions, and with quantum Monte Carlo (QMC) benchmarks for the energies of sets of configurations of the liquid in periodic boundary conditions. The DFT errors of the configuration samples of compressed water clusters are computed using QMC benchmarks. We find that the 2-body and beyond-2-body errors in the liquid are closely related to similar errors exhibited by the clusters. For both the liquid and the clusters, beyond-2-body errors of DFT make a substantial contribution to the overall errors, so that correction for 1- and 2-body errors does not suffice to give a satisfactory description. For BLYP, a recent representation of 3-body energies due to Medders, Babin, and Paesani [J. Chem. Theory Comput. 9, 1103 (2013)] gives a reasonably good way of correcting for beyond-2-body errors, after which the remaining errors are typically 0.5 mE h ≃ 15 meV/monomer for the liquid and the

  1. Identifying systematic DFT errors in catalytic reactions

    DEFF Research Database (Denmark)

    Christensen, Rune; Hansen, Heine Anton; Vegge, Tejs

    2015-01-01

    Using CO2 reduction reactions as examples, we present a widely applicable method for identifying the main source of errors in density functional theory (DFT) calculations. The method has broad applications for error correction in DFT calculations in general, as it relies on the dependence...... of the applied exchange–correlation functional on the reaction energies rather than on errors versus the experimental data. As a result, improved energy corrections can now be determined for both gas phase and adsorbed reaction species, particularly interesting within heterogeneous catalysis. We show...... that for the CO2 reduction reactions, the main source of error is associated with the C[double bond, length as m-dash]O bonds and not the typically energy corrected OCO backbone....

  2. Benchmark CCSD(T) and DFT study of binding energies in Be7 - 12: in search of reliable DFT functional for beryllium clusters

    Science.gov (United States)

    Labanc, Daniel; Šulka, Martin; Pitoňák, Michal; Černušák, Ivan; Urban, Miroslav; Neogrády, Pavel

    2018-05-01

    We present a computational study of the stability of small homonuclear beryllium clusters Be7 - 12 in singlet electronic states. Our predictions are based on highly correlated CCSD(T) coupled cluster calculations. Basis set convergence towards the complete basis set limit as well as the role of the 1s core electron correlation are carefully examined. Our CCSD(T) data for binding energies of Be7 - 12 clusters serve as a benchmark for performance assessment of several density functional theory (DFT) methods frequently used in beryllium cluster chemistry. We observe that, from Be10 clusters on, the deviation from CCSD(T) benchmarks is stable with respect to size, and fluctuating within 0.02 eV error bar for most examined functionals. This opens up the possibility of scaling the DFT binding energies for large Be clusters using CCSD(T) benchmark values for smaller clusters. We also tried to find analogies between the performance of DFT functionals for Be clusters and for the valence-isoelectronic Mg clusters investigated recently in Truhlar's group. We conclude that it is difficult to find DFT functionals that perform reasonably well for both beryllium and magnesium clusters. Out of 12 functionals examined, only the M06-2X functional gives reasonably accurate and balanced binding energies for both Be and Mg clusters.

  3. DFT investigation of the vibrational properties of GC Watson-Crick and Hoogsteen base pairs in the presence of Mg²⁺, Ca²⁺, and Cu²⁺ ions.

    Science.gov (United States)

    Morari, Cristian; Muntean, Cristina M; Tripon, Carmen; Buimaga-Iarinca, Luiza; Calborean, Adrian

    2014-04-01

    The binding effects of Mg²⁺, Ca²⁺, and Cu²⁺ ions on the vibrational properties of guanine-cytosine base pairs have been performed using density functional theory investigations. Both Watson-Crick and Hoogsteen configurations of the base pairs were investigated. In Watson-Crick configuration, the metal was coordinated at N7 atom of guanine, while in the case of Hoogsteen configuration, the coordination is at N3 atom of guanine. We have pointed out the geometric properties of the metal-GC base pairs structure, as well as the vibrational bands that can be used to detect the presence of metallic ions in the Watson-Crick and Hoogsteen GC structures. For the geometric models used by us, the vibrational amplitudes of metallic atoms were stronger for wavenumbers lower than 500 cm⁻¹. This suggests that in the experimental studies on DNA the presence of the three metallic atoms (Mg, Ca, and Cu) can be explicitly detected at low frequencies.

  4. The role of charge transfer in the oxidation state change of Ce atoms in the TM13-CeO2(111) systems (TM = Pd, Ag, Pt, Au): a DFT + U investigation.

    Science.gov (United States)

    Tereshchuk, Polina; Freire, Rafael L H; Ungureanu, Crina G; Seminovski, Yohanna; Kiejna, Adam; Da Silva, Juarez L F

    2015-05-28

    Despite extensive studies of transition metal (TM) clusters supported on ceria (CeO2), fundamental issues such as the role of the TM atoms in the change in the oxidation state of Ce atoms are still not well understood. In this work, we report a theoretical investigation based on static and ab initio molecular dynamics density functional theory calculations of the interaction of 13-atom TM clusters (TM = Pd, Ag, Pt, Au) with the unreduced CeO2(111) surface represented by a large surface unit cell and employing Hubbard corrections for the strong on-site Coulomb correlation in the Ce f-electrons. We found that the TM13 clusters form pyramidal-like structures on CeO2(111) in the lowest energy configurations with the following stacking sequence, TM/TM4/TM8/CeO2(111), while TM13 adopts two-dimensional structures at high energy structures. TM13 induces a change in the oxidation state of few Ce atoms (3 of 16) located in the topmost Ce layer from Ce(IV) (itinerant Ce f-states) to Ce(III) (localized Ce f-states). There is a charge flow from the TM atoms to the CeO2(111) surface, which can be explained by the electronegativity difference between the TM (Pd, Ag, Pt, Au) and O atoms, however, the charge is not uniformly distributed on the topmost O layer due to the pressure induced by the TM13 clusters on the underlying O ions, which yields a decrease in the ionic charge of the O ions located below the cluster and an increase in the remaining O ions. Due to the charge flow mainly from the TM8-layer to the topmost O-layer, the charge cannot flow from the Ce(IV) atoms to the O atoms with the same magnitude as in the clean CeO2(111) surface. Consequently, the effective cationic charge decreases mainly for the Ce atoms that have a bond with the O atoms not located below the cluster, and hence, those Ce atoms change their oxidation state from IV to III. This increases the size of the Ce(III) compared with the Ce(IV) cations, which builds-in a strain within the topmost Ce layer, and

  5. Molecular structure and spectroscopic properties of 4-nitrocatechol at different pH: UV-visible, Raman, DFT and TD-DFT calculations

    International Nuclear Information System (INIS)

    Cornard, Jean-Paul; Rasmiwetti; Merlin, Jean-Claude

    2005-01-01

    We investigated theoretically, by density functional theoretical calculations and by vibrational and electronic spectroscopies, the structure and the molecular spectroscopic properties of the 4-nitrocatechol molecule with varying pH. The lower energy stable structures of the neutral, monoanion and dianion forms were compared, and influence of water solvation was examined. The Raman and UV-visible spectra of 4-nitrocatechol and of its singly deprotonated form were recorded by varying the pH from 2 to 9. A calculation of the vibrational frequencies has allowed a complete assignment of the Raman spectra of the two forms of 4-nitrocatechol, and has permitted to investigate the evolution of vibrational normal modes upon deprotonation. Based on the molecular orbital analysis and the time dependent DFT (TD-DFT) calculations, we discussed the electronic structure and the assignment of the absorption bands in the electronic spectra of 4-nitrocatechol and mono-deprotonated 4-nitrocatechol

  6. An Overview of the Adaptive Robust DFT

    Directory of Open Access Journals (Sweden)

    Djurović Igor

    2010-01-01

    Full Text Available Abstract This paper overviews basic principles and applications of the robust DFT (RDFT approach, which is used for robust processing of frequency-modulated (FM signals embedded in non-Gaussian heavy-tailed noise. In particular, we concentrate on the spectral analysis and filtering of signals corrupted by impulsive distortions using adaptive and nonadaptive robust estimators. Several adaptive estimators of location parameter are considered, and it is shown that their application is preferable with respect to non-adaptive counterparts. This fact is demonstrated by efficiency comparison of adaptive and nonadaptive RDFT methods for different noise environments.

  7. z-transform DFT filters and FFT's

    DEFF Research Database (Denmark)

    Bruun, G.

    1978-01-01

    The paper shows how discrete Fourier transformation can be implemented as a filter bank in a way which reduces the number of filter coefficients. A particular implementation of such a filter bank is directly related to the normal complex FFT algorithm. The principle developed further leads to types...... of DFT filter banks which utilize a minimum of complex coefficients. These implementations lead to new forms of FFT's, among which is acos/sinFFT for a real signal which only employs real coefficients. The new FFT algorithms use only half as many real multiplications as does the classical FFT....

  8. Unbiased structural search of small copper clusters within DFT

    International Nuclear Information System (INIS)

    Cogollo-Olivo, Beatriz H.; Seriani, Nicola; Montoya, Javier A.

    2015-01-01

    Highlights: • We have been able to identify novel metastable structures for small Cu clusters. • We have shown that a linear structure reported for Cu_3 is actually a local maximum. • Some of the structures reported in literature are actually unstable within DFT. • Some of the isomer structures found shows the limits of educated guesses. - Abstract: The atomic structure of small Cu clusters with 3–6 atoms has been investigated by density functional theory and random search algorithm. New metastable structures have been found that lie merely tens of meV/atom above the corresponding ground state, and could therefore be present at thermodynamic equilibrium at room temperature or slightly above. Moreover, we show that the previously proposed linear configuration for Cu_3 is in fact a local maximum of the energy. Finally, we argue that the random search algorithm also provides qualitative information about the attraction basin of each structure in the energy landscape.

  9. Charge transfer properties of pentacene adsorbed on silver: DFT study

    Energy Technology Data Exchange (ETDEWEB)

    N, Rekha T.; Rajkumar, Beulah J. M., E-mail: beulah-rajkumar@yahoo.co.in [PG & Research Department of Physics, Lady Doak College, Madurai 625002 (India)

    2015-06-24

    Charge transfer properties of pentacene adsorbed on silver is investigated using DFT methods. Optimized geometry of pentacene after adsorption on silver indicates distortion in hexagonal structure of the ring close to the silver cluster and deviations in co-planarity of carbon atoms due to the variations in bond angles and dihedral angles. Theoretically simulated absorption spectrum has a symmetric surface plasmon resonance peak around 486nm corresponding to the transfer of charge from HOMO-2 to LUMO. Theoretical SERS confirms the process of adsorption, tilted orientation of pentacene on silver surface and the charge transfers reported. Localization of electron density arising from redistribution of electrostatic potential together with a reduced bandgap of pentacene after adsorption on silver suggests its utility in the design of electro active organic semiconducting devices.

  10. Molecular structure and DFT investigations on new cobalt(II ...

    Indian Academy of Sciences (India)

    tion process was demonstrated.9 Late-transition metals, especially Ni, Pd ..... in table S2 (Supplementary Information). Most of the ... to molecular system because of atomic charges affect ... structure, acidity–basicity behavior and other proper-.

  11. Adaptive DFT-Based Interferometer Fringe Tracking

    Science.gov (United States)

    Wilson, Edward; Pedretti, Ettore; Bregman, Jesse; Mah, Robert W.; Traub, Wesley A.

    2005-12-01

    An automatic interferometer fringe tracking system has been developed, implemented, and tested at the Infrared Optical Telescope Array (IOTA) Observatory at Mount Hopkins, Arizona. The system can minimize the optical path differences (OPDs) for all three baselines of the Michelson stellar interferometer at IOTA. Based on sliding window discrete Fourier-transform (DFT) calculations that were optimized for computational efficiency and robustness to atmospheric disturbances, the algorithm has also been tested extensively on offline data. Implemented in ANSI C on the 266 MHz PowerPC processor running the VxWorks real-time operating system, the algorithm runs in approximately [InlineEquation not available: see fulltext.] milliseconds per scan (including all three interferograms), using the science camera and piezo scanners to measure and correct the OPDs. The adaptive DFT-based tracking algorithm should be applicable to other systems where there is a need to detect or track a signal with an approximately constant-frequency carrier pulse. One example of such an application might be to the field of thin-film measurement by ellipsometry, using a broadband light source and a Fourier-transform spectrometer to detect the resulting fringe patterns.

  12. Adaptive DFT-Based Interferometer Fringe Tracking

    Directory of Open Access Journals (Sweden)

    Wesley A. Traub

    2005-09-01

    Full Text Available An automatic interferometer fringe tracking system has been developed, implemented, and tested at the Infrared Optical Telescope Array (IOTA Observatory at Mount Hopkins, Arizona. The system can minimize the optical path differences (OPDs for all three baselines of the Michelson stellar interferometer at IOTA. Based on sliding window discrete Fourier-transform (DFT calculations that were optimized for computational efficiency and robustness to atmospheric disturbances, the algorithm has also been tested extensively on offline data. Implemented in ANSI C on the 266 MHz PowerPC processor running the VxWorks real-time operating system, the algorithm runs in approximately 2.0 milliseconds per scan (including all three interferograms, using the science camera and piezo scanners to measure and correct the OPDs. The adaptive DFT-based tracking algorithm should be applicable to other systems where there is a need to detect or track a signal with an approximately constant-frequency carrier pulse. One example of such an application might be to the field of thin-film measurement by ellipsometry, using a broadband light source and a Fourier-transform spectrometer to detect the resulting fringe patterns.

  13. Theoretical investigation of the Cs*Hen>=3 exciplexes

    International Nuclear Information System (INIS)

    Zbiri, Mohamed; Daul, Claude

    2005-01-01

    The X 2 Σ 1/2 , A 2 Π 1/2 , B 2 Σ 1/2 , and A 2 Π 3/2 states of Cs*He n exciplexes, with n={3,...,9}, are studied using first principle density functional theory (DFT) formalism combined with the zeroth order regular approximation (ZORA). The zero points energies (ZPEs) E 0 for Cs*He n are calculated at a first step, in order to estimate the stability of the studied exciplexes. Relativistic calculations are carried out including spin-orbit effect (SO), and potential energy surfaces of Cs*He 6 are shown. The electronic distribution shapes of the studied molecules are also discussed, and their emission lines are evaluated and compared to a new discovered experimental emission spectra, which has been recently assigned, using a semi-empirical model, to Cs(AΠ 1/2 )He 7 . Our first principle calculation suggests that the discovered emission line is most probably due to a decay of Cs(AΠ 1/2 )He 6

  14. Structure-activity relations of 2-(methylthio)benzimidazole by FTIR, FT-Raman, NMR, DFT and conceptual DFT methods.

    Science.gov (United States)

    Arjunan, V; Raj, Arushma; Ravindran, P; Mohan, S

    2014-01-24

    The vibrational fundamental modes of 2-(methylthio)benzimidazole (2MTBI) have been analysed by combining FTIR, FT-Raman and quantum chemical calculations. The structural parameters of the compound are determined from the optimised geometry by B3LYP with 6-31G(∗∗), 6-311++G(∗∗) and cc-pVTZ basis sets and giving energies, harmonic vibrational frequencies, depolarisation ratios, IR intensities and Raman activities. (1)H and (13)C NMR spectra have been analysed and (1)H and (13)C nuclear magnetic resonance chemical shifts are calculated using the gauge independent atomic orbital (GIAO) method. The structure-activity relationship of the compound is also investigated by conceptual DFT methods. The chemical reactivity and site selectivity of the molecule has been determined with the help of global and local reactivity descriptors. Copyright © 2013 Elsevier B.V. All rights reserved.

  15. A DFT+nonhomogeneous DMFT approach for finite systems

    International Nuclear Information System (INIS)

    Kabir, Alamgir; Turkowski, Volodymyr; Rahman, Talat S

    2015-01-01

    For reliable and efficient inclusion of electron–electron correlation effects in nanosystems we formulate a combined density functional theory/nonhomogeneous dynamical mean-field theory (DFT+DMFT) approach which employs an approximate iterated perturbation theory impurity solver. We further apply the method to examine the size-dependent magnetic properties of iron nanoparticles containing 11–100 atoms. We show that for the majority of clusters the DFT+DMFT solution is in very good agreement with experimental data, much better compared to the DFT and DFT+U results. In particular, it reproduces the oscillations in magnetic moment with size as observed experimentally. We thus demonstrate that the DFT+DMFT approach can be used for accurate and realistic description of nanosystems containing about hundred atoms. (paper)

  16. 3D-FT MRI of the facial nerve

    International Nuclear Information System (INIS)

    Girard, N.; Raybaud, C.; Poncet, M.

    1994-01-01

    Contrast-enhanced 3D-FT MRI of the intrapetrous facial nerve was obtained in 38 patients with facial nerve disease, using a 1.0 T magnet and fast gradient-echo acquisition sequences. Contiguous millimetric sections were obtained, which could be reformatted in any desired plane. Acutely ill patients, were examined within the first 2 months, included: 24 with Bell's palsy and 6 with other acute disorders (Herpes zoster, trauma, neuroma, meningeal metastasis, middle ear granuloma). Six patients investigated more than a year after the onset of symptoms included 3 with congenital cholesteatoma, 2 with neuromas and one with a chronic Bell's palsy. The lesion was found incidentally in two cases (a suspected neurofibroma and a presumed drop metastasis from an astrocytoma). Patients with tumours had nodular, focally-enhancing lesions, except for the leptomeningeal metastasis in which the enhancement was linear. Linear, diffuse contrast enhancement of the facial nerve was found in trauma, and in the patient with a middle ear granuloma. Of the 24 patients with an acute Bell's palsy 15 exhibited linear contrast enhancement of the facial nerve. Three of these were lost to follow-up, but correlation of clinical outcome and contrast enhancement showed that only 4 of the 11 patients who made a complete recovery and all 10 patients with incomplete recovery demonstrated enhancement. Possible explanations for these findings are suggested by pathological data from the literature. 3D-FT imaging of the facial nerve thus yields direct information about the of the nerve condition and defines the morphological abnormalities. It can also demonstrate contrast enhancement which seems to have some prognostic value in acute idiopathic Bell's palsy. (orig.)

  17. 3D-FT MRI of the facial nerve

    Energy Technology Data Exchange (ETDEWEB)

    Girard, N. (Neuroradiology, Hopital Nord, 13 Marseille (France)); Raybaud, C. (Neuroradiology, Hopital Nord, 13 Marseille (France)); Poncet, M. (Neuroradiology, Hopital Nord, 13 Marseille (France))

    1994-08-01

    Contrast-enhanced 3D-FT MRI of the intrapetrous facial nerve was obtained in 38 patients with facial nerve disease, using a 1.0 T magnet and fast gradient-echo acquisition sequences. Contiguous millimetric sections were obtained, which could be reformatted in any desired plane. Acutely ill patients, were examined within the first 2 months, included: 24 with Bell's palsy and 6 with other acute disorders (Herpes zoster, trauma, neuroma, meningeal metastasis, middle ear granuloma). Six patients investigated more than a year after the onset of symptoms included 3 with congenital cholesteatoma, 2 with neuromas and one with a chronic Bell's palsy. The lesion was found incidentally in two cases (a suspected neurofibroma and a presumed drop metastasis from an astrocytoma). Patients with tumours had nodular, focally-enhancing lesions, except for the leptomeningeal metastasis in which the enhancement was linear. Linear, diffuse contrast enhancement of the facial nerve was found in trauma, and in the patient with a middle ear granuloma. Of the 24 patients with an acute Bell's palsy 15 exhibited linear contrast enhancement of the facial nerve. Three of these were lost to follow-up, but correlation of clinical outcome and contrast enhancement showed that only 4 of the 11 patients who made a complete recovery and all 10 patients with incomplete recovery demonstrated enhancement. Possible explanations for these findings are suggested by pathological data from the literature. 3D-FT imaging of the facial nerve thus yields direct information about the of the nerve condition and defines the morphological abnormalities. It can also demonstrate contrast enhancement which seems to have some prognostic value in acute idiopathic Bell's palsy. (orig.)

  18. A comparison of different discrimination parameters for the DFT-based PSD method in fast scintillators

    International Nuclear Information System (INIS)

    Liu, G.; Yang, J.; Luo, X.L.; Lin, C.B.; Peng, J.X.; Yang, Y.

    2013-01-01

    Although the discrete Fourier transform (DFT) based pulse shape discrimination (PSD) method, realized by transforming the digitized scintillation pulses into frequency coefficients by using DFT, has been proven to effectively discriminate neutrons and γ rays, its discrimination performance depends strongly on the selection of the discrimination parameter obtained by the combination of these frequency coefficients. In order to thoroughly understand and apply the DFT-based PSD in organic scintillation detectors, a comparison of three different discrimination parameters, i.e. the amplitude of zero-frequency component, the amplitude difference between the amplitude of zero-frequency component and the amplitude of base-frequency component, and the ratio of the amplitude of base-frequency component to the amplitude of zero-frequency component, is described in this paper. An experimental setup consisting of an Americium–Beryllium (Am–Be) source, a BC501A liquid scintillator detector, and a 5Gsample/s 8-bit oscilloscope was built to assess the performance of the DFT-based PSD with each of these discrimination parameters in terms of the figure-of-merit (based on the separation of the event distributions). The third technique, which uses the ratio of the amplitude of base-frequency component to the amplitude of zero-frequency component as the discrimination parameter, is observed to provide the best discrimination performance in this research. - Highlights: • The spectrum difference between neutron pulse and γ-ray pulse was investigated. • The DFT-based PSD with different parameter definitions was assessed. • The way of using the ratio of magnitude spectrum provides the best performance. • The performance differences were explained from noise suppression features

  19. Benchmarking DFT and TD-DFT Functionals for the Ground and Excited States of Hydrogen-Rich Peptide Radicals.

    Science.gov (United States)

    Riffet, Vanessa; Jacquemin, Denis; Cauët, Emilie; Frison, Gilles

    2014-08-12

    We assess the pros and cons of a large panel of DFT exchange-correlation functionals for the prediction of the electronic structure of hydrogen-rich peptide radicals formed after electron attachment on a protonated peptide. Indeed, despite its importance in the understanding of the chemical changes associated with the reduction step, the question of the attachment site of an electron and, more generally, of the reduced species formed in the gas phase through electron-induced dissociation (ExD) processes in mass spectrometry is still a matter of debate. For hydrogen-rich peptide radicals in which several positive groups and low-lying π* orbitals can capture the incoming electron in ExD, inclusion of full Hartree-Fock exchange at long-range interelectronic distance is a prerequisite for an accurate description of the electronic states, thereby excluding several popular exchange-correlation functionals, e.g., B3LYP, M06-2X, or CAM-B3LYP. However, we show that this condition is not sufficient by comparing the results obtained with asymptotically correct range-separated hybrids (M11, LC-BLYP, LC-BPW91, ωB97, ωB97X, and ωB97X-D) and with reference CASSCF-MRCI and EOM-CCSD calculations. The attenuation parameter ω significantly tunes the spin density distribution and the excited states vertical energies. The investigated model structures, ranging from methylammonium to hexapeptide, allow us to obtain a description of the nature and energy of the electronic states, depending on (i) the presence of hydrogen bond(s) around the cationic site(s), (ii) the presence of π* molecular orbitals (MOs), and (iii) the selected DFT approach. It turns out that, in the present framework, LC-BLYP and ωB97 yields the most accurate results.

  20. Chlorophenols Sorption on Multi-Walled Carbon Nanotubes: DFT Modeling and Structure-Property Relationship Analysis

    OpenAIRE

    Watkins, Marquita; Sizochenko, Natalia; Moore, Quentarius; Golebiowski, Marek; Leszczynska, Danuta; Leszczynski, Jerzy

    2017-01-01

    Presence of chlorophenols in drinking water could be hazardous to human health. Optimization and computational modeling of experimental conditions of adsorption lead to understanding the mechanisms of this process and to creating the efficient experimental equipment. In the current study, we investigated multi-walled carbon nanotubes by means of density functional theory (DFT) approach. This is applied to study selected types of interactions between six solvents, five types of nanotubes, and ...

  1. Vibrational investigation on FT-IR and FT-Raman spectra, IR intensity, Raman activity, peak resemblance, ideal estimation, standard deviation of computed frequencies analyses and electronic structure on 3-methyl-1,2-butadiene using HF and DFT (LSDA/B3LYP/B3PW91) calculations.

    Science.gov (United States)

    Ramalingam, S; Jayaprakash, A; Mohan, S; Karabacak, M

    2011-11-01

    FT-IR and FT-Raman (4000-100 cm(-1)) spectral measurements of 3-methyl-1,2-butadiene (3M12B) have been attempted in the present work. Ab-initio HF and DFT (LSDA/B3LYP/B3PW91) calculations have been performed giving energies, optimized structures, harmonic vibrational frequencies, IR intensities and Raman activities. Complete vibrational assignments on the observed spectra are made with vibrational frequencies obtained by HF and DFT (LSDA/B3LYP/B3PW91) at 6-31G(d,p) and 6-311G(d,p) basis sets. The results of the calculations have been used to simulate IR and Raman spectra for the molecule that showed good agreement with the observed spectra. The potential energy distribution (PED) corresponding to each of the observed frequencies are calculated which confirms the reliability and precision of the assignment and analysis of the vibrational fundamentals modes. The oscillation of vibrational frequencies of butadiene due to the couple of methyl group is also discussed. A study on the electronic properties such as HOMO and LUMO energies, were performed by time-dependent DFT (TD-DFT) approach. The calculated HOMO and LUMO energies show that charge transfer occurs within the molecule. The thermodynamic properties of the title compound at different temperatures reveal the correlations between standard heat capacities (C) standard entropies (S), and standard enthalpy changes (H). Crown Copyright © 2011. Published by Elsevier B.V. All rights reserved.

  2. nmr spectroscopic study and dft calculations of vibrational analyses

    African Journals Online (AJOL)

    Preferred Customer

    2Plant, Drug and Scientific Research Centre, Anadolu University, 26470, ... Density functional theory (DFT) calculations provide excellent agreement with ..... simple correlation between 1JCH and the hybridization of the carbon atom involved; ...

  3. Redox Potentials of Ligands and Complexes – a DFT Approach

    African Journals Online (AJOL)

    NICO

    Electron affinity (EA) of an atom or molecule is the associated energy change that occurs .... As a consequence of the foregoing evidence we resolved to embark on a ... Density functional theory (DFT) calculations were performed using the ...

  4. DFT Study On Effects of CO2 Contamination in Non-Aqueous Li-Air Batteries

    DEFF Research Database (Denmark)

    Mekonnen, Yedilfana Setarge; Mýrdal, Jón Steinar Garðarsson; Vegge, Tejs

    2013-01-01

    Density Functional Theory (DFT) studies on the effects of carbon dioxide (CO2) contamination at the cathode of rechargeable non-aqueous Li-O2 batteries, where the insulating material Lithium peroxide (Li2O2) is the main discharge product. The Li2O2 growth mechanism and overpotentials are investig...... and result in an increased battery capacity. However, CO2 contamination on the Li2O2 surface confirms an asymmetric increase in the overpotentials; particularly the charging overvoltage exhibits sustantial increase, which would reduce the efficiency of the Li-air battery.......Density Functional Theory (DFT) studies on the effects of carbon dioxide (CO2) contamination at the cathode of rechargeable non-aqueous Li-O2 batteries, where the insulating material Lithium peroxide (Li2O2) is the main discharge product. The Li2O2 growth mechanism and overpotentials...

  5. GW quasiparticle bandgaps of anatase TiO2 starting from DFT + U.

    Science.gov (United States)

    Patrick, Christopher E; Giustino, Feliciano

    2012-05-23

    We investigate the quasiparticle band structure of anatase TiO(2), a wide gap semiconductor widely employed in photovoltaics and photocatalysis. We obtain GW quasiparticle energies starting from density-functional theory (DFT) calculations including Hubbard U corrections. Using a simple iterative procedure we determine the value of the Hubbard parameter yielding a vanishing quasiparticle correction to the fundamental bandgap of anatase TiO(2). The bandgap (3.3 eV) calculated using this optimal Hubbard parameter is smaller than the value obtained by applying many-body perturbation theory to standard DFT eigenstates and eigenvalues (3.7 eV). We extend our analysis to the rutile polymorph of TiO(2) and reach similar conclusions. Our work highlights the role of the starting non-interacting Hamiltonian in the calculation of GW quasiparticle energies in TiO(2) and suggests an optimal Hubbard parameter for future calculations.

  6. DFT study of the structures and energetics of 98-atom AuPd clusters.

    Science.gov (United States)

    Bruma, Alina; Ismail, Ramli; Paz-Borbón, L Oliver; Arslan, Haydar; Barcaro, Giovanni; Fortunelli, Alessandro; Li, Z Y; Johnston, Roy L

    2013-01-21

    The energetics, structures and segregation of 98-atom AuPd nanoclusters are investigated using a genetic algorithm global optimization technique with the Gupta empirical potential (comparing three different potential parameterisations) followed by local minimizations using Density Functional Theory (DFT) calculations. A shell optimization program algorithm is employed in order to study the energetics of the highly symmetric Leary Tetrahedron (LT) structure and optimization of the chemical ordering of a number of structural motifs is carried out using the Basin Hopping Monte Carlo approach. Although one of the empirical potentials is found to favour the LT structure, it is shown that Marks Decahedral and mixed FCC-HCP motifs are lowest in energy at the DFT level.

  7. Benchmarking Hydrogen and Carbon NMR Chemical Shifts at HF, DFT, and MP2 Levels.

    Science.gov (United States)

    Flaig, Denis; Maurer, Marina; Hanni, Matti; Braunger, Katharina; Kick, Leonhard; Thubauville, Matthias; Ochsenfeld, Christian

    2014-02-11

    An extensive study of error distributions for calculating hydrogen and carbon NMR chemical shifts at Hartree-Fock (HF), density functional theory (DFT), and Møller-Plesset second-order perturbation theory (MP2) levels is presented. Our investigation employs accurate CCSD(T)/cc-pVQZ calculations for providing reference data for 48 hydrogen and 40 carbon nuclei within an extended set of chemical compounds covering a broad range of the NMR scale with high relevance to chemical applications, especially in organic chemistry. Besides the approximations of HF, a variety of DFT functionals, and conventional MP2, we also present results with respect to a spin component-scaled MP2 (GIAO-SCS-MP2) approach. For each method, the accuracy is analyzed in detail for various basis sets, allowing identification of efficient combinations of method and basis set approximations.

  8. DFT studies of hydrocarbon combustion on metal surfaces.

    Science.gov (United States)

    Arya, Mina; Mirzaei, Ali Akbar; Davarpanah, Abdol Mahmood; Barakati, Seyed Masoud; Atashi, Hossein; Mohsenzadeh, Abas; Bolton, Kim

    2018-02-02

    Catalytic combustion of hydrocarbons is an important technology to produce energy. Compared to conventional flame combustion, the catalyst enables this process to operate at lower temperatures; hence, reducing the energy required for efficient combustion. The reaction and activation energies of direct combustion of hydrocarbons (CH → C + H) on a series of metal surfaces were investigated using density functional theory (DFT). The data obtained for the Ag, Au, Al, Cu, Rh, Pt, and Pd surfaces were used to investigate the validity of the Brønsted-Evans-Polanyi (BEP) and transition state scaling (TSS) relations for this reaction on these surfaces. These relations were found to be valid (R 2  = 0.94 for the BEP correlation and R 2  = 1.0 for the TSS correlation) and were therefore used to estimate the energetics of the combustion reaction on Ni, Co, and Fe surfaces. It was found that the estimated transition state and activation energies (E TS  = -69.70 eV and E a  = 1.20 eV for Ni, E TS  = -87.93 eV and E a  = 1.08 eV for Co and E TS  = -92.45 eV and E a  = 0.83 eV for Fe) are in agreement with those obtained by DFT calculations (E TS  = -69.98 eV and E a  = 1.23 eV for Ni, E TS  = -87.88 eV and E a  = 1.08 eV for Co and E TS  = -92.57 eV and E a  = 0.79 eV for Fe). Therefore, these relations can be used to predict energetics of this reaction on these surfaces without doing the time consuming transition state calculations. Also, the calculations show that the activation barrier for CH dissociation decreases in the order Ag ˃ Au ˃ Al ˃ Cu ˃ Pt ˃ Pd ˃ Ni > Co > Rh > Fe.

  9. OH-initiated transformation and hydrolysis of aspirin in AOPs system: DFT and experimental studies.

    Science.gov (United States)

    He, Lin; Sun, Xiaomin; Zhu, Fanping; Ren, Shaojie; Wang, Shuguang

    2017-08-15

    Advanced oxidation processes (AOPs) are widely used in wastewater treatment of pharmaceutical and personal care products (PPCPs). In this work, the OH-initiated transformation as well as the hydrolysis of a typical PPCPs, aspirin, was investigated using density functional theory (DFT) calculations and laboratory experiments. For DFT calculations, the frontier electron densities and bond dissociation energies were analyzed. Profiles of the potential energy surface were constructed, and all the possible pathways were discussed. Additionally, rate constants for each pathway were calculated with transition state theory (TST) method. UV/H 2 O 2 experiments of aspirin were performed and degradation intermediates were identified by UPLC-MS-MS analysis. Different findings from previous experimental works were reported that the H-abstraction pathways at methyl position were dominated and OH-addition pathways on benzene ring were also favored. Meantime, hydroxyl ASA was confirmed as the main stable intermediate. Moreover, it was the first time to use DFT method to investigate the hydrolysis mechanisms of organic ester compound. Copyright © 2017 Elsevier B.V. All rights reserved.

  10. A DFT-D study of structural and energetic properties of TiO2 modifications

    International Nuclear Information System (INIS)

    Moellmann, Jonas; Ehrlich, Stephan; Tonner, Ralf; Grimme, Stefan

    2012-01-01

    The structures and relative energies of the three naturally occurring modifications of titanium dioxide (rutile, brookite and anatase) were investigated. For an accurate description, atom-pairwise dispersion-corrected density functional theory (DFT-D) was applied. The DFT-D3 scheme was extended non-empirically to improve the description of Ti atoms in bulk systems. New dispersion coefficients were derived from TDDFT calculations for electrostatically embedded TiO 2 clusters. The dispersion coefficient C 6 TiTi is reduced by a factor of 18 compared to the free atom. The three TiO 2 modifications were optimized in periodic plane-wave calculations with dispersion-corrected GGA (PBE, revPBE) and hybrid density functionals (PBE0, revPBE0). The calculated lattice parameters are in good agreement with experimental data, in particular the dispersion-corrected PBE0 and revPBE0 hybrid functionals. Although the observed relative stabilities could not be reproduced in all cases, dispersion corrections improve the results. For an accurate description of bulk metal oxides, London dispersion is a prominent force that should not be neglected when energies and structures are computed with DFT. Additionally, the influence of dispersion interactions on the relaxation of the TiO 2 (110) surface is investigated.

  11. Tetramer model of leukoemeraldine-emeraldine electrochemistry in the presence of trihalogenoacetic acids. DFT approach.

    Science.gov (United States)

    Barbosa, Nuno Almeida; Grzeszczuk, Maria; Wieczorek, Robert

    2015-01-15

    First results of the application of the DFT computational approach to the reversible electrochemistry of polyaniline are presented. A tetrameric chain was used as the simplest model of the polyaniline polymer species. The system under theoretical investigation involved six tetramer species, two electrons, and two protons, taking part in 14 elementary reactions. Moreover, the tetramer species were interacting with two trihalogenoacetic acid molecules. Trifluoroacetic, trichloroacetic, and tribromoacetic acids were found to impact the redox transformation of polyaniline as shown by cyclic voltammetry. The theoretical approach was considered as a powerful tool for investigating the main factors of importance for the experimental behavior. The DFT method provided molecular structures, interaction energies, and equilibrium energies of all of the tetramer-acid complexes. Differences between the energies of the isolated tetramer species and their complexes with acids are discussed in terms of the elementary reactions, that is, ionization potentials and electron affinities, equilibrium constants, electrode potentials, and reorganization energies. The DFT results indicate a high impact of the acid on the reorganization energy of a particular elementary electron-transfer reaction. The ECEC oxidation path was predicted by the calculations. The model of the reacting system must be extended to octamer species and/or dimeric oligomer species to better approximate the real polymer situation.

  12. DFT Studies on Interaction between Lanthanum and Hydroxyamide

    Science.gov (United States)

    Pati, Anindita; Kundu, T. K.; Pal, Snehanshu

    2018-03-01

    Extraction and separation of individual rare earth elements has been a challenge as they are chemically very similar. Solvent extraction is the most suitable way for extraction of rare earth elements. Acidic, basic, neutral, chelating are the major classes of extractants for solvent extraction of rare earth elements. The coordination complex of chelating extractants is very selective with positively charged metal ion. Hence they are widely used. Hydroxyamide is capable of forming chelates with metal cations. In this present study interactions of hydroxyamide ligand with lanthanum have been investigated using density functional theory (DFT). Two different functional such as raB97XD and B3LYP are applied along with 6-31+G(d,p) basis set for carbon, nitrogen, hydrogen and SDD basis set for lanthanum. Stability of formed complexes has been evaluated based on calculated interaction energies and solvation energies. Frontier orbital (highest occupied molecular orbital or HOMO and lowest unoccupied molecular orbital or LUMO) energies of the molecule have also been calculated. Electronegativity, chemical hardness, chemical softness and chemical potential are also determined for these complexes to get an idea about the reactivity. From the partial charge distribution it is seen that oxygen atoms in hydroxyamide have higher negative charge. The double bonded oxygen atom present in the hydroxyamide structure has higher electron density and so it forms bond with lanthanum but the singly bonded oxygen atom in the hydroxyamide structure is weaker donor atom and so it is less available for interaction with lanthanum.

  13. Unbiased structural search of small copper clusters within DFT

    Energy Technology Data Exchange (ETDEWEB)

    Cogollo-Olivo, Beatriz H., E-mail: bcogolloo@unicartagena.edu.co [Maestría en Ciencias Físicas, Universidad de Cartagena, 130001 Cartagena de Indias, Bolívar (Colombia); Seriani, Nicola, E-mail: nseriani@ictp.it [Condensed Matter and Statistical Physics Section, The Abdus Salam ICTP, Strada Costiera 11, 34151 Trieste (Italy); Montoya, Javier A., E-mail: jmontoyam@unicartagena.edu.co [Instituto de Matemáticas Aplicadas, Universidad de Cartagena, 130001 Cartagena de Indias, Bolívar (Colombia); Associates Program, The Abdus Salam ICTP, Strada Costiera 11, 34151 Trieste (Italy)

    2015-11-05

    Highlights: • We have been able to identify novel metastable structures for small Cu clusters. • We have shown that a linear structure reported for Cu{sub 3} is actually a local maximum. • Some of the structures reported in literature are actually unstable within DFT. • Some of the isomer structures found shows the limits of educated guesses. - Abstract: The atomic structure of small Cu clusters with 3–6 atoms has been investigated by density functional theory and random search algorithm. New metastable structures have been found that lie merely tens of meV/atom above the corresponding ground state, and could therefore be present at thermodynamic equilibrium at room temperature or slightly above. Moreover, we show that the previously proposed linear configuration for Cu{sub 3} is in fact a local maximum of the energy. Finally, we argue that the random search algorithm also provides qualitative information about the attraction basin of each structure in the energy landscape.

  14. Electromechanical and Chemical Sensing at the Nanoscale: DFT and Transport Modeling

    Science.gov (United States)

    Maiti, Amitesh

    Of the many nanoelectronic applications proposed for near to medium-term commercial deployment, sensors based on carbon nanotubes (CNT) and metal-oxide nanowires are receiving significant attention from researchers. Such devices typically operate on the basis of the changes of electrical response characteristics of the active component (CNT or nanowire) when subjected to an externally applied mechanical stress or the adsorption of a chemical or bio-molecule. Practical development of such technologies can greatly benefit from quantum chemical modeling based on density functional theory (DFT), and from electronic transport modeling based on non-equilibrium Green's function (NEGF). DFT can compute useful quantities like possible bond-rearrangements, binding energy, charge transfer, and changes to the electronic structure, while NEGF can predict changes in electronic transport behavior and contact resistance. Effects of surrounding medium and intrinsic structural defects can also be taken into account. In this work we review some recent DFT and transport investigations on (1) CNT-based nano-electromechanical sensors (NEMS) and (2) gas-sensing properties of CNTs and metal-oxide nanowires. We also briefly discuss our current understanding of CNT-metal contacts which, depending upon the metal, the deposition technique, and the masking method can have a significant effect on device performance.

  15. Probing the molecular and electronic structure of the lichen metabolite usnic acid: A DFT study

    International Nuclear Information System (INIS)

    Galasso, V.

    2010-01-01

    Graphical abstract: DFT calculations of structural preferences, acidic properties, carbonyl vibrations, 13 C NMR chemical shifts, and absorption spectrum account for the unique structural backbone, chemical behaviour, and spectroscopic properties of usnic acid, the cortical pigment and potent reactive of lichens. - Abstract: The molecular structure of usnic acid was investigated by the density functional theory (DFT). Two keto-enol tautomers are nearly isoenergetic and more stable than other tautomers. Noteworthy is the energy difference among the three intramolecular O-H...O hydrogen bonds. The DFT/PCM calculated dissociation constants account for the acidic sequence of the three OH-groups. The electronic structure was also studied by calculating IR/Raman, NMR, and absorption features. A reliable assignment of the 'fingerprint' carbonyl stretching modes was supported by calculations on related molecules. The calculated NMR chemical shifts fit expectation in terms of a fast interconversion between the two most preferred tautomers. A variety of π → π* and n → π* excitations, localized on a single ring or involving a charge-transfer between the two lateral rings of the molecule, gives rise to the broad UV-absorption bands. This property accounts for the efficient protection against damaging solar radiation provided by usnic acid for lichens.

  16. Probing the molecular and electronic structure of the lichen metabolite usnic acid: A DFT study

    Energy Technology Data Exchange (ETDEWEB)

    Galasso, V., E-mail: galasso@univ.trieste.it [Dipartimento di Scienze Chimiche, Universita di Trieste, I-34127 Trieste (Italy)

    2010-08-23

    Graphical abstract: DFT calculations of structural preferences, acidic properties, carbonyl vibrations, {sup 13}C NMR chemical shifts, and absorption spectrum account for the unique structural backbone, chemical behaviour, and spectroscopic properties of usnic acid, the cortical pigment and potent reactive of lichens. - Abstract: The molecular structure of usnic acid was investigated by the density functional theory (DFT). Two keto-enol tautomers are nearly isoenergetic and more stable than other tautomers. Noteworthy is the energy difference among the three intramolecular O-H...O hydrogen bonds. The DFT/PCM calculated dissociation constants account for the acidic sequence of the three OH-groups. The electronic structure was also studied by calculating IR/Raman, NMR, and absorption features. A reliable assignment of the 'fingerprint' carbonyl stretching modes was supported by calculations on related molecules. The calculated NMR chemical shifts fit expectation in terms of a fast interconversion between the two most preferred tautomers. A variety of {pi} {yields} {pi}* and n {yields} {pi}* excitations, localized on a single ring or involving a charge-transfer between the two lateral rings of the molecule, gives rise to the broad UV-absorption bands. This property accounts for the efficient protection against damaging solar radiation provided by usnic acid for lichens.

  17. A computational DFT study of structural transitions in textured solid-fluid interfaces

    Science.gov (United States)

    Yatsyshin, Petr; Parry, Andrew O.; Kalliadasis, Serafim

    2015-11-01

    Fluids adsorbed at walls, in capillary pores and slits, and in more exotic, sculpted geometries such as grooves and wedges can exhibit many new phase transitions, including wetting, pre-wetting, capillary-condensation and filling, compared to their bulk counterparts. As well as being of fundamental interest to the modern statistical mechanical theory of inhomogeneous fluids, these are also relevant to nanofluidics, chemical- and bioengineering. In this talk we will show using a microscopic Density Functional Theory (DFT) for fluids how novel, continuous, interfacial transitions associated with the first-order prewetting line, can occur on steps, in grooves and in wedges, that are sensitive to both the range of the intermolecular forces and interfacial fluctuation effects. These transitions compete with wetting, filling and condensation producing very rich phase diagrams even for relatively simple geometries. We will also discuss practical aspects of DFT calculations, and demonstrate how this statistical-mechanical framework is capable of yielding complex fluid structure, interfacial tensions, and regions of thermodynamic stability of various fluid configurations. As a side note, this demonstrates that DFT is an excellent tool for the investigations of complex multiphase systems. We acknowledge financial support from the European Research Council via Advanced Grant No. 247031.

  18. Water dissociation and CO oxidation over Au/anatase catalyst. A DFT-D2 study

    Science.gov (United States)

    Saqlain, Muhammad Adnan; Hussain, Akhtar; Siddiq, Muhammad; Leitão, Alexandre A.

    2018-03-01

    With the help of DFT-D2 methodology, we have investigated the adsorption of water on clean anatase(001) and Au/anatase(001). In the former case, adsorption energies of H2O differ to small extent computed employing GGA = PW91 and DFT-D2 methods. While the GGA = PW91 predicts that water would desorb close to 650 K on the TiO2 surface, the DFT-D2 predicts that desorption is most likely to occur above 700 K. A comparison of water adsorption on TiO2 and Au/TiO2 surfaces shows that the TiO2 prefers dimer adsorption whereas the Au/TiO2 prefers monomer adsorption. We found that the diffusion of surface hydroxyls on to the Au cluster from the Au/TiO2 periphery is unlikely and it seems that the CO oxidation would occur at the Au/TiO2 boundary. The results show that water dissociation and CO oxidation steps occur easily on Au/TiO2 indicating that this could be good alternative catalyst for water gas shift reaction industry.

  19. Muon contact hyperfine field in metals: A DFT calculation

    Science.gov (United States)

    Onuorah, Ifeanyi John; Bonfà, Pietro; De Renzi, Roberto

    2018-05-01

    In positive muon spin rotation and relaxation spectroscopy it is becoming customary to take advantage of density functional theory (DFT) based computational methods to aid the experimental data analysis. DFT-aided muon site determination is especially useful for measurements performed in magnetic materials, where large contact hyperfine interactions may arise. Here we present a systematic analysis of the accuracy of the ab initio estimation of muon's hyperfine contact field on elemental transition metals, performing state-of-the-art spin-polarized plane-wave DFT and using the projector-augmented pseudopotential approach, which allows one to include the core state effects due to the spin ordering. We further validate this method in not-so-simple, noncentrosymmetric metallic compounds, presently of topical interest for their spiral magnetic structure giving rise to skyrmion phases, such as MnSi and MnGe. The calculated hyperfine fields agree with experimental values in all cases, provided the spontaneous spin magnetization of the metal is well reproduced within the approach. To overcome the known limits of the conventional mean-field approximation of DFT on itinerant magnets, we adopt the so-called reduced Stoner theory [L. Ortenzi et al., Phys. Rev. B 86, 064437 (2012), 10.1103/PhysRevB.86.064437]. We establish the accuracy of the estimated muon contact field in metallic compounds with DFT and our results show improved agreement with experiments compared to those of earlier publications.

  20. Optical Absorption Spectra and Electronic Properties of Symmetric and Asymmetric Squaraine Dyes for Use in DSSC Solar Cells: DFT and TD-DFT Studies

    Directory of Open Access Journals (Sweden)

    Reda M. El-Shishtawy

    2016-04-01

    Full Text Available The electronic absorption spectra, ground-state geometries and electronic structures of symmetric and asymmetric squaraine dyes (SQD1–SQD4 were investigated using density functional theory (DFT and time-dependent (TD-DFT density functional theory at the B3LYP/6-311++G** level. The calculated ground-state geometries reveal pronounced conjugation in these dyes. Long-range corrected time dependent density functionals Perdew, Burke and Ernzerhof (PBE, PBE1PBE (PBE0, and the exchange functional of Tao, Perdew, Staroverov, and Scuseria (TPSSh with 6-311++G** basis set were employed to examine optical absorption properties. In an extensive comparison between the optical data and DFT benchmark calculations, the BEP functional with 6-311++G** basis set was found to be the most appropriate in describing the electronic absorption spectra. The calculated energy values of lowest unoccupied molecular orbitals (LUMO were 3.41, 3.19, 3.38 and 3.23 eV for SQD1, SQD2, SQD3, and SQD4, respectively. These values lie above the LUMO energy (−4.26 eV of the conduction band of TiO2 nanoparticles indicating possible electron injection from the excited dyes to the conduction band of the TiO2 in dye-sensitized solar cells (DSSCs. Also, aromaticity computation for these dyes are in good agreement with the data obtained optically and geometrically with SQD4 as the highest aromatic structure. Based on the optimized molecular geometries, relative positions of the frontier orbitals, and the absorption maxima, we propose that these dyes are suitable components of photovoltaic DSSC devices.

  1. Charge Transfer Enhancement in the D-π-A Type Porphyrin Dyes: A Density Functional Theory (DFT and Time-Dependent Density Functional Theory (TD-DFT Study

    Directory of Open Access Journals (Sweden)

    Guo-Jun Kang

    2016-11-01

    Full Text Available The electronic geometries and optical properties of two D-π-A type zinc porphyrin dyes (NCH3-YD2 and TPhe-YD were systematically investigated by density functional theory (DFT and time-dependent density functional theory (TD-DFT to reveal the origin of significantly altered charge transfer enhancement by changing the electron donor of the famous porphyrin-based sensitizer YD2-o-C8. The molecular geometries and photophysical properties of dyes before and after binding to the TiO2 cluster were fully investigated. From the analyses of natural bond orbital (NBO, extended charge decomposition analysis (ECDA, and electron density variations (Δρ between the excited state and ground state, it was found that the introduction of N(CH32 and 1,1,2-triphenylethene groups enhanced the intramolecular charge-transfer (ICT character compared to YD2-o-C8. The absorption wavelength and transition possess character were significantly influenced by N(CH32 and 1,1,2-triphenylethene groups. NCH3-YD2 with N(CH32 groups in the donor part is an effective way to improve the interactions between the dyes and TiO2 surface, light having efficiency (LHE, and free energy change (ΔGinject, which is expected to be an efficient dye for use in dye-sensitized solar cells (DSSCs.

  2. FAST TRACK COMMUNICATION A DFT + DMFT approach for nanosystems

    Science.gov (United States)

    Turkowski, Volodymyr; Kabir, Alamgir; Nayyar, Neha; Rahman, Talat S.

    2010-11-01

    We propose a combined density-functional-theory-dynamical-mean-field-theory (DFT + DMFT) approach for reliable inclusion of electron-electron correlation effects in nanosystems. Compared with the widely used DFT + U approach, this method has several advantages, the most important of which is that it takes into account dynamical correlation effects. The formalism is illustrated through different calculations of the magnetic properties of a set of small iron clusters (number of atoms 2 <= N <= 5). It is shown that the inclusion of dynamical effects leads to a reduction in the cluster magnetization (as compared to results from DFT + U) and that, even for such small clusters, the magnetization values agree well with experimental estimations. These results justify confidence in the ability of the method to accurately describe the magnetic properties of clusters of interest to nanoscience.

  3. Conformational, vibrational, NMR and DFT studies of N-methylacetanilide.

    Science.gov (United States)

    Arjunan, V; Santhanam, R; Rani, T; Rosi, H; Mohan, S

    2013-03-01

    A detailed conformational, vibrational, NMR and DFT studies of N-methylacetanilide have been carried out. In DFT, B3LYP method have been used with 6-31G(**), 6-311++G(**) and cc-pVTZ basis sets. The vibrational frequencies were calculated resulting in IR and Raman frequencies together with intensities and Raman depolarisation ratios. The dipole moment derivatives were computed analytically. Owing to the complexity of the molecule, the potential energy distributions of the vibrational modes of the compound are also calculated. Isoelectronic molecular electrostatic potential surface (MEP) and electron density surface were examined. (1)H and (13)C NMR isotropic chemical shifts were calculated and the assignments made are compared with the experimental values. The energies of important MO's of the compound were also determined from TD-DFT method. Copyright © 2012 Elsevier B.V. All rights reserved.

  4. Prediction Errors of Molecular Machine Learning Models Lower than Hybrid DFT Error.

    Science.gov (United States)

    Faber, Felix A; Hutchison, Luke; Huang, Bing; Gilmer, Justin; Schoenholz, Samuel S; Dahl, George E; Vinyals, Oriol; Kearnes, Steven; Riley, Patrick F; von Lilienfeld, O Anatole

    2017-11-14

    We investigate the impact of choosing regressors and molecular representations for the construction of fast machine learning (ML) models of 13 electronic ground-state properties of organic molecules. The performance of each regressor/representation/property combination is assessed using learning curves which report out-of-sample errors as a function of training set size with up to ∼118k distinct molecules. Molecular structures and properties at the hybrid density functional theory (DFT) level of theory come from the QM9 database [ Ramakrishnan et al. Sci. Data 2014 , 1 , 140022 ] and include enthalpies and free energies of atomization, HOMO/LUMO energies and gap, dipole moment, polarizability, zero point vibrational energy, heat capacity, and the highest fundamental vibrational frequency. Various molecular representations have been studied (Coulomb matrix, bag of bonds, BAML and ECFP4, molecular graphs (MG)), as well as newly developed distribution based variants including histograms of distances (HD), angles (HDA/MARAD), and dihedrals (HDAD). Regressors include linear models (Bayesian ridge regression (BR) and linear regression with elastic net regularization (EN)), random forest (RF), kernel ridge regression (KRR), and two types of neural networks, graph convolutions (GC) and gated graph networks (GG). Out-of sample errors are strongly dependent on the choice of representation and regressor and molecular property. Electronic properties are typically best accounted for by MG and GC, while energetic properties are better described by HDAD and KRR. The specific combinations with the lowest out-of-sample errors in the ∼118k training set size limit are (free) energies and enthalpies of atomization (HDAD/KRR), HOMO/LUMO eigenvalue and gap (MG/GC), dipole moment (MG/GC), static polarizability (MG/GG), zero point vibrational energy (HDAD/KRR), heat capacity at room temperature (HDAD/KRR), and highest fundamental vibrational frequency (BAML/RF). We present numerical

  5. Implementation of DFT application on ternary optical computer

    Science.gov (United States)

    Junjie, Peng; Youyi, Fu; Xiaofeng, Zhang; Shuai, Kong; Xinyu, Wei

    2018-03-01

    As its characteristics of huge number of data bits and low energy consumption, optical computing may be used in the applications such as DFT etc. which needs a lot of computation and can be implemented in parallel. According to this, DFT implementation methods in full parallel as well as in partial parallel are presented. Based on resources ternary optical computer (TOC), extensive experiments were carried out. Experimental results show that the proposed schemes are correct and feasible. They provide a foundation for further exploration of the applications on TOC that needs a large amount calculation and can be processed in parallel.

  6. DFT and TD-DFT computation of charge transfer complex between o-phenylenediamine and 3,5-dinitrosalicylic acid

    International Nuclear Information System (INIS)

    Afroz, Ziya; Zulkarnain,; Ahmad, Afaq; Alam, Mohammad Jane; Faizan, Mohd; Ahmad, Shabbir

    2016-01-01

    DFT and TD-DFT studies of o-phenylenediamine (PDA), 3,5-dinitrosalicylic acid (DNSA) and their charge transfer complex have been carried out at B3LYP/6-311G(d,p) level of theory. Molecular geometry and various other molecular properties like natural atomic charges, ionization potential, electron affinity, band gap, natural bond orbital (NBO) and frontier molecular analysis have been presented at same level of theory. Frontier molecular orbital and natural bond orbital analysis show the charge delocalization from PDA to DNSA.

  7. Study of a Conformational Equilibrium of Lisinopril by HPLC, NMR, and DFT

    Directory of Open Access Journals (Sweden)

    Sondes Bouabdallah

    2014-01-01

    Full Text Available The isomerization of lisinopril has been investigated using chromatographic, NMR spectroscopic, and theoretical calculations. The NMR data, particularly the NOEDIFF experiments, show that the major species that was eluted first is the trans form. The proportion was 77% and 23% for the trans and cis, respectively. The thermodynamic parameters (ΔH, ΔS, and ΔG were determined by varying the temperature in the NMR experiments. The interpretations of the experimental data were further supported by DFT/B3LYP calculations.

  8. Thermal properties of black phosphorene and doped phosphorene (C, N & O): A DFT study

    Science.gov (United States)

    Devi, Anjna; Singh, Amarjeet

    2018-04-01

    In this work, we present the results from a DFT based computational study of pristine phosphorene and doped (C, N & O) phosphorene. We systematically investigated the lattice thermal properties of black phosphorene and the effect of doping on its thermal properties. We first determined the vibrational properties of pristine and doped phosphorene and from these results we calculated their thermal properties. We doped the phosphorene with C, N and O and observed that the structural stability of doped phosphorene decreases, while the thermal stability is increased as compared to pristine phosphorene. The presence of finite temperature effects in the doped system can contribute to acceleration of progress in future nano-scale technology.

  9. DFT reactivity indices in confined many-electron atoms + ∫

    Indian Academy of Sciences (India)

    Unknown

    Functional Theory (DFT) based global descriptors of chemical reactivity for atoms .... interesting due to its utility as a model in the wide variety of applications ... hydrogen atom at Rc = 2⋅0 au is expected to correspond to the energy value of ...

  10. CHANNEL ESTIMATION FOR ZT DFT-s-OFDM

    DEFF Research Database (Denmark)

    2018-01-01

    A signal modulated according to zero-tail discrete Fourier transform spread orthogonal frequency division multiplexing (ZT DFT-s-OFDM) is received over a channel. The signal is down-sampled into a first sequence comprising N samples, N corresponding to the number of used subcarriers. The first Nh...

  11. DFT computations of the lattice constant, stable atomic structure and ...

    African Journals Online (AJOL)

    This paper presents the most stable atomic structure and lattice constant of Fullerenes (C60). FHI-aims DFT code was used to predict the stable structure and the computational lattice constant of C60. These were compared with known experimental structures and lattice constants of C60. The results obtained showed that ...

