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Sample records for bond dissociation energies

  1. Accurate bond dissociation energies (D 0) for FHF- isotopologues

    Science.gov (United States)

    Stein, Christopher; Oswald, Rainer; Sebald, Peter; Botschwina, Peter; Stoll, Hermann; Peterson, Kirk A.

    2013-09-01

    Accurate bond dissociation energies (D 0) are determined for three isotopologues of the bifluoride ion (FHF-). While the zero-point vibrational contributions are taken from our previous work (P. Sebald, A. Bargholz, R. Oswald, C. Stein, P. Botschwina, J. Phys. Chem. A, DOI: 10.1021/jp3123677), the equilibrium dissociation energy (D e ) of the reaction ? was obtained by a composite method including frozen-core (fc) CCSD(T) calculations with basis sets up to cardinal number n = 7 followed by extrapolation to the complete basis set limit. Smaller terms beyond fc-CCSD(T) cancel each other almost completely. The D 0 values of FHF-, FDF-, and FTF- are predicted to be 15,176, 15,191, and 15,198 cm-1, respectively, with an uncertainty of ca. 15 cm-1.

  2. Bond dissociation & electronegativity equalization

    OpenAIRE

    Verstraelen, Toon; Ayers, Paul W.; Van Speybroeck, Veronique; Waroquier, Michel

    2012-01-01

    It is well known that the Electrongativity Equalization Mtehod (EEM) fails to describe the charge distribution upon bond dissocation. In this presentation, the bond dissocation is studied with the Atom-Condensed Kohn-Sham DFT approximated to second order (ACKS2). After reviewing the basic equations, a two-fragment system is studied in the dissociation limit. The limiting behavior of the Coulomb interaction (1/r) and the Kohn-Sham matrix elements (exponentially decaying) are plugged into the e...

  3. Predicting the activation energy of catalytic dissociation of the heteroatomic AB bond

    International Nuclear Information System (INIS)

    Two analytical formalisms, adiabatic and diabatic ones, were developed for the description of catalytic dissociation of heteroatomic bond AB interacting with a metal surface in the adsorption processes. In the adiabatic formalism, the transition state was localized on a four-dimensional potential energy surface in classical approximation. This approach generalizes the previous three-dimensional model for dissociative adsorption of homonuclear molecules X2 on metals surfaces, and it was used for studying the effect of non-parallel orientation to a surface of O2 molecules in the adsorption precursor state. The second formalism takes into account a possible quantum character of vibrations along the chemical bond AB. The calculation of the activation energy in this approach is performed by the density matrix method. This approach is applied for studying catalytic dissociation of CO molecule on a Ni(1 1 1) surface. The calculated apparent activation energy for this reaction is compared with published data for this system

  4. Collision-induced dissociation of Co+n (n=2--18) with Xe: Bond energies of cationic and neutral cobalt clusters, dissociation pathways, and structures

    International Nuclear Information System (INIS)

    The kinetic energy dependence of collision-induced dissociation (CID) of Co+n (n=2--18) with xenon is studied by using a guided ion beam mass spectrometer. Examination of the general dissociation behavior over a broad collision energy range shows that cobalt cluster cations dissociate exclusively by loss of single atoms (cluster ''evaporation''), with no evidence found for elimination of molecular cluster fragments. Bond dissociation energies for cobalt cluster cations, Co+n (n=2--18), are determined from measurements of the CID thresholds. Bond energies for neutral cobalt clusters, Con (n=4--18), are derived by combining these cationic bond energies with ionization energies for Con from the literature. The dependence of binding energy on cluster size is similar to that observed for iron clusters, and inspires some speculation regarding cluster ion structures

  5. Computation of Bond Dissociation Energies for Removal of Nitrogen Dioxide Groups in Certain Aliphatic Nitro Compounds

    Institute of Scientific and Technical Information of China (English)

    SHAO Ju-Xiang; CHENG Xin-Lu; YANG Xiang-Dong; XIANG Shi-Kai

    2006-01-01

    @@ Bond dissociation energies for removal of nitrogen dioxide groups in 10 aliphatic nitro compounds, including nitromethane, nitroethylene, nitroethane, dinitromethane, 1-nitropropane, 2-nitropropane, 1-nitrobutane,2-methyl-2-nitropropane, nitropentane, and nitrohexane, are calculated using the highly accurate complete basis set (CBS-Q) and the three hybrid density functional theory (DFT) methods B3LYP, B3PW91 and B3P86 with 6-31G** basis set.

  6. Density Functional Calculations of C-NO2 Bond Dissociation Energies for Nitroalkanes Molecules

    Institute of Scientific and Technical Information of China (English)

    2007-01-01

    Bond dissociation energies for the removal of nitrogen dioxide group in some nitroalkane energetic materials have been calculated by using the three hybrid density functional theory (DFT) methods B3LYP, B3PW91 and B3P86 with 6-31g** and 6-311g** basis sets. The computed BDEs have been compared with the available experimental results. It is found that the B3P86 method with 6-31g** and 6-311g** basis sets can obtain satisfactory bond dissociation energies (BDEs), which are in extraordinary agreement with the experimental data. Considering the smaller mean absolute deviation and maximum difference, the reliable B3P86/6-311g** method was recommended to compute the BDEs for the removal of nitrogen dioxide group in the nitroalkane energetic materials. Using the method, the BDEs of 8 other nitroalkane energetic materials have been calculated and the maximum difference from experimental value is 1.76 kcal·mol-1 (for the BDE of tC4H9-NO2), which further proves the reliability of B3P86/6-311g** method. In addition, it is noted that the BDEs of C-NO2 bond change slightly for main chain nitroalkane compounds with the maximum difference of only 3.43 kcal mol-1.

  7. Prediction of the bond lengths, vibrational frequencies, and bond dissociation energy of octahedral seaborgium hexacarbonyl, Sg(CO)6

    International Nuclear Information System (INIS)

    The recent syntheses of several new elements (including the recent reports of elements 116 and 118), coupled with the controversy surrounding the naming of elements 104--109, have stimulated a great interest in the chemistry of the transactinide elements. This contribution addresses hypothetical hexacarbonyl complex of seaborgium (Sg, element 106), which is predicted to be a 6d-block transition element with six valence electrons, analogous to Cr, Mo, and W. The authors have previously predicted that, if it were to exist, Sg(CO)6 would exhibit metal-carbonyl bonding that is very similar to that in Cr(CO)6, Mo(CO)6, and W(CO)6, and quite unlike that of the unknown valence isoelectronic actinide complex U(CO)6. This finding is in accord with the scant experimental data available for Sg. The relativistic DV-Xα method used in the earlier paper facilitated the analysis of the molecular orbitals of Sg(CO)6, but did not allow for the calculation of total-energy properties, such as bond lengths and vibrational frequencies. Here the authors will use the superior methodology they have applied to other transactinide molecules to compare the bond lengths, vibrational frequencies, and CO dissociation energy of hypothetical Sg(CO)6 to those of Mo(CO)6 and W(CO)6

  8. Heterolytic and Homolytic N-NO Bond Dissociation Energies of N-Nitroso-benzenesulfonylmethylamines in Acetonitrile

    Institute of Scientific and Technical Information of China (English)

    HAO Wei-Fang; Tang Hui; ZHU Xiao-Qing; CHENG Jin-Pei

    2003-01-01

    @@ Great interests have been accumulated in recent years in the chemistry and biochemistry of nitric oxide (NO) since the remarkable discoveries of its key roles in a wide range of human physiological processes. To elucidate the mechanistic details of NO migration from its donor to its acceptor, it is necessary to determine the Y-NO bind energy that registers the thermodynamic driving force for NO release and capture. In this paper the heterolytic and homolytic N-NO bond dissociation energies [ i. e., △Hhet(N-NO) and △Hhomo(N-NO)] for ten N-nitroso-p-substituted-benzensulfonyl methylamines in acetonitrile are offered, which were obtained from titration calorimetry and thermodynamic cycles, respectively (Scheme 1).

  9. Quantum chemical calculations of bond dissociation energies for COOH scission and electronic structure in some acids

    Institute of Scientific and Technical Information of China (English)

    Zeng Hui; Zhao Jun; Xiao Xun

    2013-01-01

    Quantum chemical calculations are performed to investigate the equilibrium C-COOH bond distances and the bond dissociation energies (BDEs) for 15 acids.These compounds are studied by utilizing the hybrid density functional theory (DFT) (B3LYP,B3PW91,B3P86,PBE1PBE) and the complete basis set (CBS-Q) method in conjunction with the 6-31 lG** basis as DFT methods have been found to have low basis sets sensitivity for small and medium molecules in our previous work.Comparisons between the computational results and the experimental values reveal that CBS-Q method,which can produce reasonable BDEs for some systems in our previous work,seems unable to predict accurate BDEs here.However,the B3P86 calculated results accord very well with the experimental values,within an average absolute error of 2.3 kcal/mol.Thus,B3P86 method is suitable for computing the reliable BDEs of C-COOH bond for carboxylic acid compounds.In addition,the energy gaps between the highest occupied molecular orbital (HOMO) and the lowest unoccupied molecular orbital (LUMO) of studied compounds are estimated,based on which the relative thermal stabilities of the studied acids are also discussed.

  10. Quantum chemical calculations of bond dissociation energies for COOH scission and electronic structure in some acids

    International Nuclear Information System (INIS)

    Quantum chemical calculations are performed to investigate the equilibrium C—COOH bond distances and the bond dissociation energies (BDEs) for 15 acids. These compounds are studied by utilizing the hybrid density functional theory (DFT) (B3LYP, B3PW91, B3P86, PBE1PBE) and the complete basis set (CBS—Q) method in conjunction with the 6-311G** basis as DFT methods have been found to have low basis sets sensitivity for small and medium molecules in our previous work. Comparisons between the computational results and the experimental values reveal that CBS—Q method, which can produce reasonable BDEs for some systems in our previous work, seems unable to predict accurate BDEs here. However, the B3P86 calculated results accord very well with the experimental values, within an average absolute error of 2.3 kcal/mol. Thus, B3P86 method is suitable for computing the reliable BDEs of C—COOH bond for carboxylic acid compounds. In addition, the energy gaps between the highest occupied molecular orbital (HOMO) and the lowest unoccupied molecular orbital (LUMO) of studied compounds are estimated, based on which the relative thermal stabilities of the studied acids are also discussed. (atomic and molecular physics)

  11. C-H and N-H bond dissociation energies of small aromatic hydrocarbons

    Energy Technology Data Exchange (ETDEWEB)

    Barckholtz, C.; Barckholtz, T.A.; Hadad, C.M.

    1999-01-27

    A survey of computational methods was undertaken to calculate the homolytic bond dissociation energies (BDEs) of the C-H and N-H bonds in monocyclic aromatic molecules that are representative of the functionalities present in coal. These include six-membered rings (benzene, pyridine, pyridazine, pyrimidine, pyrazine) and five-membered rings (furan, thiophene, pyrrole, oxazole). By comparison of the calculated C-H BDEs with the available experimental values for these aromatic molecules, the B3LYP/6-31G(d) level of theory was selected to calculate the BDEs of polycyclic aromatic hydrocarbons (PAHs), including carbonaceous PAHs (naphthalene, anthracene, pyrene, coronene) and heteroatomic PAHs (benzofuran, benzothiophene, indole, benzoxazole, quinoline, isoquinoline, dibenzofuran, carbazole). The cleavage of a C-H or a N-H bond generates a {sigma} radical that is, in general, localized at the site from which the hydrogen atom was removed. However, delocalization of the unpaired electron results in {approximately} 7 kcal {center{underscore}dot} mol{sup {minus}1} stabilization of the radical with respect to the formation of phenyl when the C-H bond is adjacent to a nitrogen atom in the azabenzenes. Radicals from five-membered rings are {approximately} 6 kcal {center{underscore}dot} mol{sup {minus}1} less stable than those formed from six-membered rings due to both localization of the spin density and geometric factors. The location of the heteroatoms in the aromatic ring affects the C-H bond strengths more significantly than does the size of the aromatic network. Therefore, in general, the monocyclic aromatic molecules can be used to predict the C-H BDE of the large PAHs within 1 kcal {center{underscore}dot} mol{sup {minus}1}.

  12. Theoretical Study of the N-NO2 Bond Dissociation Energies for Energetic Materials with Density Functional Theory

    Institute of Scientific and Technical Information of China (English)

    LI Xiao-Hong; TANG Zheng-Xin; Abraham F.Jalbout; ZHANG Xian-Zhou; CHENG Xin-Lu

    2008-01-01

    The N-NO2 bond dissociation energies (BDEs) for 7 energetic materials were computed by means of accurate density functional theory (B3LYP, B3PW91 and B3P86) with 6-31G** and 6-311G** basis sets. By comparing the computed energies and experimental results, we find that the B3P86/6-311G** method can give good results of BDE, which has the mean absolute deviation of 1.30 kcal/mol. In addition, substituent effects were also taken into account. It is noted that the Hammett constants of substituent groups are related to the BDEs of the N-NO2 bond and the bond dissociation energies of the energetic materials studied decrease when increasing the number of NO2 group.

  13. The solvent and substituent effects on bond dissociation energies of NO-donor molecules containing the N-NO bond

    Indian Academy of Sciences (India)

    Li Xiao-Hong; Li Wei-Bin; Zhang Xian-Zhou

    2010-07-01

    Quantum chemical calculations are used to estimate the equilibrium N-NO bond dissociation energies (BDEs) for 15 NO-donor molecules in acetonitrile. These compounds are studied by employing the hybrid density functional theory (B3LYP, B3PW91, B3P86) methods together with 6-31G∗∗ basis set. The basis set superposition error (BSSE) and zero-point vibrational energy (ZPVE) are considered. The results are compared with the available experimental results. It is demonstrated that B3LYP/6-31G** is accurate to compute the reliable BDEs for the NO-donor molecules. The solvent effects on the N-NO BDEs are analysed and the result shows that the N-NO BDEs in a vacuum computed by B3P86/6-31G∗∗ method are the closest to the computed values in acetontrile and the average solvent effect is 0.78 kcal/mol. Subsequently, the substituent effects on the N-NO BDEs are further analysed and it is found that electron donating group stabilizes the radical and as a result BDE decreases; whereas electron withdrawing group stabilizes the ground state of the molecule and thus increases the BDE.

  14. The application of Guided Ion Beam Tandem Mass Spectrometer; Bond dissociation energies of bare and ligated copper group cluster anions

    International Nuclear Information System (INIS)

    Threshold energies, fragmentation patterns, and integral cross sections for the reactions of collision induced dissociations of bare and ligated copper group cluster anions are determined using a Guided Ion Beam Tandem Mass Spectrometer (GIB-MS). The bond breaking patterns for the copper cluster anions show dramatic even/odd tendencies, e.g., all copper group anions generate as the predominant reaction product, Carbon monoxide is weakly bound to copper group cluster anions. Cohesive energies of the bare copper and silver cluster anions are determined and exhibit a good correspondence with estimate cohesive energies by the model of Miedema.

  15. Negligible Isotopic Effect on Dissociation of Hydrogen Bonds.

    Science.gov (United States)

    Ge, Chuanqi; Shen, Yuneng; Deng, Gang-Hua; Tian, Yuhuan; Yu, Dongqi; Yang, Xueming; Yuan, Kaijun; Zheng, Junrong

    2016-03-31

    Isotopic effects on the formation and dissociation kinetics of hydrogen bonds are studied in real time with ultrafast chemical exchange spectroscopy. The dissociation time of hydrogen bond between phenol-OH and p-xylene (or mesitylene) is found to be identical to that between phenol-OD and p-xylene (or mesitylene) in the same solvents. The experimental results demonstrate that the isotope substitution (D for H) has negligible effects on the hydrogen bond kinetics. DFT calculations show that the isotope substitution does not significantly change the frequencies of vibrational modes that may be along the hydrogen bond formation and dissociation coordinate. The zero point energy differences of these modes between hydrogen bonds with OH and OD are too small to affect the activation energy of the hydrogen bond dissociation in a detectible way at room temperature. PMID:26967376

  16. Bond-specific dissociation following excitation energy transfer for distance constraint determination in the gas phase.