  12. Experimental demonstration of OFDM/OQAM transmission with DFT-based channel estimation for visible laser light communications

    Science.gov (United States)

    He, Jing; Shi, Jin; Deng, Rui; Chen, Lin

    2017-08-01

    Recently, visible light communication (VLC) based on light-emitting diodes (LEDs) is considered as a candidate technology for fifth-generation (5G) communications, VLC is free of electromagnetic interference and it can simplify the integration of VLC into heterogeneous wireless networks. Due to the data rates of VLC system limited by the low pumping efficiency, small output power and narrow modulation bandwidth, visible laser light communication (VLLC) system with laser diode (LD) has paid more attention. In addition, orthogonal frequency division multiplexing/offset quadrature amplitude modulation (OFDM/OQAM) is currently attracting attention in optical communications. Due to the non-requirement of cyclic prefix (CP) and time-frequency domain well-localized pulse shapes, it can achieve high spectral efficiency. Moreover, OFDM/OQAM has lower out-of-band power leakage so that it increases the system robustness against inter-carrier interference (ICI) and frequency offset. In this paper, a Discrete Fourier Transform (DFT)-based channel estimation scheme combined with the interference approximation method (IAM) is proposed and experimentally demonstrated for VLLC OFDM/OQAM system. The performance of VLLC OFDM/OQAM system with and without DFT-based channel estimation is investigated. Moreover, the proposed DFT-based channel estimation scheme and the intra-symbol frequency-domain averaging (ISFA)-based method are also compared for the VLLC OFDM/OQAM system. The experimental results show that, the performance of EVM using the DFT-based channel estimation scheme is improved about 3dB compared with the conventional IAM method. In addition, the DFT-based channel estimation scheme can resist the channel noise effectively than that of the ISFA-based method.

  13. Prototropic tautomerism of 4-Methyl 1,2,4-Triazole-3-Thione molecule in solvent water medium: DFT and Car–Parrinello molecular dynamics study

    International Nuclear Information System (INIS)

    Dutta, Bipan; De, Rina; Chowdhury, Joydeep

    2015-01-01

    Highlights: • The tautomerism of 4-MTTN molecule in solvent water medium has been investigated. • CPMD presage the possibility of PT reactions through the solvent water medium. • Concerted PT processes in 4-MTTN have been estimated from the DFT and NBO analyses. • Percentage evolution and breaking of the concerned bonds are estimated. - Abstract: The ground state prototropic tautomerism of 4-Methyl 1,2,4-Triazole-3-Thione molecule in solvent water medium has been investigated with the aid of DFT and Car–Parrinello molecular dynamics (CPMD) simulation studies. The CPMD simulations envisage the possibility of proton transfer reactions of the molecule through the solvent water medium. Probable proton transfer pathways have been predicted from the DFT calculations which are substantiated by the natural bond orbital analyses. The evolution and breaking of the concerned bonds of the molecule for different proton transfer reaction pathways are also estimated.

  14. Anatase-rutile phase transformation of titanium dioxide bulk material: a DFT + U approach

    International Nuclear Information System (INIS)

    Vu, Nam H; Le, Hieu V; Cao, Thi M; Pham, Viet V; Le, Hung M; Nguyen-Manh, Duc

    2012-01-01

    The anatase-rutile phase transformation of TiO 2 bulk material is investigated using a density functional theory (DFT) approach in this study. According to the calculations employing the Perdew-Burke-Ernzerhof (PBE) exchange-correlation functional with the Vanderbilt ultrasoft pseudopotential, it is suggested that the anatase phase is more energetically stable than rutile, which is in variance with the experimental observations. Consequently, the DFT + U method is employed in order to predict the correct structural stability in titania from electronic-structure-based total energy calculations. The Hubbard U term is determined by examining the band structure of rutile with various values of U from 3 to 10 eV. At U = 5 eV, a theoretical bandgap for rutile is obtained as 3.12 eV, which is in very good agreement with the reported experimental bandgap. Hence, we choose the DFT + U method (with U = 5 eV) to investigate the transformation pathway using the newly-developed solid-state nudged elastic band (ss-NEB) method, and consequently obtain an intermediate transition structure that is 9.794 eV per four-TiO 2 above the anatase phase. When the Ti-O bonds in the transition state are examined using charge density analysis, seven Ti-O bonds (out of 24 bonds in the anatase unit cell) are broken, and this result is in excellent agreement with a previous experimental study (Penn and Banfield 1999 Am. Miner. 84 871-6).

  15. Synthesis, structural, DFT studies, docking and antibacterial activity of a xanthene based hydrazone ligand

    Science.gov (United States)

    Naseem, Saira; Khalid, Muhammad; Tahir, Muhammad Nawaz; Halim, Mohammad A.; Braga, Ataualpa A. C.; Naseer, Muhammad Moazzam; Shafiq, Zahid

    2017-09-01

    Herein, we present the synthesis of novel xanthene-based hydrazone (1). The chemical structure of 1 was resolved using spectroscopic techniques such as NMR, FT-IR, UV-VIS and X-ray crystallographic approaches. X-ray diffraction analysis shows that the compound (1) crystallizes in triclinic crystal lattice with the Pbar1 space group and diffused to form multi-layered structure due to non-covalent interactions such as intramolecular hydrogen bonding (H.B). In addition to experimental investigation, density functional theory (DFT) calculation with M06-2X/6-31G(d,p) and B3LYP/6-31G(d,p) level of theories was performed on compound (1) to obtain optimized geometry, spectroscopic and electronic properties. DFT optimized geometry shows good agreement with the experimental XRD structure. The hyper conjugative interactions and hydrogen bonding network are responsible for the stability of compound (1) as revealed by natural bond orbital (NBO) calculation. Moreover, hydrogen bonding network in the dimer is confirmed by FT-IR and thermodynamic studies showing excellent agreement with XRD and NBO findings. TD-DFT/UV-VIS analysis provides insight that maximum excitation is found in 1 which shows good agreement with experimental UV-VIS result. The global reactivity parameters are calculated using the energies of frontier molecular orbitals also disclosed that the compound is more stable might be due to hydrogen bonding network. Experimental and molecular docking studies indicated that this compound has anti-bacterial and anti-diabetic properties. The binding affinity of this compound against the multidrug efflux pump subunit AcrB OS=Escherichia coli (strain K12) and Human Pancreatic Alpha-Amylase is -9.2 and -10.00 kcal/mol which are higher than the control drugs. Pi-Pi, Pi-anaion, amide-pi and pi-alkyl bonds play key role in drug-protein complexes.

  16. TD-DFT Insight into Photodissociation of Co-C Bond in Coenzyme B12

    Directory of Open Access Journals (Sweden)

    Pawel Michal Kozlowski

    2014-02-01

    Full Text Available Coenzyme B12 (AdoCbl is one of the most biologically active forms of vitamin B12, and continues to be a topic of active research interest. The mechanism of Co-C bond cleavage in AdoCbl, and the corresponding enzymatic reactions are however, not well understood at the molecular level. In this work, time-dependent density functional theory (TD-DFT has been applied to investigate the photodissociation of coenzyme B12. To reduce computational cost, while retaining the major spectroscopic features of AdoCbl, a truncated model based on ribosylcobalamin (RibCbl was used to simulate Co-C photodissociation. Equilibrium geometries of RibCbl were obtained by optimization at the DFT/BP86/TZVP level of theory, and low-lying excited states were calculated by TD-DFT using the same functional and basis set. The calculated singlet states, and absorption spectra were simulated in both the gas phase, and water, using the polarizable continuum model (PCM. Both spectra were in reasonable agreement with experimental data, and potential energy curves based on vertical excitations were plotted to explore the nature of Co-C bond dissociation. It was found that a repulsive 3(σCo-C → σ*Co-C triplet state became dissociative at large Co-C bond distance, similar to a previous observation for methylcobalamin (MeCbl. Furthermore, potential energy surfaces (PESs obtained as a function of both Co-CRib and Co-NIm distances, identify the S1 state as a key intermediate generated during photoexcitation of RibCbl, attributed to a mixture of a MLCT (metal-to-ligand charge transfer and a σ bonding-ligand charge transfer (SBLCT states.

  17. Combined MCD/DFT/TDDFT Study of the Electronic Structure of Axially Pyridine Coordinated Metallocorroles.

    Science.gov (United States)

    Rhoda, Hannah M; Crandall, Laura A; Geier, G Richard; Ziegler, Christopher J; Nemykin, Victor N

    2015-05-18

    A series of metallocorroles were investigated by UV-vis and magnetic circular dichroism spectroscopies. The diamagnetic distorted square-pyramidal main-group corrole Ga(tpfc)py (2), the diamagnetic distorted octahedral transition-metal adduct Co(tpfc)(py)2 (3), and paramagnetic distorted octahedral transition-metal complex Fe(tpfc)(py)2 (4) [H3tpfc = tris(perfluorophenyl)corrole] were studied to investigate similarities and differences in the electronic structure and spectroscopy of the closed- and open-shell metallocorroles. Similar to the free-base H3tpfc (1), inspection of the MCD Faraday B-terms for all of the macrocycles presented in this report revealed that a ΔHOMO MCD spectra. In addition, the MCD spectra of the cobalt and the iron complexes were also complicated by a number of charge-transfer states in the visible region. Iron complex 4 also exhibits a low-energy absorption in the NIR region (1023 nm). DFT and TDDFT calculations were used to elaborate the electronic structures and provide band assignments in UV-vis and MCD spectra of the metallocorroles. DFT and TDDFT calculations predict that the orientation of the axial pyridine ligand(s) has a very minor influence on the calculated electronic structures and absorption spectra in the target systems.

  18. Thermodynamic DFT analysis of natural gas.

    Science.gov (United States)

    Neto, Abel F G; Huda, Muhammad N; Marques, Francisco C; Borges, Rosivaldo S; Neto, Antonio M J C

    2017-08-01

    Density functional theory was performed for thermodynamic predictions on natural gas, whose B3LYP/6-311++G(d,p), B3LYP/6-31+G(d), CBS-QB3, G3, and G4 methods were applied. Additionally, we carried out thermodynamic predictions using G3/G4 averaged. The calculations were performed for each major component of seven kinds of natural gas and to their respective air + natural gas mixtures at a thermal equilibrium between room temperature and the initial temperature of a combustion chamber during the injection stage. The following thermodynamic properties were obtained: internal energy, enthalpy, Gibbs free energy and entropy, which enabled us to investigate the thermal resistance of fuels. Also, we estimated an important parameter, namely, the specific heat ratio of each natural gas; this allowed us to compare the results with the empirical functions of these parameters, where the B3LYP/6-311++G(d,p) and G3/G4 methods showed better agreements. In addition, relevant information on the thermal and mechanic resistance of natural gases were investigated, as well as the standard thermodynamic properties for the combustion of natural gas. Thus, we show that density functional theory can be useful for predicting the thermodynamic properties of natural gas, enabling the production of more efficient compositions for the investigated fuels. Graphical abstract Investigation of the thermodynamic properties of natural gas through the canonical ensemble model and the density functional theory.

  19. ANTIBACTERIAL ACTIVITIES, DFT AND QSAR STUDIES OF ...

    African Journals Online (AJOL)

    Latif Hesham4. 1Department of ... [5] and characterized, see Figure 1. In the present study, our aim is to investigate the antibacterial activity of 1 and 2. Moreover, ..... in Figure 3. The pink color parts embody the regions of negative electrostatic.

  20. Appropriate description of intermolecular interactions in the methane hydrates: an assessment of DFT methods.

    Science.gov (United States)

    Liu, Yuan; Zhao, Jijun; Li, Fengyu; Chen, Zhongfang

    2013-01-15

    Accurate description of hydrogen-bonding energies between water molecules and van der Waals interactions between guest molecules and host water cages is crucial for study of methane hydrates (MHs). Using high-level ab initio MP2 and CCSD(T) results as the reference, we carefully assessed the performance of a variety of exchange-correlation functionals and various basis sets in describing the noncovalent interactions in MH. The functionals under investigation include the conventional GGA, meta-GGA, and hybrid functionals (PBE, PW91, TPSS, TPSSh, B3LYP, and X3LYP), long-range corrected functionals (ωB97X, ωB97, LC-ωPBE, CAM-B3LYP, and LC-TPSS), the newly developed Minnesota class functionals (M06-L, M06-HF, M06, and M06-2X), and the dispersion-corrected density functional theory (DFT) (DFT-D) methods (B97-D, ωB97X-D, PBE-TS, PBE-Grimme, and PW91-OBS). We found that the conventional functionals are not suitable for MH, notably, the widely used B3LYP functional even predicts repulsive interaction between CH(4) and (H(2)O)(6) cluster. M06-2X is the best among the M06-Class functionals. The ωB97X-D outperforms the other DFT-D methods and is recommended for accurate first-principles calculations of MH. B97-D is also acceptable as a compromise of computational cost and precision. Considering both accuracy and efficiency, B97-D, ωB97X-D, and M06-2X functional with 6-311++G(2d,2p) basis set without basis set superposition error (BSSE) correction are recommended. Though a fairly large basis set (e.g., aug-cc-pVTZ) and BSSE correction are necessary for a reliable MP2 calculation, DFT methods are less sensitive to the basis set and BSSE correction if the basis set is sufficient (e.g., 6-311++G(2d,2p)). These assessments provide useful guidance for choosing appropriate methodology of first-principles simulation of MH and related systems. © 2012 Wiley Periodicals, Inc. Copyright © 2012 Wiley Periodicals, Inc.

  1. DFT Study of dimers of dimethyl sulfoxide in gas phase

    Directory of Open Access Journals (Sweden)

    Reza Fazaeli

    2014-10-01

    Full Text Available Density functional (DFT calculations at M05-2x/aug-cc-pVDZ level were used to analyze the interactions between dimethyl sulfoxide (DMSO dimers. The structures obtained have been ana-lyzed with the Atoms in Molecules (AIMs and Natural Bond Orbital (NBO methodologies. Four minima were located on the potential energy surface of the dimers. Three types of interac-tions are observed, CH•••O, CH•••S hydrogen bonds and orthogonal interaction between the lone pair of the oxygen with the electron-deficient region of the sulfur atom. Stabilization energies of dimers including BSSE and ZPE are in the range 27–40 kJmol-1. The most stable conformers of dimers at DFT level is cyclic structure with antiparallel orientation of S=O groups pairing with three C–H∙∙∙O and a S∙∙∙O interactions.

  2. DFT Study of Optical Properties of Pt-based Complexes

    Science.gov (United States)

    Oprea, Corneliu I.; Dumbravǎ, Anca; Moscalu, Florin; Nicolaides, Atnanassios; Gîrţu, Mihai A.

    2010-01-01

    We report Density Functional Theory (DFT) calculations providing the geometrical and electronic structures, as well as the vibrational and optical properties of the homologous series of Pt-pyramidalized olefin complexes (CH2)n-(C8H10)Pt(PH3)2, where n = 0, 1, and 2, in their neutral and oxidized states. All complexes were geometry optimized for the singlet ground state in vacuum using DFT methods with B3LYP exchange-correlation functional and the Effective Core Potential LANL2DZ basis set, within the frame of Gaussian03 quantum chemistry package. We find the coordination geometry of Pt to be distorted square planar, with dihedral angles ranging from 0°, for n = 0 and 1, which have C2V symmetry to 3.4°, for n = 2 with C2 symmetry. The Mulliken charge analysis allows a discussion of the oxidation state of the Pt ion. Electronic transitions were calculated at the same level of theory by means of Time Dependant-DFT. For n = 2 the electronic absorption bands are located in the UV region of the spectrum, the transitions being assigned to metal to ligand charge transfers. The relevance of these Pt-based compounds as possible pigments for dye-sensitized solar cells is discussed.

  3. Screened coulomb hybrid DFT study on electronic structure and optical properties of anionic and cationic Te-doped anatase TiO2

    KAUST Repository

    Harb, Moussab

    2013-01-01

    The origin of the enhanced visible-light optical absorption in Te-doped bulk anatase TiO2 is investigated in the framework of DFT and DFPT within HSE06 in order to ensure accurate electronic structure and optical transition predictions. Various

  4. Solid-State NMR and DFT Studies on the Formation of Well-Defined Silica-Supported Tantallaaziridines: From Synthesis to Catalytic Application

    KAUST Repository

    Hamzaoui, Bilel; Pelletier, Jeremie; Abou-Hamad, Edy; Chen, Yin; El Eter, Mohamad; Chermak, Edrisse; Cavallo, Luigi; Basset, Jean-Marie

    2016-01-01

    spectroscopy, elemental analysis, and 1H,13C HETCOR and DQ TQ solid-state (SS) NMR spectroscopy. The formation mechanism, by β-H abstraction, was investigated by SS NMR spectroscopy and supported by DFT calculations. The C-H activation of the dimethylamide

  5. Synthesis, characterization, spectroscopic properties and DFT study of a new pyridazinone family

    Science.gov (United States)

    Arrue, Lily; Rey, Marina; Rubilar-Hernandez, Carlos; Correa, Sebastian; Molins, Elies; Norambuena, Lorena; Zarate, Ximena; Schott, Eduardo

    2017-11-01

    Nitrogen compounds are widely investigated due to their pharmacological properties such as antihypertensive, antinociceptive, antibacterial, antifungal, analgesic, anticancer and inhibition activities and lately even as pesticide. In this context, we present the synthesis of new compounds: (E)-6-(3,4-dimethoxyphenyl)-3-(3-(3,4-dimethoxyphenyl)acryloyl)-1-(4-R-phenyl)- 5,6-dihydropyridazin-4(1H)-one (with R = sbnd H(1), -Cl(2), -Br(3), sbnd I(4) and sbnd COOH(5)) that was carried out by reaction of (1E, 6E)-1,7-bis(3,4-dimethoxyphenyl)hepta-1,6-diene-3,5-dione with a substituted phenylamine with general formula p-R-C6H4sbnd NH2 (R = sbnd H (1), sbnd Cl (2), -Br(3), sbnd I(4) and sbnd COOH(5)). This is the first synthesis report of a pyridazinone using as precursors a curcuminoid derivative and a diazonium salt formed in situ. All compounds were characterized by EA, FT-IR, UV-Vis, Emission,1H- and13C-NMR spectroscopy and the crystalline and molecular structure of 4 was solved by X-rays diffraction method. DFT and TD-DFT quantum chemical calculations were also employed to characterize the compounds and provide a rational explanation to the spectroscopic properties. To assess the biological activity of the systems, we focused on pesticide tests on compound 2, which showed an inhibitory effect in plant growth of Agrostis tenuis Higland.

  6. Benchmarking fully analytic DFT force fields for vibrational spectroscopy: A study on halogenated compounds

    Science.gov (United States)

    Pietropolli Charmet, Andrea; Cornaton, Yann

    2018-05-01

    This work presents an investigation of the theoretical predictions yielded by anharmonic force fields having the cubic and quartic force constants are computed analytically by means of density functional theory (DFT) using the recursive scheme developed by M. Ringholm et al. (J. Comput. Chem. 35 (2014) 622). Different functionals (namely B3LYP, PBE, PBE0 and PW86x) and basis sets were used for calculating the anharmonic vibrational spectra of two halomethanes. The benchmark analysis carried out demonstrates the reliability and overall good performances offered by hybrid approaches, where the harmonic data obtained at the coupled cluster with single and double excitations level of theory augmented by a perturbational estimate of the effects of connected triple excitations, CCSD(T), are combined with the fully analytic higher order force constants yielded by DFT functionals. These methods lead to reliable and computationally affordable calculations of anharmonic vibrational spectra with an accuracy comparable to that yielded by hybrid force fields having the anharmonic force fields computed at second order Møller-Plesset perturbation theory (MP2) level of theory using numerical differentiation but without the corresponding potential issues related to computational costs and numerical errors.

  7. Synthesis, FTIR, FT-Raman, UV-visible, ab initio and DFT studies on benzohydrazide.

    Science.gov (United States)

    Arjunan, V; Rani, T; Mythili, C V; Mohan, S

    2011-08-01

    A systematic vibrational spectroscopic assignment and analysis of benzohydrazide (BH) has been carried out by using FTIR and FT-Raman spectral data. The vibrational analysis were aided by electronic structure calculations--ab initio (RHF) and hybrid density functional methods (B3LYP and B3PW91) performed with 6-31G(d,p) and 6-311++G(d,p) basis sets. Molecular equilibrium geometries, electronic energies, IR intensities, harmonic vibrational frequencies, depolarization ratios and Raman activities have been computed. Potential energy distribution (PED) and normal mode analysis have also been performed. The assignments proposed based on the experimental IR and Raman spectra have been reviewed and complete assignment of the observed spectra have been proposed. UV-visible spectrum of the compound was also recorded and the electronic properties, such as HOMO and LUMO energies and λ(max) were determined by time-dependent DFT (TD-DFT) method. The geometrical, thermodynamical parameters and absorption wavelengths were compared with the experimental data. The interactions of carbonyl and hydrazide groups on the benzene ring skeletal modes were investigated. Copyright © 2011 Elsevier B.V. All rights reserved.

  8. Channel estimation in DFT-based offset-QAM OFDM systems.

    Science.gov (United States)

    Zhao, Jian

    2014-10-20

    Offset quadrature amplitude modulation (offset-QAM) orthogonal frequency division multiplexing (OFDM) exhibits enhanced net data rates compared to conventional OFDM, and reduced complexity compared to Nyquist FDM (N-FDM). However, channel estimation in discrete-Fourier-transform (DFT) based offset-QAM OFDM is different from that in conventional OFDM and requires particular study. In this paper, we derive a closed-form expression for the demultiplexed signal in DFT-based offset-QAM systems and show that although the residual crosstalk is orthogonal to the decoded signal, its existence degrades the channel estimation performance when the conventional least-square method is applied. We propose and investigate four channel estimation algorithms for offset-QAM OFDM that vary in terms of performance, complexity, and tolerance to system parameters. It is theoretically and experimentally shown that simple channel estimation can be realized in offset-QAM OFDM with the achieved performance close to the theoretical limit. This, together with the existing advantages over conventional OFDM and N-FDM, makes this technology very promising for optical communication systems.

  9. Structural and Molecular Characterization of meso-Substituted Zinc Porphyrins: A DFT Supported Study

    Directory of Open Access Journals (Sweden)

    Giuseppe Mele

    2011-12-01

    Full Text Available Structural parameters of a range of over 100 meso-substituted zinc porphyrins were reviewed and compared to show how far the nature of the functional group may affect the interatomic distances and bond angles within the porphyrin core. It was proved that even despite evident deformations of the molecular structure, involving twisting of the porphyrin's central plane, the coupled π-bonding system remains flexible and stable. DFT calculations were applied to a number of selected porphyrins representative for the reviewed compounds to emphasize the relevance of theoretical methods in structural investigations of complex macrocyclic molecular systems. Experimental and DFT-simulated IR spectral data were reported and analyzed in context of the individual molecular features introduced by the meso substituents into the porphyrin moiety base. Raw experimental spectral data, including 1H- and 13C-NMR, UV-Vis, FTIR, XRD, and other relevant physicochemical details have been provided for a specially chosen reference zinc porphyrin functionalized by tert-butylphenyl groups.

  10. 6-Aminocoumarin-naphthoquinone conjugates: design, synthesis, photophysical and electrochemical properties and DFT calculations

    Energy Technology Data Exchange (ETDEWEB)

    Miranda, Fabio S.; Ronconi, Celia M.; Sousa, Mikaelly O.B.; Silveira, Gleiciani Q.; Vargas, Maria D., E-mail: miranda@vm.uff.br, E-mail: mdvargascp@gmail.com [Universidade Federal Fluminense (UFF), Niteroi, RJ (Brazil). Inst. de Quimica

    2014-01-15

    Four novel 6-aminocoumarin-naphthoquinone conjugates were synthesized and their photophysical and electrochemical properties, investigated. 2-Chloro-3-(2-oxo-2H-chromen-6- ylamino)-1,4-naphthoquinone 1 did not present appreciable fluorescence in solution in comparison with 6-aminocoumarin, 6-AC. In order to understand the reasons for the fluorescence quenching in this compound, two strategies were attempted. Firstly, compound 1 was N-methylated to remove the intramolecular N-H...O=C electrostatic interaction that maintained the two units fixed, but the emission properties of the product 2 were not significantly different from those of 1. Time-dependent density functional theory (TD-DFT) calculations of compounds 1 and 2 indicate that the fluorescence quenching is related to the electron acceptor character of the naphthoquinone ring. The second strategy, therefore, involved the substitution of the chlorine atom in position 2 of the naphthoquinone nucleus for different electron donor groups (compounds 3-5), but again the emission properties did not change significantly. To explain these experimental findings, TD-DFT calculations of the ground (S{sub 0}) and excited (S{sub 1}) states of all molecules in solution were carried out. The results suggest that the energy states in these conjugates are such that the fluorescent group (6-AC) donates electrons to the naphthoquinone LUMO resulting in an oxidative photoinduced electron transfer (oxidative-PET). (author)

  11. DFT study of Al doped armchair SWCNTs

    Energy Technology Data Exchange (ETDEWEB)

    Dhiman, Shobhna, E-mail: s-dhiman@hotmail.com [Department of Applied Science, PEC, University of Technology, Chandigarh -160012 (India); Rani, Anita [Guru Nanak College for Girls, Sri Muktsar Sahib, Punjab-152026 (India); Kumar, Ranjan; Dharamvir, Keya [Department of Physics, Panjab University, Chandigarh-160014 (India)

    2016-05-23

    Electronic properties of endohedrally doped armchair single-walled carbon nanotubes (SWCNTs) with a chain of six Al atoms have been studied using ab-initio density functional theory. We investigate the binding energy/atom, ionization potential, electron Affinity and Homo-Lumo gap of doped armchair SWNTs from (4,4) to (6,6) with two ends open. BE/dopant atom and ionization potential is maximum for (6, 6) doped armchair carbon nanotube; suggest that it is more stable than (4, 4) and (5, 5) doped tubes. HOMO - LUMO gap of Al doped arm chair carbon nanotubes decreases linearly with the increase in diameter of the tube. This shows that confinement induce a strong effect on electronic properties of doped tubes. These combined systems can be used for future nano electronics. The ab–initio calculations were performed with SIESTA code using generalized gradient approximation (GGA).

  12. Charge transfer complex between 2,3-diaminopyridine with chloranilic acid. Synthesis, characterization and DFT, TD-DFT computational studies

    Science.gov (United States)

    Al-Ahmary, Khairia M.; Habeeb, Moustafa M.; Al-Obidan, Areej H.

    2018-05-01

    New charge transfer complex (CTC) between the electron donor 2,3-diaminopyridine (DAP) with the electron acceptor chloranilic (CLA) acid has been synthesized and characterized experimentally and theoretically using a variety of physicochemical techniques. The experimental work included the use of elemental analysis, UV-vis, IR and 1H NMR studies to characterize the complex. Electronic spectra have been carried out in different hydrogen bonded solvents, methanol (MeOH), acetonitrile (AN) and 1:1 mixture from AN-MeOH. The molecular composition of the complex was identified to be 1:1 from Jobs and molar ratio methods. The stability constant was determined using minimum-maximum absorbances method where it recorded high values confirming the high stability of the formed complex. The solid complex was prepared and characterized by elemental analysis that confirmed its formation in 1:1 stoichiometric ratio. Both IR and NMR studies asserted the existence of proton and charge transfers in the formed complex. For supporting the experimental results, DFT computations were carried out using B3LYP/6-31G(d,p) method to compute the optimized structures of the reactants and complex, their geometrical parameters, reactivity parameters, molecular electrostatic potential map and frontier molecular orbitals. The analysis of DFT results strongly confirmed the high stability of the formed complex based on existing charge transfer beside proton transfer hydrogen bonding concordant with experimental results. The origin of electronic spectra was analyzed using TD-DFT method where the observed λmax are strongly consisted with the computed ones. TD-DFT showed the contributed states for various electronic transitions.

  13. DFT/TD-DFT characterization of conjugational electronic structures and spectral properties of materials based on thieno[3,2-b][1]benzothiophene for organic photovoltaic and solar cell applications

    Directory of Open Access Journals (Sweden)

    Mohamed Bourass

    2017-07-01

    Full Text Available In this work, a theoretical study on five organic π-conjugated molecules based on thieno[3,2-b][1]benzothiophene using together quantum methods, density functional theory (DFT and its derivative time dependent-density functional theory (TD-DFT is reported. Different electron side groups were introduced as a bridge to investigate their effects on the electronic structure; The HOMO, LUMO, chemical hardness (η, chemical potential (μ, electronegativity (χ, electrophilicity power (ω, reorganization energy total (λtotal, open circuit voltage (Voc, the gap energy and NBO analysis of these compounds have been reported and discussed in this paper. Thus, our aim is to explore their electronic and spectroscopic properties on the basis of the DFT quantum chemical calculations, and at the same time, we are interested to make an idea on the parameters influencing the photovoltaic efficiency toward a better understanding of the structure–property relationships. The calculated results of these compounds reveal that C4, C5, with thiophene and thienopyrazine as a bridge group respectively, can be used as a potential donor of electron in organic Bulk Heterojunction solar cells (BHJ, due to its best electronic and optical properties and good photovoltaic parameters. The study of electronic, optical and structural properties of these compounds could help to design more efficient functional photovoltaic organic materials.

  14. Self-consistent DFT +U method for real-space time-dependent density functional theory calculations

    Science.gov (United States)

    Tancogne-Dejean, Nicolas; Oliveira, Micael J. T.; Rubio, Angel

    2017-12-01

    We implemented various DFT+U schemes, including the Agapito, Curtarolo, and Buongiorno Nardelli functional (ACBN0) self-consistent density-functional version of the DFT +U method [Phys. Rev. X 5, 011006 (2015), 10.1103/PhysRevX.5.011006] within the massively parallel real-space time-dependent density functional theory (TDDFT) code octopus. We further extended the method to the case of the calculation of response functions with real-time TDDFT+U and to the description of noncollinear spin systems. The implementation is tested by investigating the ground-state and optical properties of various transition-metal oxides, bulk topological insulators, and molecules. Our results are found to be in good agreement with previously published results for both the electronic band structure and structural properties. The self-consistent calculated values of U and J are also in good agreement with the values commonly used in the literature. We found that the time-dependent extension of the self-consistent DFT+U method yields improved optical properties when compared to the empirical TDDFT+U scheme. This work thus opens a different theoretical framework to address the nonequilibrium properties of correlated systems.

  15. Quantitative structure-activity relationships of the antimalarial agent artemisinin and some of its derivatives - a DFT approach.

    Science.gov (United States)

    Rajkhowa, Sanchaita; Hussain, Iftikar; Hazarika, Kalyan K; Sarmah, Pubalee; Deka, Ramesh Chandra

    2013-09-01

    Artemisinin form the most important class of antimalarial agents currently available, and is a unique sesquiterpene peroxide occurring as a constituent of Artemisia annua. Artemisinin is effectively used in the treatment of drug-resistant Plasmodium falciparum and because of its rapid clearance of cerebral malaria, many clinically useful semisynthetic drugs for severe and complicated malaria have been developed. However, one of the major disadvantages of using artemisinins is their poor solubility either in oil or water and therefore, in order to overcome this difficulty many derivatives of artemisinin were prepared. A comparative study on the chemical reactivity of artemisinin and some of its derivatives is performed using density functional theory (DFT) calculations. DFT based global and local reactivity descriptors, such as hardness, chemical potential, electrophilicity index, Fukui function, and local philicity calculated at the optimized geometries are used to investigate the usefulness of these descriptors for understanding the reactive nature and reactive sites of the molecules. Multiple regression analysis is applied to build up a quantitative structure-activity relationship (QSAR) model based on the DFT based descriptors against the chloroquine-resistant, mefloquine-sensitive Plasmodium falciparum W-2 clone.

  16. DFT Study of Electronic and Optical Properties of Small Oligothiophenes Based on Terthiophene End-capped by Several Donor Groups

    Directory of Open Access Journals (Sweden)

    El Alamy Aziz

    2017-07-01

    Full Text Available Eight small molecules based on terthiophene end-capped by several donor groups have been carried out using density functional theory (DFT and time-dependent (TDDFT methods in neutral and doped states. The theoretical ground-state geometry, electronic structure and optical properties of the studied molecules were obtained by the DFT and TD-DFT methods at the B3LYP level with 6-31G(d basis set. Theoretical knowledge of the highest occupied molecular orbital (HOMO, the lowest unoccupied molecular orbital (LUMO energy levels the gap energy (Eg and the open-circuit voltage (Voc of the studied compounds are calculated and discussed. The effects of the donor group substituents on the geometries and optoelectronic properties of these materials are discussed to investigate the relationship between molecular structure and optoelectronic properties. The results of this work suggest some of these materials as a good candidate for organic solar cells. DOI: http://dx.doi.org/10.17807/orbital.v9i3.995

  17. Computational study of AuSi{sub n} (n=1-9) nanoalloy clusters invoking DFT based descriptors

    Energy Technology Data Exchange (ETDEWEB)

    Ranjan, Prabhat; Kumar, Ajay [Department of Mechatronics, Manipal University Jaipur Dehmi Kalan, Jaipur-303007 (India); Chakraborty, Tanmoy, E-mail: tanmoy.chakraborty@jaipur.manipal.edu, E-mail: tanmoychem@gmail.com [Department of Chemistry, Manipal University Jaipur Dehmi Kalan, Jaipur-303007 (India)

    2016-04-13

    Nanoalloy clusters formed between Au and Si are topics of great interest today from both scientific and technological point of view. Due to its remarkable catalytic, electronic, mechanical and magnetic properties Au-Si nanoalloy clusters have extensive applications in the field of microelectronics, catalysis, biomedicine, and jewelry industry. Density Functional Theory (DFT) is a new paradigm of quantum mechanics, which is very much popular to study the electronic properties of materials. Conceptual DFT based descriptors have been invoked to correlate the experimental properties of nanoalloy clusters. In this venture, we have systematically investigated AuSi{sub n} (n=1-9) nanoalloy clusters in the theoretical frame of the B3LYP exchange correlation. The experimental properties of AuSi{sub n} (n=1-9) nanoalloy clusters are correlated in terms of DFT based descriptors viz. HOMO-LUMO gap, Electronegativity (χ), Global Hardness (η), Global Softness (S) and Electrophilicity Index (ω). The calculated HOMO-LUMO gap exhibits interesting odd-even alteration behaviour, indicating that even numbered clusters possess higher stability as compare to their neighbour odd numbered clusters. This study also reflects a very well agreement between experimental bond length and computed data.

  18. DFT+U study of self-trapping, trapping, and mobility of oxygen-type hole polarons in barium stannate

    Science.gov (United States)

    Geneste, Grégory; Amadon, Bernard; Torrent, Marc; Dezanneau, Guilhem

    2017-10-01

    The charge-transfer insulating perovskite oxides currently used as fuel cell electrolytes undergo, at high temperature, an oxidation reaction 1/2 O2(g ) +VO••→OOX+2 h• , that produces oxygen-type holes. Understanding the nature and mobility of these oxygen-type holes is an important step to improve the performance of devices, but presents a theoretical challenge since, in their localized form, they cannot be captured by standard density functional theory. Here, we employ the DFT+U formalism with a Hubbard correction on the p orbitals of oxygen to investigate several properties of these holes, in the particular case of BaSnO3. We describe the small oxygen-type hole polarons, the self-trapping at their origin, and their trapping by trivalent dopants (Ga, Sc, In, Lu, Y, Gd, La). Strong similarities with protonic defects are observed concerning the evolution of the trapping energy with ionic radius of the dopant. Moreover, we show that long-range diffusion of holes is a complex phenomenon, that proceeds by a succession of several mechanisms. However, the standard implementation of DFT+U within the projector augmented-wave (PAW) formalism leads to use very large, unphysical values of U for the O-p orbital. We propose here a slightly modified DFT+U scheme, that takes into account the fact that the O-p is truncated in usual DFT+U implementation in PAW. This scheme yields more physical values of U than the ones traditionally used in the literature, and describes well the properties of the hole polaron.

  19. Advantages of GPU technology in DFT calculations of intercalated graphene

    Science.gov (United States)

    Pešić, J.; Gajić, R.

    2014-09-01

    Over the past few years, the expansion of general-purpose graphic-processing unit (GPGPU) technology has had a great impact on computational science. GPGPU is the utilization of a graphics-processing unit (GPU) to perform calculations in applications usually handled by the central processing unit (CPU). Use of GPGPUs as a way to increase computational power in the material sciences has significantly decreased computational costs in already highly demanding calculations. A level of the acceleration and parallelization depends on the problem itself. Some problems can benefit from GPU acceleration and parallelization, such as the finite-difference time-domain algorithm (FTDT) and density-functional theory (DFT), while others cannot take advantage of these modern technologies. A number of GPU-supported applications had emerged in the past several years (www.nvidia.com/object/gpu-applications.html). Quantum Espresso (QE) is reported as an integrated suite of open source computer codes for electronic-structure calculations and materials modeling at the nano-scale. It is based on DFT, the use of a plane-waves basis and a pseudopotential approach. Since the QE 5.0 version, it has been implemented as a plug-in component for standard QE packages that allows exploiting the capabilities of Nvidia GPU graphic cards (www.qe-forge.org/gf/proj). In this study, we have examined the impact of the usage of GPU acceleration and parallelization on the numerical performance of DFT calculations. Graphene has been attracting attention worldwide and has already shown some remarkable properties. We have studied an intercalated graphene, using the QE package PHonon, which employs GPU. The term ‘intercalation’ refers to a process whereby foreign adatoms are inserted onto a graphene lattice. In addition, by intercalating different atoms between graphene layers, it is possible to tune their physical properties. Our experiments have shown there are benefits from using GPUs, and we reached an

  20. Advantages of GPU technology in DFT calculations of intercalated graphene

    International Nuclear Information System (INIS)

    Pešić, J; Gajić, R

    2014-01-01

    Over the past few years, the expansion of general-purpose graphic-processing unit (GPGPU) technology has had a great impact on computational science. GPGPU is the utilization of a graphics-processing unit (GPU) to perform calculations in applications usually handled by the central processing unit (CPU). Use of GPGPUs as a way to increase computational power in the material sciences has significantly decreased computational costs in already highly demanding calculations. A level of the acceleration and parallelization depends on the problem itself. Some problems can benefit from GPU acceleration and parallelization, such as the finite-difference time-domain algorithm (FTDT) and density-functional theory (DFT), while others cannot take advantage of these modern technologies. A number of GPU-supported applications had emerged in the past several years (www.nvidia.com/object/gpu-applications.html). Quantum Espresso (QE) is reported as an integrated suite of open source computer codes for electronic-structure calculations and materials modeling at the nano-scale. It is based on DFT, the use of a plane-waves basis and a pseudopotential approach. Since the QE 5.0 version, it has been implemented as a plug-in component for standard QE packages that allows exploiting the capabilities of Nvidia GPU graphic cards (www.qe-forge.org/gf/proj). In this study, we have examined the impact of the usage of GPU acceleration and parallelization on the numerical performance of DFT calculations. Graphene has been attracting attention worldwide and has already shown some remarkable properties. We have studied an intercalated graphene, using the QE package PHonon, which employs GPU. The term ‘intercalation’ refers to a process whereby foreign adatoms are inserted onto a graphene lattice. In addition, by intercalating different atoms between graphene layers, it is possible to tune their physical properties. Our experiments have shown there are benefits from using GPUs, and we reached an

  1. Hydrogen molecule on lithium adsorbed graphene: A DFT study

    International Nuclear Information System (INIS)

    Kaur, Gagandeep; Gupta, Shuchi; Gaganpreet; Dharamvir, Keya

    2016-01-01

    Electronic structure calculations for the adsorption of molecular hydrogen on lithium (Li) decorated and pristine graphene have been studied systematically using SIESTA code [1] within the framework of the first-principle DFT under the Perdew-Burke-Ernzerhof (PBE) form of the generalized gradient approximation (GGA)[2], including spin polarization. The energy of adsorption of hydrogen molecule on graphene is always enhanced by the presence of co-adsorbed lithium. The most efficient adsorption configuration is when H 2 is lying parallel to lithium adsorbed graphene which is in contrast to its adsorption on pristine graphene (PG) where it prefers perpendicular orientation.

  2. Reaction pathways of the dissociation of methylal: A DFT study

    Energy Technology Data Exchange (ETDEWEB)

    Frey, H -M; Beaud, P; Gerber, T; Mischler, B; Radi, P P; Tzannis, A -P [Paul Scherrer Inst. (PSI), Villigen (Switzerland)

    1999-08-01

    Schemata for modelling combustion processes do not yet include reaction rates for oxygenated fuels like methylal (DMM) which is considered as an additive or replacement for diesel due to its low sooting propensity. Density functional theory (DFT) studies of the possible reaction pathways for different dissociation steps of methylal are presented. Cleavage of a hydrogen bond to the methoxy group or the central carbon atom were simulated at the BLYP/6-311++G{sup **} level of theory. The results are compared to the experiment when dissociating and/or ionising DMM with femtosecond pulses. (author) 1 fig., 1 tab., 1 ref.

  3. Digital circuit testing a guide to DFT and other techniques

    CERN Document Server

    Wong, Francis C

    1991-01-01

    Recent technological advances have created a testing crisis in the electronics industry--smaller, more highly integrated electronic circuits and new packaging techniques make it increasingly difficult to physically access test nodes. New testing methods are needed for the next generation of electronic equipment and a great deal of emphasis is being placed on the development of these methods. Some of the techniques now becoming popular include design for testability (DFT), built-in self-test (BIST), and automatic test vector generation (ATVG). This book will provide a practical introduction to

  4. Error compensation of IQ modulator using two-dimensional DFT

    Energy Technology Data Exchange (ETDEWEB)

    Ohshima, Takashi, E-mail: ohshima@spring8.or.jp [RIKEN, 1-1-1, Kouto, Sayo-cho, Sayo-gun, Hyogo 679-5148 (Japan); Maesaka, Hirokazu [RIKEN, 1-1-1, Kouto, Sayo-cho, Sayo-gun, Hyogo 679-5148 (Japan); Matsubara, Shinichi [Japan Synchrotron Radiation Institute, 1-1-1, Kouto, Sayo-cho, Sayo-gun, Hyogo 679-5198 (Japan); Otake, Yuji [RIKEN, 1-1-1, Kouto, Sayo-cho, Sayo-gun, Hyogo 679-5148 (Japan)

    2016-06-01

    It is important to precisely set and keep the phase and amplitude of an rf signal in the accelerating cavity of modern accelerators, such as an X-ray Free Electron Laser (XFEL) linac. In these accelerators an acceleration rf signal is generated or detected by an In-phase and Quadrature (IQ) modulator, or a demodulator. If there are any deviations of the phase and the amplitude from the ideal values, crosstalk between the phase and the amplitude of the output signal of the IQ modulator or the demodulator arises. This causes instability of the feedback controls that simultaneously stabilize both the rf phase and the amplitude. To compensate for such deviations, we developed a novel compensation method using a two-dimensional Discrete Fourier Transform (DFT). Because the observed deviations of the phase and amplitude of an IQ modulator involve sinusoidal and polynomial behaviors on the phase angle and the amplitude of the rf vector, respectively, the DFT calculation with these basis functions makes a good approximation with a small number of compensation coefficients. Also, we can suppress high-frequency noise components arising when we measure the deviation data. These characteristics have advantages compared to a Look Up Table (LUT) compensation method. The LUT method usually demands many compensation elements, such as about 300, that are not easy to treat. We applied the DFT compensation method to the output rf signal of a C-band IQ modulator at SACLA, which is an XFEL facility in Japan. The amplitude deviation of the IQ modulator after the DFT compensation was reduced from 15.0% at the peak to less than 0.2% at the peak for an amplitude control range of from 0.1 V to 0.9 V (1.0 V full scale) and for a phase control range from 0 degree to 360 degrees. The number of compensation coefficients is 60, which is smaller than that of the LUT method, and is easy to treat and maintain.

  5. SU-C-204-03: DFT Calculations of the Stability of DOTA-Based-Radiopharmaceuticals

    Energy Technology Data Exchange (ETDEWEB)

    Khabibullin, A.R.; Woods, L.M. [University of South Florida, Tampa, Florida (United States); Karolak, A.; Budzevich, M.M.; Martinez, M.V. [H. Lee Moffitt Cancer Center and Research Institute, Tampa, Florida (United States); McLaughlin, M.L.; Morse, D.L. [University of South Florida, Tampa, Florida (United States); H. Lee Moffitt Cancer Center and Research Institute, Tampa, Florida (United States)

    2016-06-15

    Purpose: Application of the density function theory (DFT) to investigate the structural stability of complexes applied in cancer therapy consisting of the 1,4,7,10-tetraazacyclododecane-1,4,7,10-tetraacetic acid (DOTA) chelated to Ac225, Fr221, At217, Bi213, and Gd68 radio-nuclei. Methods: The possibility to deliver a toxic payload directly to tumor cells is a highly desirable aim in targeted alpha particle therapy. The estimation of bond stability between radioactive atoms and the DOTA chelating agent is the key element in understanding the foundations of this delivery process. Thus, we adapted the Vienna Ab-initio Simulation Package (VASP) with the projector-augmented wave method and a plane-wave basis set in order to study the stability and electronic properties of DOTA ligand chelated to radioactive isotopes. In order to count for the relativistic effect of radioactive isotopes we included Spin-Orbit Coupling (SOC) in the DFT calculations. Five DOTA complex structures were represented as unit cells, each containing 58 atoms. The energy optimization was performed for all structures prior to calculations of electronic properties. Binding energies, electron localization functions as well as bond lengths between atoms were estimated. Results: Calculated binding energies for DOTA-radioactive atom systems were −17.792, −5.784, −8.872, −13.305, −18.467 eV for Ac, Fr, At, Bi and Gd complexes respectively. The displacements of isotopes in DOTA cages were estimated from the variations in bond lengths, which were within 2.32–3.75 angstroms. The detailed representation of chemical bonding in all complexes was obtained with the Electron Localization Function (ELF). Conclusion: DOTA-Gd, DOTA-Ac and DOTA-Bi were the most stable structures in the group. Inclusion of SOC had a significant role in the improvement of DFT calculation accuracy for heavy radioactive atoms. Our approach is found to be proper for the investigation of structures with DOTA

  6. Electrochemical and DFT studies of {beta}-amino-alcohols as corrosion inhibitors for brass

    Energy Technology Data Exchange (ETDEWEB)

    Gao, Guo [State Key Laboratory of Fine Chemicals, School of Chemical Engineering, Dalian University of Technology, Dalian 116012 (China)]. E-mail: gaogaoguoguo@yahoo.com.cn; Liang, Chenghao [State Key Laboratory of Fine Chemicals, School of Chemical Engineering, Dalian University of Technology, Dalian 116012 (China); Electromechanics and Materials Engineering College, Dalian Maritime University, Dalian 116026 (China)

    2007-03-20

    The electrochemical performance of 1-diethylamino-propan-2-ol (EAP) and 1,3-bis-diethylamino-propan-2-ol (DEAP) for brass in simulated atmospheric water is evaluated by potentiodynamic curves and electrochemical impedance spectroscopy (EIS). The experimental results show that the investigated compounds, which can effectively retard the anodic dissolution of brass, are anodic inhibitors. Furthermore, the inhibition efficiency of DEAP is higher than that of EAP at the same concentration. This observation is supported by density functional theoretical (DFT) parameters such as the highest occupied molecule energy level (E {sub HOMO}), the lowest unoccupied molecule energy level (E {sub LUMO}), the energy difference ({delta}E) between E {sub HOMO} and E {sub LUMO}, Mulliken charges and the HOMO orbital.

  7. Molecular design of high performance fused heteroacene radical cations: A DFT study

    International Nuclear Information System (INIS)

    Kawabata, Hiroshi; Ohmori, Shigekazu; Matsushige, Kazumi; Tachikawa, Hiroto

    2008-01-01

    Hybrid density functional theory (DFT) calculations have been carried out for neutral and radical cation of fused furan oligomer, denoted by F(n) where n means number of furan rings in the oligomer, to elucidate the electronic structures at ground and low-lying excited states. A polymer of fused furan was also investigated using one-dimensional periodic boundary condition (PBC) for comparison. It was found that the reorganization energy of radical cation of F(n) from vertical hole trapping point to its relaxed structure is significantly small. Also, the reorganization energy decreased gradually with increasing n, indicating that F(n) has an effective hole transport property. It was found that the cation radical of F(n) has a low energy band at near IR region, which is strongly correlated to hole conductivity. The relation between the electronic states and hole conductivity was discussed on the basis of theoretical calculations

  8. Synthesis, Characterisation and DFT Calculations of Azo-Imine Dyes

    Directory of Open Access Journals (Sweden)

    Sevil Özkınalı

    2017-11-01

    Full Text Available In this study, azo dyes containing an imine group were synthesised by coupling p-hydroxybenzylidene aniline with the diazonium salts of p-toluidine, 4-aminophenol, aniline, p-chloroaniline, p-fluoroaniline, and p-nitroaniline. The compounds were characterised by melting point, elemental, UV-Vis and IR analyses as well as 1H-NMR and 13C-NMR spectroscopies. Moreover, the experimental data were supplemented with density functional theory (DFT calculations. The experimental data on FT-IR and UV–Vis spectra of the compounds were compared with theoretical results. The DFT calculations were performed to obtain the ground state geometries of the compounds using the B3LYP hybrid functional level with 6-311++g(2d,2p basis set. Frontier molecular orbital energies, band gap energies and some chemical reactivity parameters, such as chemical hardness and electronegativity, were calculated and compared with experimental values. A significant correlation was observed between the dipole moment and polarities of the solvents and the absorption wavelength of the compounds.

  9. Reactive sites influence in PMMA oligomers reactivity: a DFT study

    Science.gov (United States)

    Paz, C. V.; Vásquez, S. R.; Flores, N.; García, L.; Rico, J. L.

    2018-01-01

    In this work, we present a theoretical study of methyl methacrylate (MMA) living anionic polymerization. The study was addressed to understanding two important experimental observations made for Michael Szwarc in 1956. The unexpected effect of reactive sites concentration in the propagation rate, and the self-killer behavior of MMA (deactivating of living anionic polymerization). The theoretical calculations were performed by density functional theory (DFT) to obtain the frontier molecular orbitals values. These values were used to calculate and analyze the chemical interaction descriptors in DFT-Koopmans’ theorem. As a result, it was observed that the longest chain-length species (related with low concentration of reactive sites) exhibit the highest reactivity (behavior associated with the increase of the propagation rate). The improvement in this reactivity was attributed to the crosslinking produced in the polymethyl methacrylate chains. Meanwhile, the self-killer behavior was associated with the intermolecular forces present in the reactive sites. This behavior was associated to an obstruction in solvation, since the active sites remained active through all propagation species. The theoretical results were in good agreement with the Szwarc experiments.

  10. The adsorption and dissociation of water molecule on goethite (010) surface: A DFT approach

    Energy Technology Data Exchange (ETDEWEB)

    Zhou, Long, E-mail: shuweixia@ouc.edu.cn [Key Laboratory of Marine Chemistry Theory and Technology, Ministry of Education, Ocean University of China, College of Chemistry and Chemical Engineering (China); Xiu, Fangyuan [Key Laboratory of Marine Chemistry Theory and Technology, Ministry of Education, Ocean University of China, College of Chemistry and Chemical Engineering (China); Qiu, Meng [Qingdao Institute of Bioenergy and Bioprocess Technology (China); Xia, Shuwei; Yu, Liangmin [Key Laboratory of Marine Chemistry Theory and Technology, Ministry of Education, Ocean University of China, College of Chemistry and Chemical Engineering (China)

    2017-01-15

    Graphical abstract: The optimized structure of hydrated goethite (010) surface with medium water coverage (water density about 6.7 H{sub 2}O/nm{sup 2}). - Highlights: • Stable adsorption and dissociation structure of H{sub 2}O on goethite (010) surface was investigated by DFT. • Reasonable path for water dissociation was proposed by transitional state analysis. • The mechanism of water adsorption on goethite and binding nature were revealed by PDOS. - Abstract: Using density functional theory (DFT) calculation, we investigate the configuration, stability and electronic properties of fresh cleaved (010) goethite surface (Pnma) and this surface exposed to water monolayer at low, medium and high coverage. Water is predicted to be chemisorbed to the surface, together with the surface reconstruction. The interaction energy of the most stable configuration of both low and medium coverage per water molecule is almost the same (−1.17 eV), while that of high coverage is much lower (less than 1.03 eV). It indicates that highly hydrated surface is less stable. PDOS analysis reveals the adsorption of H{sub 2}O is due to the formation of Fe−O bond, caused by overlapping of Fe's 3d and O's 2p orbitals. Dissociation processes at low and medium water coverage are non-spontaneous; while at high coverage, it can undertake spontaneously both thermodynamically and dynamically. The dissociation paths of all three water coverage are the similar. The proton from one adsorbed water is likely to dissociate to bind to the vicinal surface μ{sub 3}−O as an intermediate product; the proton belonged to μ{sub 3}−O transferred to the neighbor surface μ{sub 2}−O as the dissociative configuration.

  11. Acidity enhancement of niobia by sulfation: An experimental and DFT study

    Energy Technology Data Exchange (ETDEWEB)

    Rocha, Angela S., E-mail: angela.sanches.rocha@gmail.com [Universidade do Estado do Rio de Janeiro, Departamento de Físico-Química, Instituto de Química, Rio de Janeiro (Brazil); Costa, Gustavo C. [Universidade do Estado do Rio de Janeiro, Departamento de Físico-Química, Instituto de Química, Rio de Janeiro (Brazil); Tamiasso-Martinhon, Priscila; Sousa, Célia; Rocha, Alexandre B. [Universidade Federal do Rio de Janeiro, Departamento de Físico-Química, Instituto de Química, Rio de Janeiro (Brazil)

    2017-01-15

    Acidic solids are used as catalyst at several industrial processes and studies to improve their activities have been developed by different groups. One method well known is sulfating oxide to create new acid sites, but investigations about sulfated niobia are still scarce. This work studied the influence of sulfation on the niobia acidity by using a very simple reaction model, the esterification of acetic acid with ethanol, performed at 60 °C and 1 atm. Niobia and sulfated niobia samples were characterized by N{sub 2} adsorption, X-ray diffraction, FTIR and titration with n-butylamine. To investigate the nature of sulfate groups formed on the surface of niobia, calculations based on the Density Functional Theory (DFT) have been performed for two models: pure niobia with hydroxylated surface and sulfated niobia where one OH{sup −} surface group was replaced by a HSO{sub 4}{sup −}. The experimental results indicated that the sulfation treatment leads to an increase in the specific surface area, acidity and, consequently, in the activity of niobia, with small changes in the crystal structure of the solid. The presence of sulfate groups was evidenced by FTIR spectra and calculations have indicated HSO{sub 4}{sup −} species bounded to the surface. Density Functional Perturbation Theory (DFPT) was also employed to obtain infrared intensities in the region of sulfate vibration bands. - Highlights: • Sulfation treatment has improved the acidity of niobium oxide. • A sulfate group on niobia (T-Nb{sub 2}O{sub 5}) was proposed using DFT method. • Niobia and sulfated niobia are used for esterification of acetic acid with ethanol.

  12. Room temperature ferromagnetism and half metallicity in nickel doped ZnS: Experimental and DFT studies

    Energy Technology Data Exchange (ETDEWEB)

    Akhtar, Muhammad Saeed [School of Materials, The University of Manchester, Oxford Road, Manchester M13 9PL (United Kingdom); Centre of Excellence in Solid State Physics, University of the Punjab, Lahore 54590 (Pakistan); Malik, Mohammad Azad, E-mail: Azad.malik@manchester.ac.uk [School of Materials, The University of Manchester, Oxford Road, Manchester M13 9PL (United Kingdom); Riaz, Saira; Naseem, Shahzad [Centre of Excellence in Solid State Physics, University of the Punjab, Lahore 54590 (Pakistan)

    2015-06-15

    The nickel doped nanocrystalline ZnS thin films were deposited onto glass substrates by chemical bath deposition (CBD). Also ZnS:Ni nanoparticles were synthesized by CBD/co-precipitation method. Powder X-ray diffraction (p-XRD) studies demonstrate that both thin films and nanoparticles correspond to sphalerite (cubic) phase of ZnS with slight shift towards higher 2θ values due to incorporation of nickel in the ZnS lattice. The crystallite sizes estimated by Scherrer equation were 4 and 2.6 nm for ZnNiS thin films and nanoparticles, respectively. Scanning Electron Microscopy (SEM) images reveal that the morphology of thin films is based on quasi-spherical particles with nano scale dimensions. Energy Dispersive X-ray (EDX) spectroscopy confirms that the as-deposited thin films have a stoichiometry consistent with the nickel doped ZnS. Full-potential linearized augmented plane wave (FP-L/APW) method based on spin-polarized density functional theory (DFT) was employed to investigate the electronic and magnetic properties of ZnNiS for the doping concentration. Exchange-correlation functional was studied using generalized gradient approximation (GGA + U) method. Electronic band structures and density of states (DOS) demonstrate 100% spin polarization (half metallicity) with ferromagnetic exchange interactions. Superconducting quantum interference device (SQUID) analysis confirms the theoretical observation of ferromagnetism in nickel doped ZnS. These ZnS based half metallic ferromagnets seem to have virtuous applications in future spintronic devices. - Highlights: • ZnS.Ni thin films and nanoparticles were deposited onto glass substrates by CBD. • p-XRD correspond to sphalerite (cubic) phase of ZnS with slight shift in peaks. • DFT was employed to investigate the properties of ZnS.Ni. • DOS demonstrate 100% spin polarization with ferromagnetic exchange interactions. • SQUID analysis confirms the theoretical observations of nickel doped ZnS.

  13. Acidity enhancement of niobia by sulfation: An experimental and DFT study

    International Nuclear Information System (INIS)

    Rocha, Angela S.; Costa, Gustavo C.; Tamiasso-Martinhon, Priscila; Sousa, Célia; Rocha, Alexandre B.

    2017-01-01

    Acidic solids are used as catalyst at several industrial processes and studies to improve their activities have been developed by different groups. One method well known is sulfating oxide to create new acid sites, but investigations about sulfated niobia are still scarce. This work studied the influence of sulfation on the niobia acidity by using a very simple reaction model, the esterification of acetic acid with ethanol, performed at 60 °C and 1 atm. Niobia and sulfated niobia samples were characterized by N 2 adsorption, X-ray diffraction, FTIR and titration with n-butylamine. To investigate the nature of sulfate groups formed on the surface of niobia, calculations based on the Density Functional Theory (DFT) have been performed for two models: pure niobia with hydroxylated surface and sulfated niobia where one OH − surface group was replaced by a HSO 4 − . The experimental results indicated that the sulfation treatment leads to an increase in the specific surface area, acidity and, consequently, in the activity of niobia, with small changes in the crystal structure of the solid. The presence of sulfate groups was evidenced by FTIR spectra and calculations have indicated HSO 4 − species bounded to the surface. Density Functional Perturbation Theory (DFPT) was also employed to obtain infrared intensities in the region of sulfate vibration bands. - Highlights: • Sulfation treatment has improved the acidity of niobium oxide. • A sulfate group on niobia (T-Nb 2 O 5 ) was proposed using DFT method. • Niobia and sulfated niobia are used for esterification of acetic acid with ethanol.

  14. Synthesis of novel styryl derivatives from 4-chloro-2-(morpholin-4-yl)-1,3-thiazole-5-carbaldehyde, study of their photophysical properties and TD-DFT computations

    International Nuclear Information System (INIS)

    Sekar, Nagaiyan; Umape, Prashant G.; Padalkar, Vikas S.; Tayade, Rajratna P.; Ramasami, Ponnadurai

    2014-01-01

    Novel fluorescent styryl push–pull compounds having electron donating thiazole unit were synthesized by condensing 4-chloro-2-(morpholin-4-yl)-1,3-thiazole-5-carbaldehyde with active methylene compounds via classical Knoevenagel condensation. The synthesized styryl molecules were characterized by spectral analysis. Photophysical properties of these styryl derivatives were analyzed and the effect of change in solvent polarity and viscosity on their absorptive and emissive properties has been investigated. Density functional theory (DFT) and time dependent-density functional theory (TD-DFT) computations have been used to understand the structural, molecular, electronic and photophysical parameters of push–pull dyes. Bakhshiev and Kawski–Chamma–Viallet correlations were used to calculate the ratio of ground to excited state dipole moment of the synthesized novel styryl compounds. -- Highlights: •Novel styryl derivatives are synthesized from thiazole aldehyde. •Photophysical properties of styryl derivatives were evaluated and supported by TD-DFT computations. •Experimental photophysical results are in good agreement with the theoretical results obtained by TD-DFT computations. •Compounds show fluorescence in solid state as well as in solvents of different polarities

  15. Spectroscopic and DFT studies of calix[4]arene: time-dependent DFT calculations for elucidating the variation in the excitation energies with geometry

    Energy Technology Data Exchange (ETDEWEB)

    Boo, Bong Hyun; Kwak, Hae Ran; Hong, Seung Ki [Chungnam National University, Daejeon (Korea, Republic of); Park, Chan Jo [Korea Research Institute of Chemical Technology, Daejeon (Korea, Republic of); No, Kwang Hyun [Sookmyung Womens University, Seoul (Korea, Republic of)

    2010-08-15

    We have searched low-lying conformers of calix[4]arene and found one global minimum having a cone shape, together with three conformers such as partial cone-shape conformers. We then elucidated the thermodynamics for the conformational changes by performing density-functional theory (DFT) calculations. The time-dependent DFT calculation enabled us to assign the absorption spectrum and to reveal a variation of the excitation energies with geometry.

  16. Proton affinities of anionic bases: Trends across the periodic table, structural effects, and DFT validation

    NARCIS (Netherlands)

    Swart, M.; Bickelhaupt, F.M.

    2006-01-01

    We have carried out an extensive exploration of the gas-phase basicity of archetypal anionic bases across the periodic system using the generalized gradient approximation of density functional theory (DFT) at BP86/QZ4P//BP86/TZ2P. First, we validate DFT as a reliable tool for computing proton

  17. Coherent optical DFT-spread OFDM transmission using orthogonal band multiplexing.

    Science.gov (United States)

    Yang, Qi; He, Zhixue; Yang, Zhu; Yu, Shaohua; Yi, Xingwen; Shieh, William

    2012-01-30

    Coherent optical OFDM (CO-OFDM) combined with orthogonal band multiplexing provides a scalable and flexible solution for achieving ultra high-speed rate. Among many CO-OFDM implementations, digital Fourier transform spread (DFT-S) CO-OFDM is proposed to mitigate fiber nonlinearity in long-haul transmission. In this paper, we first illustrate the principle of DFT-S OFDM. We then experimentally evaluate the performance of coherent optical DFT-S OFDM in a band-multiplexed transmission system. Compared with conventional clipping methods, DFT-S OFDM can reduce the OFDM peak-to-average power ratio (PAPR) value without suffering from the interference of the neighboring bands. With the benefit of much reduced PAPR, we successfully demonstrate 1.45 Tb/s DFT-S OFDM over 480 km SSMF transmission.

  18. Extensive TD-DFT Benchmark: Singlet-Excited States of Organic Molecules.

    Science.gov (United States)

    Jacquemin, Denis; Wathelet, Valérie; Perpète, Eric A; Adamo, Carlo

    2009-09-08

    Extensive Time-Dependent Density Functional Theory (TD-DFT) calculations have been carried out in order to obtain a statistically meaningful analysis of the merits of a large number of functionals. To reach this goal, a very extended set of molecules (∼500 compounds, >700 excited states) covering a broad range of (bio)organic molecules and dyes have been investigated. Likewise, 29 functionals including LDA, GGA, meta-GGA, global hybrids, and long-range-corrected hybrids have been considered. Comparisons with both theoretical references and experimental measurements have been carried out. On average, the functionals providing the best match with reference data are, one the one hand, global hybrids containing between 22% and 25% of exact exchange (X3LYP, B98, PBE0, and mPW1PW91) and, on the other hand, a long-range-corrected hybrid with a less-rapidly increasing HF ratio, namely LC-ωPBE(20). Pure functionals tend to be less consistent, whereas functionals incorporating a larger fraction of exact exchange tend to underestimate significantly the transition energies. For most treated cases, the M05 and CAM-B3LYP schemes deliver fairly small deviations but do not outperform standard hybrids such as X3LYP or PBE0, at least within the vertical approximation. With the optimal functionals, one obtains mean absolute deviations smaller than 0.25 eV, though the errors significantly depend on the subset of molecules or states considered. As an illustration, PBE0 and LC-ωPBE(20) provide a mean absolute error of only 0.14 eV for the 228 states related to neutral organic dyes but are completely off target for cyanine-like derivatives. On the basis of comparisons with theoretical estimates, it also turned out that CC2 and TD-DFT errors are of the same order of magnitude, once the above-mentioned hybrids are selected.

  19. Probing the adsorption mechanism in thiamazole bound to the silver surface with Surface-enhanced Raman Scattering and DFT

    Science.gov (United States)

    Biswas, Nandita; Thomas, Susy; Sarkar, Anjana; Mukherjee, Tulsi; Kapoor, Sudhir

    2009-09-01

    Surface-enhanced Raman scattering (SERS) of thiamazole have been investigated in aqueous solution. Thiamazole is an important anti-thyroid drug that is used in the treatment of hyperthyroidism (over activity of the thyroid gland). Due to its medicinal importance, the surface adsorption properties of thiamazole have been studied. The experimental Raman and SERS data are supported with DFT calculations using B3LYP functional with LANL2DZ basis set. From the SERS spectra as well as theoretical calculations, it has been inferred that thiamazole is chemisorbed to the silver surface directly through the sulphur atom and the ring N atom, with a tilted orientation.

  20. Coordination Behavior of Ni2+, Cu2+, and Zn2+ in Tetrahedral 1-Methylimidazole Complexes: A DFT/CSD Study

    OpenAIRE

    Tetteh, Samuel

    2018-01-01

    The interaction between nickel (Ni2+), copper (Cu2+), and zinc (Zn2+) ions and 1-methylimidazole has been studied by exploring the geometries of eleven crystal structures in the Cambridge Structural Database (CSD). The coordination behavior of the respective ions was further investigated by means of density functional theory (DFT) methods. The gas-phase complexes were fully optimized using B3LYP/GENECP functionals with 6-31G∗ and LANL2DZ basis sets. The Ni2+ and Cu2+ complexes show distorted ...

  1. Doped phosphorene for hydrogen capture: A DFT study

    Science.gov (United States)

    Zhang, Hong-ping; Hu, Wei; Du, Aijun; Lu, Xiong; Zhang, Ya-ping; Zhou, Jian; Lin, Xiaoyan; Tang, Youhong

    2018-03-01

    Hydrogen capture and storage is the core of hydrogen energy application. With its high specific surface area, direct bandgap, and variety of potential applications, phosphorene has attracted much research interest. In this study, density functional theory (DFT) is utilized to study the interactions between doped phosphorenes and hydrogen molecules. The effects of different dopants and metallic or nonmetallic atoms on phosphorene/hydrogen interactions is systematically studied by adsorption energy, electron density difference, partial density of states analysis, and Hirshfeld population. Our results indicate that the metallic dopants Pt, Co, and Ni can help to improve the hydrogen capture ability of phosphorene, whereas the nonmetallic dopants have no effect on it. Among the various metallic dopants, Pt performs very differently, such that it can help to dissociate H2 on phosphorene. Specified doped phosphorene could be a promising candidate for hydrogen storage, with behaviors superior to those of intrinsic graphene sheet.

  2. Surface Pourbaix diagrams and oxygen reduction activity of Pt, Ag and Ni(111) surfaces studied by DFT

    DEFF Research Database (Denmark)

    Hansen, Heine Anton; Rossmeisl, Jan; Nørskov, Jens Kehlet

    2008-01-01

    The electrochemical most stable surface structures is investigated as function of pH and potential for Pt, Ag and Ni based on DFT calculations and constructed surface Pourbaix diagrams. It is also explained why metals such as Ag and Ni may be used successfully in alkaline fuel cells but not in ac......The electrochemical most stable surface structures is investigated as function of pH and potential for Pt, Ag and Ni based on DFT calculations and constructed surface Pourbaix diagrams. It is also explained why metals such as Ag and Ni may be used successfully in alkaline fuel cells...... but not in acidic PEM fuel cells. Based on density functional theory calculations we investigate the electrochemically most stable surface structures as a function of pH and electrostatic potential for Pt(111), Ag(111) and Ni(111), and we construct surface Pourbaix diagrams. We study the oxygen reduction reaction......, on the other hand, is constant vs. the standard hydrogen electrode (SHE). For Ag, this means that where the potential for dissolution and ORR are about the same at pH = 0, Ag becomes more stable relative to RHE as pH is increased. Hence the pH dependent stability offers an explanation for the possible use...

  3. 1-(2-Chlorobenzyloxy-3-[1,2,3]triazol-1-yl-propan-2-ol Derivatives: Synthesis, Characterization, and DFT-Based Descriptors Analysis

    Directory of Open Access Journals (Sweden)

    Eloisa Román-Maldonado

    2017-01-01

    Full Text Available A novel series of 1-(2-chlorobenzyloxy-3-[1,2,3]triazol-1-yl-propan-2-ol derivatives was designed and synthesized using copper catalyzed alkyne-azide cycloaddition in the key step. Theoretical investigation of molecular and electronic properties by means of global and local reactivity indexes of the synthetized compounds was carried out, using DFT (Density Functional Theory at PBEPBE/6-31++G⁎⁎ level.

  4. Role of keto–enol tautomerization in a chiral phosphoric acid catalyzed asymmetric thiocarboxylysis of meso-epoxide: a DFT study

    KAUST Repository

    Ajitha, Manjaly John; Huang, Kuo-Wei

    2015-01-01

    The mechanism of a chiral phosphoric acid catalyzed thiocarboxylysis of meso-epoxide was investigated by density functional theory (DFT) calculations (M06-2X). The nucleophilic ring opening of epoxide by thiobenzoic acid was found to proceed via a concerted termolecular transition state with a simultaneous dual proton transfer to yield the β-hydroxy thioester product. Electrostatic interactions together with the steric environment inside the chiral catalyst play an important role in determining the enantioselectivity of the reaction.

  5. Role of keto–enol tautomerization in a chiral phosphoric acid catalyzed asymmetric thiocarboxylysis of meso-epoxide: a DFT study

    KAUST Repository

    Ajitha, Manjaly John

    2015-09-15

    The mechanism of a chiral phosphoric acid catalyzed thiocarboxylysis of meso-epoxide was investigated by density functional theory (DFT) calculations (M06-2X). The nucleophilic ring opening of epoxide by thiobenzoic acid was found to proceed via a concerted termolecular transition state with a simultaneous dual proton transfer to yield the β-hydroxy thioester product. Electrostatic interactions together with the steric environment inside the chiral catalyst play an important role in determining the enantioselectivity of the reaction.

  6. On the potential of zero-tail DFT-spread-OFDM in 5G networks

    DEFF Research Database (Denmark)

    Berardinelli, Gilberto; Tavares, Fernando Menezes Leitão; Sørensen, Troels Bundgaard

    2014-01-01

    Zero-tail Discrete Fourier Transform -spread OFDM (ZT DFT-s-OFDM) modulation allows to dynamically cope with the delay spread of the multipath channel, thus avoiding the limitations of hard-coded Cyclic Prefix (CP). In this paper, we discuss the potential of ZT DFT-s-OFDM modulation for the envis......, possibility of adopting unified radio numerology among different cells, reduced latency and support of agile link direction switching. The robustness of ZT DFT-s-OFDM towards non-idealities such as phase noise and non-linear power amplifier is also discussed....

  7. Investigation of Multiconfigurational Short-Range Density Functional Theory for Electronic Excitations in Organic Molecules

    DEFF Research Database (Denmark)

    Hubert, Mickaël; Hedegård, Erik D.; Jensen, Hans Jørgen Aa

    2016-01-01

    -srDFT for a selected benchmark set of electronic excitations of organic molecules, covering the most common types of organic chromophores. This investigation confirms the expectation that the MC-srDFT method is accurate for a broad range of excitations and comparable to accurate wave function methods such as CASPT2......Computational methods that can accurately and effectively predict all types of electronic excitations for any molecular system are missing in the toolbox of the computational chemist. Although various Kohn-Sham density-functional methods (KS-DFT) fulfill this aim in some cases, they become...... and double excitations have been promising, it is nevertheless important that the accuracy of MC-srDFT is at least comparable to the best KS-DFT methods also for organic molecules that are typically of single-reference character. In this paper we therefore systematically investigate the performance of MC...

  8. Melamine derivatives as effective corrosion inhibitors for mild steel in acidic solution: Chemical, electrochemical, surface and DFT studies

    Science.gov (United States)

    Verma, Chandrabhan; Haque, J.; Ebenso, Eno E.; Quraishi, M. A.

    2018-06-01

    In present study two condensation products of melamine (triazine) and glyoxal namely, 2,2-bis(4,6-diamino-1,3,5-triazin-2-ylamino)acetaldehyde (ME-1) and (N2,N2‧E,N2,N2‧E)-N2,N2‧-(ethane-1,2-diylidene)-bis-(1,3,5-triazine-2,4,6-triamine) (ME-2) are tested as mild steel corrosion inhibitors in acidic solution (1M HCl). The inhibition efficiency of ME-1 and ME-2 increases with increase in their concentrations and maximum values of 91.47% and 94.88% were derived, respectively at 100 mgL-1 (34.20 × 10-5 M) concentration. Adsorption of ME-1 and ME-2 on the surface of metal obeyed the Langmuir adsorption isotherm. Polarization investigation revealed that ME-1 and ME-2 act as mixed type inhibitors with minor cathodic prevalence. The chemical and electrochemical analyses also supported by surface characterization methods where significant smoothness in the surface morphologies was observed in the images of SEM and AFM spectra. Several DFT indices such as EHOMO and ELUMO, ΔE, η, σ, χ, μ and ΔN were derived for both ME-1 and ME-2 molecules and correlated with experimental results. The DFT studies have also been carried out for protonated or cationic form of the inhibitor molecules by considering that in acidic medium the heteroatoms of organic inhibitors easily undergo protonation. The experimental and density functional theory (DFT) studies (neutral and protonated) were in good agreement.

  9. Molecular interactions in the complexes of toluene with butyronitrile: A DFT approach

    Science.gov (United States)

    Karthick, N. K.; Arivazhagan, G.

    2018-04-01

    Density Functional Theory (DFT) has been employed to investigate the self association of butyronitrile and the heterointeractions in the 1:2 (toluene: butyronitrile) and 1:1 complexes of toluene with butyronitrile. For this investigation the B3LYP functional with Grimme's dispersion correction (D3) term and ωB97XD functionals were used. The theoretical frequency analysis shows the unsuitability of B3LYP with D3 for the present investigation. Therefore, Natural Bonding Orbital analysis was done at the functional ωB97XD. It is found through this work that only the methylene hydrogens of butyronitrile are responsible for the self association among the butyronitrile molecules. In 1:1 complex, the red shift in the butyronitrile methyl asymmetric stretching mode is not due to the active participation of this group in heterointeractions and it is solely due to the other interactions happening in its vicinity. Only the interaction (TOL) C - H ⋯ N(BN) is present in the complex. In 1:2 complex the butyronitrile methyl/methylene hydrogens interact with the delocalized electron cloud of toluene and the toluene hydrogens interact with the butyronitrile nitrogen. Comparison of interaction energies shows that the stability of 1:2 complex is more than that of butyronitrile dimer and 1:1 complex.

  10. Scavenging performance and antioxidant activity of γ-alumina nanoparticles towards DPPH free radical: Spectroscopic and DFT-D studies.

    Science.gov (United States)

    Zamani, Mehdi; Moradi Delfani, Ali; Jabbari, Morteza

    2018-05-03

    The radical scavenging performance and antioxidant activity of γ-alumina nanoparticles towards 2,2-diphenyl-1-picrylhydrazyl (DPPH) free radical were investigated by spectroscopic and computational methods. The radical scavenging ability of γ-alumina nanoparticles in the media with different polarity (i.e. i-propanol and n-hexane) was evaluated by measuring the DPPH absorbance in UV-Vis absorption spectra. The structure and morphology of γ-alumina nanoparticles before and after adsorption of DPPH were studied using XRD, FT-IR and UV-Vis spectroscopic techniques. The adsorption of DPPH free radical on the clean and hydrated γ-alumina (1 1 0) surface was examined by dispersion corrected density functional theory (DFT-D) and natural bond orbital (NBO) calculations. Also, time-dependent density functional theory (TD-DFT) was used to predict the absorption spectra. The adsorption was occurred through the interaction of radical nitrogen N and NO 2 groups of DPPH with the acidic and basic sites of γ-alumina surface. The high potential for the adsorption of DPPH radical on γ-alumina nanoparticles was investigated. Interaction of DPPH with Brønsted and Lewis acidic sites of γ-alumina was more favored than Brønsted basic sites. The following order for the adsorption of DPPH over the different active sites of γ-alumina was predicted: Brønsted base free radicals. Copyright © 2018. Published by Elsevier B.V.

  11. Electronic Control on Linear versus Branched Alkylation of 2-/3-Aroylbenzofurans with Acrylates: Combined DFT and Synthetic Studies.

    Science.gov (United States)

    Srinivas, Kolluru; Dangat, Yuvraj; Kommagalla, Yadagiri; Vanka, Kumar; Ramana, Chepuri V

    2017-06-01

    Investigations on the factors that govern unusual branched alkylation of 2-aroylbenzofurans with acrylates by Ru-catalyzed carbonyl-directed C-H activation has been carried out by calculating the kinetics associated with the two key steps-the coordination of the acrylate with the intermediate ruthenacycle and the subsequent migratory insertion reaction-studied with the help of DFT calculations. Eight possible orientations for each mode of alkylation have been considered for the calculations. From these calculations, it has been understood that there is a synergistic operation of the steric and electronic effects favoring the branched alkylation. Further DFT investigations on the alkylation of the isomeric 3-aroylbenzofurans indicated a preference for the linear alkylation and this has been verified experimentally. Overall, the observed/calculated complementary selectivity in the alkylation of 2-/3-aroylbenzofurans with acrylates reveals that the substrate-dependent charge distribution of the Ru-C bond in the intermediate ruthenacycle is an important determining factor and thus the current work opens up a new domain of substrate design for controlling regioselectivity. © 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

  12. An EQT-based cDFT approach for a confined Lennard-Jones fluid mixture

    Energy Technology Data Exchange (ETDEWEB)

    Motevaselian, M. H.; Mashayak, S. Y.; Aluru, N. R., E-mail: aluru@illinois.edu [Department of Mechanical Science and Engineering, Beckman Institute for Advanced Science and Technology, University of Illinois at Urbana-Champaign, Urbana, Illinois 61801 (United States)

    2015-09-28

    Empirical potential-based quasi-continuum theory (EQT) provides a route to incorporate atomistic detail into continuum framework such as the Nernst-Planck equation. EQT can also be used to construct a grand potential functional for classical density functional theory (cDFT). The combination of EQT and cDFT provides a simple and fast approach to predict the inhomogeneous density, potential profiles, and thermodynamic properties of confined fluids. We extend the EQT-cDFT approach to confined fluid mixtures and demonstrate it by simulating a mixture of methane and hydrogen inside slit-like channels of graphene. We show that the EQT-cDFT predictions for the structure of the confined fluid mixture compare well with the molecular dynamics simulation results. In addition, our results show that graphene slit nanopores exhibit a selective adsorption of methane over hydrogen.

  13. All-optical generation of DFT-S-OFDM superchannels using periodic sinc pulses.

    Science.gov (United States)

    Lowery, Arthur James; Zhu, Chen; Viterbo, Emanuele; Corcoran, Bill

    2014-11-03

    Discrete-Fourier-transform spread (DFT-S) optical Orthogonal Frequency Division Multiplexed (OFDM) signals offer improved nonlinearity performance in long haul optical communications systems, and can be used to form superchannels. In this paper we propose how DFT-S-OFDM superchannels can be generated and demultiplexed using all-optical techniques, and demonstrate the feasibility using numerical simulations. We also discuss how each wavelength channel is similar to recently proposed Orthogonally Time-Division Multiplexed (OrthTDM) systems using periodic-sinc pulses from, for example, a Nyquist laser. The key difference between OrthTDM and DFT-S-OFDM is the synchronization of the symbol boundaries of every modulation tributary; because of this we show that OrthTDM cannot be formed into superchannels that can be demultiplexed without penalties, but DFT-S-OFDM can be.

  14. Methyl Iodide Oxidative Addition to Rhodium(I) Complexes: a DFT ...

    African Journals Online (AJOL)

    NJD

    to the understanding of the role of the steric and electronic prop- erties of the different .... The pure Density Functional Theory (DFT) calculations were carried out using .... Since quantum computational methods are applied for the first time to ...

  15. A Feminist Reading of a Regional Novel: Zora Neale Hurston's ...

    African Journals Online (AJOL)

    The novel, Jonah's Gourd Vine, comprises a search for self-identity for the black man and the black woman in America, as well as a search for new roles for each of the sexes during that period of transition in the African-American history just after the Slave Emancipation. Using the sociological framework qualified by the ...

  16. Synthesis and corrosion inhibition application of NATN on mild steel surface in acidic media complemented with DFT studies

    Science.gov (United States)

    Al-Baghdadi, Shaimaa B.; Hashim, Fanar G.; Salam, Ahmed Q.; Abed, Talib K.; Gaaz, Tayser Sumer; Al-Amiery, Ahmed A.; Kadhum, Abdul Amir H.; Reda, Khalid S.; Ahmed, Wahab K.

    2018-03-01

    The corrosion inhibition effectiveness of thiosemicarbazide compound, namely 3-nitro-5-(2-amino-1,3,4-thiadiazolyl)nitrobenzene (NATN), on mild steel in 1 M hydrochloric acid media has been investigated by weight loss technique. The results exhibit that the corrosion ratio of mild steel was reduced regarding to adding NATN. The corrosion inhibition rate for the NATN was 92.3% at the highest investigated NATN concentration. From the weight loss results it could be concluded that NATN with sulfur, nitrogen and oxygen atoms has clarified best corrosion inhibition achievement comparing to 3,5-dinitrobenzoic acid. Regarding to theoretical studies, DFT was employee to figured geometrical structure and electronic characteristics on NATN. The investigation have been extensive to the HOMO and LUMO analysis to evaluate the energy gap, Ionization potential, Electron Affinity, Global Hardness, Chemical Potential, Electrophilicity, Electronegativity and Polarizability.

  17. Synthesis and corrosion inhibition application of NATN on mild steel surface in acidic media complemented with DFT studies

    Directory of Open Access Journals (Sweden)

    Shaimaa B. Al-Baghdadi

    2018-03-01

    Full Text Available The corrosion inhibition effectiveness of thiosemicarbazide compound, namely 3-nitro-5-(2-amino-1,3,4-thiadiazolylnitrobenzene (NATN, on mild steel in 1 M hydrochloric acid media has been investigated by weight loss technique. The results exhibit that the corrosion ratio of mild steel was reduced regarding to adding NATN. The corrosion inhibition rate for the NATN was 92.3% at the highest investigated NATN concentration. From the weight loss results it could be concluded that NATN with sulfur, nitrogen and oxygen atoms has clarified best corrosion inhibition achievement comparing to 3,5-dinitrobenzoic acid. Regarding to theoretical studies, DFT was employee to figured geometrical structure and electronic characteristics on NATN. The investigation have been extensive to the HOMO and LUMO analysis to evaluate the energy gap, Ionization potential, Electron Affinity, Global Hardness, Chemical Potential, Electrophilicity, Electronegativity and Polarizability. Keywords: NATN, Mild steel, Weight loss, Dinitrobenzoic acid

  18. Systematic pseudopotentials from reference eigenvalue sets for DFT calculations: Pseudopotential files

    Directory of Open Access Journals (Sweden)

    Pablo Rivero

    2015-06-01

    Full Text Available We present in this article a pseudopotential (PP database for DFT calculations in the context of the SIESTA code [1–3]. Comprehensive optimized PPs in two formats (psf files and input files for ATM program are provided for 20 chemical elements for LDA and GGA exchange-correlation potentials. Our data represents a validated database of PPs for SIESTA DFT calculations. Extensive transferability tests guarantee the usefulness of these PPs.

  19. Application of DFT Filter Banks and Cosine Modulated Filter Banks in Filtering

    Science.gov (United States)

    Lin, Yuan-Pei; Vaidyanathan, P. P.

    1994-01-01

    None given. This is a proposal for a paper to be presented at APCCAS '94 in Taipei, Taiwan. (From outline): This work is organized as follows: Sec. II is devoted to the construction of the new 2m channel under-decimated DFT filter bank. Implementation and complexity of this DFT filter bank are discussed therein. IN a similar manner, the new 2m channel cosine modulated filter bank is discussed in Sec. III. Design examples are given in Sec. IV.

  20. Calorimetric, FTIR and 1H NMR measurements in combination with DFT calculations for monitoring solid-state changes of dynamics of sibutramine hydrochloride.

    Science.gov (United States)

    Pajzderska, Aleksandra; Chudoba, Dorota M; Mielcarek, Jadwiga; Wąsicki, Jan

    2012-10-01

    Two forms of sibutramine hydrochloride, monohydrate and anhydrous, have been investigated by calorimetric methods, Fourier transform infrared (FTIR) absorption and (1) H nuclear magnetic resonance (NMR) measurements as well as by density functional theory (DFT) of vibrational frequencies and infrared intensities, calculations of steric hindrances and Monte Carlo simulations. The results of FTIR spectra combined with DFT calculations permitted identification of the bands corresponding to the dynamics and vibrations of water molecules. NMR study and Monte Carlo simulations revealed the occurrence of reorientation jumps of the methyl groups in sibutramine cation and also revealed that the reorientation of isopropyl group is possible only in sibutramine monohydrate hydrochloride. The hydration of sibutramine hydrochloride causes a change in the conformation of sibutramine cation. Copyright © 2012 Wiley-Liss, Inc.

  1. Simulated structure and imaging of NTCDI on Si(1 1 1)-7 × 7 : a combined STM, NC-AFM and DFT study

    Science.gov (United States)

    Jarvis, S. P.; Sweetman, A. M.; Lekkas, I.; Champness, N. R.; Kantorovich, L.; Moriarty, P.

    2015-02-01

    The adsorption of naphthalene tetracarboxylic diimide (NTCDI) on Si(1 1 1)-7 × 7 is investigated through a combination of scanning tunnelling microscopy (STM), noncontact atomic force microscopy (NC-AFM) and density functional theory (DFT) calculations. We show that NTCDI adopts multiple planar adsorption geometries on the Si(1 1 1)-7 × 7 surface which can be imaged with intramolecular bond resolution using NC-AFM. DFT calculations reveal adsorption is dominated by covalent bond formation between the molecular oxygen atoms and the surface silicon adatoms. The chemisorption of the molecule is found to induce subtle distortions to the molecular structure, which are observed in NC-AFM images.

  2. DFT Perspective on the Thermochemistry of Carbon Nitride Synthesis

    KAUST Repository

    Melissen, Sigismund T. A. G.

    2016-10-11

    Graphitic (g)-CxNyHz has become a popular family of photoharvesters in photocatalytic water splitting cells, as well as other applications in chemistry. In this Article, different g-CxNyHz structures were studied thermochemically using DFT. Following a benchmark study with different families of functionals, the B3LYP functional was shown to accurately capture the thermochemistry of carbon nitride synthesis. A triple-ζ polarized basis set, in combination with Civalleri’s modification to Grimme’s D2 formalism (with s6 = 0.5) for dispersion interactions, yielded accurate geometries. Grimme’s D3 formalism with Becke–Johnson damping was used to refine the energetic description of dispersion interactions. The stepwise cycloaddition of cyanamide to form melamine was shown to be exergonic, whereas the stepwise deamination of melamine to form g-C3N4 was shown to be endergonic. Of those structures respecting the [C6N9H3]n chemical formula, the structure commonly known as “melon” was found to be most stable, whereas the sp3-hybridized [C6N9H3]n elucidated by Horvath-Bordon et al. was found to be the least stable. Fully polymerized triazine-based g-C3N4 appeared slightly more stable than heptazine-based g-C3N4.

  3. Calculation on uranium carbon oxygen system molecular structure by DFT

    International Nuclear Information System (INIS)

    Zhang Guangfeng; Wang Xiaolin; Zou Lexi; Sun Ying; Xue Weidong; Zhu Zhenghe; Wang Hongyan

    2001-01-01

    The authors study on the possible molecular structures U-C-O, U-O-C, C-U-O (angular structure C a nd linear structure C ∞υ ) of carbon monoxide interacting on uranium metal surface by Density functional theory (DFT). The uranium atom is used RECP (Relativistic Effective Core Potential) and contracted valence basis sets (6s5p2d4f)/[3s3p2d2f], and for carbon and oxygen atoms all are 6-311G basis sets. The author presents the results of energy optimum which shows that triple and quintuple state are more stable. The authors get the electronic state, geometry structure, energy, harmonic frequency, mechanical property, etc. of these twelve triple and quintuple state relative stable structures. The normal vibrational analytical figure of angular structure (C s ) and linear structure (C ∞υ ) is given at the same time. It is indicated that angular structure has lower energy than linear structure, moreover the angular structure of U-C-O( 3 A ) has the lowest energy. The bond strength between uranium atom and carbon monoxide is weak and between uranium atom and oxygen atom is slightly stronger than between uranium atom and carbon atom which the authors can know by superposition population and bond energy analysis among atoms

  4. DFT Perspective on the Thermochemistry of Carbon Nitride Synthesis

    KAUST Repository

    Melissen, Sigismund T. A. G.; Steinmann, Stephan N.; Le Bahers, Tangui; Sautet, Philippe

    2016-01-01

    Graphitic (g)-CxNyHz has become a popular family of photoharvesters in photocatalytic water splitting cells, as well as other applications in chemistry. In this Article, different g-CxNyHz structures were studied thermochemically using DFT. Following a benchmark study with different families of functionals, the B3LYP functional was shown to accurately capture the thermochemistry of carbon nitride synthesis. A triple-ζ polarized basis set, in combination with Civalleri’s modification to Grimme’s D2 formalism (with s6 = 0.5) for dispersion interactions, yielded accurate geometries. Grimme’s D3 formalism with Becke–Johnson damping was used to refine the energetic description of dispersion interactions. The stepwise cycloaddition of cyanamide to form melamine was shown to be exergonic, whereas the stepwise deamination of melamine to form g-C3N4 was shown to be endergonic. Of those structures respecting the [C6N9H3]n chemical formula, the structure commonly known as “melon” was found to be most stable, whereas the sp3-hybridized [C6N9H3]n elucidated by Horvath-Bordon et al. was found to be the least stable. Fully polymerized triazine-based g-C3N4 appeared slightly more stable than heptazine-based g-C3N4.

  5. 3-Iodobenzaldehyde: XRD, FT-IR, Raman and DFT studies.

    Science.gov (United States)

    Kumar, Chandraju Sadolalu Chidan; Parlak, Cemal; Tursun, Mahir; Fun, Hoong-Kun; Rhyman, Lydia; Ramasami, Ponnadurai; Alswaidan, Ibrahim A; Keşan, Gürkan; Chandraju, Siddegowda; Quah, Ching Kheng

    2015-06-15

    The structure of 3-iodobenzaldehyde (3IB) was characterized by FT-IR, Raman and single-crystal X-ray diffraction techniques. The conformational isomers, optimized geometric parameters, normal mode frequencies and corresponding vibrational assignments of 3IB were examined using density functional theory (DFT) method, with the Becke-3-Lee-Yang-Parr (B3LYP) functional and the 6-311+G(3df,p) basis set for all atoms except for iodine. The LANL2DZ effective core basis set was used for iodine. Potential energy distribution (PED) analysis of normal modes was performed to identify characteristic frequencies. 3IB crystallizes in monoclinic space group P21/c with the O-trans form. There is a good agreement between the theoretically predicted structural parameters, and vibrational frequencies and those obtained experimentally. In order to understand halogen effect, 3-halogenobenzaldehyde [XC6H4CHO; X=F, Cl and Br] was also studied theoretically. The free energy difference between the isomers is small but the rotational barrier is about 8kcal/mol. An atypical behavior of fluorine affecting conformational preference is observed. Copyright © 2015 Elsevier B.V. All rights reserved.

  6. DFT application for chlorin derivatives photosensitizer drugs modeling

    Science.gov (United States)

    Machado, Neila; Carvalho, B. G.; Téllez Soto, C. A.; Martin, A. A.; Favero, P. P.

    2018-04-01

    Photodynamic therapy is an alternative form of cancer treatment that meets the desire for a less aggressive approach to the body. It is based on the interaction between a photosensitizer, activating light, and molecular oxygen. This interaction results in a cascade of reactions that leads to localized cell death. Many studies have been conducted to discover an ideal photosensitizer, which aggregates all the desirable characteristics of a potent cell killer and generates minimal side effects. Using Density Functional Theory (DFT) implemented in the program Vienna Ab-initio Simulation Package, new chlorin derivatives with different functional groups were simulated to evaluate the different absorption wavelengths to permit resonant absorption with the incident laser. Gaussian 09 program was used to determine vibrational wave numbers and Natural Bond Orbitals. The chosen drug with the best characteristics for the photosensitizer was a modified model of the original chlorin, which was called as Thiol chlorin. According to our calculations it is stable and is 19.6% more efficient at optical absorption in 708 nm in comparison to the conventional chlorin e6. Vibrational modes, optical and electronic properties were predicted. In conclusion, this study is an attempt to improve the development of new photosensitizer drugs through computational methods that save time and contribute to decrease the numbers of animals for model application.

  7. Proton transfers in the Strecker reaction revealed by DFT calculations

    Directory of Open Access Journals (Sweden)

    Shinichi Yamabe

    2014-08-01

    Full Text Available The Strecker reaction of acetaldehyde, NH3, and HCN to afford alanine was studied by DFT calculations for the first time, which involves two reaction stages. In the first reaction stage, the aminonitrile was formed. The rate-determining step is the deprotonation of the NH3+ group in MeCH(OH-NH3+ to form 1-aminoethanol, which occurs with an activation energy barrier (ΔE≠ of 9.6 kcal/mol. The stereochemistry (R or S of the aminonitrile product is determined at the NH3 addition step to the carbonyl carbon of the aldehyde. While the addition of CN− to the carbon atom of the protonated imine 7 appears to scramble the stereochemistry, the water cluster above the imine plane reinforces the CN− to attack the imine group below the plane. The enforcement hinders the scrambling. In the second stage, the aminonitrile transforms to alanine, where an amide Me-CH(NH2-C(=O-NH2 is the key intermediate. The rate-determining step is the hydrolysis of the cyano group of N(amino-protonated aminonitrile which occurs with an ΔE≠ value of 34.7 kcal/mol. In the Strecker reaction, the proton transfer along the hydrogen bonds plays a crucial role.

  8. Low-lying excited states by constrained DFT

    Science.gov (United States)

    Ramos, Pablo; Pavanello, Michele

    2018-04-01

    Exploiting the machinery of Constrained Density Functional Theory (CDFT), we propose a variational method for calculating low-lying excited states of molecular systems. We dub this method eXcited CDFT (XCDFT). Excited states are obtained by self-consistently constraining a user-defined population of electrons, Nc, in the virtual space of a reference set of occupied orbitals. By imposing this population to be Nc = 1.0, we computed the first excited state of 15 molecules from a test set. Our results show that XCDFT achieves an accuracy in the predicted excitation energy only slightly worse than linear-response time-dependent DFT (TDDFT), but without incurring into problems of variational collapse typical of the more commonly adopted ΔSCF method. In addition, we selected a few challenging processes to test the limits of applicability of XCDFT. We find that in contrast to TDDFT, XCDFT is capable of reproducing energy surfaces featuring conical intersections (azobenzene and H3) with correct topology and correct overall energetics also away from the intersection. Venturing to condensed-phase systems, XCDFT reproduces the TDDFT solvatochromic shift of benzaldehyde when it is embedded by a cluster of water molecules. Thus, we find XCDFT to be a competitive method among single-reference methods for computations of excited states in terms of time to solution, rate of convergence, and accuracy of the result.

  9. DFT calculations on electronic properties of ZnO thin films deposited by spray pyrolysis

    Energy Technology Data Exchange (ETDEWEB)

    Cordeiro, J.M.; Reynoso, V.C.; Azevedo, D.H.M. [Universidade Estadual Paulista Julio de Mesquita Filho (UNESP), SP (Brazil)

    2016-07-01

    Full text: Introduction - Thin films of Zinc oxide (ZnO) has a wide range of technological applications, as transparent conducting electrodes in solar cells, flat panel displays, and sensors, for example. More recently applications in optoelectronics, like light emitter diodes and laser diodes, due to its large band gap, are been explored. Studies of ZnO thin films are important for these applications. Methodology - In this study thin films of ZnO have been deposited by spray pyrolysis on glass substrate. The films were characterized by XRD and UV-VIS techniques and the electronic properties as a function of the film thickness have been investigated by DFT calculations with B3LYP hybrid potential implemented in the CRYSTAL09 code. Results - The diffractograms obtained for the ZnO thin films as a function of the thickness are shown. The films exhibit a hexagonal wurtzite structure with preferred c-axis orientation in (002) direction of ZnO crystal. A quantum mechanical approach based on the periodic Density Functional Theory (DFT), with B3LYP hybrid potential was used to investigate the electronic structure of the films as a function of the thickness. The CRYSTAL09 code has been used for the calculations on the wurtzite hexagonal structure of ZnO - spatial group P63mc. For optimizing the geometry of the pure ZnO crystal, the experimental lattice parameters were got as follows: a= 0.325 nm, b= 0.325 nm, c= 0.5207 nm with c/a= 1.602. Considering to the calculations of the band structure, it is suggested that the semiconducting properties of ZnO arises from the overlapping of the 4s orbital of the conducting band of Zn and the 2p orbital of the top of valence band of O. Conclusions - The structure of ZnO thin film deposited on glass substrate present preferential orientation in (002) direction. Variation in the optical properties as a function of the film thickness was observed. The band gap energy was determined from optical analysis to be ∼ 3.27 eV. The refractive

  10. Electronic and optical properties of 2D graphene-like ZnS: DFT calculations

    International Nuclear Information System (INIS)

    Lashgari, Hamed; Boochani, Arash; Shekaari, Ashkan; Solaymani, Shahram; Sartipi, Elmira; Mendi, Rohollah Taghavi

    2016-01-01

    Graphical abstract: - Highlights: • DFT has been applied to investigate the optical properties of 2D-ZnS and 3D-ZnS. • The electronic and the optical properties of 3D-ZnS and 2D-ZnS are compared. • At visible range of energies the transparency of 2D-ZnS is more than the 3D. - Abstract: Density-functional theory has been applied to investigate the electronic and optical properties of graphene-like two-dimensional ZnS in the (0001) direction of its Wurtzite phase. A comparison with 3D-ZnS has been carried out within the PBE- and EV-GGA. The electronic properties of 2D- and 3D-ZnS have been derived by the examination of the electronic band structures and density of states. The optical properties have been determined through the study of the dielectric function, reflectivity, electron loss function, refractive and extinction indices, the absorption index and optical conductivity. It is found that the transparency of 2D-ZnS is greater than the 3D over the visible range. A thorough study of the dielectric function has been performed so that the peaks and the transition bands have been specified. The electron loss function demonstrates that the plasmonic frequency for 2D- and 3D-ZnS is accrued at 11.22 and 19.93 eV within the PBE-GGA, respectively.

  11. Theoretical simulations on the antioxidant mechanism of naturally occurring flavonoid: A DFT approach

    International Nuclear Information System (INIS)

    Praveena, R.; Sadasivam, K.

    2016-01-01

    Synthetic antioxidants such as butylated hydroxyanisole (BHA) and butylated hydroxytoluene (BHT) are found to be toxic, hence non-carcinogenic naturally occurring radical scavengers especially flavonoids have gained considerable importance in the past two decades. In the present investigation, the radical scavenging activity of C-glycosyl flavonoids is evaluated using theoretical approach which could broaden its scope in therapeutic applications. Gas and solvent phase studies of structural and molecular characteristics of C-glycosyl flavonoid, isovitexin is investigated through hydrogen atom transfer mechanism (HAT), Electron transfer-proton transfer (ET–PT) and Sequential proton loss electron transfer (SPLET) by Density functional theory (DFT) using hybrid parameters. The computed values of the adiabatic ionization potential, electron affinity, hardness, softness, electronegativity and electrophilic index indicate that isovitexin possess good radical scavenging activity. The behavior of different –OH groups in polyphenolic compounds is assessed by considering electronic effects of the neighbouring groups and the overall geometry of molecule which in turn helps in analyzing the antioxidant capacity of the polyphenolic molecule. The studies indicate that the H–atom abstraction from 4’–OH site is preferred during the radical scavenging process. From Mulliken spin density analysis and FMOs, B–ring is found to be more delocalized center and capable of electron donation. Comparison of antioxidant activity of vitexin and isovitexin leads to the conclusion that isovitexin acts as a better radical scavenger. This is an evidence for the importance of position of glucose unit in the flavonoid.

  12. Theoretical simulations on the antioxidant mechanism of naturally occurring flavonoid: A DFT approach

    Energy Technology Data Exchange (ETDEWEB)

    Praveena, R. [Department of Chemistry, Bannari Amman Institute of Technology, Sathyamangalam, Erode, Tamil Nadu (India); Sadasivam, K. [Department of Physics, Bannari Amman Institute of Technology, Sathyamangalam, Erode, Tamil Nadu (India)

    2016-05-06

    Synthetic antioxidants such as butylated hydroxyanisole (BHA) and butylated hydroxytoluene (BHT) are found to be toxic, hence non-carcinogenic naturally occurring radical scavengers especially flavonoids have gained considerable importance in the past two decades. In the present investigation, the radical scavenging activity of C-glycosyl flavonoids is evaluated using theoretical approach which could broaden its scope in therapeutic applications. Gas and solvent phase studies of structural and molecular characteristics of C-glycosyl flavonoid, isovitexin is investigated through hydrogen atom transfer mechanism (HAT), Electron transfer-proton transfer (ET–PT) and Sequential proton loss electron transfer (SPLET) by Density functional theory (DFT) using hybrid parameters. The computed values of the adiabatic ionization potential, electron affinity, hardness, softness, electronegativity and electrophilic index indicate that isovitexin possess good radical scavenging activity. The behavior of different –OH groups in polyphenolic compounds is assessed by considering electronic effects of the neighbouring groups and the overall geometry of molecule which in turn helps in analyzing the antioxidant capacity of the polyphenolic molecule. The studies indicate that the H–atom abstraction from 4’–OH site is preferred during the radical scavenging process. From Mulliken spin density analysis and FMOs, B–ring is found to be more delocalized center and capable of electron donation. Comparison of antioxidant activity of vitexin and isovitexin leads to the conclusion that isovitexin acts as a better radical scavenger. This is an evidence for the importance of position of glucose unit in the flavonoid.

  13. Crystal structure, vibrational and DFT simulation studies of melaminium dihydrogen phosphite monohydrate

    Science.gov (United States)

    Arjunan, V.; Kalaivani, M.; Marchewka, M. K.; Mohan, S.

    2013-08-01

    The crystal structure investigations of melamine with phosphorous acid, namely melaminium dihydrogenphosphite monohydrate (C3N6H7·H2PO3·H2O) have been investigated by means of single crystal X-ray diffraction method. The title compound crystallizes in monoclinic crystal system, and the space group is P21/c with a = 10.069 Å, b = 21.592 Å, c = 12.409 Å and Z = 12. The vibrational assignments and analysis of melaminium dihydrogen phosphite monohydrate have also been performed by FTIR, FT-Raman and far-infrared spectral studies. The quantum chemical simulations were performed with DFT (B3LYP) method using 6-31G**, cc-pVTZ, and 6-311++G** basis sets to determine the energy, structural, thermodynamic parameters and vibrational frequencies of melaminium dihydrogen phosphite monohydrate. The hydrogen atom from phosphorous acid was transferred to the melamine molecule giving the singly protonated melaminium cation. The ability of ions to form spontaneous three-dimensional structure through weak Osbnd H···O and Nsbnd H···O hydrogen bonds shows notable vibrational effects.

  14. Benchmarking the DFT+U method for thermochemical calculations of uranium molecular compounds and solids.

    Science.gov (United States)

    Beridze, George; Kowalski, Piotr M

    2014-12-18

    Ability to perform a feasible and reliable computation of thermochemical properties of chemically complex actinide-bearing materials would be of great importance for nuclear engineering. Unfortunately, density functional theory (DFT), which on many instances is the only affordable ab initio method, often fails for actinides. Among various shortcomings, it leads to the wrong estimate of enthalpies of reactions between actinide-bearing compounds, putting the applicability of the DFT approach to the modeling of thermochemical properties of actinide-bearing materials into question. Here we test the performance of DFT+U method--a computationally affordable extension of DFT that explicitly accounts for the correlations between f-electrons - for prediction of the thermochemical properties of simple uranium-bearing molecular compounds and solids. We demonstrate that the DFT+U approach significantly improves the description of reaction enthalpies for the uranium-bearing gas-phase molecular compounds and solids and the deviations from the experimental values are comparable to those obtained with much more computationally demanding methods. Good results are obtained with the Hubbard U parameter values derived using the linear response method of Cococcioni and de Gironcoli. We found that the value of Coulomb on-site repulsion, represented by the Hubbard U parameter, strongly depends on the oxidation state of uranium atom. Last, but not least, we demonstrate that the thermochemistry data can be successfully used to estimate the value of the Hubbard U parameter needed for DFT+U calculations.

  15. Spectroscopic and DFT study of solvent effects on the electronic absorption spectra of sulfamethoxazole in neat and binary solvent mixtures

    Science.gov (United States)

    Almandoz, M. C.; Sancho, M. I.; Blanco, S. E.

    2014-01-01

    The solvatochromic behavior of sulfamethoxazole (SMX) was investigated using UV-vis spectroscopy and DFT methods in neat and binary solvent mixtures. The spectral shifts of this solute were correlated with the Kamlet and Taft parameters (α, β and π*). Multiple lineal regression analysis indicates that both specific hydrogen-bond interaction and non specific dipolar interaction play an important role in the position of the absorption maxima in neat solvents. The simulated absorption spectra using TD-DFT methods were in good agreement with the experimental ones. Binary mixtures consist of cyclohexane (Cy)-ethanol (EtOH), acetonitrile (ACN)-dimethylsulfoxide (DMSO), ACN-dimethylformamide (DMF), and aqueous mixtures containing as co-solvents DMSO, ACN, EtOH and MeOH. Index of preferential solvation was calculated as a function of solvent composition and non-ideal characteristics are observed in all binary mixtures. In ACN-DMSO and ACN-DMF mixtures, the results show that the solvents with higher polarity and hydrogen bond donor ability interact preferentially with the solute. In binary mixtures containing water, the SMX molecules are solvated by the organic co-solvent (DMSO or EtOH) over the whole composition range. Synergistic effect is observed in the case of ACN-H2O and MeOH-H2O, indicating that at certain concentrations solvents interact to form association complexes, which should be more polar than the individual solvents of the mixture.

  16. Role of the lattice dynamics in La2-xBaxCuO4 superconductor based on DFT method

    Directory of Open Access Journals (Sweden)

    A Tavana

    2010-09-01

    Full Text Available Electron-phonon coupling parameters are calculated for La2-x BaxCuO4 cuprate superconductor in a wide range of dopings, from undoped to overdoped compounds. In this study we aim to study the quality of such calculations based on DFT method so, the results of σ GGA+U electronic structure calculations are also investigated. The obtained value for electron-phonon coupling is in the same order of previous calculations but, the value obtained for the Hubbard U parameter shows that, such methods are poor in the estimation of electronic correlations to decide about the role of phonons in these compounds based on their results. Moreover, existence of several structural phase transitions with temperature and doping, lead to larger error in these calculations. Based on the calculated phonon dispersions, structural phase transitions can be resulted which shows the ability of DFT in the study of structural properties and the weakness of the strongly correlations in this properties.

  17. Mechanism and Regioselectivity of Rh(III)-Catalyzed Intermolecular Annulation of Aryl-Substituted Diazenecarboxylates and Alkenes: DFT Insights

    KAUST Repository

    Ajitha, Manjaly John

    2016-02-05

    The mechanism of Rh-catalyzed intermolecular annulation of aryl-substituted diazenecarboxylates and alkenes was investigated using density functional theory (DFT) (PCM-M062X/6-311+G(d,p)//M062X/6-31G(d)). The acetate ligand (OAc)-assisted C-H activation via the formation of a five-membered rhodacycle (I-TS1; ΔG‡ = 19.4 kcal/mol) is more favorable compared to that via a four-membered intermediate (II-TS1; ΔG‡ = 27.8 kcal/mol). Our results also revealed that the seven-membered intermediate (I-3, ΔGrel = -6.8 kcal/mol) formed after the alkene insertion could undergo a coordination switch with the adjacent nitrogen atom (via TScs; ΔG‡ = 16.5 kcal/mol) to produce a thermodynamically stable six-membered intermediate (II-3, ΔGrel = -10.4 kcal/mol), eventually leading to a cyclization process followed by a barrierless ligand-assisted protonation to yield the final product. The β-hydride elimination product was found to be kinetically and thermodynamically undesirable. The rate-determining step is identified as the initial C-H activation, consistent with the previous kinetic studies. Notably, DFT studies offered important insights on the ability of the substrate (diazene carboxylate) to promote the switchable coordination site selectivity during the reaction to achieve a lower energy pathway. © 2016 American Chemical Society.

  18. Thermoanalytical, spectroscopic and DFT studies of heavy trivalent lanthanides and yttrium(III) with oxamate as ligand

    Energy Technology Data Exchange (ETDEWEB)

    Caires, Flavio Junior; Gaglieri, Caroline, E-mail: caires.flavio@fc.unesp.br [Universidade Estadual Paulista Julio de Mesquita Filho (UNESP), Bauru, SP (Brazil). Faculdade de Ciencias; Nunes, Wilhan Donizete Goncalves; Nascimento, Andre Luiz Carneiro Soares do; Teixeira, Jose Augusto; Zangaro, Georgia Alvim Coelho; Treu-Filho, Oswaldo; Ionashiro, Massao [Universidade Estadual Paulista Julio de Mesquita Filho (UNESP), Araraquara, SP (Brazil)

    2017-07-15

    Solid-state LnL{sub 3}∙nH{sub 2}O complexes, where Ln stands for trivalent lanthanides (Tb to Lu) or yttrium(III) and L is oxamate (NH{sub 2}COCO{sub 2}{sup -}), have been synthesized. The characterization of the complexes was performed by using elemental analysis (EA), complexometric titration with EDTA, thermoanalytical techniques such as simultaneous thermogravimetry and differential scanning calorimetry (TG-DSC), evolved gas analysis (TG-FTIR), infrared spectroscopy (IR) and powder X-ray diffraction (XRPD). The results provided information about thermal behavior, crystallinity, stoichiometry, coordination sites, as well as the products released during thermal degradation of the complexes studied. Theoretical calculation of yttrium oxamate, as representative of all complexes was performed using density functional theory (DFT) for studying the molecular structure and vibrational spectrum of the investigated molecule in the ground state. The optimized geometrical parameters and theoretical vibrational spectrum obtained by DFT calculations are in good agreement with the experimental results. (author)

  19. Study on the Reactivity of Amino Acid Chemosensor, NPFNP, with Ethanol: Structural Elucidation through Single Crystal XRD and DFT Calculations

    Directory of Open Access Journals (Sweden)

    Beena Varghese

    2017-01-01

    Full Text Available A novel ethoxy derivative of an amino acid chemosensor, 3-naphthyl-1-phenyl-5-(2ʹ-fluoro-5ʹ-nitrophenyl-2-pyrazoline (NPFNP, has been synthesized and characterized by different spectroscopic methods.  A single crystal of the ethoxy derivative, 3-naphthyl-1-phenyl-5-(2ʹ-ethoxy-5ʹ-nitrophenyl-2-pyrazoline NPENP, has been obtained and characterized.  The structure holds interest as it carries biologically active pyrazoline as a central ring attaching to electron donating and withdrawing substituents. The major motivation for this work was to gain detailed insight into the structural parameters of this compound for investigating the influence of crystal packing and geometrical dimensions on optical properties. Time-dependent DFT calculations have been employed for comparing the XRD data with theoretical parameters. The results show that the DFT method at B3LYP/6-31G level can well reproduce the structure of the title compound.

  20. A DFT study of the effects of Sc doping on electronic and optical properties of CdS nanoparticles

    Directory of Open Access Journals (Sweden)

    Ur Rehman Shafiq

    2015-12-01

    Full Text Available In the present work a systematic study was carried out to understand the influence of Sc doping on electronic and optical properties of CdS nanoparticles. The geometry optimization and symmetry computation for CdS and Sc doped CdS nanoparticles using Density Functional Theory (DFT on B3LYP level with the QZ4P for Cd and DZ2P for sulphur and Sc were performed by Amsterdam Density Functional (ADF. The results show that HOMO-LUMO gap as well as electronic and optical properties of CdS clusters vary with Sc doping. The HOMO-LUMO gap is affected by the dopant and its value decreases to 0.6 eV. Through considering the numerical integration scheme in the ADF package, we investigated different vibrational modes and our calculated Raman and IR spectra are consistent with the reported result. The calculated IR and Raman peaks of CdS and Sc doped CdS clusters were in the range of 100 to 289 cm−1, 60 cm−1 to 350 cm−1 and 99 cm−1 to 282 cm−1, 60 cm−1 to 350 cm−1, respectively, which was also confirmed by experiment as well as a blue shift occurrence. Subsequently, for deeper research of pure and doped CdS clusters, their absorption spectra were calculated using time-dependent DFT method.

  1. DFT and EXAFS, mutually enhancing tools for structure elucidation of Tc complexes

    International Nuclear Information System (INIS)

    Breynaert, E.; Bruggeman, C.; Maes, A.

    2005-01-01

    experimental Tc EXAFS/XANES spectra of the Tc-pyrogallol complexes under consideration have yielded relatively good estimates of the coordination number, surrounding atom types and bond lengths of the chemical environment of the Tc atom in the species under investigation. This information was used to construct a first guess for an initial geometry from which a DFT geometry optimization was started. The DFT-optimized geometry was in its turn used to create high quality theoretical standards with ab initio multiple scattering software like FEFF [4] which were used to perform high quality fits of the experimental EXAFS/XANES spectra being studied. The authors acknowledge a grant from KULeuven University and financial support from the KULeuven Geconcerteerde Onderzoeksacties (GOA2000/007). We also kindly acknowledge NIRAS/ONDRAF for financial support from Contract CCHO 20004004862 [1] Cui, D.Q. and T.E. Eriksen, Reduction of pertechnetate in solution by heterogeneous electron transfer from Fe(II)-containing geological material. Environmental Science and Technology, 1996. 30(7): p. 2263-2269. [2] Maes, A., et al., Quantification of the interaction of Tc with dissolved boom clay humic substances. Environmental Science and Technology, 2003. 37(4): p. 747-753. [3] Gancheff, J., et al., Density functional study of technetium and rhenium compounds. Journal of Molecular Structure-Theochem, 2002. 580: p. 107-116. [4] Zabinsky, S.I., et al., Multiple-scattering calculations of x-ray-absorption spectra. Phys. Rev. B, 1995. 52: p. p. 2995. (authors)

  2. IR and NMR spectroscopic correlation of enterobactin by DFT

    Science.gov (United States)

    Moreno, M.; Zacarias, A.; Porzel, A.; Velasquez, L.; Gonzalez, G.; Alegría-Arcos, M.; Gonzalez-Nilo, F.; Gross, E. K. U.

    2018-06-01

    Emerging and re-emerging epidemic diseases pose an ongoing threat to global health. Currently, Enterobactin and Enterobactin derivatives have gained interest, owing to their potential application in the pharmaceutical field. As it is known [J. Am. Chem. Soc (1979) 101, 20, 6097-6104], Enterobactin (H6EB) is an efficient iron carrier synthesized and secreted by many microbial species. In order to facilitate the elucidation of enterobactin and its analogues, here we propose the creation of a H6EB standard set using Density Functional Theory Infrared (IR) and NMR spectra. We used two exchange-correlation (xc) functionals (PBE including long-range corrections sbnd LC-PBEsbnd and mPW1), 2 basis sets (QZVP and 6-31G(d)) and 2 grids (fine and ultrafine) for most of the H6EB structures dependent of dihedral angles. The results show a significant difference between the Osbnd H and Nsbnd H bands, while the Cdbnd O amide and Osbnd (Cdbnd O)sbnd IR bands are often found on top of each other. The NMR DFT calculations show a strong dependence on the xc functional, basis set, and grid used for the H6EB structure. Calculated 1H and 13C NMR spectra enable the effect of the solvent to be understood in the context of the experimental measurements. The good agreement between the experimental and the calculated spectra using LC-PBE/QZVP and ultrafine grid suggest the possibility of the systems reported here to be considered as a standard set. The dependence of electrostatic potential and frontier orbitals with the catecholamide dihedral angles of H6EB is described. The matrix-assisted laser desorption/ionization time of the flight mass spectrometry (MALDI-TOF MS) of H6EB is also reported of manner to enrich the knowledge about its reactivity.