    Science.gov (United States)

    Hendricks, Nathan G; Lareau, Nichole M; Stow, Sarah M; McLean, John A; Julian, Ryan R

    2014-09-24

    Herein, we report chemistry that enables excitation energy transfer (EET) to be accurately measured via action spectroscopy on gaseous ions in an ion trap. It is demonstrated that EET between tryptophan or tyrosine and a disulfide bond leads to excited state, homolytic fragmentation of the disulfide bond. This phenomenon exhibits a tight distance dependence, which is consistent with Dexter exchange transfer. The extent of fragmentation of the disulfide bond can be used to determine the distance between the chromophore and disulfide bond. The chemistry is well suited for the examination of protein structure in the gas phase because native amino acids can serve as the donor/acceptor moieties. Furthermore, both tyrosine and tryptophan exhibit unique action spectra, meaning that the identity of the donating chromophore can be easily determined in addition to the distance between donor/acceptor. Application of the method to the Trpcage miniprotein reveals distance constraints that are consistent with a native-like fold for the +2 charge state in the gas phase. This structure is stabilized by several salt bridges, which have also been observed to be important previously in proteins that retain native-like structures in the gas phase. The ability of this method to measure specific distance constraints, potentially at numerous positions if combined with site-directed mutagenesis, significantly enhances our ability to examine protein structure in the gas phase. PMID:25174489

  17. S-OO bond dissociation energies and enthalpies of formation of the thiomethyl peroxyl radicals CH3S(O)nOO (n=0,1,2)

    International Nuclear Information System (INIS)

    Optimized geometries, S-OO bond dissociation energies and enthalpies of formation for a series of thiomethyl peroxyl radicals are investigated using high level ab initio and density functional theory methods. The results show that the S-OO bond dissociation energy is largest in the methylsulfonyl peroxyl radical, CH3S(O)2OO, which contains two sulfonic type oxygen atoms followed by the methylthiyl peroxyl radical, CH3SOO. The methylsulfinyl peroxyl radical, CH3S(O)OO, which contains only one sulfonic type oxygen shows the least stability with regard to dissociation to CH3S(O)+O2. This stabilization trend is nicely reflected in the variations of the S-OO bond distance which is found to be shortest in CH3S(O)2OO and longest in CH3S(O)OO

  18. Size-extensivity-corrected multireference configuration interaction schemes to accurately predict bond dissociation energies of oxygenated hydrocarbons.

    Science.gov (United States)

    Oyeyemi, Victor B; Krisiloff, David B; Keith, John A; Libisch, Florian; Pavone, Michele; Carter, Emily A

    2014-01-28

    Oxygenated hydrocarbons play important roles in combustion science as renewable fuels and additives, but many details about their combustion chemistry remain poorly understood. Although many methods exist for computing accurate electronic energies of molecules at equilibrium geometries, a consistent description of entire combustion reaction potential energy surfaces (PESs) requires multireference correlated wavefunction theories. Here we use bond dissociation energies (BDEs) as a foundational metric to benchmark methods based on multireference configuration interaction (MRCI) for several classes of oxygenated compounds (alcohols, aldehydes, carboxylic acids, and methyl esters). We compare results from multireference singles and doubles configuration interaction to those utilizing a posteriori and a priori size-extensivity corrections, benchmarked against experiment and coupled cluster theory. We demonstrate that size-extensivity corrections are necessary for chemically accurate BDE predictions even in relatively small molecules and furnish examples of unphysical BDE predictions resulting from using too-small orbital active spaces. We also outline the specific challenges in using MRCI methods for carbonyl-containing compounds. The resulting complete basis set extrapolated, size-extensivity-corrected MRCI scheme produces BDEs generally accurate to within 1 kcal/mol, laying the foundation for this scheme's use on larger molecules and for more complex regions of combustion PESs. PMID:25669533

  19. Substituent Effect on the C-NO2 and N-NO2 Bond Dissociation Energies of Nitroaromatic Molecules

    Institute of Scientific and Technical Information of China (English)

    FANG,Ming; LI,Zhe; FU,Yao

    2008-01-01

    Six density function theory methods (B3LYP,B3P86,MPWB1K1,MPWPW91,PBEPBE,TPSS1KCIS3) were used to calculate bond dissociation enthalpies of nitro compounds,where the B3P86 method was found to give the most accurate predictions.Using the B3P86 method meta-and para-substituted nitroaromatics were systematically studied for the first time.The remote substituent effects,Hammett relationships,and the origin of the substituent effects were discussed on the basis of the calculated results.Both meta-and para-substituted nitromethyl-benzenes showed significant substituent effects and a fair correlation against substituent constants (σ+p).The ground state effects were found to play the major role in determining the overall substituent effects.Meanwhile,nitroaminobenzenes showed irregular substituent effects and a poorer Hammett correlation,where both ground and radical state effects contributed to the overall substituent effects.

  20. Dissociation Energies of Diatomic Molecules

    Institute of Scientific and Technical Information of China (English)

    FAN Qun-Chao; SUN Wei-Guo

    2008-01-01

    Molecular dissociation energies of 10 electronic states of alkali molecules of KH, 7LID, 7LiH, 6LiH, NaK, NaLi and NaRb are studied using the highest three accurate vibrational energies of each electronic state, and an improved parameter-free analytical formula which is obtained starting from the LeRoy-Bernstein vibrational energy expression near the dissociation limit. The results show that as long as the highest three vibrational energies are accurate, the current analytical formula will give accurate theoretical dissociation energies Detheory, which are in excellent agreement with the experimental dissociation energies Dexpte.

  1. Excitation energies with linear response density matrix functional theory along the dissociation coordinate of an electron-pair bond in N-electron systems.

    Science.gov (United States)

    van Meer, R; Gritsenko, O V; Baerends, E J

    2014-01-14

    Time dependent density matrix functional theory in its adiabatic linear response formulation delivers exact excitation energies ωα and oscillator strengths fα for two-electron systems if extended to the so-called phase including natural orbital (PINO) theory. The Löwdin-Shull expression for the energy of two-electron systems in terms of the natural orbitals and their phases affords in this case an exact phase-including natural orbital functional (PILS), which is non-primitive (contains other than just J and K integrals). In this paper, the extension of the PILS functional to N-electron systems is investigated. With the example of an elementary primitive NO functional (BBC1) it is shown that current density matrix functional theory ground state functionals, which were designed to produce decent approximations to the total energy, fail to deliver a qualitatively correct structure of the (inverse) response function, due to essential deficiencies in the reconstruction of the two-body reduced density matrix (2RDM). We now deduce essential features of an N-electron functional from a wavefunction Ansatz: The extension of the two-electron Löwdin-Shull wavefunction to the N-electron case informs about the phase information. In this paper, applications of this extended Löwdin-Shull (ELS) functional are considered for the simplest case, ELS(1): one (dissociating) two-electron bond in the field of occupied (including core) orbitals. ELS(1) produces high quality ωα(R) curves along the bond dissociation coordinate R for the molecules LiH, Li2, and BH with the two outer valence electrons correlated. All of these results indicate that response properties are much more sensitive to deficiencies in the reconstruction of the 2RDM than the ground state energy, since derivatives of the functional with respect to both the NOs and the occupation numbers need to be accurate. PMID:24437859

  2. Influence of steric and intramolecular inductive effects on the variable trends in R-X (R=Alkyl) bond dissociation energy

    Institute of Scientific and Technical Information of China (English)

    2009-01-01

    The question "why are the variation trends of R-X bond dissociation energy different?" is answered. The R-X bond dissociation energy (BDE) may be influenced by three main factors: the C-X intrinsic bond energy, the 1,3 geminal repulsion, and the intramolecular charge-induced dipole. In the presence of atom X, the variation trend of BDE in R-X (R= Me, Et, i-Pr, t-Bu) is dominated by two factors, the 1,3 geminal repulsion and the intramolecular charge-induced dipole. The former decreases the R-X BDE, and the latter either increases or decreases the R-X BDE. For the series of R-X with the R-C bond (such as R-Me, R-CH == CH2, R-C≡CH, and R-CN), the 1,3 geminal repulsion decreases the R-X BDE, and the variation trends of R-C BDE decrease from Me to t-Bu. As regards the series of R-X (such as R-H, R-BH2, and R-SiH2) in which the electronegativity of atom X is smaller than that of the carbon atom, the above two factors decrease the R-X BDE, and the variation trends of the R-X BDE decrease from Me to t-Bu. As to the series of R-X (such as R-F, R-OH, R-Cl, R-Br, R-I, and R-NH2) in which the electronegativity of atom X is larger than that of the carbon atom, the 1,3 geminal repulsion decreases the R-X BDE, while the intramolecular charge-induced dipole increases the R-X BDE. In this case, the variation trends of R-X BDE depend on the competition of the two factors. As a result, some of them (e. g., R-F, R-OH) increase from Me to t-Bu, some (e. g., R-I) decrease from Me to t-Bu, and some (e. g., R-Br) change very little.

  3. Influence of steric and intramolecular inductive effects on the variable trends in R-X (R=Alkyl) bond dissociation energy

    Institute of Scientific and Technical Information of China (English)

    CAO ChenZhong

    2009-01-01

    The question "why are the variation trends of R-X bond dissociation energy different?" is answered.The R-X bond dissociation energy (BDE) may be influenced by three main factors:the C-X intrinsic bond energy,the 1,3 geminal repulsion,and the intramolecular charge-induced dipole.In the presence of atom X,the variation trend of BDE in R-X (R=Me,Et,i-Pr,t-Bu) is dominated by two factors,the 1,3 geminal repulsion and the intramolecular charge-induced dipole.The former decreases the R-X BDE,and the latter either increases or decreases the R-X BDE.For the series of R-X with the R-C bond (such as R-Me,R-CH-CH2,R-C-CH,and R-CN),the 1,3 geminal repulsion decreases the R-X BDE,and the variation trends of R-C BDE decrease from Me to t-Bu.As regards the series of R-X (such as R-H,R-BH2,and R-SiH2) in which the electronegativity of atom X is smaller than that of the carbon atom,the above two factors decrease the R-X BDE,and the variation trends of the R-X BDE decrease from Me to t-Bu.As to the series of R-X (such as R-F,R-OH,R-CI,R-Br,R-I,and R-NH2) in which the electronegativity of atom X is larger than that of the carbon atom,the 1,3 geminal repulsion decreases the R-X BDE,while the intramolecular charge-induced dipole increases the R-X BDE.In this case,the variation trends of R-X BDE depend on the competition of the two factors.As a result,some of them (e.g.,R-F,R-OH) increase from Me to t-Bu,some (e.g.,R-I) decrease from Me to t-Bu,and some (e.g.,R-Br) change very little.

  4. Models for calculation of dissociation energies of homonuclear diatomic molecules

    International Nuclear Information System (INIS)

    The variation of known dissociation energies of the transition metal diatomics across the Periodic Table is rather irregular like the bulk sublimation enthalpy, suggesting that the valence-bond model for bulk metallic systems might be applicable to the gaseous diatomic molecules and the various intermediate clusters. Available dissociation energies were converted to valence-state bonding energies considering various degrees of promotion to optimize the bonding. The degree of promotion of electrons to increase the number of bonding electrons is smaller than for the bulk, but the trends in bonding energy parallel the behavior found for the bulk metals. Thus using the established trends in bonding energies for the bulk elements, it was possible to calculate all unknown dissociation energies to provide a complete table of dissociation energies for all M2 molecules from H2 to Lr2. For solids such as Mg, Al, Si and most of the transition metals, large promotion energies are offset by strong bonding between the valence state atoms. The main question is whether bonding in the diatomics is adequate to sustain extensive promotion. The most extreme example for which a considerable difference would be expected between the bulk and the diatomics would be that of the Group IIA and IIB metals. The first section of this paper which deals with the alkaline earths Mg and Ca demonstrates a significant influence of the excited valence state even for these elements. The next section then expands the treatment to transition metals

  5. Three methods to measure RH bond energies

    International Nuclear Information System (INIS)

    In this paper the authors compare and contrast three powerful methods for experimentally measuring bond energies in polyatomic molecules. The methods are: radical kinetics; gas phase acidity cycles; and photoionization mass spectroscopy. The knowledge of the values of bond energies are a basic piece of information to a chemist. Chemical reactions involve the making and breaking of chemical bonds. It has been shown that comparable bonds in polyatomic molecules, compared to the same bonds in radicals, can be significantly different. These bond energies can be measured in terms of bond dissociation energies

  6. Competition between Covalent and Noncovalent Bond Cleavages in Dissociation of Phosphopeptide-Amine Complexes

    Energy Technology Data Exchange (ETDEWEB)

    Laskin, Julia; Yang, Zhibo; Woods, Amina S.

    2011-04-21

    Interactions between quaternary amino or guanidino groups with anions are ubiquitous in nature. Here, we present a first study focused on quantifying such interactions using complexes of phosphorylated A3pXA3-NH2 (X=S, T, Y) peptides with decamethonium (DCM) or diaguanidinodecane (DGD) ligands as model systems. Time- and collision energy-resolved surface-induced dissociation (SID) of the singly charged complexes was examined using a specially configured Fourier transform ion cyclotron resonance mass spectrometer (FTICR-MS). Dissociation thresholds and activation energies were obtained from RRKM modeling of the experimental data that has been described and carefully characterized in our previous studies. We demonstrate that covalent bond cleavages resulting in phosphate abstraction by the cationic ligand are characterized by low dissociation thresholds and relatively tight transition states. In contrast, high dissociation barriers and large positive activation entropies were obtained for cleavages of non-covalent bonds. Dissociation parameters obtained from the modeling of the experimental data are in excellent agreement with the results of density functional theory (DFT) calculations. Comparison between the experimental data and theoretical calculations indicate that phosphate abstraction by the ligand is rather localized and mainly affected by the identity of the phosphorylated side chain. The hydrogen bonding in the peptide and ligand properties play a minor role in determining the energetics and dynamics of the phosphate abstraction channel

  7. Characterization and Modeling of the Collision Induced Dissociation Patterns of Deprotonated Glycosphingolipids: Cleavage of the Glycosidic Bond

    Science.gov (United States)

    Rožman, Marko

    2016-01-01

    Glycosphingolipid fragmentation behavior was investigated by combining results from analysis of a series of negative ion tandem mass spectra and molecular modeling. Fragmentation patterns extracted from 75 tandem mass spectra of mainly acidic glycosphingolipid species (gangliosides) suggest prominent cleavage of the glycosidic bonds with retention of the glycosidic oxygen atom by the species formed from the reducing end (B and Y ion formation). Dominant product ions arise from dissociation of sialic acids glycosidic bonds whereas product ions resulting from cleavage of other glycosidic bonds are less abundant. Potential energy surfaces and unimolecular reaction rates of several low-energy fragmentation pathways leading to cleavage of glycosidic bonds were estimated in order to explain observed dissociation patterns. Glycosidic bond cleavage in both neutral (unsubstituted glycosyl group) and acidic glycosphingolipids was the outcome of the charge-directed intramolecular nucleophilic substitution (SN2) mechanism. According to the suggested mechanism, the nucleophile in a form of carboxylate or oxyanion attacks the carbon at position one of the sugar ring, simultaneously breaking the glycosidic bond and yielding an epoxide. For gangliosides, unimolecular reaction rates suggest that dominant product ions related to the cleavage of sialic acid glycosidic bonds are formed via direct dissociation channels. On the other hand, low abundant product ions related to the dissociation of other glycosidic bonds are more likely to be the result of sequential dissociation. Although results from this study mainly contribute to the understanding of glycosphingolipid fragmentation chemistry, some mechanistic findings regarding cleavage of the glycosidic bond may be applicable to other glycoconjugates.