  3. The removal of mercury ion pollution by using Fe3O4-nanocellulose: Synthesis, characterizations and DFT studies.

    Science.gov (United States)

    Zarei, Saeid; Niad, Mahmood; Raanaei, Hossein

    2018-02-15

    In this study, we have attempted to extract cellulose from Cystoseria myricaas algae. Nanocellulose, Fe 3 O 4 and Fe3O4-nanocellulose compounds are synthesized by acid hydrolysis and co-precipitation as well as sol-gel methods The synthesized compounds are characterized by x-ray diffraction, transmission electron microscopy, particle size distribution (PSD), scanning electron microscopy (SEM),energy dispersive x-ray spectroscopy, vibrating sample magnetometer and Fourier transform infrared spectroscopy. The Hg (II) uptake on Fe3O4-nanocellulose is investigated by 14 isotherm models, 12 kinetic models, adsorption activation energy as well as thermodynamic of adsorption. The polymers of algae and the interactions between Hg (II) and cellulose are investigated by density functional theory (DFT) in various conditions. The results of both simulations show a good agreement with experimental data. Copyright © 2017 Elsevier B.V. All rights reserved.

  4. The study of intermolecular interactions in NLO crystal melaminium chloride hemihydrate using DFT simulation and Hirshfeld surface analysis

    Science.gov (United States)

    Sangeetha, K.; Kumar, V. R. Suresh; Marchewka, M. K.; Binoy, J.

    2018-05-01

    Since, the intermolecular interactions play a crucial role in the formation of crystalline network, its analysis throws light on structure dependent crystalline properties. In the present study, DFT based vibrational spectral investigation has been performed in the stretching region (3500 cm-1 - 2800 cm-1) of IR and Raman spectra of melaminium chloride hemihydrates. The intermolecular interaction has been investigated by analyzing the half width of the OH and NH stretching profile of the deconvoluted spectra. Correlation of vibrational spectra with Hirshfeld surface analysis and finger print plot has been contemplated and molecular docking studies has been performed on melaminium chloride hemihydrate to assess its role in the drug transport mechanism and toxicity to human body.

  5. DFT-based prediction of reactivity of short-chain alcohol dehydrogenase

    Science.gov (United States)

    Stawoska, I.; Dudzik, A.; Wasylewski, M.; Jemioła-Rzemińska, M.; Skoczowski, A.; Strzałka, K.; Szaleniec, M.

    2017-06-01

    The reaction mechanism of ketone reduction by short chain dehydrogenase/reductase, ( S)-1-phenylethanol dehydrogenase from Aromatoleum aromaticum, was studied with DFT methods using cluster model approach. The characteristics of the hydride transfer process were investigated based on reaction of acetophenone and its eight structural analogues. The results confirmed previously suggested concomitant transfer of hydride from NADH to carbonyl C atom of the substrate with proton transfer from Tyr to carbonyl O atom. However, additional coupled motion of the next proton in the proton-relay system, between O2' ribose hydroxyl and Tyr154 was observed. The protonation of Lys158 seems not to affect the pKa of Tyr154, as the stable tyrosyl anion was observed only for a neutral Lys158 in the high pH model. The calculated reaction energies and reaction barriers were calibrated by calorimetric and kinetic methods. This allowed an excellent prediction of the reaction enthalpies (R2 = 0.93) and a good prediction of the reaction kinetics (R2 = 0.89). The observed relations were validated in prediction of log K eq obtained for real whole-cell reactor systems that modelled industrial synthesis of S-alcohols.

  6. Possible reaction pathways of the lincomycin molecule according to the DFT calculation method

    Directory of Open Access Journals (Sweden)

    Eren Bahar

    2017-01-01

    Full Text Available Human-used antibiotics are eliminated from the body with little or no transformation at all. Traces of eliminated antibiotics enter the receiving environment directly since they cannot be treated in prevalent wastewater treatment facilities. Thus, wastewaters containing traces of antibiotics have to be treated accordingly. Lincomycin is subsequently isolated from Streptomyces lincolnensis. Lincomycin and its derivatives are antibiotics exhibiting biological activity against Gram-positive bacteria, and are natural antibiotics in the environment as pollutants. This study aims to predict the degradation mechanism of lincomycin molecule in the gaseous phase and aqueous media. Probable reaction path of lincomycin molecule with OH radicals was analyzed. Optimized geometry was calculated via Gauss View 5. Subsequently, the lowest energy status was determined through geometric optimization via Gaussian 09 program. Aiming to determine the intermediates in photocatalytic degradation mechanism of lincomycin, geometric optimization of the molecule was realized through DFT method. Activation energy for the probable reaction path was calculated, and their most stable state from the thermodynamic perspective determined for the gaseous phase and aqueous media. Impact of water solvent was investigated using the conductor-like screening solvation model (COSMO. The predicted mechanism was confirmed by comparison with experimental results on simple structures reported in literature.

  7. Structural and Thermodynamic Analysis of the First Mononuclear Aqueous Aluminum Citrate Complex Using DFT Calculations.

    Science.gov (United States)

    de Noronha, Antonio Luiz Oliveira; Guimarães, Luciana; Duarte, Hélio Anderson

    2007-05-01

    Structural and thermodynamic properties of the mononuclear Al/citrate complexes have been theoretically investigated aiming to understand the coordination mechanism at an atomic level. GGA-DFT/PCM calculations have been performed for the different conformations and tautomers arising from the Al(3+) and citric acid (H3L) interaction in aqueous solution. The Gibbs reaction energies were estimated based on the reaction of the trigonal planar Al(OH)3 and H3L to form different Al-citrate complexes. The estimated Gibbs free reaction energies for the [AlL], [AlHL](+), and [Al(OH)L](-) species are in good agreement with the experimental values. In these species, the Al(3+) center is coordinated by two carboxylic and the tertiary hydroxyl groups of the citrate. Conversely to what has been proposed based on the experiments, the present theoretical calculations indicate that the citric acid hydroxyl group remains protonated upon the coordination of Al(3+). In fact, our model turns out to be more consistent with the relative pKa values of citrate protonation groups and with the hydrolysis constant of the H2O bound to Al(3+) leading to better agreement with the available experimental data.

  8. DFT Study of PH3 Physisorption and Chemisorptions on Boron Nitride Nanotubes

    Science.gov (United States)

    Rakhshi, Mahdi; Mohsennia, Mohsen; Rasa, Hossein

    2018-03-01

    The adsorption of PH3 molecules on the NiB,N-doped(4,4) and (5,5) BNNTS surfaces has been investigated using density functional theory (DFT). The adsorption energies, geometric and electronic structures of the adsorbed systems were studied to judge the possible application of NiB,N-doped BNNTS in PH3 monitoring systems. Our calculated results showed that NiB,N-doped BNNTS had much higher adsorption energy and shorter binding distances than pure BNNTS owning to chemisorptions of the PH3 molecule. The obtained density of states (DOS) and frontier orbitals demonstrated that the orbital hybridization was obvious between the PH3 molecule and NiB,N-doped BNNTS. However, due to weak physisorption according to the total electron density maps, there was no evidence for hybridization between PH3 molecule and pure BNNTS. It was shown that after doping of Ni atom, the primary symmetry of BNNTS decreased which enhanced the chemical activity of BNNTS towards PH3 molecules. According to the obtained results, we highlight the high potential application of NiB,N-doped BNNTS in the design and fabrication of PH3 sensing devices.

  9. DFT modeling of the electronic and magnetic structures and chemical bonding properties of intermetallic hydrides

    International Nuclear Information System (INIS)

    Al Alam, A.F.

    2009-06-01

    This thesis presents an ab initio study of several classes of intermetallics and their hydrides. These compounds are interesting from both a fundamental and an applied points of view. To achieve this aim two complementary methods, constructed within the DFT, were chosen: (i) pseudo potential based VASP for geometry optimization, structural investigations and electron localization mapping (ELF), and (ii) all-electrons ASW method for a detailed description of the electronic structure, chemical bonding properties following different schemes as well as quantities depending on core electrons such as the hyperfine field. A special interest is given with respect to the interplay between magneto-volume and chemical interactions (metal-H) effects within the following hydrided systems: binary Laves (e.g. ScFe 2 ) and Haucke (e.g. LaNi 5 ) phases on one hand, and ternary cerium based (e.g. CeRhSn) and uranium based (e.g. U 2 Ni 2 Sn) alloys on the other hand. (author)

  10. DFT +U Modeling of Hole Polarons in Organic Lead Halide Perovskites

    Science.gov (United States)

    Welch, Eric; Erhart, Paul; Scolfaro, Luisa; Zakhidov, Alex

    Due to the ever present drive towards improved efficiencies in solar cell technology, new and improved materials are emerging rapidly. Organic halide perovskites are a promising prospect, yet a fundamental understanding of the organic perovskite structure and electronic properties is missing. Particularly, explanations of certain physical phenomena, specifically a low recombination rate and high mobility of charge carriers still remain controversial. We theoretically investigate possible formation of hole polarons adopting methodology used for oxide perovskites. The perovskite studied here is the ABX3structure, with A being an organic cation, B lead and C a halogen; the combinations studied allow for A1,xA2 , 1 - xBX1,xX2 , 3 - xwhere the alloy convention is used to show mixtures of the organic cations and/or the halogens. Two organic cations, methylammonium and formamidinium, and three halogens, iodine, chlorine and bromine are studied. Electronic structures and polaron behavior is studied through first principle density functional theory (DFT) calculations using the Vienna Ab Initio Simulation Package (VASP). Local density approximation (LDA) pseudopotentials are used and a +U Hubbard correction of 8 eV is added; this method was shown to work with oxide perovskites. It is shown that a localized state is realized with the Hubbard correction in systems with an electron removed, residing in the band gap of each different structure. Thus, hole polarons are expected to be seen in these perovskites.

  11. SERS and DFT study of copper surfaces coated with corrosion inhibitor

    Directory of Open Access Journals (Sweden)

    Maurizio Muniz-Miranda

    2014-12-01

    Full Text Available Azole derivatives are common inhibitors of copper corrosion due to the chemical adsorption occurring on the metal surface that gives rise to a protective film. In particular, 1,2,4-triazole performs comparable to benzotriazole, which is much more widely used, but is by no means an environmentally friendly agent. In this study, we have analyzed the adsorption of 1,2,4-triazole on copper by taking advantage of the surface-enhanced Raman scattering (SERS effect, which highlights the vibrational features of organic ligand monolayers adhering to rough surfaces of some metals such as gold, silver and copper. To ensure the necessary SERS activation, a roughening procedure was implemented on the copper substrates, resulting in nanoscale surface structures, as evidenced by microscopic investigation. To obtain sufficient information on the molecule–metal interaction and the formation of an anticorrosive thin film, the SERS spectra were interpreted with the aid of theoretical calculations based on the density functional theory (DFT approach.

  12. A DFT study of cyclopropane adsorption on Pt(1 1 1). Electronic structure and bonding

    International Nuclear Information System (INIS)

    Germán, E.; López-Corral, I.; Pirillo, S.; Juan, A.; Brizuela, G.

    2014-01-01

    We have studied the adsorption of cyclopropane (c-C 3 H 6 ) on Pt(1 1 1) by means of the density functional theory (DFT). We have investigated the preferential adsorption geometry, considering different adsorption sites and bonding configurations for the molecular adsorbate. We have also computed the electronic structure and bonding interactions by means of density of states (DOS), crystal orbital overlap population (OPDOS), and overlap population (OP) analysis. Our results show a small preference for Bridge and Top adsorption sites with the cyclopropane ring parallel to the surface. Pt-C equilibrium distance is ∼3.5 Å and a weak bond is formed during adsorption. The main bonding interaction comes from the Pt-H overlap population. Pt 5p z orbitals play an important role in the bonding between c-C 3 H 6 and the surface. We have found that Van der Waals (vdW) corrections to the energies improve the adsorption values without changing the preferential site geometries.

  13. A DFT study of adsorption of glycine onto the surface of BC_2N nanotube

    International Nuclear Information System (INIS)

    Soltani, Alireza; Azmoodeh, Zivar; Javan, Masoud Bezi; Lemeski, E. Tazikeh; Karami, Leila

    2016-01-01

    Highlights: • Glycine adsorption over the pristine BC_2N nanotubes is investigated by DFT calculations. • Adsorption of glycine in its zwitterionic form is stronger in comparison with the radical form. • Adsorption of glycine from its amine head on adsorbent leads to a significant decrease in the electronic properties. - Abstract: A theoretical study of structure and the energy interaction of amino acid glycine (NH_2CH_2COOH) with BC_2N nanotube is crucial for apperception behavior occurring at the nanobiointerface. Herein, we studied the adsorption of glycine in their radical and zwitterionic forms upon the surface of BC_2N nanotube using M06 functional and 6-311G** standard basis set. We also considered the different orientations of the glycine amino acid on the surface of adsorbent. Further, we found out that the stability of glycine from its carbonyl group is higher than hydroxyl and amine groups. Our results also indicated that the electronic structure of BC_2N nanotube on the adsorption of glycine from its amine group is more altered than the other groups. Our study exhibits that opto-electronic property of adsorbent is changed after the glycine adsorption.

  14. A DFT study for the structural and electronic properties of Zn m Se n nanoclusters

    Science.gov (United States)

    Yadav, Phool Singh; Pandey, Dheeraj Kumar

    2012-09-01

    An ab initio study has been performed for the stability, structural and electronic properties of 19 small zinc selenide Zn m Se n ( m + n = 2-4) nanoclusters. Out of these nanoclusters, one nanocluster is found to be unstable due to its imaginary vibrational frequency. A B3LYP-DFT/6-311G(3df) method is used in the optimization of the geometries of the nanoclusters. We have calculated the zero point energy (ZPE), which is ignored by the other workers. The binding energies (BE), HOMO-LUMO gaps and bond lengths have been obtained for all the optimized nanoclusters. For the same value of ` m' and ` n', we designate the most stable structure the one, which has maximum final binding energy (FBE) per atom. The adiabatic and vertical ionization potentials (IP) and electron affinities (EA), dipole moments and charge on atoms have been investigated for the most stable nanoclusters. For the same value of ` m' and ` n', the nanocluster containing maximum number of Se atoms is found to be most stable.

  15. DFT/GIAO calculations of the relative contributions of hyperconjugation to the chemical shifts of ethanol

    International Nuclear Information System (INIS)

    Carneiro, J. Walkimar de M.; Dias, Jacques F.; Seidl, Peter R.; Tostes, J. Glauco R.

    2002-01-01

    Our previous DFT/GIAO calculations on different types of alcohols reveal that the rotation of the hydroxyl group can affect the chemical shift of carbons and hydrogens close to the substituent in different ways. Besides the steric and electrostatic effects that have been widely studied, hyperconjugation with the lone pairs on oxygen of the hydroxyl group leads to changes in bond lengths and angles as well as to different charge distributions. As all three of these factors also affect chemical shifts, we undertook a systematic investigation of their relative contributions to the chemical shifts of ethanol, a molecule in which there is minimum interference among these factors. Calculations by the B3LYP method at the 6-31G(d) level for ethanol conformers corresponding to a rotation around the carbon-oxygen bond at 30 dec increments are used to show how relative contributions vary with the dihedral angle formed between the carbon-carbon and oxygen-hydrogen bonds (C-C-O-H). Largest contributions to carbon chemical shifts can be attributed to changes in bond lengths while for hydrogen chemical shifts also contribute significantly differences in charge distribution. (author)

  16. Experimental and ab initio DFT calculated Raman Spectrum of Sudan I, a Red Dye

    DEFF Research Database (Denmark)

    Kunov-Kruse, Andreas Jonas; Kristensen, Steffen Buus; Liu, Chuan

    2011-01-01

    The red dye Sudan I was investigated by Raman spectroscopy using different excitation wavelengths (1064, 532 and 244 nm). A calculation of the Raman spectrum based on quantum mechanical ab initio density functional theory (DFT) was made using the RB3LYP method with the 3-21G and 6-311+G(d,p) basis...... of the Sudan I molecule was involved in the majority of the vibrations through N N and C–N stretching and various bending modes. Low-intensity bands in the lower wavenumber range (at about 721, 616, 463 and 218 cm−1) were selectively enhanced by the resonance Raman effect when using the 532 nm excitation line....... Comparison was made with other azo dyes in the literature on natural, abundant plant pigments. The results show that there is a possibility in foodstuff analysis to distinguish Sudan I from other dyes by using Raman spectroscopy with more than one laser wavelength for resonance enhancement of the different...

  17. Thz Spectroscopy and DFT Modeling of Intermolecular Vibrations in Hydrophobic Amino Acids

    Science.gov (United States)

    Williams, michael R. C.; Aschaffenburg, Daniel J.; Schmuttenmaer, Charles A.

    2013-06-01

    Vibrations that involve intermolecular displacements occur in molecular crystals at frequencies in the 0.5-5 THz range (˜15-165 cm^{-1}), and these motions are direct indicators of the interaction potential between the molecules. The intermolecular potential energy surface of crystalline hydrophobic amino acids is inherently interesting simply because of the wide variety of forces (electrostatic, dipole-dipole, hydrogen-bonding, van der Waals) that are present. Furthermore, an understanding of these particular interactions is immediately relevant to important topics like protein conformation and pharmaceutical polymorphism. We measured the low-frequency absorption spectra of several polycrystalline hydrophobic amino acids using THz time-domain spectroscopy, and in addition we carried out DFT calculations using periodic boundary conditions and an exchange-correlation functional that accounts for van der Waals dispersion forces. We chose to investigate a series of similar amino acids with closely analogous unit cells (leucine, isoleucine, and allo-isoleucine, in racemic or pseudo-racemic mixtures). This allows us to consider trends in the vibrational spectra as a function of small changes in molecular arrangement and/or crystal geometry. In this way, we gain confidence that peak assignments are not based on serendipitous similarities between calculated and observed features.

  18. First principles DFT study of dye-sensitized CdS quantum dots

    Energy Technology Data Exchange (ETDEWEB)

    Jain, Kalpna; Singh, Kh. S. [Department of Physics, D. J. College, Baraut -250611, U.P. (India); Kishor, Shyam, E-mail: shyam387@gmail.com [Department of Chemistry, J. V. College, Baraut -250611, U.P. (India); Josefesson, Ida; Odelius, Michael [Fysikum, Albanova University Center, Stockholm University, S-106 91 Stockholm (Sweden); Ramaniah, Lavanya M. [High Pressure and Synchrotron Radiation Physics Division, Bhabha Atomic Research Centre, Mumbai-400085 (India)

    2014-04-24

    Dye-sensitized quantum dots (QDs) are considered promising candidates for dye-sensitized solar cells. In order to maximize their efficiency, detailed theoretical studies are important. Here, we report a first principles density functional theory (DFT) investigation of experimentally realized dye - sensitized QD / ligand systems, viz., Cd{sub 16}S{sub 16}, capped with acetate molecules and a coumarin dye. The hybrid B3LYP functional and a 6−311+G(d,p)/LANL2dz basis set are used to study the geometric, energetic and electronic properties of these clusters. There is significant structural rearrangement in all the clusters studied - on the surface for the bare QD, and in the positions of the acetate / dye ligands for the ligated QDs. The density of states (DOS) of the bare QD shows states in the band gap, which disappear on surface passivation with the acetate molecules. Interestingly, in the dye-sensitised QD, the HOMO is found to be localized mainly on the dye molecule, while the LUMO is on the QD, as required for photo-induced electron injection from the dye to the QD.

  19. Synthesis, crystal structure of and DFT calculations on bisglycinato-bis[p-(hydroxymethylpyridine]nickel(II

    Directory of Open Access Journals (Sweden)

    FANG FANG JIAN

    2010-09-01

    Full Text Available The main aim of this study was to investigate the relationship between mIn tA new Ni(II complex of bisglycinato-bis[p-(hydroxylmethylpy-ridine] was synthesized and characterized by elemental analysis, IR, UV–Vis spectroscopy and X-ray single crystal diffraction analysis. The thermal stability of the title complex was also determined. The complex adopts a distorted octahedral geometry and possesses inversion symmetry with the Ni(II ion as the center of inversion. Density function theory (DFT calculations of the structure, electronic absorption spectra, electron structure and natural population analysis (NPA at the B3LYP/LANL2DZ level of theory were performed. The predicted geometric parameters and electronic spectra were compared with the experimental values and they supported each other. The NPA results indicate that the electronic transitions were mainly derived from the contribution of an intra-ligand (IL transition, a ligand-to-metal charge transfer (LMCT transition and a d-d transition. The electron structure calculations suggest that the central Ni(II ion uses its 4s and 3d orbitals to form covalent bonds with coordinated N and O atoms. The calculated bond orders are also consistent with the thermal decomposition results. Based on vibrational analysis, the thermodynamic properties of the title complex were predicted and the correlative equations between these thermodynamic properties and temperature are also reported.

  20. Molecular structure and vibrational spectra of Bis(melaminium) terephthalate dihydrate: A DFT computational study

    Science.gov (United States)

    Tanak, Hasan; Marchewka, Mariusz K.; Drozd, Marek

    2013-03-01

    The experimental and theoretical vibrational spectra of Bis(melaminium) terephthalate dihydrate were studied. The Fourier transform infrared (FT-IR) spectra of the Bis(melaminium) terephthalate dihydrate and its deuterated analogue were recorded in the solid phase. The molecular geometry and vibrational frequencies of Bis(melaminium) terephthalate dihydrate in the ground state have been calculated by using the density functional method (B3LYP) with 6-31++G(d,p) basis set. The results of the optimized molecular structure are presented and compared with the experimental X-ray diffraction. The molecule contains the weak hydrogen bonds of Nsbnd H⋯O, Nsbnd H⋯N and Osbnd H⋯O types, and those bonds are calculated with DFT method. In addition, molecular electrostatic potential, frontier molecular orbitals and natural bond orbital analysis of the title compound were investigated by theoretical calculations. The lack of the second harmonic generation (SHG) confirms the presence of macroscopic center of inversion.

  1. Molecular structure, vibrational spectra and DFT computational studies of melaminium N-acetylglycinate dihydrate

    Science.gov (United States)

    Tanak, H.; Pawlus, K.; Marchewka, M. K.

    2016-10-01

    Melaminium N-acetylglycinate dihydrate, an organic material has been synthesized and characterized by X-ray diffraction, FT-IR, and FT-Raman spectroscopies for the protiated and deuteriated crystals. The title complex crystallizes in the triclinic system, and the space group is P-1 with a = 5.642(1) Å, b = 7.773(2) Å, c = 15.775(3) Å, α = 77.28(1)°, β = 84.00(1)°, γ = 73.43(1)° and Z = 2. The molecular geometry, vibrational frequencies and intensity of the vibrational bands have been interpreted with the aid of structure optimization based on density functional method (B3LYP) with the 6-311++G(d,p) basis set. The obtained vibrational wavenumbers and optimized geometric parameters were seen to be in good agreement with the experimental data. The intermolecular hydrogen bonding interactions of the title compound have been investigated using the natural bonding orbital analysis. It reveals that the O-H···O, N-H···N and N-H···O intermolecular interactions significantly influence crystal packing of this molecule. The non-linear optical properties are also addressed theoretically. The predicted NLO properties of the title compound are much greater than ones of urea. In addition, DFT calculations of the title compound, molecular electrostatic potential, thermodynamic properties, frontier orbitals and chemical reactivity descriptors were also performed at 6-311++G(d,p) level of theory.

  2. DFT study on the effect of exocyclic substituents on the proton affinity of 1-methylimidazole

    International Nuclear Information System (INIS)

    Liu, Haining; Bara, Jason E.; Turner, C. Heath

    2013-01-01

    Highlights: • DFT calculations are used to predict the proton affinity of 1-methylimidazoles. • The electron-withdrawing groups dominate the predicted proton affinity. • The effects of multiple substituents on the proton affinity can be accurately predicted. • Large compound libraries can be screened for imidazoles with tailored reactivity. - Abstract: A deeper understanding of the acid/base properties of imidazole derivatives will aid the development of solvents, polymer membranes and other materials that can be used for CO 2 capture and acid gas removal. In this study, we employ density functional theory calculations to investigate the effect of various electron-donating and electron-withdrawing groups on the proton affinity of 1-methylimidazole. We find that electron-donating groups are able to increase the proton affinity relative to 1-methylimidazole, i.e., making the molecule more basic. In contrast, electron-withdrawing groups cause a decrease of the proton affinity. When multiple substituents are present, their effects on the proton affinity were found to be additive. This finding offers a quick approach for predicting and targeting the proton affinities of this series of molecules, and we show the strong correlation between the calculated proton affinities and experimental pK a values

  3. DFT study on the attacking mechanisms of H and OH radicals to G-C and A-T base pairs in water

    Energy Technology Data Exchange (ETDEWEB)

    Okutsu, N.; Shimamura, K.; Shimizu, E.; Kurita, N., E-mail: kurita@cs.tut.ac.jp [Department of Computer Science and Engineering, Toyohashi University of Technology, Toyohashi, Aichi, 441-8580 (Japan); Shulga, S. [Institute for Food Biotechnology and Genomics, National Academy of Sciences of Ukraine, Kyiv (Ukraine); Danilov, V. I. [Institute of Molecular Biology and Genetics, National Academy of Sciences of Ukraine, Kyiv (Ukraine)

    2016-02-01

    To elucidate the effect of radicals on DNA base pairs, we investigated the attacking mechanism of OH and H radicals to the G-C and A-T base pairs, using the density functional theory (DFT) calculations in water approximated by the continuum solvation model. The DFT calculations revealed that the OH radical abstracts the hydrogen atom of a NH{sub 2} group of G or A base and induces a tautomeric reaction for an A-T base pair more significantly than for a G-C base pair. On the other hand, the H radical prefers to bind to the Cytosine NH{sub 2} group of G-C base pair and induce a tautomeric reaction from G-C to G*-C*, whose activation free energy is considerably small (−0.1 kcal/mol) in comparison with that (42.9 kcal/mol) for the reaction of an A-T base pair. Accordingly, our DFT calculations elucidated that OH and H radicals have a significant effect on A-T and G-C base pairs, respectively. This finding will be useful for predicting the effect of radiation on the genetic information recorded in the base sequences of DNA duplexes.

  4. DFT study on the attacking mechanisms of H and OH radicals to G-C and A-T base pairs in water

    International Nuclear Information System (INIS)

    Okutsu, N.; Shimamura, K.; Shimizu, E.; Kurita, N.; Shulga, S.; Danilov, V. I.

    2016-01-01

    To elucidate the effect of radicals on DNA base pairs, we investigated the attacking mechanism of OH and H radicals to the G-C and A-T base pairs, using the density functional theory (DFT) calculations in water approximated by the continuum solvation model. The DFT calculations revealed that the OH radical abstracts the hydrogen atom of a NH 2 group of G or A base and induces a tautomeric reaction for an A-T base pair more significantly than for a G-C base pair. On the other hand, the H radical prefers to bind to the Cytosine NH 2 group of G-C base pair and induce a tautomeric reaction from G-C to G*-C*, whose activation free energy is considerably small (−0.1 kcal/mol) in comparison with that (42.9 kcal/mol) for the reaction of an A-T base pair. Accordingly, our DFT calculations elucidated that OH and H radicals have a significant effect on A-T and G-C base pairs, respectively. This finding will be useful for predicting the effect of radiation on the genetic information recorded in the base sequences of DNA duplexes

  5. The magnetic properties of Ce/Pd surface alloys investigated using DFT

    KAUST Repository

    Shuttleworth, I.G.

    2014-01-01

    The surface alloys that form between Ce and Pd(1 1 1), Pd(1 0 0) and both unreconstructed and missing-row type Pd(1 1 0) at low Ce coverage ( θCe=19ML) have shown permanent magnetism that is mediated in part by an RKKY-like delocalized Ce 6s-Pd 5s interaction. The Pd 4d states are significantly affected by alloying and their behavior cannot be explained by a purely spin-dependent Hamiltonian. Experimental observations of changes to the Pd 4d states are explained and the implications of Ce/Pd magnetism in reforming catalysis are discussed. © 2014 Elsevier B.V. All rights reserved.

  6. The magnetic properties of Ce/Pd surface alloys investigated using DFT

    KAUST Repository

    Shuttleworth, I.G.

    2014-06-01

    The surface alloys that form between Ce and Pd(1 1 1), Pd(1 0 0) and both unreconstructed and missing-row type Pd(1 1 0) at low Ce coverage ( θCe=19ML) have shown permanent magnetism that is mediated in part by an RKKY-like delocalized Ce 6s-Pd 5s interaction. The Pd 4d states are significantly affected by alloying and their behavior cannot be explained by a purely spin-dependent Hamiltonian. Experimental observations of changes to the Pd 4d states are explained and the implications of Ce/Pd magnetism in reforming catalysis are discussed. © 2014 Elsevier B.V. All rights reserved.

  7. Interfacial Interaction of Titania Nanoparticles and Ligated Uranyl Species: A Relativistic DFT Investigation.

    Science.gov (United States)

    Zhao, Hong-Bo; Zheng, Ming; Schreckenbach, Georg; Pan, Qing-Jiang

    2017-03-06

    To understand interfacial behavior of actinides adsorbed onto mineral surfaces and unravel their structure-property relationship, the structures, electronic properties, and energetics of various ligated uranyl species adsorbed onto TiO 2 surface nanoparticle clusters (SNCs) were examined using relativistic density functional theory. Rutile (110) and anatase (101) titania surfaces, experimentally known to be stable, were fully optimized. For the former, models studied include clean and water-free Ti 27 O 64 H 20 (dry), partially hydrated (Ti 27 O 64 H 20 )(H 2 O) 8 (sol) and proton-saturated [(Ti 27 O 64 H 20 )(H 2 O) 8 (H) 2 ] 2+ (sat), while defect-free and defected anatase SNCs involving more than 38 TiO 2 units were considered. The aquouranyl sorption onto rutile SNCs is energetically preferred, with interaction energies of -8.54, -10.36, and -2.39 eV, respectively. Energy decomposition demonstrates that the sorption is dominated by orbital attractive interactions and modified by steric effects. Greater hydrogen-bonding involvement leads to increased orbital interactions (i.e., more negative energy) from dry to sol/sat complexes, while much larger steric interaction in the sat complex significantly reduces the sorption interaction (i.e., more positive energy). For dry SNC, adsorbates were varied from aquo to aquo-carbonato, to carbonato, to hydroxo uranyl species. Longer U-O surf /U-Ti distances and more positive sorption energies were calculated upon introducing carbonato and hydroxo ligands, indicative of weaker uranyl sorption onto the substrate. This is consistent with experimental observations that the uranyl sorption rate decreases upon raising solution pH value or adding carbon dioxide. Anatase SNCs adsorbing aquouranyl are even more exothermic, because more bonds are formed than in the case of rutile. Moreover, the anatase sorption can be tuned by surface defects as well as its Ti and O stoichiometry. All the aquouranyl-SNC complexes show similar character of molecular orbitals and energetic order although differing in highest occupied molecular orbital (HOMO)-lowest unoccupied molecular orbital (LUMO) gaps and orbital energy levels, but changes can be accomplished by adding carbonato and hydroxo ligands.

  8. The DFT investigations of the electron injection in hydrazone-based sensitizers

    KAUST Repository

    Al-Sehemi, Abdullah G.; Irfan, Ahmad; Asiri, Abdullah M.

    2012-01-01

    solvent. The calculated absorption spectra in ethanol, acetonitrile, and methanol are in good agreement with experimental evidences. The absorption spectra are red shifted compared to System1. On the basis of electron injection and electronic coupling

  9. Evidence of heterogeneous dual cation sites in zeolites by combined IR and DFT investigation

    Czech Academy of Sciences Publication Activity Database

    Nachtigall, Petr; Pulido, Maria Angeles; Frolich, K.; Bulánek, R.

    2008-01-01

    Roč. 174, č. 2 (2008), s. 1005-1008 ISSN 0167-2991 R&D Projects: GA MŠk LC512; GA ČR GA203/06/0324 Institutional research plan: CEZ:AV0Z40550506 Keywords : zeolit * adsorpce * FTIR Subject RIV: CF - Physical ; Theoretical Chemistry

  10. DFT Investigation of the Palladium-Catalyzed Ene-Yne Coupling

    DEFF Research Database (Denmark)

    Henriksen, Signe Teuber; Tanner, David Ackland; Skrydstrup, T.

    2010-01-01

    ). Concerning chemoselectivity, the calculations also clarify why the ene-yne coupling is able to dominate over plausible alternative reaction pathways such as alkene homocoupiing and alkyne polymerization. The role of the phosphine ligand at various stages of the catalytic cycle has also been delineated....

  11. FT-IR, FT-Raman, UV spectra and DFT calculations on monomeric and dimeric structure of 2-amino-5-bromobenzoic acid.

    Science.gov (United States)

    Karabacak, Mehmet; Cinar, Mehmet

    2012-02-01

    In this work, the molecular conformation, vibrational and electronic transition analysis of 2-amino-5-bromobenzoic acid (2A5BrBA) were presented for the ground state using experimental techniques (FT-IR, FT-Raman and UV) and density functional theory (DFT) employing B3LYP exchange correlation with the 6-311++G(d,p) basis set. FT-IR and FT-Raman spectra were recorded in the regions of 400-4000 cm(-1) and 50-4000 cm(-1), respectively. There are four conformers, C1, C2, C3 and C4 for this molecule. The geometrical parameters, energies and wavenumbers have been obtained for all four conformers. The computational results diagnose the most stable conformer of 2A5BrBA as the C1 form. The complete assignments of fundamental vibrations were performed on the basis of the total energy distribution (TED) of the vibrational modes, calculated with scaled quantum mechanics (SQM) method. Raman activities calculated by DFT method have been converted to the corresponding Raman intensities using Raman scattering theory. The UV spectra of investigated compound were recorded in the region of 200-400 nm for ethanol and water solutions. The electronic properties were evaluated with help of time-dependent DFT (TD-DFT) theoretically and results were compared with experimental observations. The thermodynamic properties of the studied compound at different temperatures were calculated, revealing the correlations between standard heat capacity, standard entropy, standard enthalpy changes and temperatures. The observed and the calculated geometric parameters, vibrational wavenumbers and electronic transitions were compared with observed data and found to be in good agreement. Copyright © 2011 Elsevier B.V. All rights reserved.

  12. Communication: Recovering the flat-plane condition in electronic structure theory at semi-local DFT cost

    Science.gov (United States)

    Bajaj, Akash; Janet, Jon Paul; Kulik, Heather J.

    2017-11-01

    The flat-plane condition is the union of two exact constraints in electronic structure theory: (i) energetic piecewise linearity with fractional electron removal or addition and (ii) invariant energetics with change in electron spin in a half filled orbital. Semi-local density functional theory (DFT) fails to recover the flat plane, exhibiting convex fractional charge errors (FCE) and concave fractional spin errors (FSE) that are related to delocalization and static correlation errors. We previously showed that DFT+U eliminates FCE but now demonstrate that, like other widely employed corrections (i.e., Hartree-Fock exchange), it worsens FSE. To find an alternative strategy, we examine the shape of semi-local DFT deviations from the exact flat plane and we find this shape to be remarkably consistent across ions and molecules. We introduce the judiciously modified DFT (jmDFT) approach, wherein corrections are constructed from few-parameter, low-order functional forms that fit the shape of semi-local DFT errors. We select one such physically intuitive form and incorporate it self-consistently to correct semi-local DFT. We demonstrate on model systems that jmDFT represents the first easy-to-implement, no-overhead approach to recovering the flat plane from semi-local DFT.

  13. Investigation of the Linker Swing Motion in the Zeolitic Imidazolate Framework ZIF-90

    KAUST Repository

    Zheng, Bin; Fu, Fang; Wang, Lian Li; Yang, Limin; Zhu, Yihan; Du, Huiling

    2018-01-01

    The linker swing motion in the zeolitic imidazolate framework ZIF-90 is investigated by density functional theory (DFT) calculation, molecular dynamics (MD) and grand-canonical Monte Carlo (GCMC) simulations. The relation between the terminal

  14. Parallel Implementation of Gamma-Point Pseudopotential Plane-Wave DFT with Exact Exchange

    International Nuclear Information System (INIS)

    Bylaska, Eric J.; Tsemekhman, Kiril L.; Baden, Scott B.; Weare, John H.; Jonsson, Hannes

    2011-01-01

    One of the more persistent failures of conventional density functional theory (DFT) methods has been their failure to yield localized charge states such as polarons, excitons and solitons in solid-state and extended systems. It has been suggested that conventional DFT functionals, which are not self-interaction free, tend to favor delocalized electronic states since self-interaction creates a Coulomb barrier to charge localization. Pragmatic approaches in which the exchange correlation functionals are augmented with small amount of exact exchange (hybrid-DFT, e.g. B3LYP and PBE0) have shown promise in localizing charge states and predicting accurate band gaps and reaction barriers. We have developed a parallel algorithm for implementing exact exchange into pseudopotential plane-wave density functional theory and we have implemented it in the NWChem program package. The technique developed can readily be employed in plane-wave DFT programs. Furthermore, atomic forces and stresses are straightforward to implement, making it applicable to both confined and extended systems, as well as to Car-Parrinello ab initio molecular dynamic simulations. This method has been applied to several systems for which conventional DFT methods do not work well, including calculations for band gaps in oxides and the electronic structure of a charge trapped state in the Fe(II) containing mica, annite.

  15. Electronic annealing Fermi operator expansion for DFT calculations on metallic systems

    Science.gov (United States)

    Aarons, Jolyon; Skylaris, Chris-Kriton

    2018-02-01

    Density Functional Theory (DFT) calculations with computational effort which increases linearly with the number of atoms (linear-scaling DFT) have been successfully developed for insulators, taking advantage of the exponential decay of the one-particle density matrix. For metallic systems, the density matrix is also expected to decay exponentially at finite electronic temperature and linear-scaling DFT methods should be possible by taking advantage of this decay. Here we present a method for DFT calculations at finite electronic temperature for metallic systems which is effectively linear-scaling (O(N)). Our method generates the elements of the one-particle density matrix and also finds the required chemical potential and electronic entropy using polynomial expansions. A fixed expansion length is always employed to generate the density matrix, without any loss in accuracy by the application of a high electronic temperature followed by successive steps of temperature reduction until the desired (low) temperature density matrix is obtained. We have implemented this method in the ONETEP linear-scaling (for insulators) DFT code which employs local orbitals that are optimised in situ. By making use of the sparse matrix machinery of ONETEP, our method exploits the sparsity of Hamiltonian and density matrices to perform calculations on metallic systems with computational cost that increases asymptotically linearly with the number of atoms. We demonstrate the linear-scaling computational cost of our method with calculation times on palladium nanoparticles with up to ˜13 000 atoms.

  16. Diels-Alder reactions for the rational design of benzo[b]thiophenes: DFT-based guidelines for synthetic chemists

    Science.gov (United States)

    Brasca, Romina; Kneeteman, María N.; Mancini, Pedro M. E.; Fabian, Walter M. F.

    2012-02-01

    In this work we studied the capability of several diene/dienophile pairs to undergo Diels-Alder (DA) reactions leading to benzo[b]thiophenes. A variety of synthetically and commercially available nitrothiophenes were chosen as dienophiles. Methyl 5-nitro-3-thiophenecarboxylate was selected as a potential strong electrophilic candidate based on some DFT-based properties and the substitution pattern of the expected product. The mechanistic details concerning the participation of this dienophile in polar DA reactions were investigated through a theoretical point of view. The results were compared with the experimental outcomes. This methodology should allow synthetic chemists to analyze DA reactions in detail in a stage prior to the synthetic job.

  17. Thermodynamics, kinetics, and catalytic effect of dehydrogenation from MgH2 stepped surfaces and nanocluster: a DFT study

    Science.gov (United States)

    Reich, Jason; Wang, Linlin; Johnson, Duane

    2013-03-01

    We detail the results of a Density Functional Theory (DFT) based study of hydrogen desorption, including thermodynamics and kinetics with(out) catalytic dopants, on stepped (110) rutile and nanocluster MgH2. We investigate competing configurations (optimal surface and nanoparticle configurations) using simulated annealing with additional converged results at 0 K, necessary for finding the low-energy, doped MgH2 nanostructures. Thermodynamics of hydrogen desorption from unique dopant sites will be shown, as well as activation energies using the Nudged Elastic Band algorithm. To compare to experiment, both stepped structures and nanoclusters are required to understanding and predict the effects of ball milling. We demonstrate how these model systems relate to the intermediary sized structures typically seen in ball milling experiments.

  18. DFT calculations of electronic and optical properties of SrS with LDA, GGA and mGGA functionals

    Energy Technology Data Exchange (ETDEWEB)

    Sharma, Shatendra, E-mail: shatendra@gmai.com [University Science Instrumentation Centre, Jawaharlal Nehru University, New Delhi-110067 (India); Sharma, Jyotsna [School of Basic & Applied Sciences, K. R. Mangalam University, Sohna Road, Gurgaon-122103 (India); Sharma, Yogita [Department of Applied Sciences, KIIT, Sohna Road, Gurgaon-122103 (India)

    2016-05-06

    The theoretical investigations of electronic and optical properties of SrS are made using the first principle DFT calculations. The calculations are performed for the local-density approximation (LDA), generalized gradient approximation (GGA) and for an alternative form of GGA i.e. metaGGA for both rock salt type (B1, Fm3m) and cesium chloride (B2, Pm3m) structures. The band structure, density of states and optical spectra are calculated under various available functional. The calculations with LDA and GGA functional underestimate the values of band gaps with all functional, however the values with mGGA show reasonably good agreement with experimental and those calculated by using other methods.

  19. DFT based spatial multiplexing and maximum ratio transmission for mm-wawe large MIMO

    DEFF Research Database (Denmark)

    Phan-Huy, D.-T.; Tölli, A.; Rajatheva, N.

    2014-01-01

    -SM-MRT). When the DFT-SM scheme alone is used, the data streams are either mapped onto different angles of departures in the case of aligned linear arrays, or mapped onto different orbital angular momentums in the case of aligned circular arrays. Maximum ratio transmission pre-equalizes the channel......By using large point-to-point multiple input multiple output (MIMO), spatial multiplexing of a large number of data streams in wireless communications using millimeter-waves (mm-waves) can be achieved. However, according to the antenna spacing and transmitter-receiver distance, the MIMO channel...... is likely to be ill-conditioned. In such conditions, highly complex schemes such as the singular value decomposition (SVD) are necessary. In this paper, we propose a new low complexity system called discrete Fourier transform based spatial multiplexing (DFT-SM) with maximum ratio transmission (DFT...

  20. Experimental demonstration of improved fiber nonlinearity tolerance for unique-word DFT-spread OFDM systems.

    Science.gov (United States)

    Chen, Xi; Li, An; Gao, Guanjun; Shieh, William

    2011-12-19

    In this paper we experimentally demonstrate transmission performance of optical DFT-spread OFDM systems in comparison with conventional OFDM systems. A 440.8-Gb/s superchannel consisting of 8 x 55.1-Gb/s densely-spaced DFT-S OFDM signal is successfully received after 1120-km transmission with a spectral efficiency of 3.5 b/s/Hz. It is shown that DFT-S OFDM can achieve an improvement of 1 dB in Q factor and 1 dB in launch power over conventional OFDM. Additionally, unique word aided phase estimation algorithm is proposed and demonstrated enabling extremely long OFDM symbol transmission.

  1. Optical Gaps in Pristine and Heavily Doped Silicon Nanocrystals: DFT versus Quantum Monte Carlo Benchmarks.

    Science.gov (United States)

    Derian, R; Tokár, K; Somogyi, B; Gali, Á; Štich, I

    2017-12-12

    We present a time-dependent density functional theory (TDDFT) study of the optical gaps of light-emitting nanomaterials, namely, pristine and heavily B- and P-codoped silicon crystalline nanoparticles. Twenty DFT exchange-correlation functionals sampled from the best currently available inventory such as hybrids and range-separated hybrids are benchmarked against ultra-accurate quantum Monte Carlo results on small model Si nanocrystals. Overall, the range-separated hybrids are found to perform best. The quality of the DFT gaps is correlated with the deviation from Koopmans' theorem as a possible quality guide. In addition to providing a generic test of the ability of TDDFT to describe optical properties of silicon crystalline nanoparticles, the results also open up a route to benchmark-quality DFT studies of nanoparticle sizes approaching those studied experimentally.

  2. Relaxations of fluorouracil tautomers by decorations of fullerene-like SiCs: DFT studies

    Energy Technology Data Exchange (ETDEWEB)

    Kouchaki, Alireza [Department of Pharmaceutical Chemistry, Faculty of Pharmaceutical Chemistry, Pharmaceutical Sciences Branch, Islamic Azad University, Tehran (Iran, Islamic Republic of); Gülseren, Oğuz [Department of Physics, Faculty of Science, Bilkent University, Ankara (Turkey); Hadipour, Nasser [Department of Chemistry, Faculty of Science, Tarbiat Modares University, Tehran (Iran, Islamic Republic of); Mirzaei, Mahmoud, E-mail: mdmirzaei@pharm.mui.ac.ir [Bioinformatics Research Center, School of Pharmacy and Pharmaceutical Sciences, Isfahan University of Medical Sciences, Isfahan (Iran, Islamic Republic of)

    2016-06-03

    Decorations of silicon carbide (SiC) fullerene-like nanoparticles by fluorouracil (FU) and its tautomers are investigated through density functional theory (DFT) calculations. Two models of fullerene-like particles including Si{sub 12}C{sub 8} and Si{sub 8}C{sub 12} are constructed to be counterparts of decorated hybrid structures, FU@Si{sub 12}C{sub 8} and FU@Si{sub 8}C{sub 12}, respectively. The initial models including original FU and tautomeric structures and SiC nanoparticles are individually optimized and then combined for further optimizations in the hybrid forms. Covalent bonds are observed for FU@Si{sub 12}C{sub 8} hybrids, whereas non-covalent interactions are seen for FU@Si{sub 8}C{sub 12} ones. The obtained properties indicated that Si{sub 12}C{sub 8} model could be considered as a better counterpart for interactions with FU structures than Si{sub 8}C{sub 12} model. The results also showed significant effects of interactions on the properties of atoms close to the interacting regions in nanoparticles. Finally, the tautomeric structures show different behaviors in interactions with SiC nanoparticles, in which the SiC nanoparticles could be employed to detect the situations of tautomeric processes for FU structures. - Highlights: • Possibilities of interaction between fluorouracil and silicon carbides have been recognized. • Possibilities for covalent and non-covalent interactions have been indicated. • Detections of tautomeric structures have been investigated.

  3. Electrochemical and DFT study of an anticancer and active anthelmintic drug at carbon nanostructured modified electrode

    International Nuclear Information System (INIS)

    Ghalkhani, Masoumeh; Beheshtian, Javad; Salehi, Maryam

    2016-01-01

    The electrochemical response of mebendazole (Meb), an anticancer and effective anthelmintic drug, was investigated using two different carbon nanostructured modified glassy carbon electrodes (GCE). Although, compared to unmodified GCE, both prepared modified electrodes improved the voltammetric response of Meb, the carbon nanotubes (CNTs) modified GCE showed higher sensitivity and stability. Therefore, the CNTs-GCE was chosen as a promising candidate for the further studies. At first, the electrochemical behavior of Meb was studied by cyclic voltammetry and differential pulse and square wave voltammetry. A one step reversible, pH-dependent and adsorption-controlled process was revealed for electro-oxidation of Meb. A possible mechanism for the electrochemical oxidation of Meb was proposed. In addition, electronic structure, adsorption energy, band gap, type of interaction and stable configuration of Meb on the surface of functionalized carbon nanotubes were studied by using density functional theory (DFT). Obtained results revealed that Meb is weakly physisorbed on the CNTs and that the electronic properties of the CNTs are not significantly changed. Notably, CNTs could be considered as a suitable modifier for preparation of the modified electrode for Meb analysis. Then, the experimental parameters affecting the electrochemical response of Meb were optimized. Under optimal conditions, high sensitivity (b(Meb) = dI p,a (Meb) / d[Meb] = 19.65 μA μM −1 ), a low detection limit (LOD (Meb) = 19 nM) and a wide linear dynamic range (0.06–3 μM) was resulted for the voltammetric quantification of Meb. - Highlights: • Electrochemical oxidation mechanism of Meb was investigated. • A carbon nanostructure modified electrode was developed for the determination of Meb. • The modified electrode surface was characterized by SEM and impedance studies. • This study provides an effective chemically modified electrode with satisfactory repeatability and reproducibility

  4. Comparison of discrete Fourier transform (DFT) and principal component analysis/DFT as forecasting tools for absorbance time series received by UV-visible probes installed in urban sewer systems.

    Science.gov (United States)

    Plazas-Nossa, Leonardo; Torres, Andrés

    2014-01-01

    The objective of this work is to introduce a forecasting method for UV-Vis spectrometry time series that combines principal component analysis (PCA) and discrete Fourier transform (DFT), and to compare the results obtained with those obtained by using DFT. Three time series for three different study sites were used: (i) Salitre wastewater treatment plant (WWTP) in Bogotá; (ii) Gibraltar pumping station in Bogotá; and (iii) San Fernando WWTP in Itagüí (in the south part of Medellín). Each of these time series had an equal number of samples (1051). In general terms, the results obtained are hardly generalizable, as they seem to be highly dependent on specific water system dynamics; however, some trends can be outlined: (i) for UV range, DFT and PCA/DFT forecasting accuracy were almost the same; (ii) for visible range, the PCA/DFT forecasting procedure proposed gives systematically lower forecasting errors and variability than those obtained with the DFT procedure; and (iii) for short forecasting times the PCA/DFT procedure proposed is more suitable than the DFT procedure, according to processing times obtained.

  5. A rational synthesis of a novel imidazo[4,5-f][1,10]phenanthroline templated Schiff base: Characterization, photoluminescence and DFT/TD-DFT study

    Directory of Open Access Journals (Sweden)

    S. Karslıoğlu

    2017-07-01

    Full Text Available A new imidazo[4,5-f][1,10]phenanthroline (imp derivative imidazo-N5,N6-bis((4-(1H-imidazo[4,5-f][1,10]phenanthroline-2-ylphenylmethylene-1,10-phenanthroline-5,6-diamine (impap was synthesized in five steps starting from bare phenanthroline (phen precursors. The novel compound was fully characterized by 1H-NMR, IR, elemental analysis and electrospray ionization mass spectroscopy (ESI-MS techniques. Solid state emission spectrum of impap showed two distinct strong emission maxima with large Stokes shifts. The ground state gas phase geometry of impap was predicted by DFT calculations. Excited state properties of the molecule were examined through TD-DFT calculations conducted at the optimized geometry. Responsible transitions for the strong fluorescence of impap were assigned to single component charge transfer transitions with large oscillator strengths based on the ground state calculated molecular orbital contributions.

  6. Activation mechanism of ammonium ions on sulfidation of malachite (-201) surface by DFT study

    Science.gov (United States)

    Wu, Dandan; Mao, Yingbo; Deng, Jiushuai; Wen, Shuming

    2017-07-01

    The activation mechanism of ammonium ions on the sulfidation of malachite (-201) was determined by density functional theory (DFT) calculations. Results of DFT calculations indicated that interlayer sulfidation occurs during the sulfidation process of malachite (-201). The absorption of both the ammonium ion and sulfide ion on the malachite (-201) surface is stronger than that of sulfur ion. After sulfidation was activated with ammonium ion, the Cu 3d orbital peak is closer to the Fermi level and characterized by a stronger peak value. Therefore, the addition of ammonium ions activated the sulfidation of malachite (-201), thereby improving the flotation performance.

  7. Chemical Information revealed by Mössbauer spectroscopy and DFT calculations

    Energy Technology Data Exchange (ETDEWEB)

    Nakashima, Satoru, E-mail: snaka@hiroshima-u.ac.jp [Hiroshima University, Natural Science Center for Basic Research and Development (Japan)

    2017-11-15

    Mixed-valence state of binuclear metallocene derivatives and spin-crossover (SCO) phenomena of the assembled Fe(II) complexes have been studied by using Mössbauer spectroscopy. The understanding of the results obtained by Mössbauer spectra is well supported by means of X-ray structural analysis and density functional theory (DFT) calculation. Benchmark study of relativisitic DFT calculation by using Mössbauer isomer shifts of Eu, Np complexes reveals the validity of the calculation. Such study sheds light on the bonding character of 4f and 5f electron. These results are reviewed.

  8. Techniques for Computing the DFT Using the Residue Fermat Number Systems and VLSI

    Science.gov (United States)

    Truong, T. K.; Chang, J. J.; Hsu, I. S.; Pei, D. Y.; Reed, I. S.

    1985-01-01

    The integer complex multiplier and adder over the direct sum of two copies of a finite field is specialized to the direct sum of the rings of integers modulo Fermat numbers. Such multiplications and additions can be used in the implementation of a discrete Fourier transform (DFT) of a sequence of complex numbers. The advantage of the present approach is that the number of multiplications needed for the DFT can be reduced substantially over the previous approach. The architectural designs using this approach are regular, simple, expandable and, therefore, naturally suitable for VLSI implementation.

  9. A New Approach for Studying Bond Rupture/Closure of a Spiro Benzopyran Photochromic Material: Reactivity Descriptors Derived from Frontier Orbitals and DFT Computed Electrostatic Potential Energy Surface Maps

    Directory of Open Access Journals (Sweden)

    M. S. A. Abdel-Mottaleb

    2016-01-01

    Full Text Available This paper focuses on computations technique within the framework of the TD-DFT theory for studying the relationship between structure-properties of reversible conversion of photochromic materials. Specifically, we report on 1′,3′-dihydro-8-methoxy-1′,3′,3′-trimethyl-6-nitrospiro[2H-1-benzopyran-2,2′-(2H-indole] (SP and its isomers. TD-DFT calculated UV-Vis electronic spectra of the closed and open isomers of this photochromic material are in excellent agreement with the experimental results. Moreover, this paper reports on the results of theoretical investigations of reactivity indices that may govern the conversion between spiropyrans and its isomers. In addition, the solvent and rigidity of the medium significantly control the thermal bleaching of the photogenerated colored isomers and hence the switch ability pattern of the photochromic material. The effect of molecular structure computed by DFT in gas-phase and solvents on Cspiro-O bond length has been shown to correlate with photochromic properties. For this compound, DFT optimized geometry could be used to predict photochromism. Furthermore, in an attempt to predict the driving force for MC → SP, this work explores, for the first time, profitable exploitation of the calculated and visualized mapped electrostatic potential energy surfaces (ESP map. Interestingly, it seems that the electrostatic potential forces over the molecular fragments govern spirobond rupture/closure reactions. Thermodynamically, all-trans-colored isomer (CTT is the most stable merocyanine-like form.

  10. Structure prediction of nanoclusters; a direct or a pre-screened search on the DFT energy landscape?

    Science.gov (United States)

    Farrow, M R; Chow, Y; Woodley, S M

    2014-10-21

    The atomic structure of inorganic nanoclusters obtained via a search for low lying minima on energy landscapes, or hypersurfaces, is reported for inorganic binary compounds: zinc oxide (ZnO)n, magnesium oxide (MgO)n, cadmium selenide (CdSe)n, and potassium fluoride (KF)n, where n = 1-12 formula units. The computational cost of each search is dominated by the effort to evaluate each sample point on the energy landscape and the number of required sample points. The effect of changing the balance between these two factors on the success of the search is investigated. The choice of sample points will also affect the number of required data points and therefore the efficiency of the search. Monte Carlo based global optimisation routines (evolutionary and stochastic quenching algorithms) within a new software package, viz. Knowledge Led Master Code (KLMC), are employed to search both directly and after pre-screening on the DFT energy landscape. Pre-screening includes structural relaxation to minimise a cheaper energy function - based on interatomic potentials - and is found to improve significantly the search efficiency, and typically reduces the number of DFT calculations required to locate the local minima by more than an order of magnitude. Although the choice of functional form is important, the approach is robust to small changes to the interatomic potential parameters. The computational cost of initial DFT calculations of each structure is reduced by employing Gaussian smearing to the electronic energy levels. Larger (KF)n nanoclusters are predicted to form cuboid cuts from the rock-salt phase, but also share many structural motifs with (MgO)n for smaller clusters. The transition from 2D rings to 3D (bubble, or fullerene-like) structures occur at a larger cluster size for (ZnO)n and (CdSe)n. Differences between the HOMO and LUMO energies, for all the compounds apart from KF, are in the visible region of the optical spectrum (2-3 eV); KF lies deep in the UV region

  11. MP2, DFT-D, and PCM study of the HMB-TCNE complex: Thermodynamics, electric properties, and solvent effects

    Science.gov (United States)

    Kysel, Ondrej; Budzák, Scaronimon; Medveď, Miroslav; Mach, Pavel

    Geometry, thermodynamic, and electric properties of the pi-EDA complex between hexamethylbenzene (HMB) and tetracyanoethylene (TCNE) are investigated at the MP2/6-31G* and, partly, DFT-D/6-31G* levels. Solvent effects on the properties are evaluated using the PCM model. Fully optimized HMB-TCNE geometry in gas phase is a stacking complex with an interplanar distance 2.87 × 10-10 m and the corresponding BSSE corrected interaction energy is -51.3 kJ mol-1. As expected, the interplanar distance is much shorter in comparison with HF and DFT results. However the crystal structures of both (HMB)2-TCNE and HMB-TCNE complexes have interplanar distances somewhat larger (3.18 and 3.28 × 10-10 m, respectively) than our MP2 gas phase value. Our estimate of the distance in CCl4 on the basis of PCM solvent effect study is also larger (3.06-3.16 × 10-10 m). The calculated enthalpy, entropy, Gibbs energy, and equilibrium constant of HMB-TCNE complex formation in gas phase are: DeltaH0 = -61.59 kJ mol-1, DeltaSc0 = -143 J mol-1 K-1, DeltaG0 = -18.97 kJ mol-1, and K = 2,100 dm3 mol-1. Experimental data, however, measured in CCl4 are significantly lower: DeltaH0 = -34 kJ mol-1, DeltaSc0 = -70.4 J mol-1 K-1, DeltaG0 = -13.01 kJ mol-1, and K = 190 dm3 mol-1. The differences are caused by solvation effects which stabilize more the isolated components than the complex. The total solvent destabilization of Gibbs energy of the complex relatively to that of components is equal to 5.9 kJ mol-1 which is very close to our PCM value 6.5 kJ mol-1. MP2/6-31G* dipole moment and polarizabilities are in reasonable agreement with experiment (3.56 D versus 2.8 D for dipole moment). The difference here is due to solvent effect which enlarges interplanar distance and thus decreases dipole moment value. The MP2/6-31G* study supplemented by DFT-D parameterization for enthalpy calculation, and by the PCM approach to include solvent effect seems to be proper tools to elucidate the properties of pi

  12. An analytical study of the improved nonlinear tolerance of DFT-spread OFDM and its unitary-spread OFDM generalization.