  8. Mechanical switching and coupling between two dissociation pathways in a P-selectin adhesion bond

    Science.gov (United States)

    Evans, Evan; Leung, Andrew; Heinrich, Volkmar; Zhu, Cheng

    2004-08-01

    Many biomolecular bonds exhibit a mechanical strength that increases in proportion to the logarithm of the rate of force application. Consistent with exponential decrease in bond lifetime under rising force, this kinetically limited failure reflects dissociation along a single thermodynamic pathway impeded by a sharp free energy barrier. Using a sensitive force probe to test the leukocyte adhesion bond P-selectin glycoprotein ligand 1 (PSGL-1)-P-selectin, we observed a linear increase of bond strength with each 10-fold increase in the rate of force application from 300 to 30,000 pN/sec, implying a single pathway for failure. However, the strength and lifetime of PSGL-1-P-selectin bonds dropped anomalously when loaded below 300 pN/sec, demonstrating unexpectedly faster dissociation and a possible second pathway for failure. Remarkably, if first loaded by a "jump" in force to 20-30 pN, the bonds became strong when subjected to a force ramp as slow as 30 pN/sec and exhibited the same single-pathway kinetics under all force rates. Applied in this way, a new "jump/ramp" mode of force spectroscopy was used to show that the PSGL-1-P-selectin bond behaves as a mechanochemical switch where force history selects between two dissociation pathways with markedly different properties. Furthermore, replacing PSGL-1 by variants of its 19-aa N terminus and by the crucial tetrasaccharide sialyl LewisX produces dramatic changes in the failure kinetics, suggesting a structural basis for the two pathways. The two-pathway switch seems to provide a mechanism for the "catch bond" response observed recently with PSGL-1-P-selectin bonds subjected to small-constant forces.

  9. Bond length effects during the dissociation of O2 on Ni(1 1 1)

    International Nuclear Information System (INIS)

    Graphical abstract: - Highlights: • The dissociation of O2 on Ni(1 1 1) has been investigated using the Nudged Elastic Band (NEB) technique. • An exceptional correlation has been identified between the O/Ni bond order and the O2 bond length for a series of sterically different reaction paths. • Direct magnetic phenomena accompany these processes suggesting further mechanisms for experimental control. - Abstract: The interaction between O2 and Ni(1 1 1) has been investigated using spin-polarised density functional theory. A series of low activation energy (EA = 103–315 meV) reaction pathways corresponding to precursor and non-precursor mediated adsorption have been identified. It has been seen that a predominantly pathway-independent correlation exists between O−Ni bond order and the O2 bond length. This correlation demonstrates that the O−O interaction predominantly determines the bonding of this system

  10. Active Thermochemical Tables: Sequential Bond Dissociation Enthalpies of Methane, Ethane, and Methanol and the Related Thermochemistry.

    Science.gov (United States)

    Ruscic, Branko

    2015-07-16

    Active Thermochemical Tables (ATcT) thermochemistry for the sequential bond dissociations of methane, ethane, and methanol systems were obtained by analyzing and solving a very large thermochemical network (TN). Values for all possible C-H, C-C, C-O, and O-H bond dissociation enthalpies at 298.15 K (BDE298) and bond dissociation energies at 0 K (D0) are presented. The corresponding ATcT standard gas-phase enthalpies of formation of the resulting CHn, n = 4-0 species (methane, methyl, methylene, methylidyne, and carbon atom), C2Hn, n = 6-0 species (ethane, ethyl, ethylene, ethylidene, vinyl, ethylidyne, acetylene, vinylidene, ethynyl, and ethynylene), and COHn, n = 4-0 species (methanol, hydroxymethyl, methoxy, formaldehyde, hydroxymethylene, formyl, isoformyl, and carbon monoxide) are also presented. The ATcT thermochemistry of carbon dioxide, water, hydroxyl, and carbon, oxygen, and hydrogen atoms is also included, together with the sequential BDEs of CO2 and H2O. The provenances of the ATcT enthalpies of formation, which are quite distributed and involve a large number of relevant determinations, are analyzed by variance decomposition and discussed in terms of principal contributions. The underlying reasons for periodic appearances of remarkably low and/or unusually high BDEs, alternating along the dissociation sequences, are analyzed and quantitatively rationalized. The present ATcT results are the most accurate thermochemical values currently available for these species. PMID:25760799

  11. C---lH...O and O...H...O bonded intermediates in the dissociation of low energy methyl glycolate radical cations

    Science.gov (United States)

    Suh, Dennis; Kingsmill, Carol A.; Ruttink, Paul J. A.; Burgers, Peter C.; Terlouw, Johan K.

    1995-08-01

    Low energy methyl glycolate radical cations HOCH2C(=O)OCH3+, 1, abundantly lose HCO, yielding protonated methyl formate H---C(OH)OCH3+. Tandem mass spectrometry based experiments on 2H, 13C and 18O labelled isotopologues show that this loss is largely (about 75%) atom specific. Analysis of the atom connectivity in the product ions indicates that the reaction proceeds analogously to the loss of HCO and CH3CO from ionized acetol HOCH2C(=O)CH3+ and acetoin HOCH(CH3)C(=O)CH3+, respectively. The mechanism, it is proposed, involves isomerization of 1 to the key intermediate CH2=O... H---C(=O)OCH3+, an H-bridged ion-dipole complex of neutral formaldehyde and ionized methyl formate. Next, charge transfer takes place to produce CH3OC(H)=O...HC(H)=O+, an H-bridged ion-dipole complex of ionized formaldehyde and neutral methyl formate, followed by proton transfer to generate the products. Preliminary ab initio calculations executed at the UMP3/6-31G*//6-31G*+ZPVE level of theory are presented in support of this proposal. The non-specific loss of HCO from 1 (about 25%) is rationalized to occur via the same mechanism, but after communication with isomeric dimethyl carbonate ions CH3OC(=O)OCH3+, 2, via the O...H...O bonded intermediate [CH2=O...H...O=C---OCH3]+. The latter pathway is even more important in the formation of CH2OH+ ions from 1 which, it is shown, is not a simple bond cleavage reaction, but may involve consecutive or concerted losses of CH3 and CO2 from the above O...H...O bonded species. Ionized methyl lactate HOCH(CH3)C(=O)OCH3+, the higher homologue of 1, shows a unimolecular chemistry which is akin to that of 1.

  12. Energy distribution in dissociations of polyatomic molecules

    International Nuclear Information System (INIS)

    In this thesis studies are reported of fragmentation processes in polyatomic molecules. In order to find out which dessocaciation reactions take place, how they are brought about by the internal energy of the reactant, and to investigate the structure of the dissociating 'transition state', the fragment mass and the corresponding kinetic energy release (KER) are determined by differential translational spectroscopy using a position and time sensitive two-particle coincidence detector. The results are interpreted using the statistical theory of unimolecular dissociation. It turns out that the standard assumptions of the theory, especially in calculating KER-distributions, are not realistic in all molecules considered. Dissociation is induced by the neutralization with alkali metal vapour. In ch. 2 the experimental method and the analysis of the data (dissociation pathways, branching ratios and ε-d-distributions) are introduced and exemplified by measurements of cyclohexane, which represents the upper limit in precursor and fragment mass accessible in the apparatus. In ch. 3 a study is reported of the molecules methylchloride (CH3Cl) and the acetylradical (CH3CO). In spite of their similar geometric structures, completely different dissociation mechanisms have been found. Methylchloride dissociates via a repulsive state; acetyl radicals show energy scrambling. The energy distribution from dissociating acetyl exemplifies dynamical effects in the dissociation. In ch. 4 an investigation of a number of prototype hydrocarbons is presented. The dissociation pathways of several small linear alkanes indicate that neutralization takes place to unknown repulsive potentials, of which the position and steepness are determined from the kinetic energy release. (author). 118 refs.; 40 figs.; 5 tabs

  13. The dissociative chemisorption of water on Ni(111): Mode- and bond-selective chemistry on metal surfaces

    International Nuclear Information System (INIS)

    A fully quantum approach based on an expansion in vibrationally adiabatic eigenstates is used to explore the dissociative chemisorption of H2O, HOD, and D2O on Ni(111). For this late barrier system, excitation of both the bending and stretching modes significantly enhances dissociative sticking. The vibrational efficacies vary somewhat from mode-to-mode but are all relatively close to one, in contrast to methane dissociation, where the behavior is less statistical. Similar to methane dissociation, the motion of lattice atoms near the dissociating molecule can significantly modify the height of the barrier to dissociation, leading to a strong variation in dissociative sticking with substrate temperature. Given a rescaling of the barrier height, our results are in reasonable agreement with measurements of the dissociative sticking of D2O on Ni(111), for both laser-excited molecules with one or two quanta of excitation in the antisymmetric stretch and in the absence of laser excitation. Even without laser excitation, the beam contains vibrationally excited molecules populated at the experimental source temperature, and these make significant contributions to the sticking probability. At high collision energies, above the adiabatic barrier heights, our results correlate with these barrier heights and mode softening effects. At lower energies, dissociative sticking occurs primarily via vibrationally nonadiabatic pathways. We find a preference for O–H over O–D bond cleavage for ground state HOD molecules at all but the highest collision energies, and excitation of the O–H stretch gives close to 100% O–H selectivity at lower energies. Excitation of the O–D stretch gives a lower O–D cleavage selectivity, as the interaction with the surface leads to energy transfer from the O–D stretch into the O–H bond, when mode softening makes these vibrations nearly degenerate

  14. The dissociative chemisorption of water on Ni(111): Mode- and bond-selective chemistry on metal surfaces

    Energy Technology Data Exchange (ETDEWEB)

    Farjamnia, Azar; Jackson, Bret, E-mail: jackson@chem.umass.edu [Department of Chemistry, University of Massachusetts, Amherst, Massachusetts 01003 (United States)

    2015-06-21

    A fully quantum approach based on an expansion in vibrationally adiabatic eigenstates is used to explore the dissociative chemisorption of H{sub 2}O, HOD, and D{sub 2}O on Ni(111). For this late barrier system, excitation of both the bending and stretching modes significantly enhances dissociative sticking. The vibrational efficacies vary somewhat from mode-to-mode but are all relatively close to one, in contrast to methane dissociation, where the behavior is less statistical. Similar to methane dissociation, the motion of lattice atoms near the dissociating molecule can significantly modify the height of the barrier to dissociation, leading to a strong variation in dissociative sticking with substrate temperature. Given a rescaling of the barrier height, our results are in reasonable agreement with measurements of the dissociative sticking of D{sub 2}O on Ni(111), for both laser-excited molecules with one or two quanta of excitation in the antisymmetric stretch and in the absence of laser excitation. Even without laser excitation, the beam contains vibrationally excited molecules populated at the experimental source temperature, and these make significant contributions to the sticking probability. At high collision energies, above the adiabatic barrier heights, our results correlate with these barrier heights and mode softening effects. At lower energies, dissociative sticking occurs primarily via vibrationally nonadiabatic pathways. We find a preference for O–H over O–D bond cleavage for ground state HOD molecules at all but the highest collision energies, and excitation of the O–H stretch gives close to 100% O–H selectivity at lower energies. Excitation of the O–D stretch gives a lower O–D cleavage selectivity, as the interaction with the surface leads to energy transfer from the O–D stretch into the O–H bond, when mode softening makes these vibrations nearly degenerate.

  15. Effect of an external electric field on the dissociation energy and the electron density properties: The case of the hydrogen bonded dimer HFHF

    OpenAIRE

    Mata, Ignasi; Molins Grau, Elíes; Alkorta, Ibon; Espinosa Hernández, Enrique

    2009-01-01

    The effect of a homogeneous external electric field parallel to the hydrogen bond in the FHFH dimer has been studied by theoretical methods. The quantum theory of atoms in molecules methodology has been used for analyzing the electron distribution of the dimer, calculated with different hydrogen bond distances and external field magnitudes. It is shown that an electric field in the opposite direction to the dipole moment of the system strengthens the interaction due to a larger mutual polariz...

  16. The Breathing Orbital Valence Bond Method in Diffusion Monte Carlo: C-H Bond Dissociation ofAcetylene

    Energy Technology Data Exchange (ETDEWEB)

    Domin, D.; Braida, Benoit; Lester Jr., William A.

    2008-05-30

    This study explores the use of breathing orbital valence bond (BOVB) trial wave functions for diffusion Monte Carlo (DMC). The approach is applied to the computation of the carbon-hydrogen (C-H) bond dissociation energy (BDE) of acetylene. DMC with BOVB trial wave functions yields a C-H BDE of 132.4 {+-} 0.9 kcal/mol, which is in excellent accord with the recommended experimental value of 132.8 {+-} 0.7 kcal/mol. These values are to be compared with DMC results obtained with single determinant trial wave functions, using Hartree-Fock orbitals (137.5 {+-} 0.5 kcal/mol) and local spin density (LDA) Kohn-Sham orbitals (135.6 {+-} 0.5 kcal/mol).

  17. A study of the ground and excited states of Al3 and Al3-. II. Computational analysis of the 488 nm anion photoelectron spectrum and a reconsideration of the Al3 bond dissociation energy

    Science.gov (United States)

    Miller, Stephen R.; Schultz, Nathan E.; Truhlar, Donald G.; Leopold, Doreen G.

    2009-01-01

    Computational results are reported for the ground and low-lying excited electronic states of Al3- and Al3 and compared with the available spectroscopic data. In agreement with previous assignments, the six photodetachment transitions observed in the vibrationally resolved 488nm photoelectron spectrum of Al3- are assigned as arising from the ground X˜A1'1(A11) and excited B23 states of Al3- and accessing the ground X˜A1'2(A12) and excited A2″2(B12), A24, and B22 states of Al3 (with C2v labels for D3h states in parentheses). Geometries and vibrational frequencies obtained by PBE0 hybrid density functional calculations using the 6-311+G(3d2f) basis set and energies calculated using coupled cluster theory with single and double excitations and a quasiperturbative treatment of connected triple excitations (CCSD(T)) with the aug-cc-pVxZ {x =D, T, Q} basis sets with exponential extrapolation to the complete basis set limit are in good agreement with experiment. Franck-Condon spectra calculated in the harmonic approximation, using either the Sharp-Rosenstock-Chen method which includes Duschinsky rotation or the parallel-mode Hutchisson method, also agree well with the observed spectra. Possible assignments for the higher-energy bands observed in the previously reported UV photoelectron spectra are suggested. Descriptions of the photodetachment transition between the Al3- and Al3 ground states in terms of natural bond order (NBO) analyses and total electron density difference distributions are discussed. A reinterpretation of the vibrational structure in the resonant two-photon ionization spectrum of Al3 is proposed, which supports its original assignment as arising from the X˜A1'2 ground state, giving an Al3 bond dissociation energy, D0(Al2-Al), of 2.403±0.001eV. With this reduction by 0.3eV from the currently recommended value, the present calculated dissociation energies of Al3, Al3-, and Al3+ are consistent with the experimental data.

  18. The Dissociation Energies of CH4 and C2H2 Revisited

    Science.gov (United States)

    Partridge, Harry; Bauschlicher, Charles W., Jr.; Langhoff, Stephen R. (Technical Monitor)

    1995-01-01

    The bond dissociation energies of CH4 and C2H2 and their fragments are investigated using basis set extrapolations and high levels of correlation. The computed bond dissociation energies (D(sub e)) are accurate to within 0.2 kcal/mol. The agreement with the experimental (D(sub 0)) values is excellent if we assume that the zero-point energy of C2H is 9.18 kcal/mol. The effect of core (1s) correlation on the bond dissociation energies of C-H bonds is shown to vary from 0.2 to 0.7 kcal/mol and that for C-C bonds varies from 0.4 to 2.2 kcal/mol.

  19. Benchmark Calculations for Bond Dissociation Enthalpies of Unsaturated Methyl Esters and the Bond Dissociation Enthalpies of Methyl Linolenate.