    Science.gov (United States)

    Shulkind, Gal; Nazarathy, Moshe

    2012-11-05

    DFT-spread (DFT-S) coherent optical OFDM was numerically and experimentally shown to provide improved nonlinear tolerance over an optically amplified dispersion uncompensated fiber link, relative to both conventional coherent OFDM and single-carrier transmission. Here we provide an analytic model rigorously accounting for this numerical result and precisely predicting the optimal bandwidth per DFT-S sub-band (or equivalently the optimal number of sub-bands per optical channel) required in order to maximize the link non-linear tolerance (NLT). The NLT advantage of DFT-S OFDM is traced to the particular statistical dependency introduced among the OFDM sub-carriers by means of the DFT spreading operation. We further extend DFT-S to a unitary-spread generalized modulation format which includes as special cases the DFT-S scheme as well as a new format which we refer to as wavelet-spread (WAV-S) OFDM, replacing the spreading DFTs by Hadamard matrices which have elements +/-1 hence are multiplier-free. The extra complexity incurred in the spreading operation is almost negligible, however the performance improvement with WAV-S relative to plain OFDM is more modest than that achieved by DFT-S, which remains the preferred format for nonlinear tolerance improvement, outperforming both plain OFDM and single-carrier schemes.

  13. Proton affinities of maingroup-element hydrides and noble gases: trends across the periodic table, structural effects, and DFT validation

    NARCIS (Netherlands)

    Swart, M.; Rosler, E.; Bickelhaupt, F.M.

    2006-01-01

    We have carried out an extensive exploration of the gas-phase basicity of archetypal neutral bases across the periodic system using the generalized gradient approximation (GGA) of the density functional theory (DFT) at BP86/QZ4P//BP86/TZ2P. First, we validate DFT as a reliable tool for computing

  14. Explosive and pollutant TNP detection by structurally flexible SOFs: DFT-D3, TD-DFT study and in vitro recognition

    Energy Technology Data Exchange (ETDEWEB)

    Ghosh, Pritam [Surface Engineering & Tribology Group, CSIR-Central Mechanical Engineering Research Institute, Mahatma Gandhi Avenue, Burdwan, Durgapur 713209, West Bengal (India); Chemistry Department, Jadavpur University, Kolkata 32, West Bengal (India); Roy, Partha [Chemistry Department, Jadavpur University, Kolkata 32, West Bengal (India); Ghosh, Ananta [Chemistry Department, Burdwan Raj College, The University of Burdwan, West Bengal (India); Jana, Saibal [Department of Chemistry, Indian Institute of Technology Kharagpur, Kharagpur 721 302 (India); Murmu, Naresh Chandra [Surface Engineering & Tribology Group, CSIR-Central Mechanical Engineering Research Institute, Mahatma Gandhi Avenue, Burdwan, Durgapur 713209, West Bengal (India); Mukhopadhyay, Subhra Kanti [Department of Microbiology, The University of Burdwan, Burdwan 713104 (India); Banerjee, Priyabrata, E-mail: pr_banerjee@cmeri.res.in [Surface Engineering & Tribology Group, CSIR-Central Mechanical Engineering Research Institute, Mahatma Gandhi Avenue, Burdwan, Durgapur 713209, West Bengal (India); Academy of Scientific and Innovative Research at CSIR-Central Mechanical Engineering Research Institute (CMERI), Mahatma Gandhi Avenue, Durgapur 713209, West Bengal (India)

    2017-05-15

    Explosive and Pollutant Nitro Aromatics (epNACs) like 2,4,6-trinitrophenol (TNP) has been detected from various surface water specimens by luminescent Schiff base Organic Frameworks (SOFs) by fluorometric method. Fluorescence intensity of the receptor SOFs have been quenched in presence of TNP due to RET and ICT, which has been confirmed through solid and solution level spectroscopic studies like FT-IR, {sup 1}H-NMR, fluorescence titration. Modern DFT (DFT-D3) calculations of the possible host guest conformers have been performed for exploration of plausible route of interaction between receptor and epNACs. The outcome of theoretical calculations is in line with experimental findings where TNP and receptor conformation mimic parallel displaced type π- π interaction. TD-DFT has been executed with both receptor and receptor ···TNP adduct, the fluorescence quenching is in line with experimental outcome. Limit of TNP detection has been found as low as 5 μM with 2.97×10{sup 4} M{sup -1} as binding constant. In real time stepping, TNP as mutagenic agent for aquatic life has been detected inside prokaryotic cells like candidia albicans in ppm level.

  15. The nature of excess electrons in anatase and rutile from hybrid DFT and RPA.

    Science.gov (United States)

    Spreafico, Clelia; VandeVondele, Joost

    2014-12-21

    The behavior of excess electrons in undoped and defect free bulk anatase and rutile TiO2 has been investigated by state-of-the-art electronic structure methods including hybrid density functional theory (DFT) and the random phase approximation (RPA). Consistent with experiment, charge trapping and polaron formation is observed in both anatase and rutile. The difference in the anisotropic shape of the polarons is characterized, confirming for anatase the large polaron picture. For anatase, where polaron formation energies are small, charge trapping is observed also with standard hybrid functionals, provided the simulation cell is sufficiently large (864 atoms) to accommodate the lattice relaxation. Even though hybrid orbitals are required as a starting point for RPA in this system, the obtained polaron formation energies are relatively insensitive to the amount of Hartree-Fock exchange employed. The difference in trapping energy between rutile and anatase can be obtained accurately with both hybrid functionals and RPA. Computed activation energies for polaron hopping and delocalization clearly show that anatase and rutile might have different charge transport mechanisms. In rutile, only hopping is likely, whereas in anatase hopping and delocalization are competing. Delocalization will result in conduction-band-like and thus enhanced transport. Anisotropic conduction, in agreement with experimental data, is observed, and results from the tendency to delocalize in the [001] direction in rutile and the (001) plane in anatase. For future work, our calculations serve as a benchmark and suggest RPA on top on hybrid orbitals (PBE0 with 30% Hartree-Fock exchange), as a suitable method to study the rich chemistry and physics of TiO2.

  16. Electrochemical and DFT study of an anticancer and active anthelmintic drug at carbon nanostructured modified electrode.

    Science.gov (United States)

    Ghalkhani, Masoumeh; Beheshtian, Javad; Salehi, Maryam

    2016-12-01

    The electrochemical response of mebendazole (Meb), an anticancer and effective anthelmintic drug, was investigated using two different carbon nanostructured modified glassy carbon electrodes (GCE). Although, compared to unmodified GCE, both prepared modified electrodes improved the voltammetric response of Meb, the carbon nanotubes (CNTs) modified GCE showed higher sensitivity and stability. Therefore, the CNTs-GCE was chosen as a promising candidate for the further studies. At first, the electrochemical behavior of Meb was studied by cyclic voltammetry and differential pulse and square wave voltammetry. A one step reversible, pH-dependent and adsorption-controlled process was revealed for electro-oxidation of Meb. A possible mechanism for the electrochemical oxidation of Meb was proposed. In addition, electronic structure, adsorption energy, band gap, type of interaction and stable configuration of Meb on the surface of functionalized carbon nanotubes were studied by using density functional theory (DFT). Obtained results revealed that Meb is weakly physisorbed on the CNTs and that the electronic properties of the CNTs are not significantly changed. Notably, CNTs could be considered as a suitable modifier for preparation of the modified electrode for Meb analysis. Then, the experimental parameters affecting the electrochemical response of Meb were optimized. Under optimal conditions, high sensitivity (b(Meb)=dIp,a(Meb)/d[Meb]=19.65μAμM(-1)), a low detection limit (LOD (Meb)=19nM) and a wide linear dynamic range (0.06-3μM) was resulted for the voltammetric quantification of Meb. Copyright © 2016 Elsevier B.V. All rights reserved.

  17. Nickel/zinc-catalyzed decarbonylative addition of anhydrides to alkynes: a DFT study.

    Science.gov (United States)

    Meng, Qingxi; Li, Ming

    2013-10-01

    Density functional theory (DFT) was used to investigate the nickel- or nickel(0)/zinc- catalyzed decarbonylative addition of phthalic anhydrides to alkynes. All intermediates and transition states were optimized completely at the B3LYP/6-31+G(d,p) level. Calculated results indicated that the decarbonylative addition of phthalic anhydrides to alkynes was exergonic, and the total free energy released was -87.6 kJ mol(-1). In the five-coordinated complexes M4a and M4b, the insertion reaction of alkynes into the Ni-C bond occurred prior to that into the Ni-O bond. The nickel(0)/zinc-catalyzed decarbonylative addition was much more dominant than the nickel-catalyzed one in whole catalytic decarbonylative addition. The reaction channel CA→M1'→T1'→M2'→T2'→M3a'→M4a'→T3a1'→M5a1' →T4a1'→M6a'→P was the most favorable among all reaction pathways of the nickel- or nickel(0)/zinc- catalyzed decarbonylative addition of phthalic anhydrides to alkynes. And the alkyne insertion reaction was the rate-determining step for this channel. The additive ZnCl2 had a significant effect, and it might change greatly the electron and geometry structures of those intermediates and transition states. On the whole, the solvent effect decreased the free energy barriers.

  18. Experimental and DFT studies on the antioxidant activity of a C-glycoside from Rhynchosia capitata

    Science.gov (United States)

    Praveena, R.; Sadasivam, K.; Kumaresan, R.; Deepha, V.; Sivakumar, Raman

    2013-02-01

    Rhynchosia capitata (=Glycine capitata) Heyne ex roth, was found to possess polyphenolics including flavonoids, which acts as potential antioxidant. The study of ethanolic extract of roots and leaves reveals that the leaves possess high polyphenolics including flavonoids than roots. This was also confirmed by DPPH radical scavenging activity. Leaf powder of the plant was extracted with different solvents by soxhlet apparatus in the order of increasing polarity. The DPPH scavenging activity of methanol fraction was found to be high compared to the crude extract and other fractions. Nitric oxide scavenging activity was dominant in chloroform fraction compared to methanol fraction. Presence of flavonoids especially vitexin, a C-glycoside in methanol and chloroform fractions were confirmed by high pressure thin layer chromatography (HPTLC) analysis. The structural and molecular characteristics of naturally occurring flavonoid, vitexin was investigated in gas phase using density functional theory (DFT) approach with B3LYP/6-311G(d,p) level of theory. Analysis of bond dissociation enthalpy (BDE) reveals that the OH site that requires minimum energy for dissociation is 4'-OH from B-ring. To explore the radical scavenging activity of vitexin, the adiabatic ionization potential, electron affinity, hardness, softness, electronegativity and electrophilic index properties were computed and interpreted. The nonvalidity of Koopman's theorem has been verified by the computation of Eo and Ev energy magnitudes. Interestingly, from BDE calculations it was observed that BDE for 4'-OH, 5-OH and 7-OH are comparatively low for vitexin than its aglycone apigenin and this may be due to the presence of C-8 glucoside in vitexin. To substantiate this, plot of frontier molecular orbital and spin density distribution analysis for neutral and the corresponding radical species for the compound vitexin have been presented.

  19. Describing excited state relaxation and localization in TiO2 nanoparticles using TD-DFT

    International Nuclear Information System (INIS)

    Berardo, Enrico; Hu, Han-Shi; Van Dam, Hubertus J. J.; Shevlin, Stephen A.; Woodley, Scott M.; Kowalski, Karol; Zwijnenburg, Martijn A.

    2014-01-01

    We have investigated the description of excited state relaxation in naked and hydrated TiO 2 nanoparticles using Time-Dependent Density Functional Theory (TD-DFT) with three common hybrid exchange-correlation (XC) potentials; B3LYP, CAM-B3LYP and BHLYP. Use of TD-CAM-B3LYP and TD-BHLYP yields qualitatively similar results for all structures, which are also consistent with predictions of coupled cluster theory for small particles. TD-B3LYP, in contrast, is found to make rather different predictions; including apparent conical intersections for certain particles that are not observed with TD-CAM-B3LYP nor with TD-BHLYP. In line with our previous observations for vertical excitations, the issue with TD-B3LYP appears to be the inherent tendency of TD-B3LYP, and other XC potentials with no or a low percentage of Hartree-Fock Like Exchange, to spuriously stabilize the energy of charge-transfer (CT) states. Even in the case of hydrated particles, for which vertical excitations are generally well described with all XC potentials, the use of TD-B3LYP appears to result in CT-problems for certain particles. We hypothesize that the spurious stabilization of CT-states by TD-B3LYP even may drive the excited state optimizations to different excited state geometries than those obtained using TD-CAM-B3LYP or TD-BHLYP. In conclusion, focusing on the TD-CAM-B3LYP and TD-BHLYP results, excited state relaxation in naked and hydrated TiO 2 nanoparticles is predicted to be associated with a large Stokes' shift

  20. Pt/Au nanoalloy supported on alumina and chlorided alumina: DFT and experimental analysis

    Science.gov (United States)

    Sharifi, N.; Falamaki, C.; Ghorbanzadeh Ahangari, M.

    2018-04-01

    Density functional theory (DFT) was used to explore the adsorption of Pt/Au nanoalloy onto a pure and chlorided γ-Al2O3(110) surface, which has been applied in numerous catalytic reactions. First, we considered the adsorption properties of Pt clusters (n ≤ 5) onto the Al2O3(110) surface to determine the most stable Pt cluster on alumina surface in reforming processes. After full structural relaxations of Pt clusters at various configurations on alumina, our computed results expressed that the minimum binding energy (‑5.67 eV) is accrued for Pt4 cluster and the distance between the nearest Pt atom in the cluster to the alumina surface is equal to 1.13 Å. Then, we investigated the binding energies, geometries, and electronic properties of adsorbed Aun clusters (n ≤ 6) on the γ-Al2O3(110) surface. Our studied showed that Au5 was the most thermodynamically stable structure on γ-Al2O3. Finally, we inspected these properties for adsorbed Au clusters onto the Pt4-decorated alumina (Aun/Pt4-alumina) system. The binding energy of the Au4/Pt4-alumina system was ‑5.01 eV, and the distance between Au4 cluster and Pt4-alumina was 1.33 Å. The Au4/Pt4alumina system was found to be the most stable nanometer-sized catalyst design. At last, our first-principles calculations predicted that the best position of embedment Cl on the Au4/Pt4-alumina.

  1. Enhanced hydrogen storage on Li-doped defective graphene with B substitution: A DFT study

    Energy Technology Data Exchange (ETDEWEB)

    Zhou, Yanan [School of Chemical Engineering, Sichuan University, Chengdu 610065, Sichuan (China); Chu, Wei, E-mail: chuwei1965@scu.edu.cn [School of Chemical Engineering, Sichuan University, Chengdu 610065, Sichuan (China); Jing, Fangli [School of Chemical Engineering, Sichuan University, Chengdu 610065, Sichuan (China); Zheng, Jian [State Key Laboratory Cultivation Base for Nonmetal Composites and Functional Materials, Southwest University of Science and Technology, Mianyang, 621010 (China); Sun, Wenjing [China-America Cancer Research Institute, Key Laboratory for Medical Molecular Diagnostics of Guangdong Province, Guangdong Medical University, Dongguan, Guangdong 523808 (China); Xue, Ying [Key Laboratory Green Chemistry & Technology of Ministry of Education (MOE), College of Chemistry, Sichuan University, Chengdu 610064, Sichuan (China)

    2017-07-15

    Highlights: • Li atoms were found to be well dispersed on defective structures without clustering. • First H{sub 2} with five different initial configurations on Li/MV, Li/DV, Li/BMV, Li/BDV were explored in order. • Each system could bind up to three H{sub 2} molecules with hydrogen average adsorption energies close to the range of 0.2–0.4 eV. • H{sub 2} molecules bind with systems through weak electrostatic interaction between Li cation and induced H{sub 2} dipole. • H{sub 2} adsorption and desorption on the studied systems can process under ambient conditions. - Abstract: The characteristics of hydrogen adsorption on Li-doped defective graphene systems were investigated using density functional theory (DFT) calculations. Four types of defective structures were selected. Li atoms were well dispersed on the defective graphene without clustering, evidenced by the binding energy value between Li and defective graphene than that of Li-Li{sub x}. Additionally, as the amount of adsorbed H{sub 2} molecules increase, the H{sub 2} molecules show tilting configuration toward the Li adatom. This is beneficial for more hydrogen adsorption under the electrostatic interaction. On these four stable structures, there were up to three polarized H{sub 2} molecules adsorbed on per Li adatom, with the average hydrogen adsorption energy in the range of approximately 0.2–0.4 eV. These results provide new focus on the nature of Li-doped defective graphene with sometimes B substitution medium, which could be considered as a promising candidate for hydrogen storage.

  2. DFT study of the interaction between DOTA chelator and competitive alkali metal ions.

    Science.gov (United States)

    Frimpong, E; Skelton, A A; Honarparvar, B

    2017-09-01

    1, 4, 7, 10-tetraazacyclododecane-1, 4, 7, 10-tetracetic acid (DOTA) is an important chelator for radiolabeling of pharmaceuticals. The ability of alkali metals found in the body to complex with DOTA and compete with radio metal ions can alter the radiolabeling process. Non-covalent interactions between DOTA complexed with alkali metals Li + , Na + , K + and Rb + , are investigated with density functional theory using B3LYP and ωB97XD functionals. Conformational possibilities of DOTA were explored with a varying number of carboxylic pendant arms of DOTA in close proximity to the ions. It is found that the case in which four arms of DOTA are interacting with ions is more stable than other conformations. The objective of this study is to explore the electronic structure properties upon complexation of alkali metals Li + Na + , K + and Rb + with a DOTA chelator. Interaction energies, relaxation energies, entropies, Gibbs free energies and enthalpies show that the stability of DOTA, complexed with alkali metals decreases down the group of the periodic table. Implicit water solvation affects the complexation of DOTA-ions leading to decreases in the stability of the complexes. NBO analysis through the natural population charges and the second order perturbation theory, revealed a charge transfer between DOTA and alkali metals. Conceptual DFT-based properties such as HOMO/LUMO energies, ΔE HOMO-LUMO and chemical hardness and softness indicated a decrease in the chemical stability of DOTA-alkali metal complexes down the alkali metal series. This study serves as a guide to researchers in the field of organometallic chelators, particularly, radiopharmaceuticals in finding the efficient optimal match between chelators and various metal ions. Copyright © 2017 Elsevier Inc. All rights reserved.

  3. DFT study of oxygen adsorption on Mo{sub 2}C(001) and (201) surfaces at different conditions

    Energy Technology Data Exchange (ETDEWEB)

    Cheng, Lihong, E-mail: chenglihong001@126.com [School of Materials and Mechanical & Electrical Engineering, Jiangxi Science and Technology Normal University, Nanchang 330013, Jiangxi (China); Li, Wenkui; Chen, Zhiqin; Ai, Jianping; Zhou, Zehua [School of Materials and Mechanical & Electrical Engineering, Jiangxi Science and Technology Normal University, Nanchang 330013, Jiangxi (China); Liu, Jianwen, E-mail: liujw@nsccsz.gov.cn [National Supercomputing Center in Shenzhen, Shenzhen 518055 (China)

    2017-07-31

    Highlights: • O adsorption manners on Mo{sub 2}C surfaces were calculated by DFT method. • Stable oxygen adsorption states and coverage were identified at given T and p. • O{sub 2} results in full oxidation while H{sub 2}O and CO{sub 2} cause partial oxidation of Mo{sub 2}C surfaces. • Hydrogen could be used to avoid Mo{sub 2}C surface oxidation. - Abstract: Density functional theory (DFT) calculations were performed to investigate oxygen adsorption on Mo{sub 2}C(001) and (201)surfaces at different coverage. The energies and structures of oxygen from lowest to saturated coverages were clearly identified on each surface. Thermodynamics method was introduced to reveal the roles of temperature, pressure as well as oxygen sources (O{sub 2}, H{sub 2}O and CO{sub 2}) on the surface oxygen coverage, which is related to the surface oxidation. On the basis of phase diagram, we can easily identify the stable oxygen coverage at different defined conditions. In addition, it reveals that O{sub 2} is the strongest oxidant, which results in the full coverage of oxygen on both surfaces in a wide range of temperature and pressure. Then, H{sub 2}O and CO{sub 2} are weaker oxidants, which could only cause partial oxidation of Mo{sub 2}C surfaces. These results indicate the facile oxidation of Mo{sub 2}C catalyst. The possible ways to avoid surface oxidation are keeping higher temperature and H{sub 2} pressure in the gas phase.

  4. Molecular design of donor-acceptor dyes for efficient dye-sensitized solar cells I: a DFT study.

    Science.gov (United States)

    El-Shishtawy, Reda M; Asiri, Abdullah M; Aziz, Saadullah G; Elroby, Shaaban A K

    2014-06-01

    Dye-sensitized solar cells (DSSCs) have drawn great attention as low cost and high performance alternatives to conventional photovoltaic devices. The molecular design presented in this work is based on the use of pyran type dyes as donor based on frontier molecular orbitals (FMO) and theoretical UV-visible spectra in combination with squaraine type dyes as an acceptor. Density functional theory has been used to investigate several derivatives of pyran type dyes for a better dye design based on optimization of absorption, regeneration, and recombination processes in gas phase. The frontier molecular orbital (FMO) of the HOMO and LUMO energy levels plays an important role in the efficiency of DSSCs. These energies contribute to the generation of exciton, charge transfer, dissociation and exciton recombination. The computations of the geometries and electronic structures for the predicted dyes were performed using the B3LYP/6-31+G** level of theory. The FMO energies (EHOMO, ELUMO) of the studied dyes are calculated and analyzed in the terms of the UV-visible absorption spectra, which have been examined using time-dependent density functional theory (TD-DFT) techniques. This study examined absorption properties of pyran based on theoretical UV-visible absorption spectra, with comparisons between TD-DFT using B3LYP, PBE, and TPSSH functionals with 6-31+G (d) and 6-311++G** basis sets. The results provide a valuable guide for the design of donor-acceptor (D-A) dyes with high molar absorptivity and current conversion in DSSCs. The theoretical results indicated 4-(dicyanomethylene)-2-methyl-6-(p-dimethylaminostyryl)-4H-pyran dye (D2-Me) can be effectively used as a donor dye for DSSCs. This dye has a low energy gap by itself and a high energy gap with squaraine acceptor type dye, the design that reduces the recombination and improves the photocurrent generation in solar cell.

  5. DFT studies for the substituent effect on the diels-alder reaction of 1,4-diaza-1,3-butadienes

    International Nuclear Information System (INIS)

    Lee, Gab Yong

    2001-01-01

    DFT calculations have been performed on several substituted 1,4-diaza-1,3-butadienes (1,4-DABs) with electron donating and withdrawing groups at the terminal two nitrogens to investigate the reactivity of Diels-Alder reaction with acrolein. The calculated FMO (Frontier Molecular orbital) energies for the optimized 1,4-disubstituted-1,4DABs have been used to explain both normal and inverse electron demand Diels-Alder reactions. It is shown that the electron donating and withdrawing substituents lead to the normal(HOMO diene controlled) and inverse electron demand (LUMO diene controlled) Diels-Alder reactions, respectively

  6. Highly efficient regioselective synthesis, spectroscopic characterizations and DFT calculations of novel hydroxymethylated 1,4-disubstituted-1,2,3-triazole-based sulfonamides

    Science.gov (United States)

    Taheri, Elmira; Mirjafary, Zohreh; Saeidian, Hamid

    2018-04-01

    The novel hydroxymethylated 1,4-disubstituted-1,2,3-triazole-based sulfonamides were synthesized in excellent yields and high regioselectivity via a one-pot, two-step, three-component reaction of N-propargylsulfonamides, sodium azide, and epoxide derivatives under green conditions. Green and mild reaction condition, commercially readily available and inexpensive starting materials, wide scope and easy work-up are the key features of the present method. The Li+ and Na+ ion affinities of the model structure have been also investigated by density functional theory (DFT) studies to find the applicability of these products as ligand in coordination chemistry.

  7. Structural characterization of Am(III) formate complexes. Combining EXAFS spectroscopy with DFT and thermodynamical calculations

    Energy Technology Data Exchange (ETDEWEB)

    Rossberg, Andre [Helmholtz-Zentrum Dresden-Rossendorf e.V., Dresden (Germany). Molecular Structures; Froehlich, D.R. [Heidelberg Univ. (Germany). Physikalisch-Chemisches Inst.

    2017-06-01

    We used iterative transformation factor analysis (ITFA) in order to isolate the EXAFS spectral contributions of the complexing ligand from a Am(III)/formate pH-series. Thermodynamic calculations were used as constraint for ITFA and for density functional theory (DFT) calculations to identify the coordination mode within the formed complexes.

  8. The Influence of Square Planar Platinum Complexes on DNA Bases Pairing. An ab initio DFT Study

    Czech Academy of Sciences Publication Activity Database

    Burda, J. V.; Šponer, Jiří; Leszczynski, J.

    2001-01-01

    Roč. 3, č. 19 (2001), s. 4404-4411 ISSN 1463-9076 R&D Projects: GA MŠk LN00A032 Institutional research plan: CEZ:AV0Z4040901 Keywords : DNA base pairing * platinated base pairs * ab initio DFT study Subject RIV: CF - Physical ; Theoretical Chemistry Impact factor: 1.787, year: 2001

  9. Stepwise or concerted? DFT study on the mechanism of ionic Diels-Alder reaction of chromanes

    Directory of Open Access Journals (Sweden)

    Haghdadi Mina

    2016-01-01

    Full Text Available The stepwise and concerted Ionic Diels-Alder reaction between phenyl (pyridin-2-ylmethylene oxonium and styrene derivatives are explored using theoretical method. The results support using computational method via persistent intermediates. The DFT method was essential to reproduce a reasonable potential energy surface for these challenging systems.

  10. DFT study of zigzag (n, 0) single-walled carbon nanotubes: C-13 NMR chemical shifts

    Czech Academy of Sciences Publication Activity Database

    Kupka, T.; Stachów, M.; Stobinski, L.; Kaminský, Jakub

    2016-01-01

    Roč. 67, Jun (2016), s. 14-19 ISSN 1093-3263 R&D Projects: GA ČR(CZ) GA14-03564S Institutional support: RVO:61388963 Keywords : zigzag SWCNT * cyclacenes * theoretical modeling * DFT * NMR Subject RIV: CF - Physical ; Theoretical Chemistry Impact factor: 1.754, year: 2016

  11. Quantum-mechanical DFT calculation supported Raman spectroscopic study of some amino acids in bovine insulin.

    Science.gov (United States)

    Tah, Bidisha; Pal, Prabir; Roy, Sourav; Dutta, Debodyuti; Mishra, Sabyashachi; Ghosh, Manash; Talapatra, G B

    2014-08-14

    In this article Quantum mechanical (QM) calculations by Density Functional Theory (DFT) have been performed of all amino acids present in bovine insulin. Simulated Raman spectra of those amino acids are compared with their experimental spectra and the major bands are assigned. The results are in good agreement with experiment. We have also verified the DFT results with Quantum mechanical molecular mechanics (QM/MM) results for some amino acids. QM/MM results are very similar with the DFT results. Although the theoretical calculation of individual amino acids are feasible, but the calculated Raman spectrum of whole protein molecule is difficult or even quite impossible task, since it relies on lengthy and costly quantum-chemical computation. However, we have tried to simulate the Raman spectrum of whole protein by adding the proportionate contribution of the Raman spectra of each amino acid present in this protein. In DFT calculations, only the contributions of disulphide bonds between cysteines are included but the contribution of the peptide and hydrogen bonds have not been considered. We have recorded the Raman spectra of bovine insulin using micro-Raman set up. The experimental spectrum is found to be very similar with the resultant simulated Raman spectrum with some exceptions. Copyright © 2014 Elsevier B.V. All rights reserved.

  12. Structures of cefradine dihydrate and cefaclor dihydrate from DFT-D calculations

    DEFF Research Database (Denmark)

    van de Streek, Jacco; Rantanen, Jukka; Bond, Andrew D

    2013-01-01

    in the zwitterionic form in the two dihydrate structures. A potential ambiguity concerning the orientation of the cyclohexadienyl ring in cefradine dihydrate is also clarified, and on the basis of the calculated energies it is shown that disorder should not be expected at room temperature. The DFT-D methods can...

  13. Vibrational absorption spectra, DFT and SCC-DFTB conformational study and analysis of [Leu]enkephalin

    DEFF Research Database (Denmark)

    Abdali, Salim; Niehaus, T.A.; Jalkanen, Karl J.

    2003-01-01

    . Ab initio (DFT at the B3LYP/6-31G* level of theory) and semi-empirical (SCC-DFTB) with and without dispersion correction were applied to simulate the VA spectra of [Leu] enkephalin. In these calculations structures taken from X-ray measurements for different conformers of the molecule were used...

  14. Ab Initio and DFT Potential Energy Surfaces for Cyanuric Chloride Reactions

    National Research Council Canada - National Science Library

    Pai, Sharmila

    1998-01-01

    ... on the potential energy surface were calculated using the 6-31G and 6-311 +Gbasis sets. DFT(B3LYP) geometry optimizations and zero-point corrections for critical points on the potential energy surface were calculated with the 6-31G, 6-311...

  15. Exploring Systematic Discrepancies in DFT Calculations of Chlorine Nuclear Quadrupole Couplings

    Czech Academy of Sciences Publication Activity Database

    Socha, Ondřej; Hodgkinson, P.; Widdifield, C. M.; Yates, J. R.; Dračínský, Martin

    2017-01-01

    Roč. 121, č. 21 (2017), s. 4103-4113 ISSN 1089-5639 R&D Projects: GA ČR GA15-11223S Institutional support: RVO:61388963 Keywords : NMR spectroscopy * DFT calculations * quadrupolar coupling Subject RIV: CF - Physical ; Theoretical Chemistry OBOR OECD: Physical chemistry Impact factor: 2.847, year: 2016

  16. DFT study of the mechanism and stereoselectivity of the 1,3-dipolar ...

    Indian Academy of Sciences (India)

    and methyl acrylate) using DFT method. An ana- lysis of ..... field (SCRF)30,46 model based on the polarizable con- tinuum model (PCM) of Tomasi's group47 have been applied. ... stereoselectivity relative to the gas-phase since the trends of ...

  17. Structural changes in the water tetramer. A combined Monte Carlo and DFT study

    Czech Academy of Sciences Publication Activity Database

    Vítek, A.; Kalus, R.; Paidarová, Ivana

    2010-01-01

    Roč. 12, č. 41 (2010), s. 13657-13666 ISSN 1463-9076 R&D Projects: GA AV ČR IAA401870702 Institutional research plan: CEZ:AV0Z40400503 Keywords : Monte Carlo Study * DFT study * water tetramer Subject RIV: CF - Physical ; Theoretical Chemistry Impact factor: 3.454, year: 2010

  18. RHF and DFT study of the optimized molecular structure and atomic ...

    African Journals Online (AJOL)

    Restricted HartreeFock (RHF) and Density Functional Theory (DFT) studies were carried out on the organic semi conductor material Pentacene. 6-31G and 6-31G* basis sets were used to optimize the molecule and compute the charge distribution at both levels of theory. The results show that the Carbon-Hydrogen bonds in ...

  19. Experimental and DFT study of thiol-stabilized Pt/CNTs catalysts.

    Science.gov (United States)

    Li, L; Chen, S G; Wei, Z D; Qi, X Q; Xia, M R; Wang, Y Q

    2012-12-28

    Using a combination of experiments and density functional theory (DFT) calculations, we explored the mechanisms of the stabilization effect of the thiolized (-SH) group on the Pt/SH-CNTs catalyst. Pt particles supported on the hydroxyl functionalized CNTs (Pt/OH-CNTs) are synthesized as a baseline for comparison. Experimentally, the platinum on OH-CNTs has a stronger tendency for aggregation than that on SH-CNTs. The differences in the oxidation resistance, migration activation energy, and corrosion resistance between the Pt/SH-CNTs and Pt/OH-CNTs are calculated using DFT. The DFT calculations indicate that the -SH group enhances the oxidation resistance of the Pt cluster and CNTs and restricts Pt migration on the CNTs. DFT calculations also suggest that the enhanced stability of Pt/SH-CNTs originates from the increased interaction between Pt and SH-CNTs and the depressed d-band center of the Pt NPs. Thus, the functional groups on the CNTs used for stabilization of supported Pt NPs should provide a deposit and anchor site for Pt NPs and maintain the perfect structure of CNTs rather than destroying it.

  20. Pyrone-based Cu(II) complexes, their characterization, DFT based ...

    Indian Academy of Sciences (India)

    ... of P. G. Studies and. Research in Chemistry and Pharmacy, R. D. University, Jabalpur 482 001, India ... fascination.2,3 Such type of metal complexes are quite interesting due to .... in the ground state were optimized by the DFT method using B3LYP ..... Vogel A I 1996 In A Text Book of Qualitative Inorganic. Analysis (7th ...

  1. Implementation of Constrained DFT for Computing Charge Transfer Rates within the Projector Augmented Wave Method

    DEFF Research Database (Denmark)

    Melander, Marko; Jónsson, Elvar Örn; Mortensen, Jens Jørgen

    2016-01-01

    molecules to periodic systems in one-, two-, or three-dimensions. As such, this implementation is relevant for a wide variety of applications. We also present how to extract the electronic coupling element and reorganization energy from the resulting diabatic cDFT-PAW wave functions for the parametrization...

  2. Synthesis, X-ray crystallography, and DFT calculations of a novel phosphoramide

    Czech Academy of Sciences Publication Activity Database

    Shariatinia, Z.; Dušek, Michal; Eigner, Václav

    2014-01-01

    Roč. 640, č. 14 (2014), 2945-2955 ISSN 0044-2313 R&D Projects: GA ČR(CZ) GA14-03276S Institutional support: RVO:68378271 Keywords : phosphoramide * x-ray structure * DFT Subject RIV: BM - Solid Matter Physics ; Magnetism Impact factor: 1.160, year: 2014

  3. Synthesis, spectroscopy, X-ray crystallography, and DFT computations of nanosized phosphazenes

    Czech Academy of Sciences Publication Activity Database

    Shariatinia, Z.; Moghadam, E.J.; Maghsoudi, N.; Mousavi, H.S.M.; Dušek, Michal; Eigner, Václav

    2015-01-01

    Roč. 641, č. 5 (2015), s. 967-978 ISSN 0044-2313 Grant - others:AV ČR(CZ) Praemium Academiae Institutional support: RVO:68378271 Keywords : phosphazene * ultrasonic * nanoparticle * x-ray crystallography * DFT calculation Subject RIV: BM - Solid Matter Physics ; Magnetism Impact factor: 1.261, year: 2015

  4. Study of uncertainties of height measurements of monoatomic steps on Si 5 × 5 using DFT

    Czech Academy of Sciences Publication Activity Database

    Campbell, A.C.; Jelínek, Pavel; Klapetek, P.

    2017-01-01

    Roč. 28, č. 3 (2017), 1-6, č. článku 034005. ISSN 0957-0233 Institutional support: RVO:68378271 Keywords : DFT * AFM Subject RIV: BM - Solid Matter Physics ; Magnetism OBOR OECD: Condensed matter physics (including formerly solid state physics, supercond.) Impact factor: 1.585, year: 2016

  5. A DFT study on benzene adsorption over tungsten sulfides: surface model and adsorption geometries

    NARCIS (Netherlands)

    Koide, R.; Hensen, E.J.M.; Paul, J.F.; Cristol, S.; Payen, E.; Nakamura, H.; Santen, van R.A.

    2007-01-01

    Benzene adsorption on a WS2(100) surface was studied by ab initio periodic DFT computations. Benzene adsorption is facile on the bridge site of the bare W edge via ¿2 or ¿3 coordination. Taking into account the stable configuration at the W edge under typical hydrotreating reaction conditions (623

  6. DFT calculations on N2O decomposition by binuclear Fe complexes in Fe/ZSM-5

    NARCIS (Netherlands)

    Yakovlev, A.L.; Zhidomirov, G.M.; Santen, van R.A.

    2001-01-01

    N2O decomposition catalyzed by oxidized Fe clusters localized in the micropores of Fe/ZSM-5 has been studied using the DFT approach and a binuclear cluster model of the active site. Three different reaction routes were found, depending on temperature and water pressure. The results show that below

  7. Complexation of the lithium cation with beauvericin: experimental and DFT study

    Czech Academy of Sciences Publication Activity Database

    Makrlík, E.; Toman, Petr; Vaňura, P.

    2012-01-01

    Roč. 1024, 26 September (2012), s. 142-145 ISSN 0022-2860 R&D Projects: GA ČR(CZ) GAP205/10/2280 Institutional research plan: CEZ:AV0Z40500505 Institutional support: RVO:61389013 Keywords : extraction * DFT * complexation Subject RIV: BM - Solid Matter Physics ; Magnetism Impact factor: 1.404, year: 2012

  8. Complexation of the cesium cation with lithium ionophore VIII: extraction and DFT study

    Czech Academy of Sciences Publication Activity Database

    Makrlík, E.; Novák, Vít; Vaňura, P.; Bouř, Petr

    2013-01-01

    Roč. 298, č. 3 (2013), s. 2065-2068 ISSN 0236-5731 Institutional support: RVO:61388963 Keywords : cesium cation * lithium ionophore VIII * complexation * extraction and stability constants * water-nitrobenzene system * DFT calculations * structures Subject RIV: CB - Analytical Chemistry , Separation Impact factor: 1.415, year: 2013

  9. SeO2 adsorption on CaO surface: DFT and experimental study on the adsorption of multiple SeO2 molecules

    Science.gov (United States)

    Fan, Yaming; Zhuo, Yuqun; Li, Liangliang

    2017-10-01

    SeO2 adsorption mechanisms on CaO surface were firstly investigated by both density functional theory (DFT) calculations and adsorption experiments. Adsorption of multiple SeO2 on the CaO (001) surface was investigated using slab model. Based on the results of adsorption energy and surface property, a double-layer adsorption mechanisms were proposed. In experiments, the SeO2 adsorption products were prepared in a U-shaped quartz reactor at 200 °C. The surface morphology was investigated by field emission scanning electron microscopy (FE-SEM). The superficial and total SeO2 mass fractions were measured by X-ray photoelectron spectroscopy (XPS) and inductively coupled plasma atomic emission spectroscopy (ICP-AES), respectively. The surface valence state and bulk structure are determined by XPS and X-Ray Diffraction (XRD). The experimental results are in good agreement with the DFT results. In conclusion, the fundamental SeO2 chemisorption mechanisms on CaO surface were suggested.

  10. Substituted group and side chain effects for the porphyrin and zinc(II)–porphyrin derivatives: A DFT and TD-DFT study

    International Nuclear Information System (INIS)

    Tai, Chin-Kuen; Chuang, Wen-Hua; Wang, Bo-Cheng

    2013-01-01

    The DFT/B3LYP/LANL2DZ and TD-DFT calculations have been performed to generate the optimized structures, electronic and photo-physical properties for the porphyrin and zinc(II)–porphyrin (metalloporphyrin) derivatives. The substituted group and side chain effects for these derivatives are discussed in this study. According to the calculation results, the side chain moiety extends the π-delocalization length from the porphyrin core to the side chain moiety. The substituted group with a stronger electron-donating ability increases the energy level of highest occupied molecular orbital (E HOMO ). The side chain moiety with a lower resonance energy decreases E HOMO , the energy level of the lowest unoccupied molecular orbital (E LUMO ), and the energy gap (E g ) between HOMO and LUMO in the porphyrin and zinc(II)–porphyrin derivatives. The natural bonding orbital (NBO) analysis determines the possible electron transfer mechanism from the electron-donating to -withdrawing groups (the side chain moiety) in these porphyrin derivatives. The projected density of state (PDOS) analysis shows that the electron-donating group affects the electron density distribution in both HOMO and LUMO, and the side chain moiety influence the electron density distribution in LUMO. The calculated photo-physical properties (absorption wavelengths and the related oscillator strength, f) in dichloromethane environment for porphyrin and zinc(II)–porphyrin derivatives have been simulated by using the TD-DFT method within the Polarizable Continuum Model (PCM). The present of both of the substituted group and the side chain moiety in these derivatives results in a red shift and broadening of the range of the absorption peaks of the Q/Soret band as compared to porphin. -- Highlights: • Side chain moiety extends the π-delocalization for the porphyrins. • Substituted group increases the energy of highest occupied molecular orbital. • Side chain moiety influences the Q/Soret band of

  11. Mutual effects of copper and phosphate on their interaction with γ-Al2O3: combined batch macroscopic experiments with DFT calculations.

    Science.gov (United States)

    Ren, Xuemei; Yang, Shitong; Tan, Xiaoli; Chen, Changlun; Sheng, Guodong; Wang, Xiangke

    2012-10-30

    The mutual effects of Cu(II) and phosphate on their interaction with γ-Al(2)O(3) are investigated by using batch experiments combined with density functional theory (DFT) calculations. The results of batch experiments show that coexisting phosphate promotes the retention of Cu(II) on γ-Al(2)O(3), whereas phosphate retention is not affected by coexisting Cu(II) at low initial phosphate concentrations (≤ 3.6 mg P/L). Cu-phosphate aqueous complexes control Cu(II) retention through the formation of type B ternary surface complexes (where phosphate bridges γ-Al(2)O(3) and Cu(II)) at pH 5.5. This deduction is further supported by the results of DFT calculations. More specifically, the DFT calculation results indicate that the type B ternary surface complexes prefer to form outer-sphere or monodentate inner-sphere binding mode under our experimental conditions. The enhancement of phosphate retention on γ-Al(2)O(3) in the presence of Cu(II) at high initial phosphate concentrations (>3.6 mg P/L) may be attributed to the formation of 1:2 Cu(II)-phosphate species and/or surface precipitates. Understanding the mutual effects of phosphate and Cu(II) on their mobility and transport in mineral/water environments is more realistic to design effective remediation strategies for reducing their negative impacts on aquatic/terrestrial environments. Copyright © 2012 Elsevier B.V. All rights reserved.

  12. Ammonia dynamics in magnesium ammine from DFT and neutron scattering

    DEFF Research Database (Denmark)

    Tekin, Adem; Hummelshøj, Jens Strabo; Jacobsen, Hjalte Sylvest

    2010-01-01

    Energy storage in the form of ammonia bound in metal salts, so-called metal ammines, combines high energy density with the possibility of fast and reversible NH3 ab- and desorption kinetics. The mechanisms and processes involved in the NH3 kinetics are investigated by density functional theory (D...

  13. Fluorescent vinyl and styryl coumarins: A comprehensive DFT study ...

    Indian Academy of Sciences (India)

    Kiran Avhad

    2017-11-14

    Nov 14, 2017 ... Nonlinear optical properties of 3-styryl and 3-vinyl coumarin dyes have been investigated with ..... Figure 4. Dipole moment (μ in Debye) graph in the ground state (S0) and excited state (S1) in .... It gives information on shape,.

  14. Spectro-electrochemical and DFT study of tenoxicam metabolites formed by electrochemical oxidation

    International Nuclear Information System (INIS)

    Ramírez-Silva, M.T.; Guzmán-Hernández, D.S.; Galano, A.; Rojas-Hernández, A.; Corona-Avendaño, S.; Romero-Romo, M.; Palomar-Pardavé, M.

    2013-01-01

    Highlights: • Tenoxicam deprotonation and electrochemical oxidation were studied. • Both spectro-electrochemical and theoretical DFT studies were considered. • It was found that the ampholitic species of tenoxicam is a zwitterion. • Electrochemical oxidation of tenoxicam yields two non-electroactive products. • The nature of these fragments was further confirmed by a chromatography study. -- Abstract: From experimental (spectro-electrochemical) and theoretical (DFT) studies, the mechanisms of tenoxicam deprotonation and electrochemical oxidation were assessed. From these studies, new insights on the nature of the ampholitic species involved during tenoxicam's deprotonation in aqueous solution are presented; see scheme A. Moreover, it is shown that, after the analysis of two different reaction schemes that involve up to 10 different molecules and 12 reaction paths, the electrochemical oxidation of tenoxicam, yields two non-electroactive products that are predominately formed by its fragmentation, after the loss of two electrons. The nature of these fragments was further confirmed by a chromatography study

  15. The power of joint application of LEED and DFT in quantitative surface structure determination

    International Nuclear Information System (INIS)

    Heinz, K; Hammer, L; Mueller, S

    2008-01-01

    It is demonstrated for several cases that the joint application of low-energy electron diffraction (LEED) and structural calculations using density functional theory (DFT) can retrieve the correct surface structure even though single application of both methods fails. On the experimental side (LEED) the failure can be due to the simultaneous presence of weak and very strong scatterers or to an insufficient data base leaving different structures with the same quality of fit between experimental data and calculated model intensities. On the theory side (DFT) it can be difficult to predict the coverage of an adsorbate or two different structures may own almost the same total energy, but only one of the structures is assumed in experiment due to formation kinetics. It is demonstrated how in the different cases the joint application of both methods-which yield about the same structural precision-offers a way out of the dilemma

  16. Ethylene dissociation on flat and stepped Ni(111): A combined STM and DFT study

    DEFF Research Database (Denmark)

    Vang, R.T.; Honkala, Johanna Karoliina; Dahl, S.

    2006-01-01

    The dissociative adsorption of ethylene (C(2)H(4)) on Ni(111) was studied by scanning tunneling microscopy (STM) and density functional theory (DFT) calculations. The STM studies reveal that ethylene decomposes exclusively at the step edges at room temperature. However, the step edge sites...... are poisoned by the reaction products and thus only a small brim of decomposed ethylene is formed. At 500 K decomposition on the (111) facets leads to a continuous growth of carbidic islands, which nucleate along the step edges. DFT calculations were performed for several intermediate steps...... in the decomposition of ethylene on both Ni(111) and the stepped Ni(211) surface. In general the Ni(211) surface is found to have a higher reactivity than the Ni(111) surface. Furthermore, the calculations show that the influence of step edge atoms is very different for the different reaction pathways. In particular...

  17. Diffusion of anthracene derivatives on Cu(111) studied by STM and DFT

    Science.gov (United States)

    Wyrick, Jonathan; Bartels, Ludwig; Einstein, Theodore

    2014-03-01

    Substituted anthracenes have drawn attention due to their ability to diffuse uniaxially on a Cu(111) surface. We compare anthracene to three of its derivatives whose 9,10 hydrogens are replaced by elements of the chalcogen group that act as linkers binding the molecules to a Cu(111) substrate. DFT calculations shed light on STM imaging and diffusion studies on the three substituted species. We present an analysis of the DFT results in which energetic contributions to the diffusion barriers are partitioned among the Kohn-Sham orbitals, allowing us to make assignments as to how each orbital affects diffusion for each species and draw comparisons between them. Present address: Center for Nanoscale Science and Technology, NIST, Gaithersburg, MD.

  18. Simplified DFT methods for consistent structures and energies of large systems

    Science.gov (United States)

    Caldeweyher, Eike; Gerit Brandenburg, Jan

    2018-05-01

    Kohn–Sham density functional theory (DFT) is routinely used for the fast electronic structure computation of large systems and will most likely continue to be the method of choice for the generation of reliable geometries in the foreseeable future. Here, we present a hierarchy of simplified DFT methods designed for consistent structures and non-covalent interactions of large systems with particular focus on molecular crystals. The covered methods are a minimal basis set Hartree–Fock (HF-3c), a small basis set screened exchange hybrid functional (HSE-3c), and a generalized gradient approximated functional evaluated in a medium-sized basis set (B97-3c), all augmented with semi-classical correction potentials. We give an overview on the methods design, a comprehensive evaluation on established benchmark sets for geometries and lattice energies of molecular crystals, and highlight some realistic applications on large organic crystals with several hundreds of atoms in the primitive unit cell.

  19. Demostration of 520 Gb/s/λ pre-equalized DFT-spread PDM-16QAM-OFDM signal transmission.

    Science.gov (United States)

    Li, Fan; Yu, Jianjun; Cao, Zizheng; Chen, Ming; Zhang, Junwen; Li, Xinying

    2016-02-08

    In this paper, we successfully transmit 8 × 520 Gb/s pre-equalized DFT-spread PDM-16QAM orthogonal frequency-division multiplexing (OFDM) signal over 840 km SMF with BER under 2.4 × 10(-2). We discuss how to obtain accurate tranceivers' response during pre-equalization for DFT-spread OFDM with coherent detection and we find conventional OFDM symbols training sequences (TSs) outperform DFT-spread OFDM symbols TSs in obtaining channel response for pre-equalization and equalization. Additionally, the optimal IFFT/FFT size is explored for the pre-equalized DFT-spread PDM-16QAM-OFDM transmission systems. It is the first time to realize 400 Gb/s/λ net rate OFDM signal transmission.

  20. Mechanism and Regioselectivity of Rh(III)-Catalyzed Intermolecular Annulation of Aryl-Substituted Diazenecarboxylates and Alkenes: DFT Insights

    KAUST Repository

    Ajitha, Manjaly John; Huang, Kuo-Wei

    2016-01-01

    is identified as the initial C-H activation, consistent with the previous kinetic studies. Notably, DFT studies offered important insights on the ability of the substrate (diazene carboxylate) to promote the switchable coordination site selectivity during

  1. NMR, MP2 and DFT Study of Thiophenoxyketenimines (o-ThioSchiff bases)

    DEFF Research Database (Denmark)

    Saeed, Bahjat Ali; Elias, Rita Sabah; Kamounah, Fadhil S.

    2018-01-01

    Five new thiophenoxyketinimines have been synthesized. 1 H and 13 C NMR spectra as well as deuterium isotope effects on 13 C chemical shifts are determined, and spectra are assigned. DFT and MP2 calculations of both structures, chemical shifts, and isotope effects on chemical shifts are done...... that calculations at the MP2 level are best to obtain correct "C═S" chemical shifts....

  2. Spirocyclic character of ixazomib citrate revealed by comprehensive XRD, NMR and DFT study

    Czech Academy of Sciences Publication Activity Database

    Skořepová, E.; Čerňa, I.; Vlasáková, R.; Zvoníček, V.; Tkadlecová, M.; Dušek, Michal

    2017-01-01

    Roč. 1148, Nov (2017), s. 22-27 ISSN 0022-2860 R&D Projects: GA MŠk LO1603 EU Projects: European Commission(XE) CZ.2.16/3.1.00/24510 Institutional support: RVO:68378271 Keywords : ixazomib citrate * molecular structure * stereoisomers * crystal structure * NMR * DFT Subject RIV: BM - Solid Matter Physics ; Magnetism OBOR OECD: Condensed matter physics (including formerly solid state physics, supercond.) Impact factor: 1.753, year: 2016

  3. Combining DFT, Cluster Expansions, and KMC to Model Point Defects in Alloys

    Science.gov (United States)

    Modine, N. A.; Wright, A. F.; Lee, S. R.; Foiles, S. M.; Battaile, C. C.; Thomas, J. C.; van der Ven, A.

    In an alloy, defect energies are sensitive to the occupations of nearby atomic sites, which leads to a distribution of defect properties. When radiation-induced defects diffuse from their initially non-equilibrium locations, this distribution becomes time-dependent. The defects can become trapped in energetically favorable regions of the alloy leading to a diffusion rate that slows dramatically with time. Density Functional Theory (DFT) allows the accurate determination of ground state and transition state energies for a defect in a particular alloy environment but requires thousands of processing hours for each such calculation. Kinetic Monte-Carlo (KMC) can be used to model defect diffusion and the changing distribution of defect properties but requires energy evaluations for millions of local environments. We have used the Cluster Expansion (CE) formalism to ``glue'' together these seemingly incompatible methods. The occupation of each alloy site is represented by an Ising-like variable, and products of these variables are used to expand quantities of interest. Once a CE is fit to a training set of DFT energies, it allows very rapid evaluation of the energy for an arbitrary configuration, while maintaining the accuracy of the underlying DFT calculations. These energy evaluations are then used to drive our KMC simulations. We will demonstrate the application of our DFT/MC/KMC approach to model thermal and carrier-induced diffusion of intrinsic point defects in III-V alloys. Sandia National Laboratories is a multi-program laboratory managed and operated by Sandia Corporation, a wholly owned subsidiary of Lockheed Martin Corporation, for the U.S. Department of Energy's National Nuclear Security Administration under Contract DE.

  4. Thermodynamic study of complexation of thorium with pyridine monocarboxylates by calorimetry and DFT calculations

    International Nuclear Information System (INIS)

    Rama Mohana Rao, D.; Rawat, Neetika; Sawant, R.M.; Tomar, B.S.; Manna, D.; Ghanty, T.K.

    2013-01-01

    Stability constants of Th(IV) complexes with pyridine mono-carboxylates, namely, picolinate, nicotinate and isonicotinate have been determined following potentiometric titration of the metal ion and ligand mixtures with NaOH solution of known concentration. These data were used during the analysis of the calorimetric titration data to obtain the enthalpy of complexation reactions. The experimental data have been compared with that obtained from the DFT based theoretical calculations. (author)

  5. Accurate structures and energetics of neutral-framework zeotypes from dispersion-corrected DFT calculations

    Science.gov (United States)

    Fischer, Michael; Angel, Ross J.

    2017-05-01

    Density-functional theory (DFT) calculations incorporating a pairwise dispersion correction were employed to optimize the structures of various neutral-framework compounds with zeolite topologies. The calculations used the PBE functional for solids (PBEsol) in combination with two different dispersion correction schemes, the D2 correction devised by Grimme and the TS correction of Tkatchenko and Scheffler. In the first part of the study, a benchmarking of the DFT-optimized structures against experimental crystal structure data was carried out, considering a total of 14 structures (8 all-silica zeolites, 4 aluminophosphate zeotypes, and 2 dense phases). Both PBEsol-D2 and PBEsol-TS showed an excellent performance, improving significantly over the best-performing approach identified in a previous study (PBE-TS). The temperature dependence of lattice parameters and bond lengths was assessed for those zeotypes where the available experimental data permitted such an analysis. In most instances, the agreement between DFT and experiment improved when the experimental data were corrected for the effects of thermal motion and when low-temperature structure data rather than room-temperature structure data were used as a reference. In the second part, a benchmarking against experimental enthalpies of transition (with respect to α-quartz) was carried out for 16 all-silica zeolites. Excellent agreement was obtained with the PBEsol-D2 functional, with the overall error being in the same range as the experimental uncertainty. Altogether, PBEsol-D2 can be recommended as a computationally efficient DFT approach that simultaneously delivers accurate structures and energetics of neutral-framework zeotypes.