    Science.gov (United States)

    Li, Xiaoyu; Xu, Xuefei; You, Xiaoqing; Truhlar, Donald G

    2016-06-16

    It is important to determine an appropriate computational method for obtaining accurate thermochemical properties of large biodiesel molecules such as methyl linolenate. In this study, we use Kohn-Sham density functional theory (DFT) and coupled cluster theory to calculate bond dissociation enthalpies (BDEs) of seven fragment molecules of methyl linolenate, in particular, propene, methyl formate, cis-3-hexene, 1,4-pentadiene, 1-pentene, butane, and methyl butanoate. The results are compared to BDEs obtained from experiments and to Oyeyemi et al.'s multireference averaged coupled pair functional (MRACPF2) calculations. We found that with extrapolation to the complete basis set (CBS) limit, the BDEs derived from coupled cluster calculations with single, double, and triple excitations (CCSDT) and from CCSDT with a perturbative treatment of connected quadruple excitations, CCSDT(2)Q/CBS, are closer to the available experimental values than those obtained by MRACPF2 for propene and methyl formate. The CCSDT/CBS calculations were chosen as the reference for validating the DFT methods. Among the density functionals, we found that M08-HX has the best performance with a mean unsigned deviation (MUD) from CCSDT/CBS of only 1.0 kcal/mol, whereas the much more expensive MRACPF2 has an MUD of 1.1 kcal/mol. We then used the most successfully validated density functionals to calculate the BDEs of methyl linolenate and compared the results with the MRACPF2 BDEs. The present study identifies several Kohn-Sham exchange-correlation functionals that should be useful for modeling ester combustion, especially the M08-HX, M06-2X, M05-2X, M08-SO, and MPWB1K global-hybrid meta functionals, the M11 and MN12-SX range-separated-hybrid meta functionals, the ωB97 range-separated hybrid gradient approximation functional, and the SOGGA11-X global-hybrid gradient approximation functional. PMID:27191950

  20. Quantum dynamics of polyatomic dissociative chemisorption on transition metal surfaces: mode specificity and bond selectivity.

    Science.gov (United States)

    Jiang, Bin; Yang, Minghui; Xie, Daiqian; Guo, Hua

    2016-06-27

    Dissociative chemisorption is the initial and often rate-limiting step in many heterogeneous processes. As a result, an in-depth understanding of the reaction dynamics of such processes is of great importance for the establishment of a predictive model of heterogeneous catalysis. Overwhelming experimental evidence has suggested that these processes have a non-statistical nature and excitations in various reactant modes have a significant impact on reactivity. A comprehensive characterization of the reaction dynamics requires a quantum mechanical treatment on a global potential energy surface. In this review, we summarize recent progress in constructing high-dimensional potential energy surfaces for polyatomic molecules interacting with transition metal surfaces based on the plane-wave density functional theory and in quantum dynamical studies of dissociative chemisorption on these potential energy surfaces. A special focus is placed on the mode specificity and bond selectivity in these gas-surface collisional processes, and their rationalization in terms of the recently proposed Sudden Vector Projection model. PMID:26100606

  1. A Redetermination of the Dissociation Energy of MgO(+)

    Science.gov (United States)

    Bauschlicher, Charles W., Jr.; Langhoff, Stephen R.; Partridge, Harry

    1994-01-01

    In 1986, we reported a dissociation energy (D(sub 0) of 2.31 eV for the X(sup 2)Pi ground state of MgO(+). This value was determined by computing the dissociation energy to the Mg(2+) + O(-) limit and adjusting the value to the Mg(+) + O limit using the experimental Ionization Potential (IP) of Mg(+) and the Electron Affinity (EA) of O. The success of this method relies on the assumption that there is little covalent contribution to the bonding. The very small (0.04 eV) correlation contribution to the binding energy was taken as corroboration for the validity of this approach. Our earlier theoretical value was estimated to be accurate to at least 0.2 eV. It is in excellent agreement with the subsequent value of 2.30 +/- 0.13 eV determined by Freiser and co-workers from photodissociation experiments. It is also consistent with the upper (less than 3.1 eV) and lower (greater than 1.1 eV) bounds determined by Rowe obtained by studying the reactions of Mg(+) with 03 and NO2. However, it is inconsistent with an upper bound of 1.7 eV reported by Kappes and Staley based on their failure to observe MgO(+) in the reaction of Mg(+) with N2O. The picture became somewhat clouded, however, by the recent guided-ion beam mass spectrometric studies of Dalleska and Armentrout. Their initial analysis of the reaction data for Mg(+) + O2 lead to a bond dissociation energy of 2.92 +/- 0.25 eV, which is considerably larger than the value of 2.47 +/- 0.06 eV deduced from their studies of the Mg(+)+NO2 reaction.

  2. Dissociation of Biological Catch-Bond by Periodic Perturbation

    OpenAIRE

    Pereverzev, Yuriy V.; Prezhdo, Oleg V.

    2006-01-01

    The analysis of the P-selectin/PSGL-1 catch-slip bond that is periodically driven by a detaching force predicts that in the frequency range on the order of 1 s−1 the bond lifetime undergoes significant changes with respect to both frequency and amplitude of the force. The result indicates how variations in the heart rate could have a substantial effect on leukocyte and lymphoid cell transport and adhesion to endothelial cells and platelets during inflammatory processes.

  3. Generation of pyridyl coordinated organosilicon cation pool by oxidative Si-Si bond dissociation

    Directory of Open Access Journals (Sweden)

    Itami Kenichiro

    2007-02-01

    Full Text Available Abstract An organosilicon cation stabilized by intramolecular pyridyl coordination was effectively generated and accumulated by oxidative Si-Si bond dissociation of the corresponding disilane using low temperature electrolysis, and was characterized by NMR and CSI-MS.

  4. Accurate studies on dissociation energies of diatomic molecules

    Institute of Scientific and Technical Information of China (English)

    SUN; WeiGuo; FAN; QunChao

    2007-01-01

    The molecular dissociation energies of some electronic states of hydride and N2 molecules were studied using a parameter-free analytical formula suggested in this study and the algebraic method (AM) proposed recently. The results show that the accurate AM dissociation energies DeAM agree excellently with experimental dissociation energies Deexpt, and that the dissociation energy of an electronic state such as the 23△g state of 7Li2 whose experimental value is not available can be predicted using the new formula.

  5. A Comprehensive Analysis in Terms of Molecule-Intrinsic Quasi-Atomic Orbitals. IV. Bond Breaking and Bond Forming along the Dissociative Reaction Path of Dioxetane.

    Science.gov (United States)

    West, Aaron C; Schmidt, Michael W; Gordon, Mark S; Ruedenberg, Klaus

    2015-10-15

    The quantitative analysis of molecular density matrices in terms of oriented quasi-atomic orbitals (QUAOs) is shown to yield detailed conceptual insight into the dissociation of dioxetane on the basis of ab initio wave functions. The QUAOs persist and can be followed throughout the reaction path. The kinetic bond orders and the orbital populations of the QUAOs quantitatively reveal the changes of the bonding interactions along the reaction path. At the transition state the OO bond is broken, and the molecule becomes a biradical. After the transition state the reaction path bifurcates. The minimum energy path gently descends from the transition state via a valley-ridge inflection point to a second saddle point, from which two new minimum energy paths lead to two equivalent formaldehyde dimers. The CC bond breaks, and the π-bonds of the formaldehyde fragments form in close vicinity of the second saddle point. The changes of the interactions in this region are elucidated by the analysis of the rearrangements of the QUAOs. PMID:26371996

  6. 与蛋白质调控DNA空穴迁移相关的具有负离解能特征的亚稳态氢键%Metastable Hydrogen-bonds Featuring Negative Dissociation Energies in Protein-bound DNA in Hole Migration

    Institute of Scientific and Technical Information of China (English)

    王梅; 王军; 步宇翔

    2015-01-01

    利用密度泛函理论方法研究了作为空穴迁移载体的蛋白质复合的DNA三聚体( Protonated arginine…guanine…cytosine, ArgH+-GC)的氢键性质.结果表明,空穴迁移通过该载体单元时此类氢键表现为亚稳态,且具有明显的负离解能.正常情况下ArgH+基团在大小沟均能与GC碱对形成氢键,且具有正的离解能.然而,当空穴转移至此将削弱氢键至亚稳态,使之具有一定的离解势垒和负的离解能.这种势垒抑制的负离解能现象意味着由于空穴俘获导致此三聚体结构单元在它的 ArgH+…N7/O6键区储存了一定的能量(约108.78 kJ/mol).该氢键离解通道受控于此键区两个相关组分之间的静电排斥和氢键吸引之间的平衡以及这两个相反作用随氢键距离不同的衰减速率.基于电子密度分布的拓扑性质以及键临界点的Laplacian数值分析澄清了此类特殊的能量现象主要源自通过高能氢键(ArgH+…N7/O6)连接的授受体间的静电排斥.进一步空穴俘获诱导的G→C质子转移可扩展负离解能区至ArgH+…N7/O6和Watson-Crick( WC)氢键区.另外, ArgH+结合到GC的大小沟增加其电离势,因此削弱其空穴传导能力,削弱程度取决于ArgH+与GC的距离.推而广之,在protonated lysine-GC和protonated histidine-GC体系也可观察到类似的现象.显然,此类性质可调的亚稳态氢键可调控DNA空穴迁移机理.此工作为理解蛋白质调控的DNA空穴迁移机理提供了重要的能量学信息.%We theoretically investigated the properties of hydrogen bonds in the protein-bound DNA trimer( protona-ted arginine…guanine…cytosine, ArgH+-GC) units as hole migration carriers using density functional theory calcula-tions. Results suggest these hydrogen bonds are metastable and feature considerable negative dissociation energies up-on hole migration through the ArgH+-GC units of the carriers. Normally, the ArgH+ group can H-bond with the gua-nine-cytosine( GC

  7. Coulomb dissociation at nonrelativistic and relativistic energies

    International Nuclear Information System (INIS)

    The author studies the breakup of deuterons on nuclei in the framework of DWBA theories which are based on the spectator model. The discrepancies for heavy targets are explained by the mechanism of the Coulomb dissociation. (HSI)

  8. Zero-Point Energy Constraint for Unimolecular Dissociation Reactions. Giving Trajectories Multiple Chances To Dissociate Correctly.

    Science.gov (United States)

    Paul, Amit K; Hase, William L

    2016-01-28

    A zero-point energy (ZPE) constraint model is proposed for classical trajectory simulations of unimolecular decomposition and applied to CH4* → H + CH3 decomposition. With this model trajectories are not allowed to dissociate unless they have ZPE in the CH3 product. If not, they are returned to the CH4* region of phase space and, if necessary, given additional opportunities to dissociate with ZPE. The lifetime for dissociation of an individual trajectory is the time it takes to dissociate with ZPE in CH3, including multiple possible returns to CH4*. With this ZPE constraint the dissociation of CH4* is exponential in time as expected for intrinsic RRKM dynamics and the resulting rate constant is in good agreement with the harmonic quantum value of RRKM theory. In contrast, a model that discards trajectories without ZPE in the reaction products gives a CH4* → H + CH3 rate constant that agrees with the classical and not quantum RRKM value. The rate constant for the purely classical simulation indicates that anharmonicity may be important and the rate constant from the ZPE constrained classical trajectory simulation may not represent the complete anharmonicity of the RRKM quantum dynamics. The ZPE constraint model proposed here is compared with previous models for restricting ZPE flow in intramolecular dynamics, and connecting product and reactant/product quantum energy levels in chemical dynamics simulations. PMID:26738691

  9. Hydrogen Dissociation in Generalized Hartree-Fock Theory: Breaking the diatomic bond

    Science.gov (United States)

    Jerke, Jonathan; Masood, Samina; Tymczak, Cj

    Generalized Hartree Fock theory predicts molecular Hydrogen dissociation without correlation. A variational Gaussian-Sinc linear superposition is the basis of 50 calculations with 3-4 significant digits of quality. The spin singlet covalent bond spontaneously breaks into a pair of uncorrelated doublets at atomic separation of 1.22 Angstroms. Quantum spin numbers and energetic comparison with Configuration Interaction theory--correlation--point to a first order phase transition in the molecular Hydrogen bond without correlation. Welch Foundation (Grant J-1675), the ARO (Grant W911Nf-13-1-0162), the Texas Southern University High Performance Computing Center (http:/hpcc.tsu.edu/; Grant PHY-1126251) and NSF-CREST CRCN project (Grant HRD-1137732).

  10. Molecular dissociation in presence of catalysts: Interpreting bond breaking as a quantum dynamical phase transition

    CERN Document Server

    Ruderman, A; Santos, E; Pastawski, H M

    2015-01-01

    In this work we show that the molecular chemical bond formation and dissociation in presence of the d-band of a metal catalyst can be described as a Quantum Dynamical Phase Transition (QDPT). This agree with DFT calculations that predict sudden jumps in some observables as the molecule breaks. According to our model this phenomenon emerges because the catalyst provides for a non- Hermitian Hamiltonian. We show that when the molecule approaches the surface, as occurs in the Heyrovsky reaction of H 2, the bonding H 2 orbital has a smooth crossover into a bonding molecular orbital built with the closest H orbital and the surface metal d-states. The same occurs for the antibonding state. Meanwhile, two resonances appear within the continuous spectrum of the d- band which are associated with bonding and antibonding orbitals between the furthest H atom and the d-states at the second metallic layer. These move towards the band center where they collapse into a pure metallic resonance and an almost isolated H orbital...

  11. Molecular dissociation in the presence of catalysts: interpreting bond breaking as a quantum dynamical phase transition

    International Nuclear Information System (INIS)

    In this work we show that molecular chemical bond formation and dissociation in the presence of the d-band of a metal catalyst can be described as a quantum dynamical phase transition (QDPT). This agrees with DFT calculations that predict sudden jumps in some observables as the molecule breaks. According to our model this phenomenon emerges because the catalyst provides for a non-Hermitian Hamiltonian. We show that when the molecule approaches the surface, as occurs in the Heyrovsky reaction of H2, the bonding H2 orbital has a smooth crossover into a bonding molecular orbital built with the closest H orbital and the surface metal d-states. The same occurs for the antibonding state. Meanwhile, two resonances appear within the continuous spectrum of the d-band, which are associated with bonding and antibonding orbitals between the furthest H atom and the d-states at the second metallic layer. These move toward the band center, where they collapse into a pure metallic resonance and an almost isolated H orbital. This phenomenon constitutes a striking example of the non-trivial physics enabled when one deals with non-Hermitian Hamiltonian beyond the usual wide band approximation. (paper)

  12. Hydrogen bonding of the dissociated histidine ligand is not required for formation of a proximal NO adduct in cytochrome c'.

    Science.gov (United States)

    Ghafoor, Dlzar D; Kekilli, Demet; Abdullah, Gaylany H; Dworkowski, Florian S N; Hassan, Hamid G; Wilson, Michael T; Strange, Richard W; Hough, Michael A

    2015-09-01

    Cytochromes c', that occur in methanotrophic, denitrifying and photosynthetic bacteria, form unusual proximal penta-coordinate NO complexes via a hexa-coordinate distal NO intermediate. Their NO binding properties are similar to those of the eukaryotic NO sensor, soluble guanylate cyclase, for which they provide a valuable structural model. Previous studies suggested that hydrogen bonding between the displaced proximal histidine (His120) ligand (following its dissociation from heme due to trans effects from the distally bound NO) and a conserved aspartate residue (Asp121) could play a key role in allowing proximal NO binding to occur. We have characterized three variants of Alcaligenes xylosoxidans cytochrome c' (AXCP) where Asp121 has been replaced by Ala, Ile and Gln, respectively. In all variants, hydrogen bonding between residue 121 and His120 is abolished yet 5-coordinate proximal NO species are still formed. Our data therefore demonstrate that the His120-Asp121 bond is not essential for proximal NO binding although it likely provides an energy minimum for the displaced His ligand. All variants have altered proximal pocket structure relative to native AXCP. PMID:26100643

  13. The Kinetics of Dissociations of Aluminum - Oxygen Bonds in Aqueous Complexes - An NMR Study

    Energy Technology Data Exchange (ETDEWEB)

    Dr. William Casey

    2003-09-03

    OAK B262 The Kinetics of Dissociations of Aluminum--Oxygen Bonds in Aqueous Complexes--An NMR Study. In this project we determined rates and mechanisms of Al(III)-O bond rupture at mineral surfaces and in dissolved aluminum complexes. We then compared the experimental results to simulations in an attempt to predict rate coefficients. Most of the low-temperature reactions that are geochemically important involve a bonded atom or molecule that is replaced with another. We probe these reactions at the most fundamental level in order to establish a model to predict rates for the wide range of reactions that cannot be experimentally studied. The chemistry of small aluminum cluster (Figure) provides a window into the hydrolytic processes that control rates of mineral formation and the transformation of adsorbates into extended structures. The molecule shown below as an example exposes several types of oxygens to the bulk solution including seven structurally distinct sets of bridging hydroxyls. This molecule is a rich model for the aqueous interface of aluminum (hydr)oxide minerals, since it approaches colloidal dimensions in size, yet is a dissolved complex with +18 charge. We have conducted both {sup 17}O- {sup 27}Al- and {sup 19}F-NMR experiments to identify the reactive sites and to determine the rates of isotopic exchange between these sites and the bulk solution. The research was enormously successful and led to a series of papers that are being used as touchstones for assessing the accuracy of computer models of bond ruptures in water.