  6. Exploring the sensitivity of ZnO nanotubes to tyrosine nitration: A DFT approach

    International Nuclear Information System (INIS)

    Maddahi, Pari Sadat; Shahtahmassebi, Nasser; Rezaee Roknabadi, Mahmood; Moosavi, Fatemeh

    2016-01-01

    Due to association of protein tyrosine nitration (PTN) with development of some serious human disorders and diseases, in this paper, the possible applications of ZnO-based nanobiosensors in nitrated tyrosine (nTyr) detection were explored within the density functional framework. With this motivation, the interaction of nTyr with ZnO single walled nanotubes via all possible active sites of nTyr was investigated. The results show the tendency of nTyr to interact through its nitro site (forming nitro-site configuration) with ZnO SWNTs as it has the highest binding energy; while, the charge–solvent configuration involving the interaction of nTyr's phenolic ring has the second place in terms of binding energy magnitude. Regardless of which active site contributes in interaction, the binding energies exhibit an ascending trend with decrease of SWNTs' curvature. Electronic properties analysis indicates that nTyr interaction via its nitro group results in formation of some flat bands inside the band gap region leading to significant reduction of overall band gap energy. Similar behavior is also observed in charge–solvent configuration but the band gap energy is larger. These red shifts are mainly attributed to contribution of 2p orbitals of species present in nTyr. Also, the hybridization of 3d orbital of Zn atom with 2p orbitals of nitro group atomic species is found responsible for bonding formation in bioconjugated system possessing the highest binding energy. Comparison of the electronic band structure of ZnO SWNT–Tyr with that of ZnO SWNT–nTyr indicates the sensitivity of ZnO SWNTs toward tyrosine nitration hence, a considerable change in its optical spectra is expectable. This introduces ZnO SWNTs as a promising candidate for PTN detection. - Highlights: • Physical properties of ZnO SWNT conjugated with nTyr is studied by DFT method. • nTyr prefers to interact with ZnO SWNTs via the nitro site. • An ascending trend is observed in binding energy by

  7. DFT study on the galvanic interaction between pyrite (100) and galena (100) surfaces

    International Nuclear Information System (INIS)

    Ke, Baolin; Li, Yuqiong; Chen, Jianhua; Zhao, Cuihua; Chen, Ye

    2016-01-01

    Graphical abstract: - Highlights: • Galvanic interaction is weakened with the increase of contact distance. • Electronic transfer mainly occurs on the contact layers. • Galvanic effect enhances nucleophilicity of galena and electrophilicity of pyrite. • Presence of H_2O increases the galvanic interaction. - Abstract: The galvanic interaction between pyrite and galena surface has been investigated using density functional theory (DFT) method. The calculated results show that galvanic interactions between pyrite and galena surface are decreased with the increase of contact distance. The galvanic interactions still occurs even the distance larger than the sum of two atoms radius (≈2.8 Å), and the limit distance of galvanic interaction between galena and pyrite surface is about 10 Å, which is consistent with the quantum tunneling effect. Through Mulliken charge population calculation, it is found that electrons transfer from galena to pyrite. For galena surface, Pb 6s and 6p states lose electrons and S 3p state loses a small amount of electrons, which causes the electron loss of galena. For pyrite surface, Fe 4p state obtains large numbers of electrons, resulting in the decrease of positive charge of Fe atom. However, the 3p state of S atom loses a small numbers of electrons. The reactivity of mineral surface has also been studied by calculating the frontier orbitals of minerals. Results suggest that the highest occupied molecular orbital (HOMO) coefficients of galena are increased whereas those of pyrite are decreased with the enhancing galvanic interaction, indicating that the oxidation of galena surface would be enhanced due to the galvanic interaction. The Fukui indices and dual descriptor values of surface atoms suggest that the nucleophilicity of the galena surface increases, meanwhile, the electrophilicity of pyrite surface increases with the decrease of the contact distance. In addition, the density of states (DOS) of atoms results show that the

  8. Exploring the sensitivity of ZnO nanotubes to tyrosine nitration: A DFT approach

    Energy Technology Data Exchange (ETDEWEB)

    Maddahi, Pari Sadat [Department of Physics, Ferdowsi University of Mashhad, Mashhad (Iran, Islamic Republic of); Nanoresearch Center, Ferdowsi University of Mashhad, Mashhad (Iran, Islamic Republic of); Shahtahmassebi, Nasser, E-mail: Nasser@um.ac.ir [Department of Physics, Ferdowsi University of Mashhad, Mashhad (Iran, Islamic Republic of); Nanoresearch Center, Ferdowsi University of Mashhad, Mashhad (Iran, Islamic Republic of); Rezaee Roknabadi, Mahmood [Department of Physics, Ferdowsi University of Mashhad, Mashhad (Iran, Islamic Republic of); Moosavi, Fatemeh [Department of Chemistry, Ferdowsi University of Mashhad, Mashhad (Iran, Islamic Republic of)

    2016-05-27

    Due to association of protein tyrosine nitration (PTN) with development of some serious human disorders and diseases, in this paper, the possible applications of ZnO-based nanobiosensors in nitrated tyrosine (nTyr) detection were explored within the density functional framework. With this motivation, the interaction of nTyr with ZnO single walled nanotubes via all possible active sites of nTyr was investigated. The results show the tendency of nTyr to interact through its nitro site (forming nitro-site configuration) with ZnO SWNTs as it has the highest binding energy; while, the charge–solvent configuration involving the interaction of nTyr's phenolic ring has the second place in terms of binding energy magnitude. Regardless of which active site contributes in interaction, the binding energies exhibit an ascending trend with decrease of SWNTs' curvature. Electronic properties analysis indicates that nTyr interaction via its nitro group results in formation of some flat bands inside the band gap region leading to significant reduction of overall band gap energy. Similar behavior is also observed in charge–solvent configuration but the band gap energy is larger. These red shifts are mainly attributed to contribution of 2p orbitals of species present in nTyr. Also, the hybridization of 3d orbital of Zn atom with 2p orbitals of nitro group atomic species is found responsible for bonding formation in bioconjugated system possessing the highest binding energy. Comparison of the electronic band structure of ZnO SWNT–Tyr with that of ZnO SWNT–nTyr indicates the sensitivity of ZnO SWNTs toward tyrosine nitration hence, a considerable change in its optical spectra is expectable. This introduces ZnO SWNTs as a promising candidate for PTN detection. - Highlights: • Physical properties of ZnO SWNT conjugated with nTyr is studied by DFT method. • nTyr prefers to interact with ZnO SWNTs via the nitro site. • An ascending trend is observed in binding

  9. Effective one-body potential of DFT plus correlated kinetic energy density for two-electron spherical model atoms

    International Nuclear Information System (INIS)

    March, N.H.; Ludena, Eduardo V.

    2004-01-01

    For three model problems concerning two-electron spin-compensated ground states with spherical density, the third-order linear homogeneous differential equation constructed for the determination of ρ(r) is used here in conjunction with the von Weizsacker functional to characterize the one-body potential of density functional theory (DFT). Correlated von Weizsacker-type terms are compared to the exact DFT functional

  10. Spectroscopic and DFT Study of RhIII Chloro Complex Transformation in Alkaline Solutions.

    Science.gov (United States)

    Vasilchenko, Danila B; Berdyugin, Semen N; Korenev, Sergey V; O'Kennedy, Sean; Gerber, Wilhelmus J

    2017-09-05

    The hydrolysis of [RhCl 6 ] 3- in NaOH-water solutions was studied by spectrophotometric methods. The reaction proceeds via successive substitution of chloride with hydroxide to quantitatively form [Rh(OH) 6 ] 3- . Ligand substitution kinetics was studied in an aqueous 0.434-1.085 M NaOH matrix in the temperature range 5.5-15.3 °C. Transformation of [RhCl 6 ] 3- into [RhCl 5 (OH)] 3- was found to be the rate-determining step with activation parameters of ΔH † = 105 ± 4 kJ mol -1 and ΔS † = 59 ± 10 J K -1 mol -1 . The coordinated hydroxo ligand(s) induces rapid ligand substitution to form [Rh(OH) 6 ] 3- . By simulating ligand substitution as a dissociative mechanism, using density functional theory (DFT), we can now explain the relatively fast and slow kinetics of chloride substitution in basic and acidic matrices, respectively. Moreover, the DFT calculated activation energies corroborated experimental data that the kinetic stereochemical sequence of [RhCl 6 ] 3- hydrolysis in an acidic solution proceeds as [RhCl 6 ] 3- → [RhCl 5 (H 2 O)] 2- → cis-[RhCl 4 (H 2 O) 2 ] - . However, DFT calculations predict in a basic solution the trans route of substitution [RhCl 6 ] 3- → [RhCl 5 (OH)] 3- → trans-[RhCl 4 (OH) 2 ] 3- is kinetically favored.

  11. The Dirac equation in electronic structure calculations: Accurate evaluation of DFT predictions for actinides

    International Nuclear Information System (INIS)

    Wills, John M.; Mattsson, Ann E.

    2012-01-01

    Brooks, Johansson, and Skriver, using the LMTO-ASA method and considerable insight, were able to explain many of the ground state properties of the actinides. In the many years since this work was done, electronic structure calculations of increasing sophistication have been applied to actinide elements and compounds, attempting to quantify the applicability of DFT to actinides and actinide compounds and to try to incorporate other methodologies (i.e. DMFT) into DFT calculations. Through these calculations, the limits of both available density functionals and ad hoc methodologies are starting to become clear. However, it has also become clear that approximations used to incorporate relativity are not adequate to provide rigorous tests of the underlying equations of DFT, not to mention ad hoc additions. In this talk, we describe the result of full-potential LMTO calculations for the elemental actinides, comparing results obtained with a full Dirac basis with those obtained from scalar-relativistic bases, with and without variational spin-orbit. This comparison shows that the scalar relativistic treatment of actinides does not have sufficient accuracy to provide a rigorous test of theory and that variational spin-orbit introduces uncontrolled errors in the results of electronic structure calculations on actinide elements.

  12. Pd (II) complexes of bidentate chalcone ligands: Synthesis, spectral, thermal, antitumor, antioxidant, antimicrobial, DFT and SAR studies

    Science.gov (United States)

    Gaber, Mohamed; Awad, Mohamed K.; Atlam, Faten M.

    2018-05-01

    The ligation behavior of two chalcone ligands namely, (E)-3-(4-chlorophenyl)-1-(pyridin-2-yl)prop-2-en-1-one (L1) and (E)-3-(4-methoxyphenyl)-1-(pyridin-2-yl)prop-2-en-1-one (L2), towards the Pd(II) ion is determined. The structures of the complexes are elucidated by elemental analysis, spectral methods (IR, electronic and NMR spectra) as well as the conductance measurements and thermal analysis. The metal complexes exhibit a square planar geometrical arrangement. The kinetic and thermodynamic parameters for some selected decomposition steps have been calculated. The antimicrobial, antioxidant and anticancer activities of the chalcones and their Pd(II) complexes have been evaluated. Molecular orbital computations are performed using DFT at B3LYP level with 6-31 + G(d) and LANL2DZ basis sets to access reliable results to the experimental values. The calculations are performed to obtain the optimized molecular geometry, charge density distribution, extent of distortion from regular geometry. Thermodynamic parameters for the investigated compounds are also studied. The calculations confirm that the investigated complexes have square planner geometry, which is in a good agreement with the experimental observation.

  13. Synthesis, spectroscopic, DFT calculations and biological activity studies of ruthenium carbonyl complexes with 2-picolinic acid and a secondary ligand

    Science.gov (United States)

    Shohayeb, Shahera M.; Mohamed, Rania G.; Moustafa, H.; El-Medani, Samir M.

    2016-09-01

    Thermal reaction of [Ru3(CO)12] with 2-picolinic acid (Hpic) in the absence and presence of a secondary ligand (pyridine, Py, bipyridine, Bipy, or thiourea, Tu) was investigated. Four complexes with molecular formulae: [Ru(CO)3(Hpic)], 1, [Ru2(CO)5(Hpic)(Py)], 2, [Ru2(CO)5(Hpic)(Tu)], 3 and [Ru2(CO)4(Hpic)(Bipy)], 4, were isolated. All complexes were characterized based on elemental analyses, IR, 1H NMR, magnetic studies, mass spectrometry and thermal analysis. The ligand and its complexes have been screened for antibacterial activities. Density Functional Theory (DFT) calculations at the B3LYP/6-311G (d,p)_ level of theory have been carried out to investigate the equilibrium geometry of the ligands. The optimized geometry parameters of the complexes were evaluated using B3LYP method and LANL2DZ basis set. The extent of natural charge population (core, valence and rydberg), exact electronic configuration, total Lewis and total non-Lewis are estimated and discussed in terms of natural bond orbitals (NBO) analysis.

  14. DFT simulations of water adsorption and activation on low-index α-Ga2O3 surfaces.

    Science.gov (United States)

    Zhou, Xin; Hensen, Emiel J M; van Santen, Rutger A; Li, Can

    2014-06-02

    Density functional theory (DFT) calculations are used to explore water adsorption and activation on different α-Ga2O3 surfaces, namely (001), (100), (110), and (012). The geometries and binding energies of molecular and dissociative adsorption are studied as a function of coverage. The simulations reveal that dissociative water adsorption on all the studied low-index surfaces are thermodynamically favorable. Analysis of surface energies suggests that the most preferentially exposed surface is (012). The contribution of surface relaxation to the respective surface energies is significant. Calculations of electron local density of states indicate that the electron-energy band gaps for the four investigated surfaces appears to be less related to the difference in coordinative unsaturation of the surface atoms, but rather to changes in the ionicity of the surface chemical bonds. The electrochemical computation is used to investigate the hydrogen evolution reaction (HER) and the oxygen evolution reaction (OER) on α-Ga2O3 surfaces. Our results indicate that the (100) and (110) surfaces, which have low stability, are the most favorable ones for HER and OER, respectively. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  15. The qualitative and quantitative accuracy of DFT methods in computing 1J(C–F), 1J(C–N) and nJ(F–F) spin–spin coupling of fluorobenzene and fluoropyridine molecules

    International Nuclear Information System (INIS)

    Adeniyi, Adebayo A.; Ajibade, Peter A.

    2015-01-01

    The qualitative and quantitative quality of DFT methods combined with different basis sets in computing the J-coupling of the types 1 J(C–F) and n J(F–F) are investigated for the fluorobenzene and fluoropyridine derivatives. Interestingly, all of the computational methods perfectly reproduced the experimental order for n J(F–F) but many failed to reproduce the experimental order for 1 J(C–F) coupling. The functional PBEPBE gives the best quantitative values that are closer to the experimental spin–spin coupling when combined with the basis sets aug-cc-pVDZ and DGDZVP but is also part of the methods that fail to perfectly reproduce the experimental order for the 1 J(C–F) coupling. The basis set DGDZVP combined with all the methods except with PBEPBE perfectly reproduces the 1 J(C–F) experimental order. All the methods reproduce either the positive or the negative sign of the experimental spin–spin coupling except for the basis set 6-31+G(d,p) which fails to reproduce the experimental positive value of 3 J(F–F) regardless of what type of DFT methods was used. The values of the FC term is far higher than all other Ramsey terms in the one bond 1 J(C–F) coupling but in the two, three and four bonds n J(F–F) the values of PSO and SD are higher. - Graphical abstract: DFT methods were used to compute the J-coupling of molecules benf, benf2, benf2c, benf2c2, pyrf, pyrfc and pyrfc2, and are presented. Right combination of DFT functional with basis set can reproduce high level EOM-CCSD and experimental J-coupling results. All the methods can reproduce the qualitative order of the experimental J-coupling but not all reproduce the quantitative. The best quantitative results were obtained from PBEPBE combined with the high basis set aug-cc-pVDZ Also, PBEPBE combines with lower basis set DGDZVP to give a highly similar value. - Highlights: • DFT methods were used to compute the J-coupling of the molecules. • Right combination of DFT functional with basis

  16. Functionalization of [60] fullerene with butadienes: A DFT study

    International Nuclear Information System (INIS)

    Beheshtian, Javad; Peyghan, Ali Ahmadi; Bagheri, Zargham

    2012-01-01

    Highlights: ► Reaction of C 60 with 2,3-dimethylbutadiene (DMB) is theoretically investigated. ► The HOMO of DMB interacts with the LUMO of C 60 via a Diels Alder reaction. ► Work function of C 60 is decreased by increasing the number of DMB molecules. ► The reaction may facilitate the field electron emission from C 60 surface. - Abstract: We have performed a density functional study on the reaction of C 60 fullerene with one to six 2,3-dimethylbutadiene (DMB) molecule(s) which has previously been investigated by experimental researchers. Based on the obtained results, it has been found that (1) the reaction is regioselective, so that the DMB molecule prefers to be adsorbed atop a C-C bond which is shared between two hexagonal rings of C 60 (in good agreement with the experimental results) with reaction energy of −0.98 eV; (2) the HOMO of DMB interacts with the LUMO of C 60 via a Diels Alder reaction; (3) the energy of reaction and work function of C 60 are decreased by increasing the number of adsorbed DMB molecules; (4) the HOMO–LUMO energy gap of C 60 is slightly changed upon the reaction; (5) the reaction reduces the potential barrier of the field electron emission of C 60 surface.

  17. PBE-DFT theoretical study of organic photovoltaic materials based on thiophene with 1D and 2D periodic boundary conditions

    Science.gov (United States)

    Saïl, K.; Bassou, G.; Gafour, M. H.; Miloua, F.

    2015-12-01

    Conjugated organic systems such as thiophene are interesting topics in the field of organic solar cells. We theoretically investigate π-conjugated polymers constituted by n units ( n = 1-11) based on the thiophene (Tn) molecule. The computations of the geometries and electronic structures of these compounds are performed using the density functional theory (DFT) at the 6-31 G( d, p) level of theory and the Perdew-Burke-Eenzerhof (PBE) formulation of the generalized gradient approximation with periodic boundary conditions (PBCs) in one (1D) and two (2D) dimensions. Moreover, the electronic properties (HOCO, LUCO, E gap, V oc, and V bi) are determined from 1D and 2D PBC to understand the effect of the number of rings in polythiophene. The absorption properties—excitation energies ( E ex), the maximal absorption wavelength (λmax), oscillator strengths, and light harvesting—efficiency are studied using the time-dependent DFT method. Our studies show that changing the number of thiophene units can effectively modulate the electronic and optical properties. On the other hand, our work demonstrates the efficiency of theoretical calculation in the PBCs.

  18. Vibrational frequency analysis, FT-IR, DFT and M06-2X studies on tert-Butyl N-(thiophen-2yl)carbamate

    Science.gov (United States)

    Sert, Yusuf; Singer, L. M.; Findlater, M.; Doğan, Hatice; Çırak, Ç.

    2014-07-01

    In this study, the experimental and theoretical vibrational frequencies of a newly synthesized tert-Butyl N-(thiophen-2yl)carbamate have been investigated. The experimental FT-IR (4000-400 cm-1) spectrum of the molecule in the solid phase have been recorded. The theoretical vibrational frequencies and optimized geometric parameters (bond lengths and bond angles) have been calculated by using density functional theory (DFT/B3LYP: Becke, 3-parameter, Lee-Yang-Parr) and DFT/M06-2X (the highly parametrized, empirical exchange correlation function) quantum chemical methods with the 6-311++G(d,p) basis set by Gaussian 09W software, for the first time. The vibrational frequencies have been assigned using potential energy distribution (PED) analysis by using VEDA 4 software. The computational optimized geometric parameters and vibrational frequencies have been found to be in good agreement with the corresponding experimental data, and with related literature results. In addition, the highest occupied molecular orbital (HOMO) and the lowest unoccupied molecular orbital (LUMO) energies and the other related molecular energy values have been calculated and are depicted.

  19. Study of transmission function and electronic transport in one dimensional silver nanowire: Ab-initio method using density functional theory (DFT)

    Science.gov (United States)

    Thakur, Anil; Kashyap, Rajinder

    2018-05-01

    Single nanowire electrode devices have their application in variety of fields which vary from information technology to solar energy. Silver nanowires, made in an aqueous chemical reduction process, can be reacted with gold salt to create bimetallic nanowires. Silver nanowire can be used as electrodes in batteries and have many other applications. In this paper we investigated structural and electronic transport properties of Ag nanowire using density functional theory (DFT) with SIESTA code. Electronic transport properties of Ag nanowire have been studied theoretically. First of all an optimized geometry for Ag nanowire is obtained using DFT calculations, and then the transport relations are obtained using NEGF approach. SIESTA and TranSIESTA simulation codes are used in the calculations respectively. The electrodes are chosen to be the same as the central region where transport is studied, eliminating current quantization effects due to contacts and focusing the electronic transport study to the intrinsic structure of the material. By varying chemical potential in the electrode regions, an I-V curve is traced which is in agreement with the predicted behavior. Bulk properties of Ag are in agreement with experimental values which make the study of electronic and transport properties in silver nanowires interesting because they are promising materials as bridging pieces in nanoelectronics. Transmission coefficient and V-I characteristic of Ag nano wire reveals that silver nanowire can be used as an electrode device.

  20. First-principles kinetic Monte Carlo simulations of ammonia oxidation at RuO{sub 2}(110): Selectivity vs. semi-local DFT

    Energy Technology Data Exchange (ETDEWEB)

    Mangold, Claudia [Fritz-Haber-Institut der Max-Planck-Gesellschaft, Berlin (Germany); Reuter, Karsten [Fritz-Haber-Institut der Max-Planck-Gesellschaft, Berlin (Germany); Technische Universitaet, Muenchen (Germany)

    2011-07-01

    Reaching a detailed mechanistic understanding of high selectivity in surface catalytic processes is one of the central goals in present-day catalysis research. The Surface Science approach to this problem focuses on the investigation of well-defined model systems that reduce the complexity but still capture the relevant aspects. In this respect, the almost 100% selectivity reported in detailed experiments for the oxidation of NH{sub 3} to NO at RuO{sub 2}(110) presents an ideal benchmark for a quantitative theoretical analysis. To this end we perform detailed kinetic Monte Carlo simulations based on kinetic parameters derived from density-functional theory (DFT). The obtained turnover frequency for molecular nitrogen is in rather good agreement with the experimental data. However, even with an extended set of elementary processes we are not able to reproduce the experimental findings for the production of NO and therewith the selectivity. The central quantities that decisively determine the latter are the binding energy of NO and the N diffusion barrier. Suspecting the approximate energetics obtained with the employed semi-local DFT functional as reason for the discrepancy, we recalculate the kinetic parameters with different functionals and discuss the resulting effects in the kMC simulations.

  1. Experimental and theoretical studies of (FT-IR, FT-Raman, UV-Visible and DFT) 4-(6-methoxynaphthalen-2-yl) butan-2-one.

    Science.gov (United States)

    Govindasamy, P; Gunasekaran, S

    2015-01-01

    In this work, the vibrational spectral analysis was carried out by using FT-Raman and FT-IR spectroscopy in the range 4000-50 cm(-1) and 4000-450 cm(-1) respectively for 4-(6-methoxynaphthalen-2-yl) butan-2-one (abbreviated as 4MNBO) molecule. Theoretical calculations were performed by density functional theory (DFT/B3LYP) method using 6-311G(d,p) and 6-311++G(d,p) basis sets. The difference between the observed and calculated wavenumber value of most of the fundamentals were very small. The complete vibrational assignments of wavenumbers were made on the basis of potential energy distribution (PED). The UV-Vis spectrum was recorded in the methanol solution. The energy, wavelength and oscillator's strength were calculated by Time Dependent Density Functional Theory (TD-DFT) and matched to the experimental findings. The intramolecular contacts have been interpreted using natural bond orbital (NBO) and natural localized molecular orbital (NLMO) analysis. Thermodynamic properties of 4MNBO at different temperature have been calculated. The molecular electrostatic potential surface (MESP) and Frontier molecular orbital's (FMO's) analysis were investigated using theoretical calculations. Copyright © 2015 Elsevier B.V. All rights reserved.

  2. PBE–DFT theoretical study of organic photovoltaic materials based on thiophene with 1D and 2D periodic boundary conditions

    International Nuclear Information System (INIS)

    Saïl, K.; Bassou, G.; Gafour, M. H.; Miloua, F.

    2015-01-01

    Conjugated organic systems such as thiophene are interesting topics in the field of organic solar cells. We theoretically investigate π-conjugated polymers constituted by n units (n = 1–11) based on the thiophene (Tn) molecule. The computations of the geometries and electronic structures of these compounds are performed using the density functional theory (DFT) at the 6–31 G(d, p) level of theory and the Perdew–Burke–Eenzerhof (PBE) formulation of the generalized gradient approximation with periodic boundary conditions (PBCs) in one (1D) and two (2D) dimensions. Moreover, the electronic properties (HOCO, LUCO, E gap , V oc , and V bi ) are determined from 1D and 2D PBC to understand the effect of the number of rings in polythiophene. The absorption properties—excitation energies (E ex ), the maximal absorption wavelength (λ max ), oscillator strengths, and light harvesting—efficiency are studied using the time-dependent DFT method. Our studies show that changing the number of thiophene units can effectively modulate the electronic and optical properties. On the other hand, our work demonstrates the efficiency of theoretical calculation in the PBCs

  3. PBE–DFT theoretical study of organic photovoltaic materials based on thiophene with 1D and 2D periodic boundary conditions

    Energy Technology Data Exchange (ETDEWEB)

    Saïl, K., E-mail: sailkari7@yahoo.com; Bassou, G. [Université Djillali Liabès, Laboratoire de Microscopie, Microanalyse de la Matière et Spectroscopie Moléculaire (L2MSM), Faculté des Sciences Exactes (Algeria); Gafour, M. H. [Centre Universitaire Ahmed Zabana de Rélizane, Institut des Sciences Exactes et Sciences de la Nature et de la Vie, Département de Chimie (Algeria); Miloua, F. [Université Djillali Liabès, Laboratoire de Microscopie, Microanalyse de la Matière et Spectroscopie Moléculaire (L2MSM), Faculté des Sciences Exactes (Algeria)

    2015-12-15

    Conjugated organic systems such as thiophene are interesting topics in the field of organic solar cells. We theoretically investigate π-conjugated polymers constituted by n units (n = 1–11) based on the thiophene (Tn) molecule. The computations of the geometries and electronic structures of these compounds are performed using the density functional theory (DFT) at the 6–31 G(d, p) level of theory and the Perdew–Burke–Eenzerhof (PBE) formulation of the generalized gradient approximation with periodic boundary conditions (PBCs) in one (1D) and two (2D) dimensions. Moreover, the electronic properties (HOCO, LUCO, E{sub gap}, V{sub oc}, and V{sub bi}) are determined from 1D and 2D PBC to understand the effect of the number of rings in polythiophene. The absorption properties—excitation energies (E{sub ex}), the maximal absorption wavelength (λ{sub max}), oscillator strengths, and light harvesting—efficiency are studied using the time-dependent DFT method. Our studies show that changing the number of thiophene units can effectively modulate the electronic and optical properties. On the other hand, our work demonstrates the efficiency of theoretical calculation in the PBCs.

  4. Expedient and click synthesis, spectroscopic characterizations and DFT calculations of novel 1,5-bis(N-substituted 1,2,3‒triazole) benzodiazepinedione scaffolds

    Science.gov (United States)

    Paghandeh, Hossein; Saeidian, Hamid

    2018-04-01

    A practically reliable procedure for synthesis of new 1,5-bis(N-substituted 1,2,3‒triazole) benzodiazepinedione derivatives was reported by sequential amidation, propargylation and a click azide‒alkyne [3 + 2] cycloaddition reaction in a one pot fashion. The desired products were characterized by CHN analysis, 1H and 13C NMR and ESI-MS spectroscopy. Short reaction time, good yields (55-91%), mild reaction conditions and easily available and less expensive starting materials are advantages of this protocol. Natural bond orbital charge distribution and HOMO-LUMO analysis of the characterized structure of 4e have been also calculated by density functional theory (DFT) calculations. The Li+ and Na+ ion affinities of 4e have been also investigated by DFT studies to find the applicability of these products as ligand in coordination chemistry. Sodium ion affinity of 4e was determined as 60 kJ mol-1 is less than its lithium ion affinity, indicating that the lithiation of 4e is more exothermic than the sodiation.

  5. Fourier transform infrared and FT-Raman spectra, assignment, ab initio, DFT and normal co-ordinate analysis of 2-chloro-4-methylaniline and 2-chloro-6-methylaniline.

    Science.gov (United States)

    Arjunan, V; Mohan, S

    2009-03-01

    The Fourier transform infrared (FTIR) and FT-Raman spectra of 2-chloro-4-methylaniline and 2-chloro-6-methylaniline have been measured in the range 4000-400 and 4000-100cm(-1), respectively. Utilising the observed FTIR and FT-Raman data, a complete vibrational assignment and analysis of the fundamental modes of the compounds were carried out. The vibrational frequency which were determined experimentally are compared with those obtained theoretically from ab initio HF and DFT gradient calculations employing the HF/6-31G(d,p) and B3LYP/6-31G(d,p) methods for optimised geometries. The geometries and normal modes of vibration obtained from the HF and DFT methods are in good agreement with the experimental data. The normal co-ordinate analysis was also carried out on the basis of ab initio force fields utilising Wilson's FG matrix method. The manifestations of NH-pi interactions and the influence of bulky chlorine and methyl group on the vibrational modes of the amino group are investigated.

  6. SeO{sub 2} adsorption on CaO surface: DFT study on the adsorption of a single SeO{sub 2} molecule

    Energy Technology Data Exchange (ETDEWEB)

    Fan, Yaming; Zhuo, Yuqun; Lou, Yu; Zhu, Zhenwu [Key Laboratory for Thermal Science and Power Engineering of Ministry of Education, Department of Thermal Engineering, Tsinghua University, Beijing 100084 (China); Li, Liangliang [Key Laboratory of Advanced Materials, Department of Material Science and Engineering, Tsinghua University, Beijing 100084 (China)

    2017-08-15

    Highlights: • Adsorption mechanisms of SeO{sub 2} on CaO surface under O{sub 2} were firstly studied by DFT. • The adsorption energies, bond length and electron density maps were calculated. • The electronic structure changes upon adsorption were studied. - Abstract: Selenium is a hazardous element in coal. During coal combustion, most of the selenium will convert to SeO{sub 2} in the flue gas. Ca-based adsorbents, especially CaO, have been considered as a potential sorbent to adsorb SeO{sub 2} due to its low cost. In this paper, the adsorption mechanisms of single SeO{sub 2} on CaO surface were investigated by density functional theory (DFT) calculation. Both the physisorption and chemisorption structures were determined. It has been identified that the adsorption of SeO{sub 2} on CaO surface is primarily chemisorption, while physisorption takes effects at the initial stage of the process. Under O{sub 2} atmosphere, selenate is hard to form. Most of the adsorption products are selenite. Additionally, the electron density maps were obtained to reveal the surface active sites. The partial density of states (PDOS) was calculated for analyzing the electronic structural change of SeO{sub 2} and CaO surface during adsorption. The results provide fundamental information of the adsorption process, which could be meaningful for the development of new absorbents.

  7. DFT+DMFT study of strain and interface effects in LaTiO{sub 3} and LaVO{sub 3}

    Energy Technology Data Exchange (ETDEWEB)

    Dymkowski, Krzysztof; Sclauzero, Gabriele; Ederer, Claude [Materials Theory, ETH Zurich (Switzerland)

    2015-07-01

    Metal-insulator transitions in thin films of early transition metal correlated oxides are linked to both epitaxial strain and electronic reconstruction at the film/substrate interface. We separately address these two key factors for LaTiO{sub 3} and LaVO{sub 3} through density functional theory plus dynamical mean-field theory (DFT+DMFT). We find that mere epitaxial strain suffices to induce an insulator-to-metal transition in LaTiO{sub 3}, but not in LaVO{sub 3}, in agreement with recent experiments. We show that this difference can be explained by the combined effect of strain-induced changes in the crystal field splitting of t{sub 2g} orbitals and different orbital filling in these two materials. The role of the interface is investigated through DFT+DMFT simulations of LaVO{sub 3}/SrTiO{sub 3} heterostructures with varying superlattice periodicities and substrate terminations. Our aim is to assess whether the metallicity observed at the LaVO3/SrTiO3 interface could be driven by pure electronic reconstruction effects, rather than structural or stoichiometric reasons (such as, e.g., O-related defects).

  8. Electrochemical degradation of triazole fungicides in aqueous solution using TiO2-NTs/SnO2-Sb/PbO2 anode: Experimental and DFT studies

    International Nuclear Information System (INIS)

    Han, Weiqing; Zhong, Congqiang; Liang, Linyue; Sun, Yunlong; Guan, Ying; Wang, Lianjun; Sun, Xiuyun; Li, Jiansheng

    2014-01-01

    Triazole fungicides (TFs) are toxic and bio-refractory contaminants widely spread in environment. This study investigated electrochemical degradation of TFs in aqueous solution at TiO 2 -NTs/SnO 2 -Sb/PbO 2 anode with particular attention to the effect of molecular structure. Three TFs with triazole ring in one biologically treated water including tricyclazole (TC), 1H-1,2,4-triazole (Tz) and propiconazole (PPC) were selected as the target compounds. Results of bulk electrolysis showed that degradation of all TFs was fit to a pseudo first-order equation. The three compounds were degraded with the following sequence: PPC > TC> Tz in terms of their rates of oxidation. Quantum chemical calculation using the density function theory (DFT) method was combined with experimental results to describe the degradation sequence of TFs. Atom charge was calculated by DFT method and active sites of TFs were identified respectively. Analysis of intermediates by GC-MS and LC-(ESI)-MS/MS showed agreement with calculation results. In addition, the acute toxicity of TC and PPC treated solution significantly decreased after treatment by electrochemical oxidation

  9. Acidity constants from DFT-based molecular dynamics simulations

    International Nuclear Information System (INIS)

    Sulpizi, Marialore; Sprik, Michiel

    2010-01-01

    In this contribution we review our recently developed method for the calculation of acidity constants from density functional theory based molecular dynamics simulations. The method is based on a half reaction scheme in which protons are formally transferred from solution to the gas phase. The corresponding deprotonation free energies are computed from the vertical energy gaps for insertion or removal of protons. Combined to full proton transfer reactions, the deprotonation energies can be used to estimate relative acidity constants and also the Broensted pK a when the deprotonation free energy of a hydronium ion is used as a reference. We verified the method by investigating a series of organic and inorganic acids and bases spanning a wide range of pK a values (20 units). The thermochemical corrections for the biasing potentials assisting and directing the insertion are discussed in some detail.

  10. Diffusion of Li+ ion on graphene: A DFT study

    International Nuclear Information System (INIS)

    Zheng Jiming; Ren Zhaoyu; Guo Ping; Fang Li; Fan Jun

    2011-01-01

    Density functional theory investigations show that the Li + ion is stabilized at Center of hexagonal carbon ring with the distance of 1.84 Å from graphene surface. The potential barrier of Li + ion diffusion on the graphene surface, about 0.32 eV, is much lower than that of Li + ion penetrating the carbon ring which is 10.68 eV. When a vacancy of graphene exists, potential barrier about 10.25 eV for Li + ion penetrating the defect is still high, and the ability of the vacancy to sizing the Li + ion is also observed. Electronic densities of states show that the formation of a localized bond between Li atom and edge carbon of vacancy is the main reason for high potential barrier when Li + ion penetrate a vacancy. While Coulomb repulsion is the control factor for high potential barrier in case of Li + ion penetrating a carbon ring.

  11. Functionalization of [60] fullerene with butadienes: A DFT study

    Energy Technology Data Exchange (ETDEWEB)

    Beheshtian, Javad [Department of Chemistry, Shahid Rajaee Teacher Training University, P.O. Box: 16875-163, Tehran (Iran, Islamic Republic of); Peyghan, Ali Ahmadi, E-mail: ahmadi.iau@gmail.com [Young Researchers Club, Islamic Azad University, Islamshahr Branch, Tehran (Iran, Islamic Republic of); Bagheri, Zargham [Physics group, Science department, Islamic Azad University, Islamshahr Branch, P.O. Box: 33135-369, Islamshahr, Tehran (Iran, Islamic Republic of)

    2012-09-01

    Highlights: Black-Right-Pointing-Pointer Reaction of C{sub 60} with 2,3-dimethylbutadiene (DMB) is theoretically investigated. Black-Right-Pointing-Pointer The HOMO of DMB interacts with the LUMO of C{sub 60} via a Diels Alder reaction. Black-Right-Pointing-Pointer Work function of C{sub 60} is decreased by increasing the number of DMB molecules. Black-Right-Pointing-Pointer The reaction may facilitate the field electron emission from C{sub 60} surface. - Abstract: We have performed a density functional study on the reaction of C{sub 60} fullerene with one to six 2,3-dimethylbutadiene (DMB) molecule(s) which has previously been investigated by experimental researchers. Based on the obtained results, it has been found that (1) the reaction is regioselective, so that the DMB molecule prefers to be adsorbed atop a C-C bond which is shared between two hexagonal rings of C{sub 60} (in good agreement with the experimental results) with reaction energy of -0.98 eV; (2) the HOMO of DMB interacts with the LUMO of C{sub 60} via a Diels Alder reaction; (3) the energy of reaction and work function of C{sub 60} are decreased by increasing the number of adsorbed DMB molecules; (4) the HOMO-LUMO energy gap of C{sub 60} is slightly changed upon the reaction; (5) the reaction reduces the potential barrier of the field electron emission of C{sub 60} surface.

  12. Exploring d{sup 0} magnetism in doped SnO{sub 2}–a first principles DFT study

    Energy Technology Data Exchange (ETDEWEB)

    Chakraborty, Brahmananda, E-mail: brahma@barc.gov.in; Ramaniah, Lavanya M.

    2015-07-01

    In search of d{sup 0} magnetism, the magnetic behavior of SnO{sub 2} with cation substitution from group1A (Li, Na, K) and group 2A (Be, Mg, Ca) elements has been systematically studied using Density Functional Theory (DFT). While an impurity from group 1A elements switches on ferromagnetism at a lower concentration itself, sufficient hole density is required for a group 2A impurity to create a spontaneous spin polarized ground state, a finding that has not been reported in earlier investigations. Our DFT results predict for the first time that impurities from group 2A (Mg, Ca) in SnO{sub 2} can promote room temperature ferromagnetism. Further, the emergence of ferromagnetism due to doping from group 1A elements, which injects three holes per defect, has been mapped successfully onto a modified Hubbard model from the literature. Doping of a single Na atom in the supercell (concentration 6.25 at%) makes the system ferromagnetic, with a magnetic moment close to 3.0 μ{sub B} per defect, and a Curie temperature of 815 K, obtained in the mean field approximation. This agrees closely with a model prediction of 750 K. Finally, the triggering of ferromagnetism by an impurity atom from group 2A, which adds two holes per defect in the system, implies that the prescription of three holes per defect given in the literature is not a necessary criterion for hole induced ferromagnetism. Rather, the analysis of the density of states and ferromagnetic coupling indicate that the system needs a critical hole concentration to activate ferromagnetism, by pushing the Fermi level inside the valence band in order to satisfy the Stoner criterion. - Graphical abstract: Spin density (Δρ=ρ↑−ρ↓) shown in yellow color mainly concentrated on the first shell O atoms around the impurity (a)Li, (b)Na, (c) K for isovalue 0.2e (d) K for isovalue 0.1. - Highlights: • Systematic study of d{sup 0} magnetism in SnO{sub 2} doped with group 1A (Li, Na, K) and group 2A (Be, Mg, Ca).

  13. DFT-Based Simulation and Experimental Validation of the Topotactic Transformation of MgAl Layered Double Hydroxides.

    Science.gov (United States)

    Zhang, Shi-Tong; Dou, Yibo; Zhou, Junyao; Pu, Min; Yan, Hong; Wei, Min; Evans, David G; Duan, Xue

    2016-09-05

    The thermal topotactic transformation mechanism of MgAl layered double hydroxides (LDHs) is investigated by a combined theoretical and experimental study. Thermogravimetric differential thermal analysis (TG-DTA) results reveal that the LDH phase undergoes four key endothermic events at 230, 330, 450, and 800 °C. DFT calculations show that the LDH decomposes into CO2 and residual O atoms via a monodentate intermediate at 330 °C. At 450 °C, the metal cations almost maintain their original distribution within the LDH(001) facet during the thermal dehydration process, but migrate substantially along the c-axis direction perpendicular to the (001) facet; this indicates that the metal arrangement/dispersion in the LDH matrix is maintained two-dimensionally. A complete collapse of the layered structure occurs at 800 °C, which results in a totally disordered cation distribution and many holes in the final product. The structures of the simulated intermediates are highly consistent with the observed in situ powder XRD data for the MgAl LDH sample calcined at the corresponding temperatures. Understanding the structural topotactic transformation process of LDHs would provide helpful information for the design and preparation of metal/metal oxides functional materials derived from LDH precursors. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  14. Syntheses, structural elucidation, thermal properties, theoretical quantum chemical studies (DFT and biological studies of barbituric–hydrazone complexes

    Directory of Open Access Journals (Sweden)

    Amina A. Soayed

    2015-03-01

    Full Text Available Condensation of barbituric acid with hydrazine hydrate yielded barbiturichydrazone (L which was characterized using IR, 1H NMR and mass spectra. The Co(II, Ni(II and Cu(II complexes derived from this ligand have been synthesized and structurally characterized by elemental analyses, spectroscopic methods (IR, UV–Vis and ESR and thermal analyses (TGA, DTG and DTA and the structures were further elucidated using quantum chemical density functional theory. Complexes of L were found to have the ML.nH2O stoichiometry with either tetrahedral or octahedral geometry. The ESR data showed the Cu(II complex to be in a tetragonal geometry. Theoretical investigation of the electronic structure of metal complexes at the TD-DFT/B3LYP level of theory has been carried out and discussed. The fundamental vibrational wavenumbers were calculated and a good agreement between observed and scaled calculated wavenumbers was achieved. Thermal studies were performed to deduce the stabilities of the ligand and complexes. Thermodynamic parameters, such as the order of reactions (n, activation energy ΔE∗, enthalpy of reaction ΔH∗ and entropy ΔS∗ were calculated from DTA curves using Horowitz–Metzger method. The ligand L and its complexes have been screened for their antifungal and antibacterial activities and were found to possess better biological activities compared to those of unsubstituted barbituric acid complexes.

  15. Cyanidin-Based Novel Organic Sensitizer for Efficient Dye-Sensitized Solar Cells: DFT/TDDFT Study

    Directory of Open Access Journals (Sweden)

    Kalpana Galappaththi

    2017-01-01

    Full Text Available Cyanidin is widely considered as a potential natural sensitizer in dye-sensitized solar cells due to its promising electron-donating and electron-accepting abilities and cheap availability. We consider modifications of cyanidin structure in order to obtain broader UV-Vis absorption and hence to achieve better performance in DSSC. The modified molecule consists of cyanidin and the benzothiadiazolylbenzoic acid group, where the benzothiadiazolylbenzoic acid group is attached to the cyanidin molecule by replacing one hydroxyl group. The resulting structure was then computationally simulated by using the Spartan’10 software package. The molecular geometries, electronic structures, absorption spectra, and electron injections of the newly designed organic sensitizer were investigated in this work through density functional theory (DFT and time-dependent density functional theory (TDDFT calculations using the Gaussian’09W software package. Furthermore, TDDFT computational calculations were performed on cyanadin and benzothiadiazolylbenzoic acid separately, as reference. The computational studies on the new sensitizer have shown a reduced HOMO-LUMO gap; bathochromic and hyperchromic shifts of absorption spectra range up to near-infrared region revealing its enhanced ability to sensitize DSSCs.

  16. A DFT and QTAIM study of the adsorption of organic molecules over the copper-doped coronene and circumcoronene

    Science.gov (United States)

    Malček, Michal; Cordeiro, M. Natalia D. S.

    2018-01-01

    Graphene based materials are nowadays extensively studied because of their potential applications as gas sensors, biosensors or adsorbents. Doping the graphene surface with heteroatoms or transition metals can improve its electronic properties and chemical reactivity. Polyaromatic hydrocarbons coronene and circumcoronene can be used as models of tiny graphene quantum dots. The adsorption of a set of organic molecules (water, hydrogen peroxide, hydrogen sulfide, methanol, ethanol and oxygen molecule) over the copper-doped coronene and circumcoronene was theoretically studied using density functional theory (DFT) and quantum theory of atoms in molecules (QTAIM). In the case of coronene, only one site was considered for the Cu-doping, whereas in the case of circumcoronene being a polyaromatic hydrocarbon composed of 54 carbon atoms, three different sites for Cu-doping were considered. For the systems under study, the adsorption of O2 was found energetically the most favorable, with energetic outcome ranging from -3.1 to -3.7 eV related to the position of dopant Cu atom. Changes in the topology of charge densities at Cu and in its vicinity after the adsorption of studied molecules were investigated in the framework of QTAIM. In addition, QTAIM analysis of bond critical points (BCP) was employed to study the character of the newly formed chemical bonds. The results of this study point out the suitability of Cu-doped graphene materials as sensors and/or adsorbents in practical applications.

  17. TiO2/Gold nanocomposite as an extremely sensitive molecule sensor for NO2 detection: A DFT study

    Directory of Open Access Journals (Sweden)

    Amirali Abbasi

    2016-07-01

    Full Text Available First-principles calculations within density functional theory (DFT have been performed to investigate the interactions of NO2 molecules with TiO2/Gold nanocomposites in order to completely exploit the adsorption properties of these nanostructures. Given the need to further comprehend the behavior of the NO2 molecules positioned between the TiO2 nanoparticle and Au monolayer, we have geometrically optimized the complex systems consisting of the NO2 molecule oriented at appropriate positions between the nanoparticle and Au monolayer. The structural properties such as bond lengths, bond angles, adsorption energies and Mulliken population analysis and the electronic properties including the density of states and molecular orbitals have been also analyzed in detail. The results indicate that the interaction between NO2 and undoped TiO2-N/Gold nanocomposites is stronger than that between gas molecules and N-doped TiO2/Gold nanocomposites, which reveals that the pristine nanocomposite can react with NO2 molecule more efficiently. Therefore, the obtained results also suggest a theoretical basis for the potential applications of TiO2/Gold nanocomposites in gas sensing, which could help in the developing of novel TiO2 based advanced sensor devices.

  18. Hydrogen storage property of alkali and alkaline-earth metal atoms decorated C24 fullerene: A DFT study

    Science.gov (United States)

    Zhang, Yafei; Cheng, Xinlu

    2018-04-01

    The hydrogen storage behavior of alkali and alkaline-earth metal (AM = Li, Na, K, Mg, Ca) atoms decorated C24 fullerene was investigated by using density functional theory (DFT) study. Our results indicate that the AM atoms prefer to adsorb atop the center of tetragon of C24 fullerene with the largest binding energy than other possible adsorption sites. Moreover, the hydrogen storage gravimetric density of 24H2/6Li/C24, 24H2/6Na/C24 and 36H2/6Ca/C24 configurations reaches up to 12.7 wt%, 10.1 wt% and 12 wt%, higher than the year 2020 target from the US department of energy (DOE). Also, the average adsorption energies of H2 molecules of the 24H2/6Li/C24, 24H2/6Na/C24 and 36H2/6Ca/C24 configurations are -0.198 eV/H2, -0.164 eV/H2 and -0.138 eV/H2, locate the desirable range under the physical adsorption at near ambient conditions. These findings will have important implications on designing new hydrogen storage materials in the future.

  19. Biomarkers of cigarette smoking and DNA methylating agents: Raman, SERS and DFT study of 3-methyladenine and 7-methyladenine

    Science.gov (United States)

    Harroun, Scott G.; Zhang, Yaoting; Chen, Tzu-Heng; Ku, Ching-Rong; Chang, Huan-Tsung

    2017-04-01

    3-Methyladenine and 7-methyladenine are biomarkers of DNA damage from exposure to methylating agents. For example, the concentration of 3-methyladenine increases significantly in the urine of cigarette smokers. Surface-enhanced Raman spectroscopy (SERS) has shown much potential for detection of biomolecules, including DNA. Much work has been dedicated to the canonical nucleobases, with comparatively fewer investigations of modified DNA and modified DNA nucleobases. Herein, Raman spectroscopy and SERS are used to examine the adsorption orientations of 3-methyladenine and 7-methyladenine on Ag nanoparticles. Density functional theory (DFT) calculations at the B3LYP level are used to support the conclusions via simulated spectra of the nucleobases and of Ag+/nucleobase complexes. The results herein show that 7-methyladenine adsorbs upright via its N3 and N9 atoms side, similarly to adenine. 3-Methyladenine adsorbs in a very tilted or flat orientation on the Ag nanoparticles. These findings will be useful for future SERS or other nanoparticle-based bioanalytical assays for detection of these methyladenines or other modified nucleobases.

  20. Communication: Hole localization in Al-doped quartz SiO{sub 2} within ab initio hybrid-functional DFT

    Energy Technology Data Exchange (ETDEWEB)

    Gerosa, Matteo [Department of Energy, Politecnico di Milano, via Ponzio 34/3, 20133 Milano (Italy); Di Valentin, Cristiana; Pacchioni, Gianfranco [Dipartimento di Scienza dei Materiali, Università di Milano-Bicocca, via R. Cozzi 55, 20125 Milan (Italy); Bottani, Carlo Enrico, E-mail: carlo.bottani@polimi.it [Department of Energy, Politecnico di Milano, via Ponzio 34/3, 20133 Milano (Italy); Center for Nano Science and Technology @Polimi, Istituto Italiano di Tecnologia, via Pascoli 70/3, 20133 Milano (Italy); Onida, Giovanni [Dipartimento di Fisica dell’ Universita’ degli Studi di Milano and European Theoretical Spectroscopy Facility (ETSF), Via Celoria 16, 20133 Milan (Italy)

    2015-09-21

    We investigate the long-standing problem of hole localization at the Al impurity in quartz SiO{sub 2}, using a relatively recent DFT hybrid-functional method in which the exchange fraction is obtained ab initio, based on an analogy with the static many-body COHSEX approximation to the electron self-energy. As the amount of the admixed exact exchange in hybrid functionals has been shown to be determinant for properly capturing the hole localization, this problem constitutes a prototypical benchmark for the accuracy of the method, allowing one to assess to what extent self-interaction effects are avoided. We obtain good results in terms of description of the charge localization and structural distortion around the Al center, improving with respect to the more popular B3LYP hybrid-functional approach. We also discuss the accuracy of computed hyperfine parameters, by comparison with previous calculations based on other self-interaction-free methods, as well as experimental values. We discuss and rationalize the limitations of our approach in computing defect-related excitation energies in low-dielectric-constant insulators.

  1. DFT study on the adsorption of diethyl, ethyl methyl, and dimethyl ethers on the surface of gallium doped graphene

    Energy Technology Data Exchange (ETDEWEB)

    Shokuhi Rad, Ali, E-mail: a.shokuhi@gmail.com [Department of Chemical Engineering, Qaemshahr Branch, Islamic Azad University, Qaemshahr (Iran, Islamic Republic of); Sani, Emad; Binaeian, Ehsan [Department of Chemical Engineering, Qaemshahr Branch, Islamic Azad University, Qaemshahr (Iran, Islamic Republic of); Peyravi, Majid; Jahanshahi, Mohsen [Faculty of Chemical Engineering, Babol University of Technology, Babol (Iran, Islamic Republic of)

    2017-04-15

    Highlights: • Adsorption of three ether molecules on the surface of Ga-doped graphene has been investigated. • High degree of adsorption for all analytes is found. • Ga-doped graphene shows p-type semiconductor property upon adsorption of ether molecules. - Abstract: In this study, we used density functional theory (DFT) to search on the adsorption properties of three important compounds of ether family; diethyl ether (DEE), ethyl methyl ether (EME), and dimethyl ether (DME) on the surface of Gallium doped graphene (GaG). We used three functionals (B3LYP, wb97xd, and MPW1PW91) for optimization and calculation of adsorption energy. After fully optimization, we scrutinized on the charge allocations on the adsorbed ethers as well as GaG (at the area of interaction) based on natural bond orbitals (NBO). Besides, we have calculated the amount of charge transfer upon adsorption of each analyte. We revel that GaG is an ideal adsorbent for chemisorption of all above-mentioned ethers. There is a little difference between the values of adsorption; −123.5, −120, and −118.3 kJ/mol (based on wb97xd) for DEE, EME, and DME, respectively. We found significant changes in the electronic structure of both adsorbent and adsorbate upon adsorption. Moreover, results of charge analyses confirm GaG is a p-type semiconductor.

  2. Ammonia IRMS-TPD measurements and DFT calculation on acidic hydroxyl groups in CHA-type zeolites.

    Science.gov (United States)

    Suzuki, Katsuki; Sastre, German; Katada, Naonobu; Niwa, Miki

    2007-12-07

    Brønsted acidity of H-chabazite (CHA) zeolites (Si : Al(2) = 4.2) was investigated by means of ammonia infrared-mass spectrometry/temperature-programmed desorption (IRMS-TPD) methods and density functional calculations. Four IR bands were observed at 3644, 3616, 3575 and 3538 cm(-1), and they were ascribable to the acidic OH groups on four nonequivalent oxygen sites in the CHA structure. The absorption band at 3538 cm(-1) was attributed to the O(4)H in the 6-membered ring (MR), and ammonia adsorption energy (DeltaU) of this OH group was the lowest among the 4 kinds of OH groups. The other 3 bands were assigned to the acidic OH groups in 8MR. It was observed that the DeltaU in 8 and 6MR were 131 (+/-3) and 101 kJ mol(-1), respectively. On the other hand, the density functional theory (DFT) calculations within periodic boundary conditions yielded the adsorption energies on these OH groups in 8 and 6MR to be ca. 130 and 110 kJ mol(-1), respectively, in good agreement with the experimentally-observed values.

  3. DFT study on the adsorption of diethyl, ethyl methyl, and dimethyl ethers on the surface of gallium doped graphene

    International Nuclear Information System (INIS)

    Shokuhi Rad, Ali; Sani, Emad; Binaeian, Ehsan; Peyravi, Majid; Jahanshahi, Mohsen

    2017-01-01

    Highlights: • Adsorption of three ether molecules on the surface of Ga-doped graphene has been investigated. • High degree of adsorption for all analytes is found. • Ga-doped graphene shows p-type semiconductor property upon adsorption of ether molecules. - Abstract: In this study, we used density functional theory (DFT) to search on the adsorption properties of three important compounds of ether family; diethyl ether (DEE), ethyl methyl ether (EME), and dimethyl ether (DME) on the surface of Gallium doped graphene (GaG). We used three functionals (B3LYP, wb97xd, and MPW1PW91) for optimization and calculation of adsorption energy. After fully optimization, we scrutinized on the charge allocations on the adsorbed ethers as well as GaG (at the area of interaction) based on natural bond orbitals (NBO). Besides, we have calculated the amount of charge transfer upon adsorption of each analyte. We revel that GaG is an ideal adsorbent for chemisorption of all above-mentioned ethers. There is a little difference between the values of adsorption; −123.5, −120, and −118.3 kJ/mol (based on wb97xd) for DEE, EME, and DME, respectively. We found significant changes in the electronic structure of both adsorbent and adsorbate upon adsorption. Moreover, results of charge analyses confirm GaG is a p-type semiconductor.

  4. Unraveling the Role of Π - Conjugation in Thiophene Oligomers for Optoelectronic Properties by DFT/TDDFT Approach

    Directory of Open Access Journals (Sweden)

    Gajalakshmi

    Full Text Available ABSTRACT Thiophene oligomer has been investigated using DFT/TDDFT calculations with an aim to check its suitability for opto electronic applications and also to analyse the influence of π-bridge. Our results revealed that thiophene oligomers have excellent π-conjugation throughout. FMO analysis give an estimate of band gap of thiophene oligomer and further revealed HOMO are localized on π - bridge, donor group and LUMO are localized on π - bridge and acceptor group. A TDDFT calculation has been performed to understand the absorption properties of them in gas phase and solvent phase. PCM calculations convey that absorption maxima show positive solvatochromism. Among the designed candidates, the one with more π - bridge show higher wavelength of absorption maxima and would be a choice for better optoelectronic materials. NBO analysis provides support for complete delocalization in these systems. It is interesting to note that oligomer with more π-bridge display an enhanced optoelectronic properties than with less π - bridge.

  5. A DFT study of adsorption of glycine onto the surface of BC{sub 2}N nanotube

    Energy Technology Data Exchange (ETDEWEB)

    Soltani, Alireza, E-mail: Alireza.soltani46@yahoo.com [Joints, Bones and Connective Tissue Research Center, Golestan University of Medical Sciences, Gorgan (Iran, Islamic Republic of); Young Researchers and Elite Club, Gorgan Branch, Islamic Azad University, Gorgan (Iran, Islamic Republic of); Azmoodeh, Zivar [Department of Physics, Payame Noor University, P.O. Box 19395-3697, Tehran (Iran, Islamic Republic of); Javan, Masoud Bezi [Physics Department, Faculty of Sciences, Golestan University, Gorgan (Iran, Islamic Republic of); Lemeski, E. Tazikeh [Department of Chemistry, Gorgan Branch, Islamic Azad University, Gorgan (Iran, Islamic Republic of); Karami, Leila [Institute of Biochemistry and Biophysics, University of Tehran, Tehran (Iran, Islamic Republic of)

    2016-10-30

    Highlights: • Glycine adsorption over the pristine BC{sub 2}N nanotubes is investigated by DFT calculations. • Adsorption of glycine in its zwitterionic form is stronger in comparison with the radical form. • Adsorption of glycine from its amine head on adsorbent leads to a significant decrease in the electronic properties. - Abstract: A theoretical study of structure and the energy interaction of amino acid glycine (NH{sub 2}CH{sub 2}COOH) with BC{sub 2}N nanotube is crucial for apperception behavior occurring at the nanobiointerface. Herein, we studied the adsorption of glycine in their radical and zwitterionic forms upon the surface of BC{sub 2}N nanotube using M06 functional and 6-311G** standard basis set. We also considered the different orientations of the glycine amino acid on the surface of adsorbent. Further, we found out that the stability of glycine from its carbonyl group is higher than hydroxyl and amine groups. Our results also indicated that the electronic structure of BC{sub 2}N nanotube on the adsorption of glycine from its amine group is more altered than the other groups. Our study exhibits that opto-electronic property of adsorbent is changed after the glycine adsorption.

  6. A DFT-D study of the interaction of methane, carbon monoxide, and nitrogen with cation-exchanged SAPO-34

    Energy Technology Data Exchange (ETDEWEB)

    Fischer, Michael [Bremen Univ. (Germany). Fachgebiet Kristallographie; University College London (United Kingdom). Dept. of Chemistry; Bell, Robert G. [University College London (United Kingdom). Dept. of Chemistry

    2015-07-01

    Density-functional theory calculations including a semi-empirical dispersion correction (DFT-D) are employed to study the interaction of small guest molecules (CH{sub 4}, CO, N{sub 2}) with the cation sites in the silicoaluminophosphate SAPO-34. Eight different cations from three different groups (alkali cations, alkaline earth cations, transition metals) are included in the study. For each case, the total interaction energy as well as the non-dispersive contribution to the interaction are analysed. Electron density difference plots are used to investigate the nature of this non-dispersive contribution in more detail. Despite a non-negligible contribution of polarisation interactions, the total interaction remains moderate in systems containing main group cations. In SAPOs exchanged with transition metals, orbital interactions between the cations and CO and N{sub 2} lead to a very strong interaction, which makes these systems attractive as adsorbents for the selective adsorption of these species. A critical comparison with experimental heats of adsorption shows reasonable quantitative agreement for CO and N{sub 2}, but a pronounced overestimation of the interaction strength for methane. While this does not affect the conclusions regarding the suitability of TM-exchanged SAPO-34 materials for gas separations, more elaborate computational approaches may be needed to improve the quantitative accuracy for this guest molecule.

  7. A DFT-D study of the interaction of methane, carbon monoxide, and nitrogen with cation-exchanged SAPO-34

    International Nuclear Information System (INIS)

    Fischer, Michael; University College London; Bell, Robert G.

    2015-01-01

    Density-functional theory calculations including a semi-empirical dispersion correction (DFT-D) are employed to study the interaction of small guest molecules (CH 4 , CO, N 2 ) with the cation sites in the silicoaluminophosphate SAPO-34. Eight different cations from three different groups (alkali cations, alkaline earth cations, transition metals) are included in the study. For each case, the total interaction energy as well as the non-dispersive contribution to the interaction are analysed. Electron density difference plots are used to investigate the nature of this non-dispersive contribution in more detail. Despite a non-negligible contribution of polarisation interactions, the total interaction remains moderate in systems containing main group cations. In SAPOs exchanged with transition metals, orbital interactions between the cations and CO and N 2 lead to a very strong interaction, which makes these systems attractive as adsorbents for the selective adsorption of these species. A critical comparison with experimental heats of adsorption shows reasonable quantitative agreement for CO and N 2 , but a pronounced overestimation of the interaction strength for methane. While this does not affect the conclusions regarding the suitability of TM-exchanged SAPO-34 materials for gas separations, more elaborate computational approaches may be needed to improve the quantitative accuracy for this guest molecule.

  8. A DFT study of the stability of SIAs and small SIA clusters in the vicinity of solute atoms in Fe

    Science.gov (United States)

    Becquart, C. S.; Ngayam Happy, R.; Olsson, P.; Domain, C.