  14. Dissociation of OCS by high energy highly charged ion impact

    International Nuclear Information System (INIS)

    OCS is an important molecule with immense biological, chemical and astrophysical significance. Various dissociation channels of OCSq+ (where q = 2 to 4), formed in the interaction of 5 MeV u-1 Si12+ ion beam with neutral OCS, have been studied using recoil-ion momentum spectroscopy. The concerted and/or sequential nature of dissociation is inferred from the shape and slope of the coincidence islands in the 2D coincidence map. It is observed that the C+ + S+ + O channel results from concerted as well as sequential decay of OCS2+. However the other channels originate purely from the concerted process in which the two terminal fragments (oxygen and sulphur) fly back to back and the central carbon fragment is left with negligible momentum. The kinetic energy release (KER) distributions for all the fragmentation channels arising from the dissociation of OCSq+ (where q = 2 to 4) have been measured and compared with the available data in the literature. It is observed that the KER values for complete Coulomb fragmentation channels are much smaller than those of incomplete Coulomb fragmentation cases and the KER increases with the increasing charge states of the parent molecular ions. From the momentum correlation map, we estimated the geometry of the precursor molecular ion undergoing three-body dissociation and inferred that bent dissociative states are involved in most of the fragmentation channels of OCSq+. (authors)

  15. Anisotropic fragmentation in low-energy dissociative recombination

    International Nuclear Information System (INIS)

    On a dense energy grid reaching up to 75 meV electron collision energy the fragmentation angle and the kinetic energy release of neutral dissociative recombination fragments have been studied in a twin merged beam experiment. The anisotropy and the extracted rotational state contributions were found to sensitively depend on energy. Both show pronounced variations on a likewise narrow energy scale as the rotationally averaged rate coefficient. For the first time angular dependences described by Legendre polynomials higher than 2nd order could be deduced. Moreover, a slight anisotropy at zero collision energy was observed which is caused by the flattened velocity distribution of the electron beam.

  16. A pass too far: dissociation of internal energy selected paracyclophane cations, theory and experiment.

    Science.gov (United States)

    Hemberger, Patrick; Bodi, Andras; Schon, Christof; Steinbauer, Michael; Fischer, Kathrin H; Kaiser, Conrad; Fischer, Ingo

    2012-09-14

    The vacuum ultraviolet (VUV) photoionization and dissociative photoionization of three hydroxy-substituted [2.2]paracyclophane derivatives were studied yielding adiabatic ionization energies and dissociative photoionization energies (appearance energies). The simplest dissociation pathway is the breaking of both CH(2)-CH(2) bridge units and fragmenting the molecular ion in half to yield xylylene neutral and cationic fragments. The experimental data show that this process is outcompeted by a faster, higher energy channel, possibly yielding cyclooctatetraene derivatives. The role of the reaction coordinate, the effect of large amplitude motions on the density of states function at low and high energies and the temperature dependent 'population gap' in the internal energy distribution in large molecules are discussed in the context of applying statistical models to the dissociation. Computational approaches to the binding energy of paracyclophanes are marred with pitfalls. Noncovalent interactions play a major role in keeping paracyclophanes bound by some 200 kJ mol(-1) with respect to the two xylylene motifs, and the covalent CH(2)-CH(2) bonds are mostly counteracted by the geometric strain. The stabilizing effects are twofold: first, paracyclophanes are aromatic compounds, whereas xylylenes are not. Thus, the aromaticity of the molecule is induced by dimerization. Second, dispersive π-π interactions also stabilize the molecule. We evaluated 23 different computational chemistry approaches, and found that very few of the favorably scaling ones give an adequate description of this system. Among the DFT functionals tested, only PBE-D3 and perhaps M06-2X yielded consistently accurate results, comparable with MP3 and CCSD, or the G4 and CBS-QB3 composite methods. MP2 results in general suffer from significant overbonding. PMID:22847148

  17. The C-H bond dissociation enthalpies in fused N-heterocyclic compounds

    Science.gov (United States)

    Wang, Ying-Xing; Zheng, Wen-Rui; Ding, Lan-Lan

    2016-03-01

    The C-H bond dissociation enthalpies (BDEs) of the 26 N, O, S-containing mono-heterocyclic compounds were evaluated using the composite high-level ab initio methods G3 and G4. The C-H BDEs for 32 heterocyclic compounds were calculated using 8 types of density functional theory (DFT) methods. Comparing with the experimental values, the BMK method gave the lowest root mean square error (RMSE) of 7.2 kJ/mol. Therefore, the C-H BDEs of N-fused-heterocyclic compounds at different positions were investigated by the BMK method. By NBO analysis two linear relationships between the C-H BDEs of quinoline and isoquinoline with natural charges qC/ e in molecules and with natural charges qC/ e in radicals were found. The substituent effects on C(α)-H BDEs in N-fused-heterocyclic compounds were also discussed. It was found that there are two linear relationships between the C(α)-H BDEs of quinoline and isoquinoline derivatives with natural charges qC(α)/ e for the EDGs and CEGs substituents.

  18. Dissociation of internal energy-selected methyl bromide ion revealed from threshold photoelectron-photoion coincidence velocity imaging

    International Nuclear Information System (INIS)

    Dissociative photoionization of methyl bromide (CH3Br) in an excitation energy range of 10.45–16.90 eV has been investigated by using threshold photoelectron-photoion coincidence (TPEPICO) velocity imaging. The coincident time-of-flight mass spectra indicate that the ground state X2E of CH3Br+ is stable, and both A2A1 and B2E ionic excited states are fully dissociative to produce the unique fragment ion of CH3+. From TPEPICO 3D time-sliced velocity images of CH3+ dissociated from specific state-selected CH3Br+ ion, kinetic energy release distribution (KERD) and angular distribution of CH3+ fragment ion are directly obtained. Both spin-orbit states of Br(2P) atom can be clearly observed in fast dissociation of CH3Br+(A2A1) ion along C–Br rupture, while a KERD of Maxwell-Boltzmann profile is obtained in dissociation of CH3Br+(B2E) ion. With the aid of the re-calculated potential energy curves of CH3Br+ including spin-orbit coupling, dissociation mechanisms of CH3Br+ ion in A2A1 and B2E states along C–Br rupture are revealed. For CH3Br+(A2A1) ion, the CH3+ + Br(2P1/2) channel is occurred via an adiabatic dissociation by vibration, while the Br(2P3/2) formation is through vibronic coupling to the high vibrational level of X2E state followed by rapid dissociation. C–Br bond breaking of CH3Br+(B2E) ion can occur via slow internal conversion to the excited vibrational level of the lower electronic states and then dissociation

  19. Sequential bond energies and structures of the Cr+·(N2), n =1−4

    Indian Academy of Sciences (India)

    Jamal N Dawoud

    2014-11-01

    DFT calculations, with an effective core potential for the chromium ion and large polarized basis set functions have been used to calculate the sequential bond dissociation energies of the Cr+·(N2) (n = 1—4) complexes. A linear configuration was obtained for the Cr+·N2 and Cr+·(N2)2 complexes with sequential bond dissociation energies of 14.6 and 16.4 kcal mol-1, respectively. For the Cr+·(N2)3 and Cr+·(N2)4 complexes, distorted trigonal pyramidal and tetrahedral geometries were optimized with sequential bond dissociation energies of 6.5 and 5.5 kcal mol-1, respectively. - back-donation in side-on approach of the Cr+·N2 leads to the formation of a tilted structure with the Cr+ ion in central position. The di-ligated complex exhibits the strongest bond dissociation energy among these four Cr+·(N2) (n = 1—4) complexes since it has the largest Cr+—N bond order.

  20. Accurate calculation of the dissociation energy of the highly anharmonic system ClHCl(-).

    Science.gov (United States)

    Stein, Christopher; Oswald, Rainer; Botschwina, Peter; Peterson, Kirk A

    2015-05-28

    Accurate bond dissociation energies (D0) are reported for different isotopologues of the highly anharmonic system ClHCl(-). The mass-independent equilibrium dissociation energy De was obtained by a composite method with frozen-core (fc) CCSD(T) as the basic contribution. Basis sets as large as aug-cc-pV8(+d)Z were employed, and extrapolation to the complete basis set (CBS) limit was carried out. Explicitly correlated calculations with the CCSD(T)-F12b method were also performed to support the conventionally calculated values. Core-core and core-valence correlation, scalar relativity, and higher-order correlation were considered as well. Two mass-dependent contributions, namely, the diagonal Born-Oppenheimer correction and the difference in zero-point energies between the complex and the HCl fragment, were then added in order to arrive at precise D0 values. Results for (35)ClH(35)Cl(-) and (35)ClD(35)Cl(-) are 23.81 and 23.63 kcal/mol, respectively, with estimated uncertainties of 0.05 kcal/mol. In contrast to FHF(-) ( Stein , C. ; Oswald , R. ; Sebald , P. ; Botschwina , P. ; Stoll , H. , Peterson , K. A. Mol. Phys. 2013 , 111 , 2647 - 2652 ), the D0 values of the bichloride species are larger than their De counterparts, which is an unusual situation in hydrogen-bonded systems. PMID:25405989

  1. Identification of disulfide bonds in wheat gluten proteins by means of mass spectrometry/electron transfer dissociation.

    Science.gov (United States)

    Lutz, Elena; Wieser, Herbert; Koehler, Peter

    2012-04-11

    Disulfide bonds within gluten proteins play a key role in the breadmaking performance of wheat flour. In the present study, disulfide bonds of wheat gluten proteins were identified by using a new liquid chromatography-mass spectrometry (LC-MS) technique with alternating electron transfer dissociation (ETD)/collision-induced dissociation (CID). Wheat flour was partially hydrolyzed with thermolysin (pH 6.5, 37 °C, 16 h), and the digest was subjected to LC-MS with alternating ETD/CID fragmentation. Whereas CID provided peptide fragments with intact disulfide bonds, cleavage of disulfide bonds was preferred over peptide backbone fragmentations in ETD. The simultaneous observation of disulfide-linked and disulfide-cleaved peptide ions in the mass spectra not only provided distinct interpretation with high confidence but also simplified the conventional approach for determination of disulfide bonds, which often requires two separate experiments with and without chemical reduction. By application of the new method 14 cystine peptides were identified. Eight peptides confirmed previously established disulfide bonds within gluten proteins, and the other six cystine peptides were identified for the first time. One of the newly identified cystine peptides represented a "head-to-tail" cross-link between high molecular weight glutenin subunits. This type of cross-link, which has been postulated as an integral part of glutenin models published previously, has now been proven experimentally for the first time. From the six remaining cystine peptides interchain disulfide bonds between α-gliadins, γ-gliadins, and low molecular weight glutenin subunits were established. PMID:22439977

  2. Computational methods for the description of pharmacologically relevant platinum complexes--molecular structure and bond dissociation.

    Science.gov (United States)

    Kokoschka, Malte; Galgonek, Jakub; Vondrasek, Jiri; Hobza, Pavel

    2016-02-01

    Cancer is after cardiovascular disease the most frequent cause of death in Europe. In 28 of 53 countries considered in this area it is already the leading cause of death and expected to gain even more importance until the year 2020. Amongst the large arsenal of different anti-cancer drugs, platinum drugs belong to the first developed anticancer drugs and still have a large impact on cancer therapy. Nevertheless therapy with platinum-anticancer drugs is accompanied by severe adverse effects caused by frequent interactions with the amino acids of different human proteins. Computational chemistry offers methods to study such interactions and even those of not yet synthesized drugs in silico. For such studies a profound knowledge of the prediction quality of various computational methods towards platinum-drug-like complexes is necessary. By this article we are aiming on delivering important accuracy information of the frequently used computational methods. Most important findings are the high performance of the double hybrid functional B2PLYP for the calculation of geometries, even in small basis sets, followed by BP86 and PBE and the still acceptable performance of the semi-empirical Method PM6-D3H4X for extremely large systems. To follow absolute energies of the dissociation process, LPNO-CEPA and B3LYP-D3 can be suggested while SCS-MP2 shows an extremely narrow standard deviation and a low maximum error, which make it an ideal candidate for relative energy calculations in the exploration of reaction mechanisms. PMID:26777459

  3. Sticky dissociative electron transfer to polychloroacetamides. In-cage ion-dipole interaction control through the dipole moment and intramolecular hydrogen bond.

    Science.gov (United States)

    Costentin, Cyrille; Louault, Cyril; Robert, Marc; Teillout, Anne-Lucie

    2005-03-31

    The reductive cleavage of chloro- and polychloroacetamides in N,N-dimethylformamide gives new insights into the nature of the in-cage ion radical cluster formed upon dissociative electron transfer. Within the family of compounds investigated, the electrochemical reduction leads to the successive expulsion of chloride ions. At each stage the electron transfer is concerted with the breaking of the C-Cl bond and acts as the rate-determining step. The reduction further leads to the formation of the corresponding carbanion with the injection of a second electron, which is in turn protonated by a weak acid added to the solution. From the joint use of cyclic voltammetric data, the sticky dissociative electron-transfer model and quantum ab initio calculations, the interaction energies within the cluster fragments (*R, Cl-) resulting from the first electron transfer to the parent RCl molecule are obtained. It is shown that the stability of these adducts, which should be viewed as an essentially electrostatic radical-ion pair, is mainly controlled by the intensity of the dipole moment of the remaining radical part and may eventually be strengthened by the formation of an intramolecular hydrogen bond, as is the case with 2-chloroacetamide. PMID:16833619

  4. Studies on the dissociation energies for some electronic states of K2 molecule using new formula

    International Nuclear Information System (INIS)

    The dissociation energies of five electronic states X1Σg+, a3Σu+, Og-, B1Ⅱu and 33Ⅱg of alkali-metal K2 molecule are calculated using the Sun's algebraic method (AM) based on the perturbation theory. Also the dissociation energies of these states are studied using the new analytical formula proposed recently. The results show that the dissociation energies obtained by new analytical formula agree excellently with the experimental values. It appears that the dissociation energy of an electronic state whose experimental value is not available can be expected using the new formula. (authors)

  5. Ion-Induced Dipole Interactions and Fragmentation Times : C$\\alpha$ -C$\\beta$ Chromophore Bond Dissociation Channel

    CERN Document Server

    Soorkia, Satchin; Kumar, Sunil; Pérot-Taillandier, Marie; Lucas, Bruno; Jouvet, Christophe; Barat, Michel; Fayeton, Jacqueline A

    2015-01-01

    The fragmentation times corresponding to the loss of the chromophore (C$\\alpha$-- C$\\beta$ bond dissociation channel) after photoexcitation at 263 nm have been investigated for several small peptides containing tryptophan or tyrosine. For tryptophan-containing peptides, the aromatic chromophore is lost as an ionic fragment (m/z 130), and the fragmentation time increases with the mass of the neutral fragment. In contrast, for tyrosine-containing peptides the aromatic chromophore is always lost as a neutral fragment (mass = 107 amu) and the fragmentation time is found to be fast (\\textless{}20 ns). These different behaviors are explained by the role of the postfragmentation interaction in the complex formed after the C$\\alpha$--C$\\beta$ bond cleavage.

  6. Dissociative photoionization of N2 in the 24-32 eV photon energy range

    International Nuclear Information System (INIS)

    Dissociative photoionization of N2 is studied with synchrotron radiation in the 24-32 eV photon energy range. Branching ratios between the different dissociation limits are measured from coincidence time of flight ion spectra threshold photoelectron-photoion coincidence recorded for state-selected N2+ parent ions. In this energy range, N2+ molecular ions are observed to dissociate only towards the three lowest dissociation limits. Dissociations towards the second and third ones, which correspond to the formation of N+(1D) and N(2D) metastable states, respectively, occur right from their thermochemical onsets. From the second dissociation limit energy up to the third one, the N+(1D) + N(4S)/N+(3P) + N(4S) branching ratio is almost constant and equal to 0.6:0.4, except at the energy of the C 2 Σu+ (v = 12) state, where this branching ratio is found to be equal to 0.5:0.5. From the third dissociation limit onset, N2+ ions fragment only towards this limit. Possible dissociation mechanisms are discussed, involving a spin-orbit coupling between doublet and quartet states of N2+ to produce N+(1D) + N(4S) and a direct dissociation to produce N+(3P) + N(2D). No dissociation towards the other limits has been observed, in particular to produce the N+(1S), N+(5S) and N(2P) metastable states

  7. Bond-Energy and Surface-Energy Calculations in Metals

    Science.gov (United States)

    Eberhart, James G.; Horner, Steve

    2010-01-01

    A simple technique appropriate for introductory materials science courses is outlined for the calculation of bond energies in metals from lattice energies. The approach is applied to body-centered cubic (bcc), face-centered cubic (fcc), and hexagonal-closest-packed (hcp) metals. The strength of these bonds is tabulated for a variety metals and is…

  8. A simple semi-empirical approximation for bond energy

    International Nuclear Information System (INIS)

    A simple semi-empirical expression for bond energy, related with a generalized bond index, is proposed and applied within the IEH framework. The correlation with experimental data is good for the intermolecular bond energy of base pairs of nucleic acids and other hydrogen bonded systems. The intramolecular bond energies for a sample of molecules containing typical bonds and for hydrides are discussed. The results are compared with those obtained by other methods. (Author)

  9. Shattering dissociation in high-energy molecular collisions between nitrate esters

    Science.gov (United States)

    Schweigert, Igor V.; Dunlap, Brett I.

    2011-09-01

    We present ab initio molecular dynamics simulations of head-on collisions between ethyl nitrate molecules at collisional energies from 200 to 1200 kJ/mol. Above a threshold energy, an increasing fraction of the collisions led to rapid dissociation on impact—"shattering." The probability of the shattering dissociation was derived from the quasiclassical trajectories sampling the initial vibrational motion at Tvib = 300 K. Even for the zero impact parameter and a fixed orientation considered, the observed dissociation probability exhibited a wide spread (much larger than kTvib) as a function of the collision energy. This is attributed to variations in the initial vibrational phase. We propose a closed-form expression for the energy-dependent dissociation probability that captures the dependence on the phase and use it to analyze the probability of the shattering dissociation of a larger nitrate ester, pentaerythritol tetranitrate.

  10. Effects of carbonyl bond, metal cluster dissociation, and evaporation rates on predictions of nanotube production in high-pressure carbon monoxide

    Science.gov (United States)

    Scott, Carl D.; Smalley, Richard E.

    2003-01-01

    The high-pressure carbon monoxide (HiPco) process for producing single-wall carbon nanotubes (SWNTs) uses iron pentacarbonyl as the source of iron for catalyzing the Boudouard reaction. Attempts using nickel tetracarbonyl led to no production of SWNTs. This paper discusses simulations at a constant condition of 1300 K and 30 atm in which the chemical rate equations are solved for different reaction schemes. A lumped cluster model is developed to limit the number of species in the models, yet it includes fairly large clusters. Reaction rate coefficients in these schemes are based on bond energies of iron and nickel species and on estimates of chemical rates for formation of SWNTs. SWNT growth is measured by the conformation of CO2. It is shown that the production of CO2 is significantly greater for FeCO because of its lower bond energy as compared with that of NiCO. It is also shown that the dissociation and evaporation rates of atoms from small metal clusters have a significant effect on CO2 production. A high rate of evaporation leads to a smaller number of metal clusters available to catalyze the Boudouard reaction. This suggests that if CO reacts with metal clusters and removes atoms from them by forming MeCO, this has the effect of enhancing the evaporation rate and reducing SWNT production. The study also investigates some other reactions in the model that have a less dramatic influence.

  11. Ab Initio Quantum Mechanical Description of Noncovalent Interactions at Its Limits: Approaching the Experimental Dissociation Energy of the HF Dimer.

    Science.gov (United States)

    Řezáč, Jan; Hobza, Pavel

    2014-08-12

    Hydrogen fluoride dimer is a perfect model system for studying hydrogen bonding. Its size makes it possible to apply the most advanced theoretical methods available, yet it is a full-featured complex of molecules with nontrivial electronic structure and dynamic properties. Moreover, the dissociation energy of the HF dimer has been measured experimentally with an unparalleled accuracy of ±1 cm(-1)(Bohac et al. J. Chem. Phys. 1992, 9, 6681). In this work, we attempt to reproduce it by purely ab initio means, using advanced quantum-mechanical computational methods free of any empiricism. The purpose of this study is to demonstrate the capabilities of today's computational chemistry and to point out its limitations by identifying the contributions that introduce the largest uncertainty into the result. The dissociation energy is calculated using a composite scheme including large basis set CCSD(T) calculations, contributions of higher excitations up to CCSDTQ, relativistic and diagonal Born-Oppenheimer corrections and anharmonic vibrational calculations. The error of the calculated dissociation energy is 0.07 kcal/mol (25 cm(-1), 2.5%) when compared to the experiment. The major part of this error can be attributed to the inaccuracy of the calculations of the zero-point vibrational energy. PMID:26588277

  12. A new quantum isotope effect: Extreme local mode selectivity in unimolecular dissociations imposed by antagonism between dynamic propensities of educts and zero point energies of products

    International Nuclear Information System (INIS)

    We predict a new quantum isotope effect for unimolecular dissociations of molecules with two equivalent but isotopically substituted bonds l (light isotope) and h (heavy isotope), e.g., HOT where l=HO and h=OT. Consider two near-degenerate local vibrational excitations of bonds l or h, with energies between the gap of product zero point energies. Dynamically, these excitations should induce preferential fissions of bonds l or h, but energetically, these decay channels are open and closed, respectively. Therefore, local excitation of bond h must be followed by extremely slow internal vibrational energy redistribution to bond l before dissociation, whereas local excitation of bond l induces direct, rapid decay. The resulting decay rates differ by many orders of magnitudes. The effect is demonstrated by fast Fourier transform propagation of representative wavepackets for a model system, HOT→H+OT. Extended applications to more excited educts HOT also confirm an effect discovered previously for HOD, i.e., local mode selective control of competing bond fissions H+OT left-arrow HOT→HO+T

  13. Dissociation of CO induced by He2+ ions. Pt. 1: Fragmentation and kinetic energy release spectra

    International Nuclear Information System (INIS)

    The dissociation of COq+ ions (q ≤ 3) produced in collisions of keV amu-1 He2+ ions with CO has been studied by time-of-flight measurements. Both singles and coincidence time-of-flight techniques have been used to determine the kinetic energy release of the dissociating CO molecules. We describe the method to transform the singles and coincidence time-of-flight spectra into total kinetic energy distributions and discuss these distributions. They represent kinetic energy release distributions which clearly exhibit various contributions associated with different dissociation channels. In comparison with other ionization methods similarities but also clear differences are noted. (author)

  14. Aromatic C-H bond activation revealed by infrared multiphoton dissociation spectroscopy.

    Science.gov (United States)

    Jašíková, Lucie; Hanikýřová, Eva; Schröder, Detlef; Roithová, Jana

    2012-04-01

    Metal-oxide cations are models of catalyst mediating the C-H bond activation of organic substrates. One of the most powerful reagents suggested in the gas phase is based on CuO(+) . Here, we describe the activation of the aromatic C-H bonds of phenanthroline in its complex with CuO(+) . The reaction sequence starts with a hydrogen atom abstraction by the oxygen atom from the 2-position of the phenanthroline ring, followed by OH migration to the ring. Using infrared multiphoton spectroscopy, it is shown that the reaction can be energetically facilitated by additional coordination of a water ligand to the copper ion. As the reaction is intramolecular, a spectroscopic characterization of the product is mandatory in order to unambiguously address the reaction mechanism. PMID:22689621

  15. Comparative study between hadron and heavy ion dissociation at high energies

    International Nuclear Information System (INIS)

    The present work deals with the dissociation of hadrons and heavy ions at high energies. In investigating hadron nucleus and nucleus-nucleus collisions, it is important to classify the experimental data, into two main classes; the coherent. and incoherent reactions. The coherent production is the main of our study. This process called electromagnetic dissociation (ED) and can be differentiate into coulomb dissociation (CD) and diffraction dissociation (DD). This work explains the experimental data of collisions of hadrons K± (70 GeV/c) and π(340 Gc V/c) and heavy ions 6Li, 7Li, 12C and16O at Dubna energies (3-4.5 A GeV/c)with emulsion target, in the frame of some models and theories which describe the mechanism of ED dissociation

  16. Improved Optimization for the Cluster Jastrow Antisymmetric Geminal Power and Tests on Triple-Bond Dissociations

    CERN Document Server

    Neuscamman, Eric

    2016-01-01

    We present a novel specialization of the variational Monte Carlo linear method for the optimization of the recently introduced cluster Jastrow antisymmetric geminal power ansatz, achieving a lower-order polynomial cost scaling than would be possible with a naive application of the linear method and greatly improving optimization performance relative to the previously employed quasi-Newton approach. We test the methodology on highly multi-reference triple-bond stretches, achieving accuracies superior to traditional coupled cluster theory and multi-reference perturbation theory in both the typical example of N$_2$ and the transition-metal-oxide example of [ScO]$^+$.

  17. Electron-Nuclear Energy Sharing in Above-Threshold Multiphoton Dissociative Ionization of H2

    DEFF Research Database (Denmark)

    Wu, J.; Kunitski, M.; Pitzer, M.;

    2013-01-01

    We report experimental observation of the energy sharing between electron and nuclei in above-threshold multiphoton dissociative ionization of H2 by strong laser fields. The absorbed photon energy is shared between the ejected electron and nuclei in a correlated fashion, resulting in multiple...... diagonal lines in their joint energy spectrum governed by the energy conservation of all fragment particles....

  18. H2 triplet states contribution to low-energy dissociative recombination of H2+

    International Nuclear Information System (INIS)

    Motivated by the observation of the predissociation of H2 triplet states in low vibrational levels, we evaluate the contribution of triplet dissociative states to the low-energy dissociative recombination of H2+ in vibrational levels where v = 0, 1. The triplet states contribute mainly via radial couplings between monoexcited Rydberg configurations without curve crossings. The total contribution of the six triplet states leading to dissociation in H(n = 1) + H(n = 2) is found to be smaller by at least one order of magnitude than the contribution of the lowest doubly excited singlet state, (2pσu)21 Σg+

  19. Direct molecular simulation of nitrogen dissociation based on an ab initio potential energy surface

    Energy Technology Data Exchange (ETDEWEB)

    Valentini, Paolo, E-mail: vale0142@umn.edu; Schwartzentruber, Thomas E., E-mail: schwart@aem.umn.edu; Bender, Jason D., E-mail: jbender73@gmail.com; Nompelis, Ioannis, E-mail: nompelis@umn.edu; Candler, Graham V., E-mail: candler@umn.edu [Department of Aerospace Engineering and Mechanics, College of Science and Engineering, University of Minnesota, Minneapolis, Minnesota 55455 (United States)

    2015-08-15

    The direct molecular simulation (DMS) approach is used to predict the internal energy relaxation and dissociation dynamics of high-temperature nitrogen. An ab initio potential energy surface (PES) is used to calculate the dynamics of two interacting nitrogen molecules by providing forces between the four atoms. In the near-equilibrium limit, it is shown that DMS reproduces the results obtained from well-established quasiclassical trajectory (QCT) analysis, verifying the validity of the approach. DMS is used to predict the vibrational relaxation time constant for N{sub 2}–N{sub 2} collisions and its temperature dependence, which are in close agreement with existing experiments and theory. Using both QCT and DMS with the same PES, we find that dissociation significantly depletes the upper vibrational energy levels. As a result, across a wide temperature range, the dissociation rate is found to be approximately 4–5 times lower compared to the rates computed using QCT with Boltzmann energy distributions. DMS calculations predict a quasi-steady-state distribution of rotational and vibrational energies in which the rate of depletion of high-energy states due to dissociation is balanced by their rate of repopulation due to collisional processes. The DMS approach simulates the evolution of internal energy distributions and their coupling to dissociation without the need to precompute rates or cross sections for all possible energy transitions. These benchmark results could be used to develop new computational fluid dynamics models for high-enthalpy flow applications.

  20. Direct molecular simulation of nitrogen dissociation based on an ab initio potential energy surface

    International Nuclear Information System (INIS)

    The direct molecular simulation (DMS) approach is used to predict the internal energy relaxation and dissociation dynamics of high-temperature nitrogen. An ab initio potential energy surface (PES) is used to calculate the dynamics of two interacting nitrogen molecules by providing forces between the four atoms. In the near-equilibrium limit, it is shown that DMS reproduces the results obtained from well-established quasiclassical trajectory (QCT) analysis, verifying the validity of the approach. DMS is used to predict the vibrational relaxation time constant for N2–N2 collisions and its temperature dependence, which are in close agreement with existing experiments and theory. Using both QCT and DMS with the same PES, we find that dissociation significantly depletes the upper vibrational energy levels. As a result, across a wide temperature range, the dissociation rate is found to be approximately 4–5 times lower compared to the rates computed using QCT with Boltzmann energy distributions. DMS calculations predict a quasi-steady-state distribution of rotational and vibrational energies in which the rate of depletion of high-energy states due to dissociation is balanced by their rate of repopulation due to collisional processes. The DMS approach simulates the evolution of internal energy distributions and their coupling to dissociation without the need to precompute rates or cross sections for all possible energy transitions. These benchmark results could be used to develop new computational fluid dynamics models for high-enthalpy flow applications

  1. Theoretical investigation on the bond dissociation enthalpies of phenolic compounds extracted from Artocarpus altilis using ONIOM(ROB3LYP/6-311++G(2df,2p):PM6) method

    Science.gov (United States)

    Thong, Nguyen Minh; Duong, Tran; Pham, Linh Thuy; Nam, Pham Cam

    2014-10-01

    Theoretical calculations have been performed to predict the antioxidant property of phenolic compounds extracted from Artocarpus altilis. The Osbnd H bond dissociation enthalpy (BDE), ionization energy (IE), and proton dissociation enthalpy (PDE) of the phenolic compounds have been computed. The ONIOM(ROB3LYP/6-311++G(2df,2p):PM6) method is able to provide reliable evaluation for the BDE(Osbnd H) in phenolic compounds. An important property of antioxidants is determined via the BDE(Osbnd H) of those compounds extracted from A. altilis. Based on the BDE(Osbnd H), compound 12 is considered as a potential antioxidant with the estimated BDE value of 77.3 kcal/mol in the gas phase.

  2. Elementary Steps of Syngas Reactions on Mo2C(001): Adsorption Thermochemistry and Bond Dissociation

    Energy Technology Data Exchange (ETDEWEB)

    Medford, Andrew

    2012-02-16

    Density functional theory (DFT) and ab initio thermodynamics are applied in order to investigate the most stable surface and subsurface terminations of Mo{sub 2}C(001) as a function of chemical potential and in the presence of syngas. The Mo-terminated (001) surface is then used as a model surface to evaluate the thermochemistry and energetic barriers for key elementary steps in syngas reactions. Adsorption energy scaling relations and Broensted-Evans-Polanyi relationships are established and used to place Mo{sub 2}C into the context of transition metal surfaces. The results indicate that the surface termination is a complex function of reaction conditions and kinetics. It is predicted that the surface will be covered by either C{sub 2}H{sub 2} or O depending on conditions. Comparisons to transition metals indicate that the Mo-terminated Mo{sub 2}C(001) surface exhibits carbon reactivity similar to transition metals such as Ru and Ir, but is significantly more reactive towards oxygen.