    2018-03-01

    The energetics, defect volume and magnetic properties of single SIAs and small SIA clusters up to size 6 have been calculated by DFT for different configurations like the parallel 〈110〉 dumbbell, the non parallel 〈110〉 dumbbell and the C15 structure. The most stable configurations of each type have been further analyzed to determine the influence on their stability of various solute atoms (Ti, V, Cr, Mn, Co, Ni, Cu, Mo, W, Pd, Al, Si, P), relevant for steels used under irradiation. The results show that the presence of solute atoms does not change the relative stability order among SIA clusters. The small SIA clusters investigated can bind to both undersized and oversized solutes. Several descriptors have been considered to derive interesting trends from results. It appears that the local atomic volume available for the solute is the main physical quantity governing the binding energy evolution, whatever the solute type (undersized or oversized) and the cluster configuration (size and type).

  9. Symmetry properties of the electron density and following from it limits on the KS-DFT applications

    Science.gov (United States)

    Kaplan, Ilya G.

    2018-03-01

    At present, the Density Functional Theory (DFT) approach elaborated by Kohn with co-authors more than 50 years ago became the most widely used method for study molecules and solids. Using modern computation facilities, it can be applied to systems with million atoms. In the atmosphere of such great popularity, it is particularly important to know the limits of the applicability of DFT methods. In this report, I will discuss two cases when the conventional DFT approaches, using only electron density ρ and its gradients, cannot be applied (I will not consider the Ψ-versions of DFT). The first case is quite evident. In the degenerated states, the electron density may not be defined, since electronic and nuclear motions cannot be separated, the vibronic interaction mixed them. The second case is related to the spin of the state. As it was rigorously proved by group theoretical methods at the theorem level, the electron density does not depend on the total spin S of the arbitrary N-electron state. It means that the Kohn-Sham equations have the same form for states with different S. The critical survey of elaborated DFT procedures, taking into account spin, shows that they modified only exchange functionals, the correlation functionals do not correspond to the spin of the state. The point is that the conception of spin cannot be defined in the framework of the electron density formalism, which corresponds to the one-particle reduced density matrix. This is the main reason of the problems arising in the study by DFT of magnetic properties of the transition metals. The possible way of resolving these problems can be found in the two-particle reduced density matrix formulation of DFT.

  10. STUDI KOMPUTASI BERBASIS DFT TERHADAP FENOMENA QUANTUM TUNNELING DALAM ISOMERISASI METILHIDROKSIKARBENA

    Directory of Open Access Journals (Sweden)

    Jumaidil Awal

    2016-01-01

    Full Text Available Density functional theory-based methods have been applied to predict the most possible one among the isomerizations of methylhydroxycarbene considering the probability of hydrogen tunneling occurrence. B3LYP/6-31+G(d,p and M08-SO/6-31+G(d,p methods were applied in all computations using GAMESS-US software. There were three steps of computation in this research. First, electronic structure computations of both equilibrium and transition compounds involved in all isomerization alternatives in order to obtain the optimum structures of the compounds. Second, vibrational computations of optimum transition structures to ensure that each of the respective structures is well on its potential energy surface. Third, tunneling analysis accomplished by intrinsic reaction coordinate (IRC computatuins for all isomerization alternatives followed by tunneling probabilitycalculation using the Wentzel-Kramers-Brillouin (WKB formula for methylhydroxycarbene isomerizations. The result of this research showed that the DFT methods successfully produced the optimum structure of each compound. Both DFT methods also successfully mapped all the intrinsic reaction coordinates. B3LYP/6-31+G(d,p method gave tunneling probabilities of 3.55 x 10-19 for the isomerization into acetaldehyde and 3.30 x 10-20 for that into vinyl alcohol. While M08-SO/6-31+G(d,p method gave tunneling probabilities of 2.38 x 10-23 for the isomerization into acetaldehyde and 4.79 x 10-23 for that into vinyl alcohol. Keywords: DFT, methylhydroxycarbene, hydrogen tunneling, isomerization

  11. Computing sextic centrifugal distortion constants by DFT: A benchmark analysis on halogenated compounds

    Science.gov (United States)

    Pietropolli Charmet, Andrea; Stoppa, Paolo; Tasinato, Nicola; Giorgianni, Santi

    2017-05-01

    This work presents a benchmark study on the calculation of the sextic centrifugal distortion constants employing cubic force fields computed by means of density functional theory (DFT). For a set of semi-rigid halogenated organic compounds several functionals (B2PLYP, B3LYP, B3PW91, M06, M06-2X, O3LYP, X3LYP, ωB97XD, CAM-B3LYP, LC-ωPBE, PBE0, B97-1 and B97-D) were used for computing the sextic centrifugal distortion constants. The effects related to the size of basis sets and the performances of hybrid approaches, where the harmonic data obtained at higher level of electronic correlation are coupled with cubic force constants yielded by DFT functionals, are presented and discussed. The predicted values were compared to both the available data published in the literature and those obtained by calculations carried out at increasing level of electronic correlation: Hartree-Fock Self Consistent Field (HF-SCF), second order Møller-Plesset perturbation theory (MP2), and coupled-cluster single and double (CCSD) level of theory. Different hybrid approaches, having the cubic force field computed at DFT level of theory coupled to harmonic data computed at increasing level of electronic correlation (up to CCSD level of theory augmented by a perturbational estimate of the effects of connected triple excitations, CCSD(T)) were considered. The obtained results demonstrate that they can represent reliable and computationally affordable methods to predict sextic centrifugal terms with an accuracy almost comparable to that yielded by the more expensive anharmonic force fields fully computed at MP2 and CCSD levels of theory. In view of their reduced computational cost, these hybrid approaches pave the route to the study of more complex systems.

  12. Adsorption of alanine with heteroatom substituted fullerene for solar cell application: A DFT study.

    Science.gov (United States)

    Dheivamalar, S; Sugi, L; Ravichandran, K; Sriram, S

    2018-05-14

    C 20 is the most important fullerene cage and alanine is the simplest representation of a backbone unit of the protein. The absorption feasibility of alanine molecule in the Si-doped C 20 and B-doped C 20 fullerenes has been studied based on calculated electronic properties of fullerenes using density functional theory (DFT). In this work, we explore the ability of Si-doped C 20 , B-doped C 20 fullerene to interact with alanine at the DFT-B3LYP/6-31G, RHF level of theory. We find that noticeable structural change takes place in C 20 when one of its carbon is substituted with Si or B. The molecular geometry, electronic properties and vibrational analysis have also been performed on the title compounds. The NMR study reveals the aromaticity of the pure and doped fullerene compounds. Stability of the doped fullerene - alanine compound arises from hyper conjugative interactions. It leads to one of the major property of bioactivity, charge transfer and delocalization of charge and this properties has been analyzed using Natural Bond Orbital (NBO) analysis. The energy gap of the doped fullerene reveals that there is a decrease in the size of energy gap significantly, making them more reactive as compared to C 20 fullerene. Theoretical studies of the electronic spectra by using time - dependent density functional theory (TD-DFT) method were helpful to interpret the observed electronic transition state. We aim to optimize the performance of the solar cells by altering the frontier orbital energy gaps. Considering all studied properties, it may be inferred that the applicability of C 20 fullerene as the non-linear optical (NLO) material and its NLO property would increase on doping fullerene with Si and B atom. Specifically C 19 Si would be better among them. Copyright © 2018. Published by Elsevier B.V.

  13. Internal dynamics in helical molecules studied by X-ray diffraction, NMR spectroscopy and DFT calculations

    Czech Academy of Sciences Publication Activity Database

    Dračínský, Martin; Storch, Jan; Církva, Vladimír; Císařová, I.; Sýkora, Jan

    2017-01-01

    Roč. 19, č. 4 (2017), s. 2900-2907 ISSN 1463-9076 R&D Projects: GA ČR GA15-11223S; GA ČR GA15-12719S Institutional support: RVO:61388963 ; RVO:67985858 Keywords : helicene * NMR spectroscopy * DFT calculations Subject RIV: CF - Physical ; Theoretical Chemistry OBOR OECD: Physical chemistry; Physical chemistry (UCHP-M) Impact factor: 4.123, year: 2016 http://pubs.rsc.org/en/content/articlehtml/2013/cp/c6cp07552e

  14. DFT/B3LYP study of tocopherols and chromans antioxidant action energetics

    International Nuclear Information System (INIS)

    Klein, Erik; Lukes, Vladimir; Ilcin, Michal

    2007-01-01

    Gas-phase reaction enthalpies related to the individual steps of three phenolic antioxidants action mechanisms - hydrogen atom transfer (HAT), single-electron transfer-proton transfer (SET-PT) and sequential proton loss electron transfer (SPLET) for four tocopherols and seven chromans - were calculated using DFT/B3LYP method. For α-tocopherol, one of the chromans and phenol, reaction enthalpies in water were computed. In comparison to gas phase, water causes severe changes in the energetics of studied compounds antioxidant action. From the thermodynamic point of view, entering SPLET mechanism represents the most probable process in water

  15. DFT/B3LYP study of tocopherols and chromans antioxidant action energetics

    Energy Technology Data Exchange (ETDEWEB)

    Klein, Erik [Institute of Physical Chemistry and Chemical Physics, Slovak University of Technology, Radlinskeho 9, SK-812 37 Bratislava (Slovakia)], E-mail: erik.klein@stuba.sk; Lukes, Vladimir; Ilcin, Michal [Institute of Physical Chemistry and Chemical Physics, Slovak University of Technology, Radlinskeho 9, SK-812 37 Bratislava (Slovakia)

    2007-07-09

    Gas-phase reaction enthalpies related to the individual steps of three phenolic antioxidants action mechanisms - hydrogen atom transfer (HAT), single-electron transfer-proton transfer (SET-PT) and sequential proton loss electron transfer (SPLET) for four tocopherols and seven chromans - were calculated using DFT/B3LYP method. For {alpha}-tocopherol, one of the chromans and phenol, reaction enthalpies in water were computed. In comparison to gas phase, water causes severe changes in the energetics of studied compounds antioxidant action. From the thermodynamic point of view, entering SPLET mechanism represents the most probable process in water.

  16. Tuning of nanodiamond particles’ optical properties by structural defects and surface modifications: DFT modelling

    Czech Academy of Sciences Publication Activity Database

    Kratochvílová, Irena; Kovalenko, Alexander; Fendrych, František; Petráková, Vladimíra; Záliš, Stanislav; Nesladek, M.

    2011-01-01

    Roč. 21, č. 45 (2011), s. 18248-18255 ISSN 0959-9428 R&D Projects: GA ČR(CZ) GAP304/10/1951; GA AV ČR KAN200100801 Institutional research plan: CEZ:AV0Z10100520; CEZ:AV0Z40400503 Keywords : nanodiamond * luminiscence * DFT Subject RIV: BM - Solid Matter Physics ; Magnetism Impact factor: 5.968, year: 2011 http://pubs.rsc.org/en/content/articlelanding/2011/JM/C1JM13525B

  17. Estudio DFT de agregados moleculares en aerosoles y nubes estratosféricas polares

    OpenAIRE

    Verdes Gago, María de los Ángeles

    2015-01-01

    Tesis doctoral inédita leída en la Universidad Autónoma de Madrid, Facultad de Ciencias, Departamento de Química Física Aplicada. Fecha de lectura: 19-12-2015 El interés por profundizar en mecanismos de nucleación de los agregados y de las nubes estratosféricas polares, responsables de la destrucción del ozono estratosférico, ha sido la motivación para realizar los cálculos de agregados mediante la teoría del funcional de la densidad (DFT) en esta tesis, para obtener estructuras optimizada...

  18. Self-Aggregation in Pyrrole:  Matrix Isolation, Solid State Infrared Spectroscopy, and DFT Study

    OpenAIRE

    Gómez-Zavaglia, Andrea; Fausto, Rui

    2004-01-01

    Pyrrole (C4H5N) was embedded in low-temperature solid inert matrixes (argon, xenon; T = 9 K) and both the monomer and low-order aggregates characterized by FTIR spectroscopy. The spectroscopic studies were complemented by extensive theoretical [DFT(B3LYP)/6-311++G(d,p)] structural and vibrational studies carried out for the monomer and their self-aggregates (up to four units). The calculated spectrum for monomeric pyrrole fits well those obtained immediately after deposition (at 9 K) of dilut...

  19. A Reinvestigation of the Ionic Liquid Diisopropylethylammonium Formate by NMR and DFT Methods

    DEFF Research Database (Denmark)

    Hansen, Poul Erik; Lund, Torben; Krake, Jacob

    2016-01-01

    The complex between diisopropylethylamine (DIPEA) and formic acid has been reinvestigated. Mixing the compounds in the ratio 1:1 leads to a phase separation in which the upper phase is DIPEA, the lower phase is the “ionic liquid” named DIPEF. A combined NMR and DFT study shows that the lower phase...... that presented elsewhere. However, the present picture should be considered using acids and bases with a pKa difference less than 8. The formic acid content in the DIPEF ionic liquid causes desorption of the dye-sensitized solar cell (DSC) dye N719 from the photo anode and DIPEF is therefore not a suitable...

  20. Cis/trans Coordination in olefin metathesis by static and molecular dynamic DFT calculations

    KAUST Repository

    Poater, Albert

    2014-05-25

    In regard to [(N-heterocyclic carbene)Ru]-based catalysts, it is still a matter of debate if the substrate binding is preferentially cis or trans to the N-heterocyclic carbene ligand. By means of static and molecular dynamic DFT calculations, a simple olefin, like ethylene, is shown to be prone to the trans binding. Bearing in mind the higher reactivity of trans isomers in olefin metathesis, this insight helps to construct small alkene substrates with increased reactivity. © 2014 Springer Science+Business Media New York.

  1. Determination of structural and spectroscopic parameters of 4-hydroxyantipyrine, using DFT method

    International Nuclear Information System (INIS)

    Catikkas, B.; Aktan, E.

    2010-01-01

    In this study, structural and vibrational parameters were calculated. First of all, conformational analysis of 4-hydroxyantipyrine was carried out in gas phase. Then, the geometric parameters (bond length, bond angle and tortion angle) of the most stable conformer were calculated and the Infrared and Raman frequencies of fundamental modes were determined. Calculations were made by using DFT B3LYP/6-311+G(d,p) method implemented the Gaussian 03 program. Afterwards, vibrational assignments of the title molecule were calculated by using Scaled Quantum Mechanical (SQM) analysis. In conclusion, calculated values were compared with corresponding experimental results.

  2. DFT molecular modeling and NMR conformational analysis of a new longipinenetriolone diester

    Science.gov (United States)

    Cerda-García-Rojas, Carlos M.; Guerra-Ramírez, Diana; Román-Marín, Luisa U.; Hernández-Hernández, Juan D.; Joseph-Nathan, Pedro

    2006-05-01

    The structure and conformational behavior of the new natural compound (4 R,5 S,7 S,8 R,9 S,10 R,11 R)-longipin-2-en-7,8,9-triol-1-one 7-angelate-9-isovalerate (1) isolated from Stevia eupatoria, were studied by molecular modeling and NMR spectroscopy. A Monte Carlo search followed by DFT calculations at the B3LYP/6-31G* level provided the theoretical conformations of the sesquiterpene framework, which were in full agreement with results derived from the 1H- 1H coupling constant analysis.

  3. Cis/trans Coordination in olefin metathesis by static and molecular dynamic DFT calculations

    KAUST Repository

    Poater, Albert; Correa, Andrea; Pump, Eva; Cavallo, Luigi

    2014-01-01

    In regard to [(N-heterocyclic carbene)Ru]-based catalysts, it is still a matter of debate if the substrate binding is preferentially cis or trans to the N-heterocyclic carbene ligand. By means of static and molecular dynamic DFT calculations, a simple olefin, like ethylene, is shown to be prone to the trans binding. Bearing in mind the higher reactivity of trans isomers in olefin metathesis, this insight helps to construct small alkene substrates with increased reactivity. © 2014 Springer Science+Business Media New York.

  4. A facile approach towards synthesis, characterization, single crystal structure, and DFT study of 5-bromosalicylalcohol

    Energy Technology Data Exchange (ETDEWEB)

    Rastogi, Rupali, E-mail: rastogirupali@ymail.com [ITM University, Department of Chemistry (India); Tarannum, Nazia [Ch. Charan Singh University, Department of Chemistry (India); Butcher, R. J. [Howard University, Chemistry Department (United States)

    2016-03-15

    5-Bromosalicylalcohol was prepared by the interaction of NaBH{sub 4} and 5-bromosalicylaldehyde. The use of sodium borohydride makes the reaction easy, facile, economic and does not require any toxic catalyst. The compound is characterized by FTIR, {sup 1}H NMR, {sup 13}C NMR, TEM and ESI-mass spectra. Crystal structure is determined by single crystal X-ray analysis. Quantum mechanical calculations of geometries, energies and thermodynamic parameters are carried out using density functional theory (DFT/B3LYP) method with 6-311G(d,p) basis set. The optimized geometrical parameters obtained by B3LYP method show good agreement with experimental data.

  5. (E-2-Acetyl-4-[(3-methylphenyldiazenyl]phenol: an X-ray and DFT study

    Directory of Open Access Journals (Sweden)

    Orhan Büyükgüngör

    2010-03-01

    Full Text Available The title compound, C15H14N2O2, an azo dye, displays a trans configuration with respect to the N=N bridge. The dihedral angle between the aromatic rings is 0.18 (14°. There is a strong intramolecular O—H...O hydrogen bond. Geometrical parameters, determined using X-ray diffraction techniques, are compared with those calculated by density functional theory (DFT, using hybrid exchange–correlation functional, B3LYP and semi-empirical (PM3 methods.

  6. Vibrational analysis and thermodynamic properties of C120 nanotorus: a DFT study

    International Nuclear Information System (INIS)

    López-Chávez, Ernesto; Cruz-Torres, Armando; Landa Castillo-Alvarado, Fray de; Ortíz-López, Jaime; Peña-Castañeda, Yésica A.; Martínez-Magadán, José Manuel

    2011-01-01

    Density functional theory (DFT) computational methods are applied to a C 120 carbon nanotorus studied as an isolated molecular species, using the functional GGA PW91. This toroidal form of carbon contains five fold, six fold, and sevenfold rings. The calculated cohesive energy of the nanotorus, indicates that the ground state of this structure is energetically more stable than that of fullerene C 60 . Geometry and stability, Raman and IR vibrational analysis and thermodynamic properties have been reported and compared to the values obtained by other authors.

  7. DFT, Its Impact on Condensed Matter and on ``Materials-Genome'' Research

    Science.gov (United States)

    Scheffler, Matthias

    About 40 years ago, two seminal works demonstrated the power of density-functional theory (DFT) for real materials. These studies by Moruzzi, Janak, and Williams on metals and Yin and Cohen on semiconductors visualized the spatial distribution of electrons, predicted the equation of state of solids, crystal stability, pressure-induced phase transitions, and more. They also stressed the importance of identifying trends by looking at many systems (e.g. the whole transition-metal series). Since then, the field has seen numerous applications of DFT to solids, liquids, defects, surfaces, and interfaces providing important descriptions and explanations as well as predictions of experimentally not yet identified systems. - ∖ ∖ About 10 years ago, G. Ceder and his group [Ref. 3 and references therein] started with high-throughput screening calculations in the spirit of what in 2011 became the ``Materials Genome Initiative''. The idea of high-throughput screening is old (a key example is the ammonia catalyst found by A. Mittasch at BASF more than 100 years ago), but it is now increasingly becoming clear that big data of materials does not only provide direct information but that the data is structured. This enables interpolation, (modest) extrapolation, and new routes towards understanding [Ref. 5 and references therein]. - ∖ ∖ The amount of data created by ``computational materials science'' is significant. For instance, the NoMaD Repository (which includes also data from other repositories, e.g. AFLOWLIB and OQMD) now holds more than 18 million total-energy calculations. In fact, the amount of data of computational materials science is steadily increasing, and about hundred million CPU core hours are nowadays used every day, worldwide, for DFT calculations for materials. - ∖ ∖ The talk will summarize this enormous impact of DFT on materials science, and it will address the next steps, e.g. the issue how to exploit big data of materials for doing forefront

  8. A novel proof of the DFT formula for the interatomic force field of Molecular Dynamics

    International Nuclear Information System (INIS)

    Morante, S.; Rossi, G.C.

    2017-01-01

    We give a novel and simple proof of the DFT expression for the interatomic force field that drives the motion of atoms in classical Molecular Dynamics, based on the observation that the ground state electronic energy, seen as a functional of the external potential, is the Legendre transform of the Hohenberg–Kohn functional, which in turn is a functional of the electronic density. We show in this way that the so-called Hellmann–Feynman analytical formula, currently used in numerical simulations, actually provides the exact expression of the interatomic force.

  9. A novel proof of the DFT formula for the interatomic force field of Molecular Dynamics

    Energy Technology Data Exchange (ETDEWEB)

    Morante, S., E-mail: morante@roma2.infn.it [Dipartimento di Fisica, Università di Roma, “ Tor Vergata ”, INFN, Sezione di Roma 2, Via della Ricerca Scientifica - 00133 Roma (Italy); Rossi, G.C., E-mail: rossig@roma2.infn.it [Dipartimento di Fisica, Università di Roma, “ Tor Vergata ”, INFN, Sezione di Roma 2, Via della Ricerca Scientifica - 00133 Roma (Italy); Centro Fermi-Museo Storico della Fisica e Centro Studi e Ricerche E. Fermi, Compendio del Viminale, Piazza del Viminale 1, I-00184 Rome (Italy)

    2017-02-15

    We give a novel and simple proof of the DFT expression for the interatomic force field that drives the motion of atoms in classical Molecular Dynamics, based on the observation that the ground state electronic energy, seen as a functional of the external potential, is the Legendre transform of the Hohenberg–Kohn functional, which in turn is a functional of the electronic density. We show in this way that the so-called Hellmann–Feynman analytical formula, currently used in numerical simulations, actually provides the exact expression of the interatomic force.

  10. Density functional theory (DFT) as a powerful tool for designing new organic corrosion inhibitors. Part 1: An overview

    International Nuclear Information System (INIS)

    Obot, I.B.; Macdonald, D.D.; Gasem, Z.M.

    2015-01-01

    The use of computational chemistry as a tool in the design and development of organic corrosion inhibitors has been greatly enhanced by the development of density functional theory (DFT). Whereas, traditionally, corrosion scientists have identified new corrosion inhibitor molecules either by incrementally changing the structures of existing inhibitors or by testing hundreds of compounds in the laboratory, these experimental means are often very expensive and time-consuming. Thus, ongoing hardware and software advances have opened the door for powerful use of theoretical chemistry in corrosion inhibition research at a reduced cost. DFT has enabled corrosion scientist to accurately predict the inhibition efficacies of organic corrosion inhibitors based on electronic/molecular properties and reactivity indices. This review summarizes the main features of DFT, giving a brief background to selected DFT-based chemical reactivity concepts, calculations and their applications to organic corrosion inhibitor design. The paper also reviews the principles upon which modern corrosion science is based with emphasis on corrosion in the oil and gas industry and with the goal of identifying important issues in the design of new, more effective inhibitors in this field. The impact of this review is to illustrate the enormous power of DFT and to identify shortcomings in past work, including the assumption that inhibitors only interact with bare metal surfaces.

  11. PEEM microscopy and DFT calculations of catalytically active platinum surfaces and interfaces

    International Nuclear Information System (INIS)

    Spiel, C.

    2012-01-01

    The aim of this thesis was to investigate the properties of catalytically active platinum surfaces and interfaces both with experimental and theoretical methods. Using experimental methods, catalytic CO oxidation on individual grains of a polycrystalline platinum foil was studied in situ under high vacuum (HV) conditions. A polycrystalline platinum foil consists of individual µm-sized crystal grains that are mainly [100]-, [110]- and [111]-oriented and differ significantly in their catalytic activity. In order to elucidate the differences existing between the reactivity of the individual grains, a combination of photoemission electron microscopy (PEEM) and quadrupole mass spectrometry (QMS) was used in this work. The working principle of PEEM is based on the photoelectric effect where illumination of the sample with (UV-)light causes emission of photoelectrons. The emitted photoelectrons are used to visualize the sample surface (with typical resolution in the low micrometer range). The PEEM image contrast originates from differences in the local work function that may arise due to different crystallographic orientations and/or changes in the adsorbate coverage. With a combination of PEEM and QMS, it was possible to study the kinetics of catalytic CO oxidation on polycrystalline platinum foil both in a global and a laterally-resolved way simultaneously. If catalytic CO oxidation on surfaces of platinum is followed at constant temperature and oxygen partial pressure under cyclic variation of the CO pressure, a hysteresis in the CO2 production rate is observed in the bistability region with two noticeable kinetic transitions (called tA and tB) taking place at different CO pressures when the catalyst surface switches back-and-forth between two steady states of high and low reactivity while the Pt-surface is, correspondingly, either oxygen- or CO-covered. In the bistability region between τ A and τ B , the system stays (at the same values of the external parameters p

  12. Solid-State NMR and DFT Studies on the Formation of Well-Defined Silica-Supported Tantallaaziridines: From Synthesis to Catalytic Application

    KAUST Repository

    Hamzaoui, Bilel

    2016-01-27

    Single-site, well-defined, silica-supported tantallaaziridine intermediates [≡Si-O-Ta(η2-NRCH2)(NMe2)2] [R=Me (2), Ph (3)] were prepared from silica-supported tetrakis(dimethylamido)tantalum [≡Si-O-Ta(NMe2)4] (1) and fully characterized by FTIR spectroscopy, elemental analysis, and 1H,13C HETCOR and DQ TQ solid-state (SS) NMR spectroscopy. The formation mechanism, by β-H abstraction, was investigated by SS NMR spectroscopy and supported by DFT calculations. The C-H activation of the dimethylamide ligand is favored for R=Ph. The results from catalytic testing in the hydroaminoalkylation of alkenes were consistent with the N-alkyl aryl amine substrates being more efficient than N-dialkyl amines. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  13. Protonated o-semiquinone radical as a mimetic of the humic acids native radicals: A DFT approach to the molecular structure and EPR properties

    Science.gov (United States)

    Witwicki, Maciej; Jezierska, Julia

    2012-06-01

    Organic radicals are known to be an indispensable component of the humic acids (HA) structure. In HA two forms of radicals, stable (native) and short-lived (transient), are identified. Importantly, these radical forms can be easily differentiated by electron paramagnetic resonance (EPR) spectroscopy. This article provides a DFT-based insight into the electronic and molecular structure of the native radicals. The molecular models including an increase of the radical aromaticity and the hydrogen bonding between the radical and other functional groups of HA are taken under investigation. In consequence the interesting pieces of information on the structure of the native radical centers in HA are revealed and discussed, especially in terms of differences between the electronic structure of the native and transient forms.

  14. Benzothiazole analogues: Synthesis, characterization, MO calculations with PM6 and DFT, in silico studies and in vitro antimalarial as DHFR inhibitors and antimicrobial activities.

    Science.gov (United States)

    Thakkar, Sampark S; Thakor, Parth; Ray, Arabinda; Doshi, Hiren; Thakkar, Vasudev R

    2017-10-15

    Benzothiazole analogues are of interest due to their potential activity against malarial and microbial infections. In search of suitable antimicrobial and antimalarial agents, we report here the synthesis, characterization and biological activities of benzothiazole analogues (J 1-J 10). The molecules were characterized by IR, Mass, 1 H NMR, 13 C NMR and elemental analysis. The in vitro antimicrobial activity was investigated against pathogenic strains; the results were explained with the help of DFT and PM6 molecular orbital calculations. In vitro cytotoxicity and genotoxicity of the molecules were studied against S. pombe cells. In vitro antimalarial activity was studied. The active compounds J 1, J 2, J 3, J 5 and J 6 were further evaluated for enzyme inhibition efficacy against the receptor Pf-DHFR, computational and in vitro studies were carried out to examine their candidatures as lead dihydrofolate reductase inhibitors. Copyright © 2017 Elsevier Ltd. All rights reserved.

  15. Multicomponent DFT study of geometrical H/D isotope effect on hydrogen-bonded organic conductor, κ-H3(Cat EDT-ST)2

    Science.gov (United States)

    Yamamoto, Kaichi; Kanematsu, Yusuke; Nagashima, Umpei; Ueda, Akira; Mori, Hatsumi; Tachikawa, Masanori

    2017-04-01

    We theoretically investigated a significant contraction of the hydrogen-bonding O⋯O distance upon H/D substitution in our recently developed purely organic crystals, κ-H3(Cat-EDT-ST)2 (H-ST) and its isotopologue κ-D3(Cat-EDT-ST)2 (D-ST), having π-electron systems coupled with hydrogen-bonding fluctuation. The origin of this geometrical H/D isotope effect was elucidated by using the multicomponent DFT method, which takes the H/D nuclear quantum effect into account. The optimized O⋯O distance in H-ST was found to be longer than that in D-ST due to the anharmonicity of the potential energy curve along the Osbnd H bond direction, which was in reasonable agreement with the experimental trend.

  16. Combined experimental powder X-ray diffraction and DFT data to obtain the lowest energy molecular conformation of friedelin

    International Nuclear Information System (INIS)

    Oliveira, Djalma Menezes de; Mussel, Wagner da Nova; Duarte, Lucienir Pains; Silva, Gracia Divina de Fatima; Duarte, Helio Anderson; Gomes, Elionai Cassiana de Lima; Guimaraes, Luciana; Vieira Filho, Sidney A.

    2012-01-01

    Friedelin molecular conformers were obtained by Density Functional Theory (DFT) and by ab initio structure determination from powder X-ray diffraction. Their conformers with the five rings in chair-chair-chair-boat-boat, and with all rings in chair, are energy degenerated in gas-phase according to DFT results. The powder diffraction data reveals that rings A, B and C of friedelin are in chair, and rings D and E in boat-boat, conformation. The high correlation values among powder diffraction data, DFT and reported single crystal data indicate that the use of conventional X-ray diffractometer can be applied in routine laboratory analysis in the absence of a single-crystal diffractometer. (author)

  17. Evaluation of DFT methods for computing the interaction energies of homomolecular and heteromolecular dimers of monosubstituted benzene

    Science.gov (United States)

    Godfrey-Kittle, Andrew; Cafiero, Mauricio

    We present density functional theory (DFT) interaction energies for the sandwich and T-shaped conformers of substituted benzene dimers. The DFT functionals studied include TPSS, HCTH407, B3LYP, and X3LYP. We also include Hartree-Fock (HF) and second-order Møller-Plesset perturbation theory calculations (MP2), as well as calculations using a new functional, P3LYP, which includes PBE and HF exchange and LYP correlation. Although DFT methods do not explicitly account for the dispersion interactions important in the benzene-dimer interactions, we find that our new method, P3LYP, as well as HCTH407 and TPSS, match MP2 and CCSD(T) calculations much better than the hybrid methods B3LYP and X3LYP methods do.

  18. Electronic spectroscopy of HRe(CO) 5: a CASSCF/CASPT2 and TD-DFT study

    Science.gov (United States)

    Bossert, J.; Ben Amor, N.; Strich, A.; Daniel, C.

    2001-07-01

    The low-lying excited states of HRe(CO) 5 have been calculated at the CASSCF/CASPT2 and TD-DFT level of theory using relativistic effective core potentials (ECP) or ab initio model potentials (AIMP). The theoretical absorption spectrum is compared to the experimental one. Despite the similarity between the experimental absorption spectra of HMn(CO) 5 and HRe(CO) 5 in the UV/visible energy domain it is shown that the assignment differs significantly between the two molecules. The low-lying excited states of HRe(CO) 5 correspond to 5d→π *CO excitations whereas the spectrum of HMn(CO) 5 consists mainly of 3d→3d and 3d→ σ*Mn-H excitations. If the CASPT2 and TD-DFT results are quite comparable for the lowest excited states, the upper part assignment is more problematic with the TD-DFT method.

  19. Combined experimental powder X-ray diffraction and DFT data to obtain the lowest energy molecular conformation of friedelin

    Energy Technology Data Exchange (ETDEWEB)

    Oliveira, Djalma Menezes de; Mussel, Wagner da Nova; Duarte, Lucienir Pains; Silva, Gracia Divina de Fatima; Duarte, Helio Anderson; Gomes, Elionai Cassiana de Lima [Universidade Federal de Minas Gerais (UFMG), Belo Horizonte, MG (Brazil). Dept. de Quimica; Guimaraes, Luciana [Universidade Federal de Sao Joao Del-Rei (UFSJ), MG (Brazil). Dept. de Ciencias Naturais; Vieira Filho, Sidney A., E-mail: bibo@ef.ufop.br [Universidade Federal de Ouro Preto (UFOP), MG (Brazil). Dept. de Farmacia

    2012-07-01

    Friedelin molecular conformers were obtained by Density Functional Theory (DFT) and by ab initio structure determination from powder X-ray diffraction. Their conformers with the five rings in chair-chair-chair-boat-boat, and with all rings in chair, are energy degenerated in gas-phase according to DFT results. The powder diffraction data reveals that rings A, B and C of friedelin are in chair, and rings D and E in boat-boat, conformation. The high correlation values among powder diffraction data, DFT and reported single crystal data indicate that the use of conventional X-ray diffractometer can be applied in routine laboratory analysis in the absence of a single-crystal diffractometer. (author)

  20. A comparative DFT study on CO oxidation reaction over Si-doped BC2N nanosheet and nanotube

    Science.gov (United States)

    Nematollahi, Parisa; Neyts, Erik C.

    2018-05-01

    In this study, we performed density functional theory (DFT) calculations to investigate different reaction mechanisms of CO oxidation catalyzed by the Si atom embedded defective BC2N nanostructures as well as the analysis of the structural and electronic properties. The structures of all the complexes are optimized and characterized by frequency calculations at the M062X/6-31G∗ computational level. Also, The electronic structures and thermodynamic parameters of adsorbed CO and O2 molecules over Si-doped BC2N nanostructures are examined in detail. Moreover, to investigate the curvature effect on the CO oxidation reaction, all the adsorption and CO oxidation reactions on a finite-sized armchair (6,6) Si-BC2NNT are also studied. Our results indicate that there can be two possible pathways for the CO oxidation with O2 molecule: O2(g) + CO(g) → O2(ads) + CO(ads) → CO2(g) + O(ads) and O(ads) + CO(g) → CO2(g). The first reaction proceeds via the Langmuir-Hinshelwood (LH) mechanism while the second goes through the Eley-Rideal (ER) mechanism. On the other hand, by increasing the tube diameter, the energy barrier increases due to the strong adsorption energy of the O2 molecule which is related to its dissociation over the tube surface. Our calculations indicate that the two step energy barrier of the oxidation reaction over Si-BC2NNS is less than that over the Si-BC2NNT. Hence, Si-BC2NNS may serve as an efficient and highly activated substrate to CO oxidation rather than (4,4) Si-BC2NNT.

  1. A DFT study on the mechanisms for the cycloaddition reactions between 1-aza-2-azoniaallene cations and acetylenes.

    Science.gov (United States)

    Wang, Jing-mei; Li, Zhi-ming; Wang, Quan-rui; Tao, Feng-gang

    2013-01-01

    The mechanisms of cycloaddition reactions between 1-aza-2-azoniaallene cations 1 and acetylenes 2 have been investigated using the global electrophilicity and nucleophilicity of the corresponding reactants as global reactivity indexes defined within the conceptual density functional theory. The reactivity and regioselectivity of these reactions were predicted by analysis of the energies, geometries, and electronic nature of the transition state structures. The theoretical results revealed that the reaction features a tandem process: an ionic 1,3-dipolar cycloaddition to produce the cycloadducts 3 H-pyrazolium salts 3 followed by a [1,2]-shift affording the thermodynamically more stable adducts 4 or 5. The mechanism of the cycloaddition reactions can be described as an asynchronous concerted pathway with reverse electron demand. The model reaction has also been investigated at the QCISD/6-31++G(d,p) and CCSD(T)/6-31++G(d,p)//B3LYP/6-31++G(d,p) levels as well as by the DFT. The polarizable continuum model, at the B3LYP/6-31++G(d,p) level of theory, was used to study solvent effects on all the studied reactions. In solvent dichloromethane, all the initial cycloadducts 3 were obtained via direct ionic process as the result of the solvent effect. The consecutive [1,2]-shift reaction, in which intermediates 3 are rearranged to the five-membered heterocycles 4/5, is proved to be a kinetically controlled reaction, and the regioselectivity can be modulated by varying the migrant. The LOL function and RDG function based on localized electron analysis were used to analysis the covalent bond and noncovalent interactions in order to unravel the mechanism of the title reactions.

  2. Cation-exchanged SAPO-34 for adsorption-based hydrocarbon separations: predictions from dispersion-corrected DFT calculations.

    Science.gov (United States)

    Fischer, Michael; Bell, Robert G

    2014-10-21

    The influence of the nature of the cation on the interaction of the silicoaluminophosphate SAPO-34 with small hydrocarbons (ethane, ethylene, acetylene, propane, propylene) is investigated using periodic density-functional theory calculations including a semi-empirical dispersion correction (DFT-D). Initial calculations are used to evaluate which of the guest-accessible cation sites in the chabazite-type structure is energetically preferred for a set of ten cations, which comprises four alkali metals (Li(+), Na(+), K(+), Rb(+)), three alkaline earth metals (Mg(2+), Ca(2+), Sr(2+)), and three transition metals (Cu(+), Ag(+), Fe(2+)). All eight cations that are likely to be found at the SII site (centre of a six-ring) are then included in the following investigation, which studies the interaction with the hydrocarbon guest molecules. In addition to the interaction energies, some trends and peculiarities regarding the adsorption geometries are analysed, and electron density difference plots obtained from the calculations are used to gain insights into the dominant interaction types. In addition to dispersion interactions, electrostatic and polarisation effects dominate for the main group cations, whereas significant orbital interactions are observed for unsaturated hydrocarbons interacting with transition metal (TM) cations. The differences between the interaction energies obtained for pairs of hydrocarbons of interest (such as ethylene-ethane and propylene-propane) deliver some qualitative insights: if this energy difference is large, it can be expected that the material will exhibit a high selectivity in the adsorption-based separation of alkene-alkane mixtures, which constitutes a problem of considerable industrial relevance. While the calculations show that TM-exchanged SAPO-34 materials are likely to exhibit a very high preference for alkenes over alkanes, the strong interaction may render an application in industrial processes impractical due to the large amount

  3. Methyl Cation Affinities of Neutral and Anionic Maingroup-Element Hydrides: Trends Across the Periodic Table and Correlation with Proton Affinities

    NARCIS (Netherlands)

    Mulder, R. Joshua; Guerra, Celia Fonseca; Bickelhaupt, F. Matthias

    2010-01-01

    We have computed the methyl cation affinities in the gas phase of archetypal anionic and neutral bases across the periodic table using ZORA-relativistic density functional theory (DFT) at BP86/QZ4P//BP86/TZ2P. The main purpose of this work is to provide the methyl cation affinities (and

  4. A systematic theoretical study of the electronic structures of porphyrin dimers: DFT and TD-DFT calculations on diporphyrins linked by ethane, ethene, ethyne, imine, and azo bridges.

    Science.gov (United States)

    Rintoul, Llew; Harper, Shannon R; Arnold, Dennis P

    2013-11-21

    Theoretical calculations of the geometries, electronic structures and electronic absorption spectra of a series of covalently-linked porphyrin dimers are reported. The diporphyrins comprise 5,10,15-triphenylporphyrinatozinc(II) (ZnTriPP) units linked through the meso carbons by two-atom bridges, namely 1,2-ethanediyl (1), trans-1,2-ethenediyl (2), ethynediyl (3), 1,2-iminomethenediyl (4), and transdiazenediyl (5). The structures were optimised in toluene solvent by Density Functional Theory (DFT), using the integral equation formalism variant of the polarizable continuum model. The calculations were performed using the B3LYP functional and the 6-31G(d,p) basis set. The complete molecules were modelled, with no substitution of smaller groups on the periphery. In parallel, the compounds 2–5 were prepared by known or novel synthetic routes, to enable comparisons of experimental electronic absorption spectra with those calculated using time dependent-DFT at the same level of theory. As the ethane dimer 1 is not yet synthetically accessible, the model monomer meso-2-phenylethylZnTriPP was used for comparisons with the theoretical predictions. The results form a self-consistent set, enabling for the first time legitimate comparisons of the electronic structures of the series, especially regarding the degree to which the porphyrin p-systems interact by conjugation across the bridges. The theoretical calculations of the electronic transitions match the observed spectra in toluene to a remarkable degree, especially with respect to the peak maximum of the Q band, which represents to a large degree the energy of the HOMO–LUMO transition. The imine 4 is intrinsically polar due to the asymmetric bridge, and the HOMO is located almost exclusively on the ZnTriPP unit attached to the nitrogen of the imine, and the LUMO on the C-attached ring. Thus the Q-band transition is mapped as a comprehensive charge-transfer from the former ring to the latter. This may have consequences

  5. Predicting near-UV electronic circular dichroism in nucleosomal DNA by means of DFT response theory.

    Science.gov (United States)

    Norman, Patrick; Parello, Joseph; Polavarapu, Prasad L; Linares, Mathieu

    2015-09-14

    It is demonstrated that time-dependent density functional theory (DFT) calculations can accurately predict changes in near-UV electronic circular dichroism (ECD) spectra of DNA as the structure is altered from the linear (free) B-DNA form to the supercoiled N-DNA form found in nucleosome core particles. At the DFT/B3LYP level of theory, the ECD signal response is reduced by a factor of 6.7 in going from the B-DNA to the N-DNA form, and it is illustrated how more than 90% of the individual base-pair dimers contribute to this strong hypochromic effect. Of the several inter-base pair parameters, an increase in twist angles is identified as to strongly contribute to a reduced ellipticity. The present work provides first evidence that first-principles calculations can elucidate changes in DNA dichroism due to the supramolecular organization of the nucleoprotein particle and associates these changes with the local structural features of nucleosomal DNA.

  6. Effect of organic molecules on hydrolysis of peptide bond: A DFT study

    International Nuclear Information System (INIS)

    Makshakova, Olga; Ermakova, Elena

    2013-01-01

    Highlights: ► DFT study of the effects of small organic molecules on the hydrolysis reactions of peptide bonds. ► Organic molecules can activate nonenzymatic hydrolysis reaction. ► Influence of organic acids on activation energy barrier correlates with their electronegativity. - Abstract: The activation and inhibition effects of small organic molecules on peptide hydrolysis have been studied using a model compound dialanine and DFT approach. Solvent-assisted and non-assisted concerted mechanisms were analyzed. Several transition states for the systems: alanine dipeptide–water molecule in complexes with alcohol molecules, acetonitrile, dimethylsulfoxide, propionic, lactic and pyruvic acids and water molecules were localized. The formation of hydrogen bonds between dipeptide, reactive water molecule and molecules of solvents influences the activation energy barrier of the peptide bond hydrolytic reaction. Strong effect of organic acids on the activation energy barrier correlates with their electronegativity. Acetonitrile can act as an inhibitor of reaction. Mechanisms of regulation of the activation energy barrier are discussed in the terms of donor-acceptor interactions

  7. Finite-temperature orbital-free DFT molecular dynamics: Coupling PROFESS and QUANTUM ESPRESSO

    Science.gov (United States)

    Karasiev, Valentin V.; Sjostrom, Travis; Trickey, S. B.

    2014-12-01

    Implementation of orbital-free free-energy functionals in the PROFESS code and the coupling of PROFESS with the QUANTUM ESPRESSO code are described. The combination enables orbital-free DFT to drive ab initio molecular dynamics simulations on the same footing (algorithms, thermostats, convergence parameters, etc.) as for Kohn-Sham (KS) DFT. All the non-interacting free-energy functionals implemented are single-point: the local density approximation (LDA; also known as finite-T Thomas-Fermi, ftTF), the second-order gradient approximation (SGA or finite-T gradient-corrected TF), and our recently introduced finite-T generalized gradient approximations (ftGGA). Elimination of the KS orbital bottleneck via orbital-free methodology enables high-T simulations on ordinary computers, whereas those simulations would be costly or even prohibitively time-consuming for KS molecular dynamics (MD) on very high-performance computer systems. Example MD simulations on H over a temperature range 2000 K ≤ T ≤4,000,000 K are reported, with timings on small clusters (16-128 cores) and even laptops. With respect to KS-driven calculations, the orbital-free calculations are between a few times through a few hundreds of times faster.

  8. DFT study of IR and Raman spectra of phosphotrihydrazone dendrimer with terminal phenolic groups

    Science.gov (United States)

    Furer, V. L.; Vandyukov, A. E.; Majoral, J. P.; Caminade, A. M.; Kovalenko, V. I.

    2017-09-01

    FT Raman and infrared spectra of phosphotrihydrazone (S)P[N(CH3)Ndbnd CHsbnd C6H4sbnd OH]3 (G0) were recorded. This compound is a zero generation phosphorus dendrimer with terminal phenolic groups. Optimal geometry and vibrational frequencies were calculated for G0 using the density functional theory (DFT). The molecule studied has C3 symmetry. In the molecule G0, each sbnd C6H4sbnd CHdbnd Nsbnd N(CH3)sbnd P arm is flat. Optimized geometric parameters correspond to experimental data. The core of the dendrimer manifests itself as a band at 647 cm-1 in the Raman spectrum of G0 related to Pdbnd S stretching. Phenolic end functions exhibit a well-defined band at 3374 cm-1 in the experimental IR spectrum of G0. The observed frequency of the OH stretching vibrations of the phenolic groups is lower than the theoretical value due to the intermolecular Osbnd H⋯O hydrogen bond. This hydrogen bond is also responsible for the higher intensity of this band in the experimental IR spectrum compared with the theoretical value. DFT calculations suggest full assignment of normal modes. Global and local descriptors characterize the reactivity of the core and end groups.

  9. Two and Three-Dimensional Nonlocal DFT for Inhomogeneous Fluids I: Algorithms and Parallelization

    Energy Technology Data Exchange (ETDEWEB)

    Frink, Laura J. Douglas; Salinger, Andrew

    1999-08-09

    Fluids adsorbed near surfaces, macromolecules, and in porous materials are inhomogeneous, inhibiting spatially varying density distributions. This inhomogeneity in the fluid plays an important role in controlling a wide variety of complex physical phenomena including wetting, self-assembly, corrosion, and molecular recognition. One of the key methods for studying the properties of inhomogeneous fluids in simple geometries has been density functional theory (DFT). However, there has been a conspicuous lack of calculations in complex 2D and 3D geometries. The computational difficulty arises from the need to perform nested integrals that are due to nonlocal terms in the free energy functional These integral equations are expensive both in evaluation time and in memory requirements; however, the expense can be mitigated by intelligent algorithms and the use of parallel computers. This paper details our efforts to develop efficient numerical algorithms so that no local DFT calculations in complex geometries that require two or three dimensions can be performed. The success of this implementation will enable the study of solvation effects at heterogeneous surfaces, in zeolites, in solvated (bio)polymers, and in colloidal suspensions.

  10. Flux formulation of DFT on group manifolds and generalized Scherk-Schwarz compactifications

    Energy Technology Data Exchange (ETDEWEB)

    Bosque, Pascal du [Max-Planck-Institut für Physik,Föhringer Ring 6, 80805 München (Germany); Arnold-Sommerfeld-Center für Theoretische Physik,Fakultät für Physik, Ludwig-Maximilians-Universität München,Theresienstraße 37, 80333 München (Germany); Hassler, Falk [University of North Carolina, Department of Physics and Astronomy,Phillips Hall, CB #3255, 120 E. Cameron Ave., Chapel Hill, NC 27599-3255 (United States); City University of New York, The Graduate Center,365 Fifth Avenue, New York, NY 10016 (United States); Columbia University, Department of Physics,Pupin Hall, 550 West 120th St., New York, NY 10027 (United States); Lüst, Dieter [Max-Planck-Institut für Physik,Föhringer Ring 6, 80805 München (Germany); Arnold-Sommerfeld-Center für Theoretische Physik,Fakultät für Physik, Ludwig-Maximilians-Universität München,Theresienstraße 37, 80333 München (Germany)

    2016-02-04

    A flux formulation of Double Field Theory on group manifold is derived and applied to study generalized Scherk-Schwarz compactifications, which give rise to a bosonic subsector of half-maximal, electrically gauged supergravities. In contrast to the flux formulation of original DFT, the covariant fluxes split into a fluctuation and a background part. The latter is connected to a 2D-dimensional, pseudo Riemannian manifold, which is isomorphic to a Lie group embedded into O(D,D). All fields and parameters of generalized diffeomorphisms are supported on this manifold, whose metric is spanned by the background vielbein E{sub A}{sup I}∈ GL(2D). This vielbein takes the role of the twist in conventional generalized Scherk-Schwarz compactifications. By doing so, it solves the long standing problem of constructing an appropriate twist for each solution of the embedding tensor. Using the geometric structure, absent in original DFT, E{sub A}{sup I} is identified with the left invariant Maurer-Cartan form on the group manifold, in the same way as it is done in geometric Scherk-Schwarz reductions. We show in detail how the Maurer-Cartan form for semisimple and solvable Lie groups is constructed starting from the Lie algebra. For all compact embeddings in O(3,3), we calculate E{sub A}{sup I}.

  11. Synthesis, spectroscopic and DFT studies of novel 4-(morpholinomethyl)-5-oxo-1-phenylpyrrolidine-3-carboxylic acid

    Science.gov (United States)

    Devi, Poornima; Fatma, Shaheen; Bishnoi, Abha; Srivastava, Krishna; Shukla, Shraddha; Kumar, Roop

    2018-04-01

    A novel 4-(morpholinomethyl)-5-oxo-1-phenylpyrrolidine-3-carboxylic acid has been synthesized and its structural elucidation has been done by UV, FT-IR, 1H and 13C NMR spectroscopy. All quantum chemical calculations were carried out at level of density functional theory (DFT) with B3LYP function using 6-31G (d, p) basis atomic set. AIM approach has been incorporated for the analysis of various intermolecular interactions. Polarizability and hyperpolarizabilities values have been calculated along with the exploration of nonlinear optical properties of the title compound. DFT computed total first static hyperpolarizability (β0 = 0.2747 × 10-30 esu) indicates that title molecule could be an area of interest as an attractive future NLO material. For the analysis of thermal behaviour of title molecule, thermodynamic properties such as heat capacity, entropy and enthalpy change at various temperatures have been calculated. The NBO computations were done for the correlation of possible transitions with the electronic transitions. Electrophilic and nucleophilic regions were identified with the help of MESP plot. Determination of energy gap has been done by using HOMO and LUMO energy values, along with the computation of electronegativity and electrophilicity indices.

  12. Conformational analysis of capsaicin using 13C, 15N MAS NMR, GIAO DFT and GA calculations

    Science.gov (United States)

    Siudem, Paweł; Paradowska, Katarzyna; Bukowicki, Jarosław

    2017-10-01

    Capsaicin produced by plants from genus Capsicum exerts multiple pharmacological effects and has found applications in food and pharmaceutical industry. The alkaloid was studied by a combined approach: solid-state NMR, GA conformational search and GIAO DFT methods. The 13C CPMAS NMR spectra were recorded using variable contact time and dipolar dephasing experiments. The results of cross-polarization (CP) kinetics, such as TCP values and long T1ρH (100-200 ms), indicated that the capsaicin molecule is fairly mobile, especially at the end of the aliphatic chain. The15N MAS NMR spectrum showed one narrow signal at -255 ppm. Genetic algorithm (GA) search with multi modal optimization was used to find low-energy conformations of capsaicin. Theoretical GIAO DFT calculations were performed using different basis sets to characterize five selected conformations. 13C CPMAS NMR was used as a validation method and the experimental chemical shifts were compared with those calculated for selected stable conformers. Conformational analysis suggests that the side chain can be bent or extended. A comparison of the experimental and the calculated chemical shifts indicates that solid capsaicin does not have the same structure as those established by PWXRD.

  13. SERS and DFT study of p-hydroxybenzoic acid adsorbed on colloidal silver particles.

    Science.gov (United States)

    Chen, Y; Chen, S J; Li, S; Wei, J J

    2015-10-16

    In this study, normal Raman spectra of p—hydroxybenzoic acid (PHBA) powder and its surface—enhanced Raman scattering (SERS) spectra in silver colloidal solutions were measured under near infrared excitation conditions. In theoretical calculation, two models of PHBA adsorbed on the surfaces of silver nanoparticles were established. The Raman frequencies of these two models using density functional theory (DFT) method were calculated, and compared with the experimental results. It was found that the calculated Raman frequencies were in good agreement with experimental values, which indicates that there are two enhanced mechanism physical (electromagnetic, EM) enhancement and chemical (charge—transfer, CT) enhancement, in silver colloidal solutions regarding SERS effect. Furthermore, from high—quality SERS spectrum of PHBA obtained in silver colloids, we inferred that PHBA molecules in silver colloids adsorb onto the metal surfaces through carboxyl at a perpendicular orientation. The combination of SERS spectra and DFT calculation is thus useful for studies of the adsorption—orientation of a molecule on a metal colloid.

  14. Synthesis, X-ray Structure, Spectroscopic Properties and DFT Studies of a Novel Schiff Base

    Directory of Open Access Journals (Sweden)

    Kew-Yu Chen

    2014-10-01

    Full Text Available A series of Schiff bases, salicylideneaniline derivatives 1–4, was synthesized under mild conditions and characterized by 1H NMR, HRMS, UV-Vis and fluorescence spectra, and single-crystal X-ray diffraction. In solid and aprotic solvents 1–4 exist mainly as E conformers that possess an intramolecular six-membered-ring hydrogen bond. A weak intramolecular C–H×××F hydrogen bond is also observed in fluoro-functionalized Schiff base 4, which generates another S(6 ring motif. The C–H×××F hydrogen bond further stabilizes its structure and leads it to form a planar configuration. Compounds 1–3 exhibit solely a long-wavelength proton-transfer tautomer emission, while dipole-functionalized Schiff base 4 shows remarkable dual emission originated from the excited-state intramolecular charge transfer (ESICT and excited-state intramolecular proton transfer (ESIPT states. Furthermore, the geometric structures, frontier molecular orbitals (MOs and the potential energy curves for 1–4 in the ground and the first singlet excited state were fully rationalized by density functional theory (DFT and time-dependent DFT calculations.

  15. Combined UMC- DFT prediction of electron-hole coupling in unit cells of pentacene crystals.

    Science.gov (United States)

    Leal, Luciano Almeida; de Souza Júnior, Rafael Timóteo; de Almeida Fonseca, Antonio Luciano; Ribeiro Junior, Luiz Antonio; Blawid, Stefan; da Silva Filho, Demetrio Antonio; da Cunha, Wiliam Ferreira

    2017-05-01

    Pentacene is an organic semiconductor that draws special attention from the scientific community due to the high mobility of its charge carriers. As electron-hole interactions are important aspects in the regard of such property, a computationally inexpensive method to predict the coupling between these quasi-particles is highly desired. In this work, we propose a hybrid methodology of combining Uncoupled Monte Carlo Simulations (UMC) and Density functional Theory (DFT) methodologies to obtain a good compromise between computational feasibility and accuracy. As a first step in considering a Pentacene crystal, we describe its unit cell: the Pentacene Dimer. Because many conformations can be encountered for the dimer and considering the complexity of the system, we make use of UMC in order to find the most probable structures and relative orientations for the Pentacene-Pentacene complex. Following, we carry out electronic structure calculations in the scope of DFT with the goal of describing the electron-hole coupling on the most probable configurations obtained by UMC. The comparison of our results with previously reported data on the literature suggests that the methodology is well suited for describing transfer integrals of organic semiconductors. The observed accuracy together with the smaller computational cost required by our approach allows us to conclude that such methodology might be an important tool towards the description of systems with higher complexity.

  16. Sorption Speciation of Lanthanides/Actinides on Minerals by TRLFS, EXAFS and DFT Studies: A Review

    Directory of Open Access Journals (Sweden)

    Xiaoli Tan

    2010-11-01

    Full Text Available Lanthanides/actinides sorption speciation on minerals and oxides by means of time resolved laser fluorescence spectroscopy (TRLFS, extended X-ray absorption fine structure spectroscopy (EXAFS and density functional theory (DFT is reviewed in the field of nuclear disposal safety research. The theoretical aspects of the methods are concisely presented. Examples of recent research results of lanthanide/actinide speciation and local atomic structures using TRLFS, EXAFS and DFT are discussed. The interaction of lanthanides/actinides with oxides and minerals as well as their uptake are also of common interest in radionuclide chemistry. Especially the sorption and inclusion of radionuclides into several minerals lead to an improvement in knowledge of minor components in solids. In the solid-liquid interface, the speciation and local atomic structures of Eu(III, Cm(III, U(VI, and Np(IV/VI in several natural and synthetic minerals and oxides are also reviewed and discussed. The review is important to understand the physicochemical behavior of lanthanides/actinides at a molecular level in the natural environment.

  17. Adsorption of various types of amino acids on the graphene and boron-nitride nano-sheet, a DFT-D3 study

    International Nuclear Information System (INIS)

    Zhiani, Rahele

    2017-01-01

    Graphical abstract: Dispersion interactions have key role on the adsorption of different amino acids on the graphene and BN-nanosheet surfaces. - Highlights: • The Arginine amino acid makes the most stable complexes with Gra and BN nano sheet. • Dispersion interactions have key role on the amino acid adsorption. • BN nano sheet makes more stable complexes with amino acids compare to the Gra. • Water as a solvent has important effect on these interactions. - Abstract: The binding properties of the adsorption of five different classes of amino acids, namely, alanine (Ala), arginine (Arg), asparagine (Asn), histidine (His) and cysteine (Cys) on the surface of the graphene (Gra) and the born-nitride (BN) nano-sheet structures were studied from molecular viewpoint using quantum mechanics methods. Density functional theory (DFT) and DFT-D3 calculations were carried out to investigate the electronic properties and the dispersion interaction of the amino acid/adsorbent complexes. Several parameters affecting the interactions between the amino acids and the adsorbent surfaces such as solvent effect, adsorption energy and separation distance were investigated. Findings show that Arg forms the most stable complexes with the graphene and the BN nano-sheet compare to the other amino acids used in this study. The observed frequency results which were related to the band gap energies were consistent with the above statement. Results exhibit that adsorption of the amino acids on the surface of the BN nano-sheet and the graphene accompanied with the release of the energy. Calculations show that there are no bonded interactions between the amino acids and adsorbent surfaces. The polarity of the BN nano-sheet provides the more affinity towards the amino acids. These results were proved by the quantum chemistry studies.