  3. Dissociation energies of gold clusters AuN+, N=7-27

    International Nuclear Information System (INIS)

    Unimolecular decay rates and monomer-dimer branching ratios of gold clusters AuN+ (N=7-27) have been measured as a function of excitation energy in photodissociation experiments on size-selected clusters stored in a Penning trap. Part of the data set has previously been used to extract model-free values of dissociation energies [Vogel et al., Phys. Rev. Lett. 87, 013401 (2001)]. Other parts of the data set do not allow this analysis. We use these data to extract tentative dissociation energies, based on the systematics of deviations between an Arrhenius analysis and the model-free values. The observed systematics also allows an estimate of the true frequency factor which often is much higher than the Arrhenius value but in good agreement with the expected detailed balance value. The data are also reanalyzed including radiative cooling which may explain part of the discrepancy between model-free and Arrhenius dissociation-energy values

  4. Methanol Oxidative Dehydrogenation on Oxide Catalysts: Molecular and Dissociative Routes and Hydrogen Addition Energies as Descriptors of Reactivity

    Energy Technology Data Exchange (ETDEWEB)

    Deshlahra, Prashant; Iglesia, Enrique

    2014-11-13

    The oxidative dehydrogenation (ODH) of alkanols on oxide catalysts is generally described as involving H-abstraction from alkoxy species formed via O–H dissociation. Kinetic and isotopic data cannot discern between such routes and those involving kinetically-relevant H-abstraction from undissociated alkanols. Here, we combine such experiments with theoretical estimates of activation energies and entropies to show that the latter molecular routes prevail over dissociative routes for methanol reactions on polyoxometalate (POM) clusters at all practical reaction temperatures. The stability of the late transition states that mediate H-abstraction depend predominantly on the stability of the O–H bond formed, making H-addition energies (HAE) accurate and single-valued descriptors of reactivity. Density functional theory-derived activation energies depend linearly on HAE values at each O-atom location on clusters with a range of composition (H3PMo12, H4SiMo12, H3PW12, H4PV1Mo11, and H4PV1W11); both barriers and HAE values reflect the lowest unoccupied molecular orbital energy of metal centers that accept the electron and the protonation energy of O-atoms that accept the proton involved in the H-atom transfer. Bridging O-atoms form O–H bonds that are stronger than those of terminal atoms and therefore exhibit more negative HAE values and higher ODH reactivity on all POM clusters. For each cluster composition, ODH turnover rates reflect the reactivity-averaged HAE of all accessible O-atoms, which can be evaluated for each cluster composition to provide a rigorous and accurate predictor of ODH reactivity for catalysts with known structure. These relations together with oxidation reactivity measurements can then be used to estimate HAE values and to infer plausible structures for catalysts with uncertain active site structures.

  5. Experimental and Theoretical Determination of Dissociation Energies of Dispersion-Dominated Aromatic Molecular Complexes.

    Science.gov (United States)

    Frey, Jann A; Holzer, Christof; Klopper, Wim; Leutwyler, Samuel

    2016-05-11

    The dissociation energy (D0) of an isolated and cold molecular complex in the gas-phase is a fundamental measure of the strength of the intermolecular interactions between its constituent moieties. Accurate D0 values are important for the understanding of intermolecular bonding, for benchmarking high-level theoretical calculations, and for the parametrization of force-field models used in fields ranging from crystallography to biochemistry. We review experimental and theoretical methods for determining gas-phase D0 values of M·S complexes, where M is a (hetero)aromatic molecule and S is a closed-shell "solvent" atom or molecule. The experimental methods discussed involve M-centered (S0 → S1) electronic excitation, which is often followed by ionization to the M(+)·S ion. The D0 is measured by depositing a defined amount of vibrational energy in the neutral ground state, giving M(‡)·S, the neutral S1 excited state, giving M*·S, or the M(+)·S ion ground state. The experimental methods and their relative advantages and disadvantages are discussed. Based on the electronic structure of M and S, we classify the M·S complexes as Type I, II, or III, and discuss characteristic properties of their respective potential energy surfaces that affect or hinder the determination of D0. Current theoretical approaches are reviewed, which comprise methods based on a Kohn-Sham reference determinant as well as wave function-based methods based on coupled-cluster theory. PMID:27055105

  6. Free energy calculations on Transthyretin dissociation and ligand binding from Molecular Dynamics Simulations

    DEFF Research Database (Denmark)

    Sørensen, Jesper; Hamelberg, Donald; McCammon, J. Andrew

    experimental results have helped to explain this aberrant behavior of TTR, however, structural insights of the amyloidgenic process are still lacking. Therefore, we have used all-atom molecular dynamics simulation and free energy calculations to study the initial phase of this process. We have calculated the...... free energy changes of the initial tetramer dissociation under different conditions and in the presence of thyroxine....

  7. Excitation and dissociation of molecules by low-energy (0-15 eV) electrons

    International Nuclear Information System (INIS)

    The author deals with excitation and dissociation processes which result from the interaction between low-energy (0.15 eV) electrons and molecules. Low-energy electron-impact spectroscopy is used to gain a better knowledge of the electronic structure of halomethanes, ethylene and some of its halogen substituted derivatives, and some more complex organic molecules. (Auth.)

  8. Dissociation of ozonide in water

    Energy Technology Data Exchange (ETDEWEB)

    Bentley, J.; Collins, J.Y.; Chipman, D.M.

    2000-05-18

    The free energy of bond dissociation for ozonide ion radical is found to be lowered in aqueous solution by about 20 kcal/mol relative to that in the gas phase, based on electronic structure calculations. Explicit treatment of anion-water clusters indicates that the stronger hydrogen bonds to first-shell water molecules formed by O{sup {minus}} relative to O{sub 3}{sup {minus}} account for much of the lowering. Reaction field methods show that nonspecific electrostatic polarization of the bulk solvent further contributes noticeably to the lowering. The study clearly demonstrates that the aqueous free energy of ozonide bond dissociation is small, and probably endothermic. The best semitheoretical prediction of the actual value is 5 {+-} 5 kcal/mol.

  9. Dissociation energy of diatomic molecules -comment on the work of Kaur and Mahajan

    Science.gov (United States)

    Chandra, Suresh

    2001-04-01

    When observed spectrum of a diatomic molecule is expressed in terms of the Dunham coefficients Y00, Y10, Y20, Y01, and Y11 only, dissociation energy of the molecule is given by Y00 + Y102/(-4 Y20). Kaur and Mahajan [1] have used the Dunham coefficients Y10, Y20, Y01, and Y11, for 15 vibrational states of 12 diatomic molecules (Y00 is zero for the cases accounted for), but their dissociation energy cannot be reproduced by the expression Y102/(-4 Y20). Probable reason for the discrepancy has been discussed.

  10. Dissociation energy of diatomic molecules – comment on the work of Kaur and Mahajan

    Indian Academy of Sciences (India)

    Suresh Chandra

    2001-04-01

    When observed spectrum of a diatomic molecule is expressed in terms of the Dunham coefficients 00, 10, 20, 01, and 11 only, dissociation energy of the molecule is given by 00 + $^{2}_{10}$/(-420). Kaur and Mahajan [1] have used the Dunham coefficients 10, 20, 01, and 11, for 15 vibrational states of 12 diatomic molecules (00 is zero for the cases accounted for), but their dissociation energy cannot be reproduced by the expression $^{2}_{10}$/(-420). Probable reason for the discrepancy has been discussed.

  11. Determination of bond energies by mass spectrometry. Some transition metal carbonyls

    International Nuclear Information System (INIS)

    Two groups of transition metal carbonyls have been studied, M(CO)6 and M(CO)5CS complexes of the Group VIB metals and M2(CO)10 complexes of the Group VIIB metals. Results for the hexacarbonyl complexes indicate that the measured fragmentation energies are in error by 0.25 +- 0.02 eV per CO produced. This is attributed to excitation of CO to the first vibrational state. Least-squares dissociation energies calculated from corrected data for M(CO)5CS complexes indicate that the M--CS bond is 3 to 4 times stronger than the M--CO bonds. Substitution of CS for CO in going from M(CO)6 to M(CO)5CS weakens the remaining M--CO bonds by an average of 0.2 eV. Previously unreported MnTc(CO)10 and TcRe(CO)10 are prepared by halide substitution of Tc(CO)5Br and Re(CO)5Br with Mn(CO)5- and Tc(CO)5-, respectively. In the positive ion, metal and mixed-metal decacarbonyls are considered as (CO)5M+--M(CO)5 complexes possessing five strong and five weak M--CO bonds. For Mn2(CO)10 and Re2(CO)10, M+--M dissociation energies are 3.0 +- 0.1 and 4.0 +- 0.3 eV, respectively. These energies are 2.5 times greater than those reported for homolytic cleavage to M(CO)5+ and M(CO)5

  12. Determination of bond energies by mass spectrometry. Some transition metal carbonyls

    Energy Technology Data Exchange (ETDEWEB)

    Michels, G.D.

    1979-01-01

    Two groups of transition metal carbonyls have been studied, M(CO)/sub 6/ and M(CO)/sub 5/CS complexes of the Group VIB metals and M/sub 2/(CO)/sub 10/ complexes of the Group VIIB metals. Results for the hexacarbonyl complexes indicate that the measured fragmentation energies are in error by 0.25 +- 0.02 eV per CO produced. This is attributed to excitation of CO to the first vibrational state. Least-squares dissociation energies calculated from corrected data for M(CO)/sub 5/CS complexes indicate that the M--CS bond is 3 to 4 times stronger than the M--CO bonds. Substitution of CS for CO in going from M(CO)/sub 6/ to M(CO)/sub 5/CS weakens the remaining M--CO bonds by an average of 0.2 eV. Previously unreported MnTc(CO)/sub 10/ and TcRe(CO)/sub 10/ are prepared by halide substitution of Tc(CO)/sub 5/Br and Re(CO)/sub 5/Br with Mn(CO)/sub 5//sup -/ and Tc(CO)/sub 5//sup -/, respectively. In the positive ion, metal and mixed-metal decacarbonyls are considered as (CO)/sub 5/M/sup +/--M(CO)/sub 5/ complexes possessing five strong and five weak M--CO bonds. For Mn/sub 2/(CO)/sub 10/ and Re/sub 2/(CO)/sub 10/, M/sup +/--M dissociation energies are 3.0 +- 0.1 and 4.0 +- 0.3 eV, respectively. These energies are 2.5 times greater than those reported for homolytic cleavage to M(CO)/sub 5//sup +/ and M(CO)/sub 5/.

  13. Kinetic Energy Distribution of H(2p) Atoms from Dissociative Excitation of H2

    Science.gov (United States)

    Ajello, Joseph M.; Ahmed, Syed M.; Kanik, Isik; Multari, Rosalie

    1995-01-01

    The kinetic energy distribution of H(2p) atoms resulting from electron impact dissociation of H2 has been measured for the first time with uv spectroscopy. A high resolution uv spectrometer was used for the measurement of the H Lyman-alpha emission line profiles at 20 and 100 eV electron impact energies. Analysis of the deconvolved 100 eV line profile reveals the existence of a narrow line peak and a broad pedestal base. Slow H(2p) atoms with peak energy near 80 meV produce the peak profile, which is nearly independent of impact energy. The wings of H Lyman-alpha arise from dissociative excitation of a series of doubly excited Q(sub 1) and Q(sub 2) states, which define the core orbitals. The fast atom energy distribution peaks at 4 eV.

  14. Molecular Dissociation in Presence of a Catalyst II: The bond breaking role of the transition from virtual to localized states

    CERN Document Server

    Ruderman, Andres; Santos, Elizabeth; Pastawski, Horacio Miguel

    2016-01-01

    We address a molecular dissociation mechanism that is known to occur when a H 2 molecule approaches a catalyst with its molecular axis parallel to the surface. It is found that molecular dissociation is a form of quantum dynamical phase transition associated to an ana- lytic discontinuity of quite unusual nature: the molecule is destabilized by the transition from non-physical virtual states into actual local- ized states. Current description complements our recent results for a molecule approaching the catalyst with its molecular axis perpendicu- lar to the surface. Also, such a description can be seen as a further successful implementation of a non-Hermitian Hamiltonian in a well defined model.

  15. Coarse-grain model for internal energy excitation and dissociation of molecular nitrogen

    International Nuclear Information System (INIS)

    Graphical abstract: A rovibrational collisional coarse-grain model allows to reduce a detailed mechanism for the internal energy excitation and dissociation processes behind a strong shockwave in nitrogen. Highlights: ► A rovibrational coarse-grain model is developed for nitrogen. ► In this model, energy levels of an ab initio database are lumped into bins. ► Rate coefficients are averaged assuming a uniform distribution within each bin. ► The coarse-grain model is used to study a 1D strong shockwave. ► Relaxation and dissociation processes are accurately described using a few equations. - Abstract: A rovibrational collisional coarse-grain model has been developed to reduce a detailed mechanism for the internal energy excitation and dissociation processes behind a strong shockwave in a nitrogen flow. The rovibrational energy levels of the electronic ground state of the nitrogen molecule were lumped into a smaller number of bins. The reaction rate coefficients of an ab initio database developed at NASA Ames Research Center were averaged for each bin based on a uniform distribution of the energy levels within the bin. The results were obtained by coupling the Master equation for the reduced mechanism with a one-dimensional flow solver for conditions expected for reentry into Earth’s atmosphere at 10 km/s. The coarse-grain collisional model developed allow us to describe accurately the internal energy relaxation and dissociation processes based on a smaller number of equations, as opposed to existing reduced models assuming thermal equilibrium between the rotational and translational energy modes.

  16. Bonding Energy and Growth Habit of Lithium Niobate Single Crystals

    Institute of Scientific and Technical Information of China (English)

    2006-01-01

    On the basis of crystallographic structure of lithium niobate (LN), the bonding energy was quantitatively calculated by the bond valence sum model, which was employed to investigate the crystal growth. A possible relationship between the crystal growth habit and chemical bonding energy of LN crystals are found. It is found that the higher the bond energy, the slower the growth rate, and the more important the plane. The analytical results indicate that (012) plane is the most influential face for the LN crystal growth, which consists well with the standard card (JCPDS Card: 20-0631) and our previous experimental observation. The current work shows that the chemical bond analysis of LN crystals allows us to predict its growth habit and thus to obtain the expected morphology during the spontaneous growth.

  17. Comparison of Gold Bonding with Mercury Bonding

    NARCIS (Netherlands)

    Kraka, Elfi; Filatov, Michael; Cremer, Dieter

    2009-01-01

    Nine AuX molecules (X = H, O, S, Se, Te, F, Cl, Br, I), their isoelectronic HgX(+) analogues, and the corresponding neutral HgX diatomics have been investigated using NESC (Normalized Elimination of the Small Component) and B3LYP theory to determine relativistic effects for bond dissociation energie

  18. A Unified Kinetics and Equilibrium Experiment: Rate Law, Activation Energy, and Equilibrium Constant for the Dissociation of Ferroin

    Science.gov (United States)

    Sattar, Simeen

    2011-01-01

    Tris(1,10-phenanthroline)iron(II) is the basis of a suite of four experiments spanning 5 weeks. Students determine the rate law, activation energy, and equilibrium constant for the dissociation of the complex ion in acid solution and base dissociation constant for phenanthroline. The focus on one chemical system simplifies a daunting set of…

  19. The Calculation of Accurate Metal-Ligand Bond Energies

    Science.gov (United States)

    Bauschlicher, Charles W.; Partridge, Harry, III; Ricca, Alessandra; Arnold, James O. (Technical Monitor)

    1997-01-01

    The optimization of the geometry and calculation of zero-point energies are carried out at the B3LYP level of theory. The bond energies are determined at this level, as well as at the CCSD(T) level using very large basis sets. The successive OH bond energies to the first row transition metal cations are reported. For most systems there has been an experimental determination of the first OH. In general, the CCSD(T) values are in good agreement with experiment. The bonding changes from mostly covalent for the early metals to mostly electrostatic for the late transition metal systems.