  18. Synthesis, spectroscopic and TD-DFT quantum mechanical study of azo-azomethine dyes. A laser induced trans-cis-trans photoisomerization cycle.

    Science.gov (United States)

    Georgiev, Anton; Kostadinov, Anton; Ivanov, Deyan; Dimov, Deyan; Stoyanov, Simeon; Nedelchev, Lian; Nazarova, Dimana; Yancheva, Denitsa

    2018-03-05

    This paper describes the synthesis, spectroscopic characterization and quantum mechanical calculations of three azo-azomethine dyes. The dyes were synthesized via condensation reaction between 4-(dimethylamino)benzaldehyde and three different 4-aminobenzene azo dyes. Quantum chemical calculations on the optimized molecular geometry and electron densities of the trans (E) and cis (Z) isomers and their vibrational frequencies have been computed by using DFT/B3LYP density-functional theory with 6-311++G(d,p) basis set in vacuo. The thermodynamic parameters such as total electronic energy E (RB3LYP), enthalpy H 298 (sum of electronic and thermal enthalpies), free Gibbs energy G 298 (sum of electronic and thermal free Gibbs energies) and dipole moment μ were computed for trans (E) and cis (Z) isomers in order to estimate the ΔE trans→cis , Δμ trans→cis, ΔH trans→cis , ΔG trans→cis and ΔS trans→cis values. After molecular geometry optimization the electronic spectra have been obtained by TD-DFT calculations at same basis set and correlated with the spectra of vapour deposited nanosized films of the dyes. The NBO analysis was performed in order to understand the intramolecular charge transfer and energy of resonance stabilization. Solvatochromism was investigated by UV-VIS spectroscopy in five different organic solvents with increasing polarity. The dynamic photoisomerization experiments have been performed in DMF by pump lasers λ=355nm (mostly E→Z) and λ=491nm (mostly Z→E) in spectral region 300nm - 800nm at equal concentrations and times of illumination in order to investigate the photodynamical trans-cis-trans properties of the CHN and NN chromophore groups of the dyes. Copyright © 2017 Elsevier B.V. All rights reserved.

  19. Adsorption of various types of amino acids on the graphene and boron-nitride nano-sheet, a DFT-D3 study

    Energy Technology Data Exchange (ETDEWEB)

    Zhiani, Rahele, E-mail: r_zhiani2006@yahoo.com

    2017-07-01

    Graphical abstract: Dispersion interactions have key role on the adsorption of different amino acids on the graphene and BN-nanosheet surfaces. - Highlights: • The Arginine amino acid makes the most stable complexes with Gra and BN nano sheet. • Dispersion interactions have key role on the amino acid adsorption. • BN nano sheet makes more stable complexes with amino acids compare to the Gra. • Water as a solvent has important effect on these interactions. - Abstract: The binding properties of the adsorption of five different classes of amino acids, namely, alanine (Ala), arginine (Arg), asparagine (Asn), histidine (His) and cysteine (Cys) on the surface of the graphene (Gra) and the born-nitride (BN) nano-sheet structures were studied from molecular viewpoint using quantum mechanics methods. Density functional theory (DFT) and DFT-D3 calculations were carried out to investigate the electronic properties and the dispersion interaction of the amino acid/adsorbent complexes. Several parameters affecting the interactions between the amino acids and the adsorbent surfaces such as solvent effect, adsorption energy and separation distance were investigated. Findings show that Arg forms the most stable complexes with the graphene and the BN nano-sheet compare to the other amino acids used in this study. The observed frequency results which were related to the band gap energies were consistent with the above statement. Results exhibit that adsorption of the amino acids on the surface of the BN nano-sheet and the graphene accompanied with the release of the energy. Calculations show that there are no bonded interactions between the amino acids and adsorbent surfaces. The polarity of the BN nano-sheet provides the more affinity towards the amino acids. These results were proved by the quantum chemistry studies.

  20. Successes and failures of DFT functionals in acid/base and redox reactions of organic and biochemical interest

    OpenAIRE

    Silva, Pedro J.; Ramos, Maria João

    2011-01-01

    The performance of 18 different DFT functionals in the prediction of absolute and relative energies of organic and biochemical acid/base and redox reactions was evaluated, using MP2 extrapolated to the complete basis set limit and CCSD(T)/aug-cc-pVTZ energies as benchmark. Absolute reduction energies were predicted with relatively large average errors (2–4 kcal mol−1) except for the best functional, PBE0 (1.3 ± 1.2 kcal mol−1). The DFT predictions of relative reduction energies afforded mean ...

  1. Critical Assessment of TD-DFT for Excited States of Open-Shell Systems: I. Doublet-Doublet Transitions.

    Science.gov (United States)

    Li, Zhendong; Liu, Wenjian

    2016-01-12

    A benchmark set of 11 small radicals is set up to assess the performance of time-dependent density functional theory (TD-DFT) for the excited states of open-shell systems. Both the unrestricted (U-TD-DFT) and spin-adapted (X-TD-DFT) formulations of TD-DFT are considered. For comparison, the well-established EOM-CCSD (equation-of-motion coupled-cluster with singles and doubles) is also used. In total, 111 low-lying singly excited doublet states are accessed by all the three approaches. Taking the MRCISD+Q (multireference configuration interaction with singles and doubles plus the Davidson correction) results as the benchmark, it is found that both U-TD-DFT and EOM-CCSD perform well for those states dominated by singlet-coupled single excitations (SCSE) from closed-shell to open-shell, open-shell to vacant-shell, or closed-shell to vacant-shell orbitals. However, for those states dominated by triplet-coupled single excitations (TCSE) from closed-shell to vacant-shell orbitals, both U-TD-DFT and EOM-CCSD fail miserably due to severe spin contaminations. In contrast, X-TD-DFT provides balanced descriptions of both SCSE and TCSE. As far as the functional dependence is concerned, it is found that, when the Hartree-Fock ground state does not suffer from the instability problem, both global hybrid (GH) and range-separated hybrid (RSH) functionals perform grossly better than pure density functionals, especially for Rydberg and charge-transfer excitations. However, if the Hartree-Fock ground state is instable or nearly instable, GH and RSH tend to underestimate severely the excitation energies. The SAOP (statistically averaging of model orbital potentials) performs more uniformly than any other density functionals, although it generally overestimates the excitation energies of valence excitations. Not surprisingly, both EOM-CCSD and adiabatic TD-DFT are incapable of describing excited states with substantial double excitation characters.

  2. FTIR, FT-RAMAN, NMR, spectra, normal co-ordinate analysis, NBO, NLO and DFT calculation of N,N-diethyl-4-methylpiperazine-1-carboxamide molecule.

    Science.gov (United States)

    Muthu, S; Elamurugu Porchelvi, E

    2013-11-01

    The Fourier Transform Infrared (FT-IR) and FT-Raman of N,N-diethyl-4-methylpiperazine-1-carboxamide (NND4MC) have been recorded and analyzed. The structure of the compound was optimized and the structural characteristics were determined by density functional theory (DFT) using B3LYP method with 6-31G(d,p) and 6-311G(d,p) basis sets. The difference between the observed and scaled wavenumber values of most of the fundamentals is very small. The theoretically predicted FT-IR and FT-Raman spectra of the title molecule have been constructed. The detailed interpretation of the vibrational spectra has been carried out with aid of normal coordinate analysis (NCA) following the scaled quantum mechanical force field methodology. Stability of the molecule arising from hyperconjugative interactions and charge delocalization has been analyzed using natural bond orbital (NBO) analysis. The results show that electron density (ED) in the σ(*) and π(*) antibonding orbitals and second order delocalization energies (E2) confirm the occurrence of intramolecular charge transfer (ICT) within the molecule. The electronic dipole moment (μD) and the first hyperpolarizability (βtot) values of the investigated molecule were computed using Density Functional Theory (DFT/B3LYP) with 6-31G(d,p) and 6-311G(d,p) basis sets. The calculated results also show that the NND4MC molecule may have microscopy nonlinear optical (NLO) behavior with non zero values. Mulliken atomic charges of NND4MC were calculated. The (13)C nuclear magnetic resonance (NMR) chemical shifts of the molecule were calculated by the gauge independent atomic orbital (GIAO) method and compared with experimental results. The UV-Vis spectrum of the compound was recorded. The theoretical electronic absorption spectra have been calculated by using CIS, TD-DFT methods. A study on the electronic properties, such as HOMO and LUMO energies, molecular electrostatic potential (MEP) were also performed. Copyright © 2013 Elsevier B

  3. First principles investigation of structural, vibrational and thermal properties of black and blue phosphorene

    Science.gov (United States)

    Arif Khalil, R. M.; Ahmad, Javed; Rana, Anwar Manzoor; Bukhari, Syed Hamad; Tufiq Jamil, M.; Tehreem, Tuba; Nissar, Umair

    2018-05-01

    In this investigation, structural, dynamical and thermal properties of black and blue phosphorene (P) are presented through the first principles calculations based on the density functional theory (DFT). These DFT calculations depict that due to the approximately same values of ground state energy at zero Kelvin and Helmholtz free energy at room-temperature, it is expected that both structures can coexist at transition temperature. Lattice dynamics of both phases were investigated by using the finite displacement supercell approach. It is noticed on the basis of harmonic approximation thermodynamic calculations that the blue phase is thermodynamically more stable than the black phase above 155 K.

  4. Hydrogenation of CO{sub 2} to formic acid over a Cu-embedded graphene: A DFT study

    Energy Technology Data Exchange (ETDEWEB)

    Sirijaraensre, J., E-mail: fscijkp@ku.ac.th [Department of Chemistry, Faculty of Science, Kasetsart University, Bangkok 10900 (Thailand); Center for Advanced Studies in Nanotechnology and Its Applications in Chemical, Food and Agricultural Industries and NANOTEC Center for Nanoscale Materials Design for Green Nanotechnology, Kasetsart University, Bangkok 10900 (Thailand); Limtrakul, J. [Department of Materials Science and Engineering, Vidyasirimedhi Institute of Science and Technology, Rayong 21210 (Thailand)

    2016-02-28

    Graphical abstract: - Highlights: • The H{sub 2} molecule binds much more strongly on the Cu/dG than the CO{sub 2} molecule. • H{sub 2} dissociation occurs readily on the supported Cu atom. • The CO{sub 2} conversion is significantly promoted by the Cu-H on the graphene. - Abstract: DFT calculations were used to investigate the properties of the atomic copper embedded in the surface of graphene (Cu/dG) and the catalytic reaction pathway for the CO{sub 2} hydrogenation to formic acid (FA). The Cu/dG was active for the adsorption of the hydrogen molecule (H{sub 2}), and provided a reaction site for the heterolytic cleavage of H{sub 2}, leading to the formation of Cu-H deposited on a singly hydrogenated vacancy graphene (Cu-H/H-dG). The protonation of CO{sub 2} takes place facilely over the generated metal-hydride species (Cu-H). Under the dilution of H{sub 2}, the catalytic process would be hampered by the formation of copper-formate deposited on the H-dG due mainly to the very high energy demand for the transformation of the copper-formate to FA through the protonation from the H-dG. It was further found that the presence of H{sub 2} in the system plays a significant role in producing the FA on the Cu/dG catalyst. The copper-formate species can be converted into formic acid via the heterolytic cleavage of the second hydrogen molecule, yielding the FA and Cu-H species.

  5. Boosting the adsorption performance of BN nanosheet as an anode of Na-ion batteries: DFT studies

    Energy Technology Data Exchange (ETDEWEB)

    Hosseinian, A. [Department of Engineering Science, College of Engineering, University of Tehran, P.O. Box 11365-4563, Tehran (Iran, Islamic Republic of); Soleimani-amiri, S. [Department of Chemistry, Karaj Branch, Islamic Azad University, Karaj (Iran, Islamic Republic of); Arshadi, S., E-mail: chemistry_arshadi@pnu.ac.ir [Department of Chemistry, Payame Noor University, Tehran (Iran, Islamic Republic of); Vessally, E. [Department of Chemistry, Payame Noor University, Tehran (Iran, Islamic Republic of); Edjlali, L. [Department of Chemistry, Tabriz Branch, Islamic Azad University, Tabriz (Iran, Islamic Republic of)

    2017-06-28

    Despite the high advance in the Li-ion battery technology, there exist great concerns about its lifetime, safety, cost, and low-temperature performance. It is expected that the Li-ion batteries may be replaced by Na-ion batteries (NIB) because of the low cost, nontoxicity, and wide availability of sodium. Here, we investigated the potential application of BN nanosheets in anode of NIBs by means of density functional theory calculation and introduced a strategy to increase their performance. It was shown that the Na and Na{sup +} are mainly adsorbed on the center of a hexagonal ring of BN sheet with adsorption energies of −0.08 and −33.7 kcal/mol, respectively. Replacing three N atoms of the hexagonal ring with larger P atoms significantly increases the performance of the sheet as an anode of a NIB but the replacement of B by Al decreases the performance. The initial cell voltage of LIB is increased by about 0.67 V after the P-doping which causes a high storage performance with long discharge time. The results are discussed based on the energetic, structural, orbital, charge transfer and electronic properties and provide guidelines to build better high-capacity anode materials for NIBs. - Highlights: • Potential use of BN sheet as anode in Na-ion batteries (NIB) is studied by DFT. • The replacement of B by Al decreases the performance. • The cell voltage of LIB is increased by about 0.67 V after by P-doping. • The order of performance is P-BN > BN >> Al-BN.

  6. Infrared spectra and stability of CO and H2O sorption over Ag-exchanged ZSM-5 zeolite: DFT study

    International Nuclear Information System (INIS)

    Jiang Shujun; Huang Shiping; Tu Weixia; Zhu Jiqin

    2009-01-01

    The infrared spectra and stability of CO and H 2 O sorption over Ag-exchanged ZSM-5 zeolite were investigated by using density function theory (DFT). The changes of NBO charge show that the electron transfers from CO molecule to the Ag + cation to form an σ-bond, and it accompanies by the back donation of d-electrons from Ag + cation to the CO (π*) orbital as one and two CO molecules are adsorbed on Ag-ZSM-5. The free energy changes ΔG, -5.55 kcal/mol and 6.52 kcal/mol for one and two CO molecules, illustrate that the Ag + (CO) 2 complex is unstable at the room temperature. The vibration frequency of C-O stretching of one CO molecule bonded to Ag + ion at 2211 cm -1 is in good agreement with the experimental results. The calculated C-O symmetric and antisymmetric stretching frequencies in the Ag + (CO) 2 complex shift to 2231 cm -1 and 2205 cm -1 when the second CO molecule is adsorbed. The calculated C-O stretching frequency in CO-Ag-ZSM-5-H 2 O complex shifts to 2199 cm -1 , the symmetric and antisymmetric O-H stretching frequencies are 3390 cm -1 and 3869 cm -1 , respectively. The Gibbs free energy change (ΔG H 2 O ) is -6.58 kcal/mol as a H 2 O molecule is adsorbed on CO-Ag-ZSM-5 complex at 298 K. The results show that CO-Ag-ZSM-5-H 2 O complex is more stable at room temperature

  7. Mechanism of intermolecular hydroacylation of vinylsilanes catalyzed by a rhodium(I) olefin complex: a DFT study.

    Science.gov (United States)

    Meng, Qingxi; Shen, Wei; Li, Ming

    2012-03-01

    Density functional theory (DFT) was used to investigate the Rh(I)-catalyzed intermolecular hydroacylation of vinylsilane with benzaldehyde. All intermediates and transition states were optimized completely at the B3LYP/6-31G(d,p) level (LANL2DZ(f) for Rh). Calculations indicated that Rh(I)-catalyzed intermolecular hydroacylation is exergonic, and the total free energy released is -110 kJ mol(-1). Rh(I)-catalyzed intermolecular hydroacylation mainly involves the active catalyst CA2, rhodium-alkene-benzaldehyde complex M1, rhodium-alkene-hydrogen-acyl complex M2, rhodium-alkyl-acyl complex M3, rhodium-alkyl-carbonyl-phenyl complex M4, rhodium-acyl-phenyl complex M5, and rhodium-ketone complex M6. The reaction pathway CA2 + R2 → M1b → T1b → M2b → T2b1 → M3b1 → T4b → M4b → T5b → M5b → T6b → M6b → P2 is the most favorable among all reaction channels of Rh(I)-catalyzed intermolecular hydroacylation. The reductive elimination reaction is the rate-determining step for this pathway, and the dominant product predicted theoretically is the linear ketone, which is consistent with Brookhart's experiments. Solvation has a significant effect, and it greatly decreases the free energies of all species. The use of the ligand Cp' (Cp' = C(5)Me(4)CF(3)) decreased the free energies in general, and in this case the rate-determining step was again the reductive elimination reaction.

  8. ETUDE PAR DFT+U DE L’INTERACTION Ni-CeO2

    Directory of Open Access Journals (Sweden)

    Z CHAFI

    2010-12-01

    Full Text Available L’étude de l’interaction Ni-CeO2 a été entreprise en utilisant une méthode ab initio basée sur la DFT+U. Dans une première étape, les valeurs du paramètre d’Hubbard, Ueff, ont été déterminées après ajustement du paramètre de maille et de l’énergie de gap du volume de l’oxyde de cérium. Elles sont respectivement de 3 et 5 eV pour les approximations GGA et LDA. Nous avons ensuite étudié d’une part la possibilité d’insérer le nickel atomique dans le volume de CeO2. D’autre part, nous avons testé les effets de l’insertion et l’adsorption de Ni dans les surfaces les plus stables (111 et (110 de CeO2. Les résultats des calculs DFT+U sont en bon accord avec ceux que nous avons précédemment trouvé en utilisant un calcul DFT concernant les sites favorables de l’atome de nickel et le nombre de liaisons. Toutefois, l’approximation LDA+5 eV, a permis d’obtenir des énergies plus favorables ainsi que des distances comparables à celles observées expérimentalement à l’interface métal/oxyde dans les catalyseurs Ni/CeO2 synthétisés sous irradiation. Une expansion du volume est observée lors de l’insertion du nickel dans le volume de l’oxyde de cérium. Concernant l’adsorption sur les surfaces, la meilleure énergie est trouvée dans le cas où l’atome de nickel est situé en position bridge entre deux atomes d’oxygène sur la surface (110. Finalement, les calculs montrent que le nickel s’insère plus facilement dans la surface (110 avec une meilleure énergie d’insertion, obtenue par l’approximation LDA+5 eV, de 4,071 eV.

  9. Actinide-lanthanide separation by bipyridyl-based ligands. DFT calculations and experimental results

    International Nuclear Information System (INIS)

    Borisova, Nataliya E.; Eroshkina, Elizaveta A.; Korotkov, Leonid A.; Ustynyuk, Yuri A.; Alyapyshev, Mikhail Yu.; Eliseev, Ivan I.; Babain, Vasily A.

    2011-01-01

    In order to gain insights into effect of substituents on selectivity of Am/Eu separation, the synthesis and extractions tests were undertaken on the series of bipyridyl-based ligands (amides of 2,2'-bipyridyl-6,6'-dicarboxylic acid: L Ph - N,N'-diethyl-N,N'-diphenyl amide; L Bu2 - tetrabutyl amide; L Oct2 - tetraoctyl amide; L 3FPh - N,N'-diethyl-N,N'-bis-(3-fluorophenyl) amide; as well as N,N'-diethyl-N,N'-diphenyl amide of 4,4'-dibrom-2,2'-bipyridyl-6,6'-dicarboxylic acid and N,N'-diethyl-N,N'-diphenyl amide of 4,4'-dinitro-2,2'-bipyridyl-6,6'-dicarboxylic acid) as well as structure and stability of their complexes with lanthanides and actinides were studied. The extraction tests were performed for Am, lanthanide series and transition metals in polar diluents in presence of chlorinated cobalt dicarbolide and have shown high distribution coefficients for Am. Also was found that the type of substituents on amidic nitrogen exerts great influence on the extraction of light lanthanides. For understanding of the nature of this effect we made QC-calculations at DFT level, binding constants determination and X-Ray structure determination of the complexes. The UV/VIS titration performed show that the composition of all complexes of the amides with lanthanides in solution is 1:1. In spite of the binding constants are high (lgβ about 6-7 in acetonitrile solution), lanthanide ions have binding constants with the same order of magnitude for dialkyl substituted extractants. The X-Ray structures of the complexes of bipyridyl-based amides show the composition of 1:1 and the coordination number of the ions being 10. The DFT optimized structures of the compounds are in good agreement with that obtained by X-Ray. The gas phase affinity of the amides to lanthanides shows strong correlation with the distribution ratios. We can infer that the bipyridyl-based amides form complexes with metal nitrates which have similar structure in solid and gas phases and in solution, and the DFT

  10. Ferromagnetism and half metallicity induced by oxygen vacancies in the double perovskite BaSrNiWO{sub 6}: DFT study

    Energy Technology Data Exchange (ETDEWEB)

    Aharbil, Y. [Laboratoire de Chimie Physique des Matériaux LCPM, Faculté des Sciences Ben M' Sik, Casablanca (Morocco); Labrim, H. [Unité Science de la Matière/DERS/Centre National de l’Energie, des Sciences et des Techniques Nucléaires (CNESTEN), Rabat (Morocco); Benmokhtar, S.; Haddouch, M. Ait [Laboratoire de Chimie Physique des Matériaux LCPM, Faculté des Sciences Ben M' Sik, Casablanca (Morocco); Bahmad, L., E-mail: bahmad@fsr.ac.ma [Mohammed V University in Rabat, Laboratoire de Magnétisme et Physique des Hautes Energies L.M.P.H.E. URAC-12, B.P. 1014, Rabat (Morocco); Belhaj, A. [LIRST, Département de Physique, Faculté Poly-disciplinaire, Université Sultan Moulay Slimane, Béni Mellal (Morocco); Ez-Zahraouy, H.; Benyoussef, A. [Mohammed V University in Rabat, Laboratoire de Magnétisme et Physique des Hautes Energies L.M.P.H.E. URAC-12, B.P. 1014, Rabat (Morocco)

    2016-11-01

    Using the spin polarized density functional theory (DFT) and exploring the Plane-Wave Self-Consistent Field (PWscf) code implemented in Quantum-ESPRESSO package, we investigate the effect of the Oxygen vacancies (V{sub O}) and the Oxygen interstitial (O{sub i}) on the double perovskite BaSrNiWO{sub 6}. This deals with the magnetic ordering and the electronic structure in such a pure sample exhibiting the insulating anti-ferromagnetic (AFM) state. This study shows that the presence of oxygen deficient defects converts the insulating to half metal with ferromagnetic or anti-ferromagnetic states. The magnetic ordering in BaSrNiWO{sub 6−δ} depends on the position of the Oxygen vacancy in the unit cell. However, it has been shown that the Oxygen interstitial preserves the anti-ferromagnetic propriety. We have computed the formation energies of different positions of the Oxygen vacancy (V{sub O}) and the Oxygen interstitial (O{sub i}) in the BaSrNiWO{sub 6} compound. We showed that the formation of V{sub O} is easier and vice versa for the O{sub i} formation. The obtained results reveal(V{sub O}) and the Oxygen interstitial (O{sub i}) that the anti-ferromagnetic can be converted to ferromagnetic in the double perovskite BaSrNiWO{sub 6} induced by Oxygen vacancies V{sub O}. - Highlights: • We have studied the ferromagnetism and Half Metallicity in Double Perovskite BaSrNiWO{sub 6}. • We have applied the Ab-inito calculations using the DFT approach. • We showed the effects induced by Oxygen Vacancies and Oxygen interstitial. • We found that the magnetic ordering in BaSrNiWO{sub 6−δ} depends on the position of the Oxygen vacancy in the unit cell.

  11. Spectroscopic and TD-DFT studies on the dual mode fluorescent chemosensors based on pyrene thiosemicarbazones, and its application as molecular-scale logic devices

    Energy Technology Data Exchange (ETDEWEB)

    Basheer, Sabeel M. [Department of Chemistry, National Institute of Technology, Tiruchirappalli 620 015 (India); Willis, Anthony C. [Research School of Chemistry, The Australian National University, Canberra, ACT 2601 (Australia); Sreekanth, Anandaram, E-mail: sreekanth@nitt.edu [Department of Chemistry, National Institute of Technology, Tiruchirappalli 620 015 (India)

    2017-03-15

    Two newly synthesised pyrene based molecules are hereby reported as molecular switches. The absorption and emission response for receptors with and without F{sup −}, CN{sup −} and Cu{sup 2+} ions can mimic multiple logic gate such as AND, NOR, XNOR, OR, XOR, INHIBITION and TRANSFER gates. The fluorescence reversibility was checked with the alternative addition of fluoride and calcium ions, which can be explained by the “Read-Erase-Read-Write” logic loop. The calculated binding constant value show PyBTSC is better chemosensor than PyCTSC, and the binding affinity is in the order of Cu{sup 2+}Г‹Ж’F{sup -}Г‹Ж’CN{sup −.} The detailed mechanism was investigated using DFT and TD-DFT calculations. The fluorescence quenching behaviour of receptor-F complex can be explained by PET mechanism along with ESPT process. The proton attached to the nitrogen which is adjacent to pyrene moiety is first make the hydrogen bond with fluoride ion at the excited state, which has confirmed by natural bond orbital (NBO) and potential energy surface (PES) analysis. - Graphical abstract: The newly synthesised thiocarbazone derivates used as an effective and selective colourimetric and “turn on” fluorescence sensor for copper ion and ‘turn off’ for fluoride and cyanide anion. The presence and absence of ions were considered as input signals and the corresponding absorption and emission responses were consired as output. The proton transfer from the nitrogen adjacent to pyrene moiety, and which takes place at the excited state (ESPT).

  12. Low-temperature binding of NO adsorbed on MIL-100(Al)-A case study for the application of high resolution pulsed EPR methods and DFT calculations.

    Science.gov (United States)

    Mendt, Matthias; Barth, Benjamin; Hartmann, Martin; Pöppl, Andreas

    2017-12-14

    The low-temperature binding of nitric oxide (NO) in the metal-organic framework MIL-100(Al) has been investigated by pulsed electron nuclear double resonance and hyperfine sublevel correlation spectroscopy. Three NO adsorption species have been identified. Among them, one species has been verified experimentally to bind directly to an 27 Al atom and all its relevant 14 N and 27 Al hyperfine interaction parameters have been determined spectroscopically. Those parameters fit well to the calculated ones of a theoretical cluster model, which was derived by density functional theory (DFT) in the present work and describes the low temperature binding of NO to the regular coordinatively unsaturated Al 3+ site of the MIL-100(Al) structure. As a result, the Lewis acidity of that site has been characterized using the NO molecule as an electron paramagnetic resonance active probe. The DFT derived wave function analysis revealed a bent end-on coordination of the NO molecule adsorbed at that site which is almost purely ionic and has a weak binding energy. The calculated flat potential energy surface of this species indicates the ability of the NO molecule to freely rotate at intermediate temperatures while it is still binding to the Al 3+ site. For the other two NO adsorption species, no structural models could be derived, but one of them is indicated to be adsorbed at the organic part of the metal-organic framework. Hyperfine interactions with protons, weakly coupled to the observed NO adsorption species, have also been measured by pulsed electron paramagnetic resonance and found to be consistent with their attribution to protons of the MIL-100(Al) benzenetricarboxylate ligand molecules.

  13. Synthesis, spectroscopic studies, DFT calculations, electrochemical evaluation, BSA binding and molecular docking of an aroylhydrazone -based cis-dioxido Mo(VI) complex

    Science.gov (United States)

    Mohamadi, Maryam; Faghih-Mirzaei, Ehsan; Ebrahimipour, S. Yousef; Sheikhshoaie, Iran; Haase, Wolfgang; Foro, Sabine

    2017-07-01

    A cis-dioxido Mo(VI) complex, [MoO2(L)(MeOH)], [L2-: (3-methoxy-2-oxidobenzylidene) benzohydrazonate], has been synthesized and characterized using physicochemical and spectroscopic techniques including elemental analysis, FT-IR, 1HNMR, UV-Vis spectroscopy, molar conductivity and single crystal X-ray diffraction. DFT calculations in the ground state of the complex were carried out using hybrid functional B3LYP with DGDZVP as basis set. Non-linear optical properties including electric dipole moment (μ), polarizability (α) and molecular first hyperpolarizability (β) of the compound were also computed. The values of linear polarizability and first hyperpolarizability obtained for the studied molecule indicated that the compound could be a good candidate of nonlinear optical materials. TD-DFT calculation and molecular electrostatic potential (MEP) were also performed. The thermodynamic properties (heat capacity, entropy, and enthalpy) of the complex at different temperatures have been calculated. The interaction of a synthesized complex, with bovine serum albumin was also thoroughly investigated using experimental and theoretical studies. UV-Vis absorption and fluorescence quenching techniques were used to determine the binding parameters as well as the mechanism of the interaction. The values of binding constants were in the range of 104-105 M-1 demonstrating a moderate interaction between the synthesized complex and BSA making the protein suitable for transportation and delivery of the compound. Thermodynamic parameters were also indicating a binding through van der Waals force or hydrogen bond of [MoO2(L)(MeOH)] to BSA. The results obtained from docking studies were consistent to those obtained from experimental studies.

  14. Theoretical analysis of the binding of iron(III) protoporphyrin IX to 4-methoxyacetophenone thiosemicarbazone via DFT-D3, MEP, QTAIM, NCI, ELF, and LOL studies.

    Science.gov (United States)

    Nkungli, Nyiang Kennet; Ghogomu, Julius Numbonui

    2017-07-01

    Thiosemicarbazones display diverse pharmacological properties, including antimalarial activities. Their pharmacological activities have been studied in depth, but little of this research has focused on their antimalarial mode of action. To elucidate this antimalarial mechanism, we investigated the nature of the interactions between iron(III) protoporphyrin IX (Fe(III)PPIX) and the thione-thiol tautomers of 4-methoxyacetophenone thiosemicarbazone (MAPTSC). Dispersion-corrected density functional theory (DFT-D3), the quantum theory of atoms in molecules (QTAIM), the noncovalent interaction (NCI) index, the electron localization function (ELF), the localized orbital locator (LOL), and thermodynamic calculations were employed in this work. Fe(III)PPIX-MAPTSC binding is expected to inhibit hemozoin formation, thereby preventing Fe(III)PPIX detoxification in plasmodia. Preliminary studies geared toward the identification of atomic binding sites in the thione-thiol tautomers of MAPTSC were carried out using molecular electrostatic potential (MEP) maps and conceptual DFT-based local reactivity indices. The thionic sulfur and the 2 N-azomethine nitrogen/thiol sulfur of, respectively, the thione and thiol tautomers of MAPTSC were identified as the most favorable nucleophilic sites for electrophilic attack. The negative values of the computed Fe(III)PPIX-MAPTSC binding energies, enthalpies, and Gibbs free energies are indicative of the existence and stability of Fe(III)PPIX-MAPTSC complexes. MAPTSC-Fe(III) coordinate bonds and strong hydrogen bonds (N-H···O) between the NH 2 group in MAPTSC and the C=O group in one propionate side chain of Fe(III)PPIX are crucial to Fe(III)PPIX-MAPTSC binding. QTAIM, NCI, ELF, and LOL analyses revealed a subtle interplay of weak noncovalent interactions dominated by dispersive-like van der Waals interactions between Fe(III)PPIX and MAPTSC that stabilize the Fe(III)PPIX-MAPTSC complexes.

  15. Low-temperature binding of NO adsorbed on MIL-100(Al)—A case study for the application of high resolution pulsed EPR methods and DFT calculations

    Science.gov (United States)

    Mendt, Matthias; Barth, Benjamin; Hartmann, Martin; Pöppl, Andreas

    2017-12-01

    The low-temperature binding of nitric oxide (NO) in the metal-organic framework MIL-100(Al) has been investigated by pulsed electron nuclear double resonance and hyperfine sublevel correlation spectroscopy. Three NO adsorption species have been identified. Among them, one species has been verified experimentally to bind directly to an 27Al atom and all its relevant 14N and 27Al hyperfine interaction parameters have been determined spectroscopically. Those parameters fit well to the calculated ones of a theoretical cluster model, which was derived by density functional theory (DFT) in the present work and describes the low temperature binding of NO to the regular coordinatively unsaturated Al3+ site of the MIL-100(Al) structure. As a result, the Lewis acidity of that site has been characterized using the NO molecule as an electron paramagnetic resonance active probe. The DFT derived wave function analysis revealed a bent end-on coordination of the NO molecule adsorbed at that site which is almost purely ionic and has a weak binding energy. The calculated flat potential energy surface of this species indicates the ability of the NO molecule to freely rotate at intermediate temperatures while it is still binding to the Al3+ site. For the other two NO adsorption species, no structural models could be derived, but one of them is indicated to be adsorbed at the organic part of the metal-organic framework. Hyperfine interactions with protons, weakly coupled to the observed NO adsorption species, have also been measured by pulsed electron paramagnetic resonance and found to be consistent with their attribution to protons of the MIL-100(Al) benzenetricarboxylate ligand molecules.

  16. A DFT+U investigation of hydrogen adsorption on the LaFeO3(010) surface

    NARCIS (Netherlands)

    Boateng, Isaac W.; Tia, Richard; Adei, Evans; Dzade, N.Y.; Catlow, C. Richard A.; de Leeuw, Nora H.

    2017-01-01

    The ABO3 perovskite lanthanum ferrite (LaFeO3) is a technologically important electrode material for nickel–metal hydride batteries, energy storage and catalysis. However, the electrochemical hydrogen adsorption mechanism on LaFeO3 surfaces remains under debate. In the present study, we have

  17. TD-DFT Investigation of the Magnetic Circular Dichroism Spectra of Some Purine and Pyrimidine Bases of Nucleic Acids

    DEFF Research Database (Denmark)

    Fahleson, Tobias; Kauczor, Joanna; Norman, Patrick

    2015-01-01

    We present a computational study of the magnetic circular dichroism (MCD) spectra in the 200–300 nm wavelength region of purine and its derivative hypoxanthine, as well as of the pyrimidine bases of nucleic acids uracil, thymine, and cytosine, using the B3LYP and CAM–B3LYP functionals. Solvent...

  18. Investigation on the structural stability and electronic properties of InSb nanostructures – A DFT approach

    Directory of Open Access Journals (Sweden)

    V. Nagarajan

    2014-06-01

    Full Text Available The realistic InSb nanostructures namely InSb nanoring, InSb nanocube, InSb nanocube-18, InSb nanosheet, InSb nanocage and InSb nanocube-27 are simulated and optimized successfully using B3LYP/LanL2DZ basis set. The stability of InSb nanostructures is studied in terms of binding energy, vibrational studies and calculated energy. The electronic properties of InSb nanostructures are discussed using ionization potential, electron affinity and HOMO–LUMO gap. Point symmetry and dipole moment of InSb nanostructures are reported. Incorporation of impurity atom in InSb nanostructures is studied using embedding energy. The present study provides the information regarding the enhanced electronic properties of InSb nanostructure which finds its potential importance in microelectronics and optoelectronic devices.

  19. Theoretical investigations of two adamantane derivatives: A combined X-ray, DFT, QTAIM analysis and molecular docking

    Science.gov (United States)

    Al-Wahaibi, Lamya H.; Sujay, Subramaniam; Muthu, Gangadharan Ganesh; El-Emam, Ali A.; Venkataramanan, Natarajan S.; Al-Omary, Fatmah A. M.; Ghabbour, Hazem A.; Percino, Judith; Thamotharan, Subbiah

    2018-05-01

    A detailed structural analysis of two adamantane derivatives namely, ethyl 2-[(Z)-1-(adamantan-1-yl)-3-(phenyl)isothioureido]acetate I and ethyl 2-[(Z)-1-(adamantan-1-yl)-3-(4-fluorophenyl)isothioureido]acetate II is carried out to understand the effect of fluorine substitution. The introduction of fluorine atom alters the crystal packing and is completely different from its parent compound. The fluorine substitution drastically reduced the intermolecular H⋯H contacts and this reduction is compensated by intermolecular F⋯H and F⋯F contacts. The relative contributions of various intermolecular contacts present in these structures were quantified using Hirshfeld surface analysis. Energetically significant molecular pairs were identified from the crystal structures of these compounds using PIXEL method. The structures of I and II are optimized in gas and solvent phases using the B3LYP-D3/6-311++G(d,p) level of theory. The quantum theory of atoms-in-molecules (QTAIM) analysis was carried out to estimate the strengths of various intermolecular contacts present in these molecular dimers. The results suggest that the Hsbnd H bonding take part in the stabilization of crystal structures. The experimental and theoretical UV-Vis results show the variations in HOMO and LUMO energy levels. In silico docking analysis indicates that both compounds I and II may exhibit inhibitory activity against 11-β-hydroxysteroid dehydrogenase 1 (11-β-HSD1).

  20. Molecular properties of metal difluorides and their interactions with CO2 and H2O molecules: a DFT investigation.

    Science.gov (United States)

    Arokiyanathan, Agnes Lincy; Lakshmipathi, Senthilkumar

    2017-11-18

    A computational study of metal difluorides (MF 2 ; M = Ca to Zn) and their interactions with carbon dioxide and water molecules was performed. The structural parameter values obtained and the results of AIM analysis and energy decomposition analysis indicated that the Ca-F bond is weaker and less ionic than the bonds in the transition metal difluorides. A deformation density plot revealed the stablizing influence of the Jahn-Teller effect in nonlinear MF 2 molecules (e.g., where M= Sc, Ti, Cr). An anaysis of the metal K-edge peaks of the difluorides showed that shifts in the edge energy were due to the combined effects of the ionicity, effective nuclear charge, and the spin state of the metal. The interactions of CO 2 with ScF 2 (Scc3 geometry) and TiF 2 (Tic2 geometry) caused CO 2 to shift from its usual linear geometry to a bent geometry (η 2 (C=O) binding mode), while it retained its linear geometry (η 1 (O) binding mode) when it interacted with the other metal difluorides. Energy decomposition analysis showed that, among the various geometries considered, the Scc3 and Tic2 geometries possessed the highest interaction energies and orbital interaction energies. Heavier transition metal difluorides showed stronger affinities for H 2 O, whereas the lighter transition metal (Sc and Ti) difluorides preferred CO 2 . Overall, the results of this study suggest that fluorides of lighter transition metals with partially filled d orbitals (e.g., Sc and Ti) could be used for CO 2 capture under moist conditions. Graphical abstract Interaction of metal difluorides with carbon dioxide and water.

  1. Experimental and DFT study of the degradation of 4-chlorophenol on hierarchical micro-/nanostructured oxide films

    Czech Academy of Sciences Publication Activity Database

    Guerin, V. M.; Žouželka, Radek; Bíbová-Lipšová, Hana; Jirkovský, Jaromír; Rathouský, Jiří; Pauporté, T.

    2015-01-01

    Roč. 168, JUN 01 (2015), s. 132-140 ISSN 0926-3373 R&D Projects: GA MK(CZ) DF11P01OVV012 Keywords : 4-Chlorophenol degradation * DFT modeling * ZnO hierarchical nanostructures Subject RIV: CF - Physical ; Theoretical Chemistry Impact factor: 8.328, year: 2015

  2. Optimization of auxiliary basis sets for the LEDO expansion and a projection technique for LEDO-DFT.

    Science.gov (United States)

    Götz, Andreas W; Kollmar, Christian; Hess, Bernd A

    2005-09-01

    We present a systematic procedure for the optimization of the expansion basis for the limited expansion of diatomic overlap density functional theory (LEDO-DFT) and report on optimized auxiliary orbitals for the Ahlrichs split valence plus polarization basis set (SVP) for the elements H, Li--F, and Na--Cl. A new method to deal with near-linear dependences in the LEDO expansion basis is introduced, which greatly reduces the computational effort of LEDO-DFT calculations. Numerical results for a test set of small molecules demonstrate the accuracy of electronic energies, structural parameters, dipole moments, and harmonic frequencies. For larger molecular systems the numerical errors introduced by the LEDO approximation can lead to an uncontrollable behavior of the self-consistent field (SCF) process. A projection technique suggested by Löwdin is presented in the framework of LEDO-DFT, which guarantees for SCF convergence. Numerical results on some critical test molecules suggest the general applicability of the auxiliary orbitals presented in combination with this projection technique. Timing results indicate that LEDO-DFT is competitive with conventional density fitting methods. (c) 2005 Wiley Periodicals, Inc.

  3. Is HAM/3 (hydrogenic atoms in molecules, version 3 a semiempirical version of dft (density functional theory for ionization processes?

    Directory of Open Access Journals (Sweden)

    Takahata Yuji

    2004-01-01

    Full Text Available We calculated valence-electron vertical ionization potentials (VIPs of nine small molecules, plus uracil and C2F4, by several different methods: semiempirical HAM/3 and AM1 methods, different nonempirical DFT models such as uDI(B88-P86/cc-pVTZ and -epsilon(SAOP/TZP, and ab initio Hartree-Fock (HF /cc-pVTZ. HAM/3 reproduced numerical values more closely to those calculated by the nonempirical DFTs than to those obtained by HF method. Core-electron binding energies (CEBEs of aniline, nitrobenzene and p-nitro aniline, were also calculated by HAM/3 and nonempirical DFT using DE method. A nonempirical DFT model, designated as deltaE KS (PW86-PW91/TZP model, resulted accurate CEBEs (average absolute deviation of 0.14 eV with high efficiency. Although absolute magnitude of HAM/3 CEBEs has error as much as 3 eV, the error in the chemical shifts deltaCEBE is much smaller at 0.55 eV. While the CEBE results do not lead to any definite answer to the question in the title, the trends in valence-electron VIPs indicate that HAM/3 does not approximate DFT with accurate exchange-correlation potentials, but seems to simulate approximate functionals such as B88-P86.

  4. Combined FT-IR Spectroscopic and DFT Theoretical Study on Carbon Dioxide Adsorption on the Zeolite H-FER

    Czech Academy of Sciences Publication Activity Database

    Pulido, A.; Delgado, M. R.; Bludský, Ota; Rubeš, Miroslav; Nachtigall, Petr; Areán, C. O.

    2009-01-01

    Roč. 2, č. 11 (2009), s. 1187-1195 ISSN 1754-5692 R&D Projects: GA ČR GA203/09/0143; GA MŠk LC512 Institutional research plan: CEZ:AV0Z40550506 Keywords : DFT * FTIR Subject RIV: CF - Physical ; Theoretical Chemistry Impact factor: 8.500, year: 2009

  5. DFT study of the physicochemical characteristics and spectral behavior of new 8-substituted 1,3,7-trimethylxanthines

    Czech Academy of Sciences Publication Activity Database

    Stanchev, Stancho; Mitkov, J.; Georgieva, M.; Zlatkov, A.

    2013-01-01

    Roč. 113, č. 9 (2013), s. 1384-1393 ISSN 0020-7608 Institutional support: RVO:61388963 Keywords : caffeine derivates * quantum chemical properties * spectral properties * DFT methods Subject RIV: CF - Physical ; Theoretical Chemistry Impact factor: 1.166, year: 2013

  6. Successive heterolytic cleavages of H2 achieve N2 splitting on silica-supported tantalum hydrides: A DFT proposed mechanism

    KAUST Repository

    Solá ns, Xavier Luis; Chow, Catherine; Gouré , Eric; Kaya, Yasemin; Basset, Jean-Marie; Taoufik, Mostafa; Quadrelli, Elsje Alessandra; Eisenstein, Odile

    2012-01-01

    DFT(B3PW91) calculations have been carried out to propose a pathway for the N2 cleavage by H2 in the presence of silica-supported tantalum hydride complexes [(≡ SiO)2TaHx] that forms [(≡SiO)2Ta(NH)(NH2)] (Science2007, 317, 1056). The calculations

  7. Validation of molecular crystal structures from powder diffraction data with dispersion-corrected density functional theory (DFT-D)

    DEFF Research Database (Denmark)

    van de Streek, Jacco; Neumann, Marcus A

    2014-01-01

    In 2010 we energy-minimized 225 high-quality single-crystal (SX) structures with dispersion-corrected density functional theory (DFT-D) to establish a quantitative benchmark. For the current paper, 215 organic crystal structures determined from X-ray powder diffraction (XRPD) data and published...

  8. From Mahan excitons to Landau levels at high magnetic fields: 2DFT spectroscopy reveals hidden quantum correlations (Conference Presentation)

    Science.gov (United States)

    Karaiskaj, Denis

    2017-02-01

    Two-dimensional electron gases have been the subject of research for decades. Modulation doped GaAs quantum wells in the absence of magnetic fields exhibit interesting many-body physics such as the Fermi edge singularity or Mahan exciton and can be regarded as a collective excitation of the system. Under high magnetic fields Landau levels form which have been studied using transport and optical measurements. Nonlinear coherent two-dimensional Fourier transform (2DFT) spectroscopy however provides new insights into these systems. We present the 2DFT spectra of Mahan Excitons associated with the heavy-hole and light-hole resonances observed in a modulation doped GaAs/AlGaAs single quantum well [1]. These resonances are observed to be strongly coupled through many-body interactions. The 2DFT spectra were measured using co-linear, cross-linear, and co-circular polarizations and reveal striking differences. Furthermore, 2DFT spectra at high magnetic fields performed at the National High Magnetic Field Lab (NHMFL) in Tallahassee, Florida will be discussed. The spectra exhibit new features and peculiar line shapes suggesting interesting underlying physics. [1] J. Paul, C. E. Stevens, C. Liu, P. Dey, C. McIntyre, V. Turkowski, J. L. Reno, D. J. Hilton, and D. Karaiskaj, Phys. Rev. Lett.116, 157401 (2016).

  9. High-Pressure Behaviour of β-HMX Crystal Studied by DFT-LDA

    International Nuclear Information System (INIS)

    Dan, Lian; Lai-Yu, Lu; Dong-Qing, Wei; Qing-Ming, Zhang; Zi-Zheng, Gong; Yong-Xin, Guo

    2008-01-01

    Density functional theory (DFT) with local density approximation (LDA) is employed to study the structural and electronic properties of the high explosive octahydro-1,3,5,7-tetranitro-1,3,5,7-tetrazocine (HMX) under high pressure compression up to 40 GPa. Pressure dependences of the cell volume, lattice constants, and molecular geometry of solid β-HMX are presented and discussed. It is found that N-N and N-C bonds are subject to significant change. This may implies that these bonds may be related to the sensitivity. The band gap is calculated and plotted as a function of pressure. Compared the experimental results with other theoretical works we find that LDA gives good results

  10. Spectroscopic data of Labdane Diterpenes: a theoretical analysis via NMR and DFT

    International Nuclear Information System (INIS)

    Souza, Fabrine S. de; Silva, Silvana de O.; Alves, Cláudio N.; Guilhon, Giselle M.S.P.

    2015-01-01

    Labdane diterpenes exhibit important bioactivities such as cardiovascular effects in rats as well as effects in the treatment of autoimmune diseases and Alzheimer syndrome. Recently, the labdane diterpenes ent-13-epi-manoil oxide, ribenone and ribenol were isolated from Croton palanostigma. The computational method DFT/B3LYP/cc-pVDZ was used to optimize the structures of these diterpenes and to calculate infrared data. Chemical shifts (δ H and δ C ) of the minimum energy structures (local minimum) were calculated and compared with the experimental data. Comparison of the NMR data by simple linear regression (SLR) showed satisfactory statistical results with a correlation coefficient (R 2 ) and predictive ability (Q 2 ) of over 98%. The predicted NMR data were used to confirm the δ H values that have not been published. (author)

  11. DFT LCAO and plane wave calculations of SrZrO3

    International Nuclear Information System (INIS)

    Evarestov, R.A.; Bandura, A.V.; Alexandrov, V.E.; Kotomin, E.A.

    2005-01-01

    The results of the density functional (DFT) LCAO and plane wave (PW) calculations of the electronic and structural properties of four known SrZrO 3 phases (Pm3m, I4/mcm, Cmcm and Pbnm) are presented and discussed. The calculated unit cell energies and relative stability of these phases agree well with the experimental sequence of SrZrO 3 phases as the temperature increases. The lattice structure parameters optimized in the PW calculations for all four phases are in good agreement with the experimental neutron diffraction data. The LCAO and PW results for the electronic structure, density of states and chemical bonding in the cubic phase (Pm3m) are discussed in detail and compared with the results of previous PW calculations. (copyright 2005 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)

  12. DFT LCAO and plane wave calculations of SrZrO{sub 3}

    Energy Technology Data Exchange (ETDEWEB)

    Evarestov, R.A.; Bandura, A.V.; Alexandrov, V.E. [Department of Quantum Chemistry, St. Petersburg State University, 26 Universitetskiy Prospekt, Stary Peterhof 198504 (Russian Federation); Kotomin, E.A. [Max-Planck-Institut fuer Festkoerperforschung, Heisenbergstr. 1, 70569, Stuttgart (Germany)

    2005-02-01

    The results of the density functional (DFT) LCAO and plane wave (PW) calculations of the electronic and structural properties of four known SrZrO{sub 3} phases (Pm3m, I4/mcm, Cmcm and Pbnm) are presented and discussed. The calculated unit cell energies and relative stability of these phases agree well with the experimental sequence of SrZrO{sub 3} phases as the temperature increases. The lattice structure parameters optimized in the PW calculations for all four phases are in good agreement with the experimental neutron diffraction data. The LCAO and PW results for the electronic structure, density of states and chemical bonding in the cubic phase (Pm3m) are discussed in detail and compared with the results of previous PW calculations. (copyright 2005 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)

  13. Complexes of uranyl nitrate with 2,6-pyridinedicarboxamides: synthesis, crystal structure, and DFT study

    Energy Technology Data Exchange (ETDEWEB)

    Alyapyshev, Mikhail; Babain, Vasiliy [ITMO University, 49, Kronverksky pr., 197101, St. Petersburg (Russian Federation); ThreeArc Mining Ltd., 5, Stary Tolmachevskiy per., 115184, Moscow (Russian Federation); Tkachenko, Lyudmila; Lumpov, Alexander [Khlopin Radium Institute, 28, 2nd Murinskiy pr., 194021, St. Petersburg (Russian Federation); Gurzhiy, Vladislav; Zolotarev, Andrey; Dar' in, Dmitriy [St. Petersburg State University, 7-9, Universitetskaya nab., 199034, St. Petersburg (Russian Federation); Ustynyuk, Yuriy; Gloriozov, Igor [M.V. Lomonosov Moscow State University, 119991, Moscow (Russian Federation); Paulenova, Alena [Department of Nuclear Engineering, Oregon State University, Corvallis, OR (United States)

    2017-05-04

    Two complexes of uranyl nitrate with N,N,N',N'-tetrabutyl-2,6-pyridinedicarboxamide (TBuDPA) and N,N'-diethyl-N,N'-diphenyl-2,6-pyridinedicarboxamide (EtPhDPA) were synthesized and studied. The complex of tetraalkyl-2,6-pyridinedicarboxamide with metal nitrate was synthesized for the first time. XRD analysis revealed the different type of complexation: a 1:1 metal:ligand complex for EtPhDPA and complex with polymeric structure for TBuDPA. The quantum chemical calculations (DFT) confirm that both ligands form the most stable complexes that match the minimal values pre-organization energy of the ligands. (copyright 2017 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)

  14. N-propyl nitrate vibrational spectrum analysis using DFT B3LYP quantum-chemical method

    Science.gov (United States)

    Shaikhullina, R. M.; Hrapkovsky, G. M.; Shaikhullina, M. M.

    2018-05-01

    Calculation of a molecular structure, conformation and related vibrational spectra of the n- propyl nitrate C3H7NO3 was carried out by means of density functional theory (DFT) by employing the Gaussian 03 package. The molecular geometries were fully optimized by using the Becker's three-parameter hybrid exchange functional combined with the Lee–Yang–Parr correlation functional (B3LYP) and using the 6-31G(d) basis set. By scanning the dihedral angles around C-O and C-C bonds, five energetically most favorable conformers of n-propyl nitrate - TG, TT, GT, GG and G´G forms were found. Vibrational spectra of the most energetically favorable conformers were calculated. The comparative analysis of calculated and experimental spectra is carried out, the spectral features of the conformational state of n-propyl nitrate and the spectral effects of formation of intramolecular hydrogen bonds are established.

  15. Computational prediction of the pKas of small peptides through Conceptual DFT descriptors

    Science.gov (United States)

    Frau, Juan; Hernández-Haro, Noemí; Glossman-Mitnik, Daniel

    2017-03-01

    The experimental pKa of a group of simple amines have been plotted against several Conceptual DFT descriptors calculated by means of different density functionals, basis sets and solvation schemes. It was found that the best fits are those that relate the pKa of the amines with the global hardness η through the MN12SX density functional in connection with the Def2TZVP basis set and the SMD solvation model, using water as a solvent. The parameterized equation resulting from the linear regression analysis has then been used for the prediction of the pKa of small peptides of interest in the study of diabetes and Alzheimer disease. The accuracy of the results is relatively good, with a MAD of 0.36 units of pKa.

  16. Polar Diels-Alder reactions using electrophilic nitrobenzothiophenes. A combined experimental and DFT study

    Science.gov (United States)

    Della Rosa, Claudia D.; Mancini, Pedro M. E.; Kneeteman, Maria N.; Lopez Baena, Anna F.; Suligoy, Melisa A.; Domingo, Luis R.

    2015-01-01

    The reactions between 2- and 3-nitrobenzothiophenes with three dienes of different nucleophilicity, 1-methoxy-3-trimethylsilyloxy-1,3-butadiene, 1-trimethylsilyloxy-1,3-butadiene and isoprene developed in anhydrous benzene and alternative under microwave irradiation with molecular solvents or in free solvent conditions, respectively, for produce dibenzothiophenes permit to conclude that both nitroheterocycles act as electrophile with the cited dienes. In the cases of the dienes 1-methoxy-3-trimethylsilyloxy-1,3-butadiene and 1-trimethylsilyloxy-1,3-butadiene which posses major nucleophilicity the observed product is the normal cycloaddition one. However when the diene is isoprene the product with both electrophiles follow the hetero Diels-Alder way. These reactions are considered polar cycloaddition reactions and the yields are reasonables. Moreover the polar Diels-Alder reactions of nitrobenzothiophenes with electron rich dienes 1-trimethylsilyloxy-1,3-butadiene have been theoretically studied using DFT methods.

  17. Structural and vibrational properties of oxcarbazepine, an anticonvulsant substance by using DFT and SCRF calculations

    Science.gov (United States)

    Ladetto, María F.; Márquez, María B.; Brandán, Silvia A.

    2014-10-01

    In this work, we have presented a structural and vibrational study on the properties in gas and aqueous solution phases of oxcarbazepine, a polymorphic anticonvulsant substance, combining the available IR and Raman spectra with Density Functional Theory (DFT) calculations. Two stable C1 and C2 forms for the title molecule were theoretically determined by using the hybrid B3LYP/6-31G* method. The integral equation formalism variant polarised continuum model (IEFPCM) was employed to study the solvent effects by means of the self-consistent reaction field (SCRF) method. The vibrational spectra for the two forms of oxcarbazepine were completely assigned together with two dimeric species also observed in the solid phase. The presences of the two C1 and C2 forms together with the two dimeric species are supported by the IR and Raman bands between 1424 and 125 cm-1. Here, the properties for both forms of oxcarbazepine are compared and discussed.

  18. Vibrational spectroscopic and non-linear optical activity studies on nicotinanilide : A DFT approach

    Science.gov (United States)

    Premkumar, S.; Jawahar, A.; Mathavan, T.; Dhas, M. Kumara; Benial, A. Milton Franklin

    2015-06-01

    The molecular structure of nicotinanilide was optimized by the DFT/B3LYP method with cc-pVTZ basis set using Gaussian 09 program. The first order hyperpolarizability of the molecule was calculated, which exhibits the higher nonlinear optical activity. The natural bond orbital analysis confirms the presence of intramolecular charge transfer and the hydrogen bonding interaction, which leads to the higher nonlinear optical activity of the molecule. The Frontier molecular orbitals analysis of the molecule shows that the delocalization of electron density occurs within the molecule. The lower energy gap indicates that the hydrogen bond formation between the charged species. The vibrational frequencies were calculated and assigned on the basis of potential energy distribution calculation using the VEDA 4.0 program and the corresponding vibrational spectra were simulated. Hence, the nicotinanilide molecule can be a good candidate for second-order NLO material.

  19. Conformational, vibrational spectroscopic and quantum chemical studies on 5-methoxyindole-3-carboxaldehyde: A DFT approach

    Science.gov (United States)

    Jeyaseelan, S. Christopher; Hussain, Shamima; Premkumar, R.; Rekha, T. N.; Benial, A. Milton Franklin

    2018-04-01

    Indole and its derivatives are considered as good ligands for various disease causing proteins in human because of presence of the single nitrogen atom. In the present study, the potential energy surface scan was performed for the most stable molecular structure of the 5-Methoxyindole-3-carboxaldehyde (MICA) molecule. The most stable molecular structure was optimized by DFT/B3LYP method with 6-311G++ (d, p) basis set using Gaussian 09 program package. The vibrational frequencies were calculated and assigned on the basis of potential energy distribution calculations using VEDA 4.0 program. The Frontier molecular orbitals analysis was performed and related molecular propertieswere calculated. The possible electrophilic and nucleophilic reactive sites of the molecule were studied using molecular electrostatic potential analysis, which confirms the bioactivity of the molecule. The natural bond orbital analysis was also performed to confirm the bioactivity of the title molecule.

  20. Synthesis, Crystal Structure, and DFT Calculations of 1,3-Diisobutyl Thiourea

    Directory of Open Access Journals (Sweden)

    Ataf A. Altaf

    2015-01-01

    Full Text Available 1,3-Diisobutyl thiourea was synthesized and characterized by single crystal X-ray diffraction. It gives a monoclinic (α = γ = 90 and β  ≠ 90 structure with the space group P21/c. The unit cell dimensions are a = 11.5131 (4 Å, b = 9.2355 (3 Å, c = 11.3093 (5 Å, α = 90°, β = 99.569° (2, γ = 90°, V = 1185.78 (8 Å3, and Z = 4. The crystal packing is stabilized by intermolecular (N–H⋯S hydrogen bonding in the molecules. The optimized geometry and Mullikan's charges of the said molecule calculated with the help of DFT using B3LYP-6-311G model support the crystal structure.