  20. The Bond Order of C2 from a Strictly N-Representable Natural Orbital Energy Functional Perspective.

    Science.gov (United States)

    Piris, Mario; Lopez, Xabier; Ugalde, Jesus M

    2016-03-14

    The bond order of the ground electronic state of the carbon dimer has been analyzed in the light of natural orbital functional theory calculations carried out with an approximate, albeit strictly N-representable, energy functional. Three distinct solutions have been found from the Euler equations of the minimization of the energy functional with respect to the natural orbitals and their occupation numbers, which expand upon increasing values of the internuclear coordinate. In the close vicinity of the minimum energy region, two of the solutions compete around a discontinuity point. The former, corresponding to the absolute minimum energy, features two valence natural orbitals of each of the following symmetries, σ, σ*, π and π*, and has three bonding interactions and one antibonding interaction, which is very suggestive of a bond order large than two but smaller than three. The latter, features one σ-σ* linked pair of natural orbitals and three degenerate pseudo-bonding like orbitals, paired each with one triply degenerate pseudo-antibonding orbital, which points to a bond order larger than three. When correlation effects, other than Hartree-Fock for example, between the paired natural orbitals are accounted for, this second solution vanishes yielding a smooth continuous dissociation curve. Comparison of the vibrational energies and electron ionization energies, calculated on this curve, with their corresponding experimental marks, lend further support to a bond order for C2 intermediate between acetylene and ethylene. PMID:26822104

  1. Diffraction dissociation in proton-proton collisions at ISR energies

    Energy Technology Data Exchange (ETDEWEB)

    Armitage, J.C.M.; Benz, P.; Bobbink, G.J.; Erne, F.C.; Kooijman, P.; Loebinger, F.K.; Macbeth, A.A.; Montgomery, H.E.; Murphy, P.G.; Rudge, A. (European Organization for Nuclear Research, Geneva (Switzerland)

    1982-01-25

    Data are presented on the reaction pp ..-->.. pX in the range of four-momentum transfer squared 0.04 < -t < 0.80 GeV/sup 2/ and of c.m. energy squared 550 < s < 3880 GeV/sup 2/. Invariant cross sections are given as a function of M/sup 2//s, where M is the mass of the missing system X, and of t. The cross sections are shown to scale in the variable M/sup 2//s, for M/sup 2//s > 0.01. The total diffractive cross section integrated over t and M/sup 2//s up to M/sup 2//s = 0.05 rises by approximately 15% from sigmasub(dif) = 6.5 +- 0.2 mb at 550 GeV/sup 2/ to sigmasub(dif) = 7.5 +- 0.3 mb at 3880 GeV/sup 2/.

  2. Municipal bond financing of solar energy facilities

    Energy Technology Data Exchange (ETDEWEB)

    White, S.S.

    1979-12-01

    The application of the laws of municipal bond financing to solar facilities is examined. The type of facilities under consideration are outlined. The general legal principles of municipal securities financing are discussed. The effect of recent decisions applying antitrust liability to municipal corporations is also discussed. Five specific types of municipal bonds are explained. The application of Section 103 of the Internal Revenue Code of 1954, as amended, to the issuance of municipal bonds for solar facility financing is examined also. Five bond laws of five representative states are examined and whether the eight types of solar facilities under consideration could be financed under such law is discussed. The application of the general legal principle is illustrated. Three hypothetical situations are set forth and common legal issues to be confronted by city officials in proposing such financing are discussed. These issues will be raised in most financings, but the purpose is to examine the common context in which they are raised. It is concluded that if it can be shown that the purpose of the solar facilities to be financed is to benefit the public, all legal obstacles to the use of municipal financing of solar facilities can be substantially overcome.

  3. Graph-theoretical identification of dissociation pathways on free energy landscapes of biomolecular interaction.

    Science.gov (United States)

    Wang, Ling; Stumm, Boris; Helms, Volkhard

    2010-03-01

    Biomolecular association and dissociation reactions take place on complicated interaction free energy landscapes that are still very hard to characterize computationally. For large enough distances, though, it often suffices to consider the six relative translational and rotational degrees of freedom of the two particles treated as rigid bodies. Here, we computed the six-dimensional free energy surface of a dimer of water-soluble alpha-helices by scanning these six degrees of freedom in about one million grid points. In each point, the relative free energy difference was computed as the sum of the polar and nonpolar solvation free energies of the helix dimer and of the intermolecular coulombic interaction energy. The Dijkstra graph algorithm was then applied to search for the lowest cost dissociation pathways based on a weighted, directed graph, where the vertices represent the grid points, the edges connect the grid points and their neighbors, and the weights are the reaction costs between adjacent pairs of grid points. As an example, the configuration of the bound state was chosen as the source node, and the eight corners of the translational cube were chosen as the destination nodes. With the strong electrostatic interaction of the two helices giving rise to a clearly funnel-shaped energy landscape, the eight lowest-energy cost pathways coming from different orientations converge into a well-defined pathway for association. We believe that the methodology presented here will prove useful for identifying low-energy association and dissociation pathways in future studies of complicated free energy landscapes for biomolecular interaction. PMID:19603501

  4. Molecular dissociation in presence of a catalyst: II. The bond breaking role of the transition from virtual to localized states

    Science.gov (United States)

    Ruderman, A.; Dente, A. D.; Santos, E.; Pastawski, H. M.

    2016-08-01

    We address a molecular dissociation mechanism that is known to occur when a H2 molecule approaches a catalyst with its molecular axis parallel to the surface. It is found that molecular dissociation is a form of quantum dynamical phase transition associated to an analytic discontinuity of quite unusual nature: the molecule is destabilized by the transition from non-physical virtual states into actual localized states. Current description complements our recent results for a molecule approaching the catalyst with its molecular axis perpendicular to the surface (Ruderman et al 2015 J. Phys.: Condens. Matter 27 315501). Also, such a description can be seen as a further successful implementation of a non-Hermitian Hamiltonian in a well defined model.

  5. Modeling of dissociation and energy transfer in shock-heated nitrogen flows

    International Nuclear Information System (INIS)

    This work addresses the modeling of dissociation and energy transfer processes in shock heated nitrogen flows by means of the maximum entropy linear model and a newly proposed hybrid bin vibrational collisional model. Both models aim at overcoming two of the main limitations of the state of the art non-equilibrium models: (i) the assumption of equilibrium between rotational and translational energy modes of the molecules and (ii) the reliance on the quasi-steady-state distribution for the description of the population of the internal levels. The formulation of the coarse-grained models is based on grouping the energy levels into bins, where the population is assumed to follow a Maxwell-Boltzmann distribution at its own temperature. Different grouping strategies are investigated. Following the maximum entropy principle, the governing equations are obtained by taking the zeroth and first-order moments of the rovibrational master equations. The accuracy of the proposed models is tested against the rovibrational master equation solution for both flow quantities and population distributions. Calculations performed for free-stream velocities ranging from 5 km/s to 10 km/s demonstrate that dissociation can be accurately predicted by using only 2-3 bins. It is also shown that a multi-temperature approach leads to an under-prediction of dissociation, due to the inability of the former to account for the faster excitation of high-lying vibrational states

  6. Modeling of dissociation and energy transfer in shock-heated nitrogen flows

    Energy Technology Data Exchange (ETDEWEB)

    Munafò, A., E-mail: munafo@illinois.edu [Department of Aerospace Engineering, University of Illinois at Urbana-Champaign, Talbot Laboratory, 104 S. Wright St., Urbana, Illinois 61801 (United States); NASA Ames Research Center, Moffett Field, California 94035 (United States); Liu, Y., E-mail: yen.liu@nasa.gov [NASA Ames Research Center, Moffett Field, California 94035 (United States); Panesi, M., E-mail: mpanesi@illinois.edu [Department of Aerospace Engineering, University of Illinois at Urbana-Champaign, Talbot Laboratory, 104 S. Wright St., Urbana, Illinois 61801 (United States)

    2015-12-15

    This work addresses the modeling of dissociation and energy transfer processes in shock heated nitrogen flows by means of the maximum entropy linear model and a newly proposed hybrid bin vibrational collisional model. Both models aim at overcoming two of the main limitations of the state of the art non-equilibrium models: (i) the assumption of equilibrium between rotational and translational energy modes of the molecules and (ii) the reliance on the quasi-steady-state distribution for the description of the population of the internal levels. The formulation of the coarse-grained models is based on grouping the energy levels into bins, where the population is assumed to follow a Maxwell-Boltzmann distribution at its own temperature. Different grouping strategies are investigated. Following the maximum entropy principle, the governing equations are obtained by taking the zeroth and first-order moments of the rovibrational master equations. The accuracy of the proposed models is tested against the rovibrational master equation solution for both flow quantities and population distributions. Calculations performed for free-stream velocities ranging from 5 km/s to 10 km/s demonstrate that dissociation can be accurately predicted by using only 2-3 bins. It is also shown that a multi-temperature approach leads to an under-prediction of dissociation, due to the inability of the former to account for the faster excitation of high-lying vibrational states.

  7. Accuracy of the DLPNO-CCSD(T) method for non-covalent bond dissociation enthalpies from coinage metal cation complexes

    KAUST Repository

    Minenkov, Yury

    2015-08-27

    The performance of the domain based local pair-natural orbital coupled-cluster (DLPNO-CCSD(T)) method has been tested to reproduce the experimental gas phase ligand dissociation enthalpy in a series of Cu+, Ag+ and Au+ complexes. For 33 Cu+ - non-covalent ligand dissociation enthalpies all-electron calculations with the same method result in MUE below 2.2 kcal/mol, although a MSE of 1.4 kcal/mol indicates systematic underestimation of the experimental values. Inclusion of scalar relativistic effects for Cu either via effective core potential (ECP) or Douglass-Kroll-Hess Hamiltonian, reduces the MUE below 1.7 kcal/mol and the MSE to -1.0 kcal/mol. For 24 Ag+ - non-covalent ligand dissociation enthalpies the DLPNO-CCSD(T) method results in a mean unsigned error (MUE) below 2.1 kcal/mol and vanishing mean signed error (MSE). For 15 Au+ - non-covalent ligand dissociation enthalpies the DLPNO-CCSD(T) methods provides larger MUE and MSE, equal to 3.2 and 1.7 kcal/mol, which might be related to poor precision of the experimental measurements. Overall, for the combined dataset of 72 coinage metal ion complexes DLPNO-CCSD(T) results in a MUE below 2.2 kcal/mol and an almost vanishing MSE. As for a comparison with computationally cheaper density functional theory (DFT) methods, the routinely used M06 functional results in MUE and MSE equal to 3.6 and -1.7 kca/mol. Results converge already at CC-PVTZ quality basis set, making highly accurate DLPNO-CCSD(T) estimates to be affordable for routine calculations (single-point) on large transition metal complexes of > 100 atoms.

  8. Methods for associating or dissociating guest materials with a metal organic framework, systems for associating or dissociating guest materials within a series of metal organic frameworks, thermal energy transfer assemblies, and methods for transferring thermal energy

    Energy Technology Data Exchange (ETDEWEB)

    McGrail, B. Peter; Brown, Daryl R.; Thallapally, Praveen K.

    2016-08-02

    Methods for releasing associated guest materials from a metal organic framework are provided. Methods for associating guest materials with a metal organic framework are also provided. Methods are provided for selectively associating or dissociating guest materials with a metal organic framework. Systems for associating or dissociating guest materials within a series of metal organic frameworks are provided. Thermal energy transfer assemblies are provided. Methods for transferring thermal energy are also provided.

  9. How resonance assists hydrogen bonding interactions: an energy decomposition analysis.

    Science.gov (United States)

    Beck, John Frederick; Mo, Yirong

    2007-01-15

    Block-localized wave function (BLW) method, which is a variant of the ab initio valence bond (VB) theory, was employed to explore the nature of resonance-assisted hydrogen bonds (RAHBs) and to investigate the mechanism of synergistic interplay between pi delocalization and hydrogen-bonding interactions. We examined the dimers of formic acid, formamide, 4-pyrimidinone, 2-pyridinone, 2-hydroxpyridine, and 2-hydroxycyclopenta-2,4-dien-1-one. In addition, we studied the interactions in beta-diketone enols with a simplified model, namely the hydrogen bonds of 3-hydroxypropenal with both ethenol and formaldehyde. The intermolecular interaction energies, either with or without the involvement of pi resonance, were decomposed into the Hitler-London energy (DeltaEHL), polarization energy (DeltaEpol), charge transfer energy (DeltaECT), and electron correlation energy (DeltaEcor) terms. This allows for the examination of the character of hydrogen bonds and the impact of pi conjugation on hydrogen bonding interactions. Although it has been proposed that resonance-assisted hydrogen bonds are accompanied with an increasing of covalency character, our analyses showed that the enhanced interactions mostly originate from the classical dipole-dipole (i.e., electrostatic) attraction, as resonance redistributes the electron density and increases the dipole moments in monomers. The covalency of hydrogen bonds, however, changes very little. This disputes the belief that RAHB is primarily covalent in nature. Accordingly, we recommend the term "resonance-assisted binding (RAB)" instead of "resonance-assisted hydrogen bonding (RHAB)" to highlight the electrostatic, which is a long-range effect, rather than the electron transfer nature of the enhanced stabilization in RAHBs. PMID:17143867

  10. Dissociative Adsorption of Molecules on Graphene and Silicene

    CERN Document Server

    Gurel, H Hakan; Ciraci, S

    2014-01-01

    We study the interaction of H$_2$, O$_2$, CO, H$_2$O and OH molecules with the vacancy defects of graphene and silicene. Atoms around the bare vacancy reconstruct and specific chemically active sites are created. While H$_2$, O$_2$ and CO remain intact on both pristine graphene and silicene, these molecules can dissociate when they are placed at the close proximity of these chemically active sites and nucleate centers for the hydrogenation and oxygenation. Saturation of the dangling bonds at the defect sites by constituent atoms of dissociated molecules gives rise to significant modification of electronic and magnetic properties. We analyzed the mechanism of the dissociation and revealed a concerted action of surrounding host atoms together with dissociated molecules to lower the energy barrier needed for dissociation. The dissociations of H$_2$O and OH are hindered by high energy barriers. Our study suggests that graphene and silicene can be functionalized by creating meshes of single vacancy, where specific...

  11. Probing the Conformational and Functional Consequences of Disulfide Bond Engineering in Growth Hormone by Hydrogen-Deuterium Exchange Mass Spectrometry Coupled to Electron Transfer Dissociation

    DEFF Research Database (Denmark)

    Seger, Signe T; Breinholt, Jens; Faber, Johan H; Andersen, Mette D; Wiberg, Charlotte; Schjødt, Christine B; Rand, Kasper D

    2015-01-01

    Human growth hormone (hGH), and its receptor interaction, is essential for cell growth. To stabilize a flexible loop between helices 3 and 4, while retaining affinity for the hGH receptor, we have engineered a new hGH variant (Q84C/Y143C). Here, we employ hydrogen-deuterium exchange mass...... spectrometry (HDX-MS) to map the impact of the new disulfide bond on the conformational dynamics of this new hGH variant. Compared to wild type hGH, the variant exhibits reduced loop dynamics, indicating a stabilizing effect of the introduced disulfide bond. Furthermore, the disulfide bond exhibits longer...... ranging effects, stabilizing a short α-helix quite distant from the mutation sites, but also rendering a part of the α-helical hGH core slightly more dynamic. In the regions where the hGH variant exhibits a different deuterium uptake than the wild type protein, electron transfer dissociation (ETD...

  12. Activation energies for gas-phase dissociations of multiply charged ions from electrospay ionization mass spectrometry

    Energy Technology Data Exchange (ETDEWEB)

    Busman, M.; Rockwood, A.L.; Smith, R.D. [Pacific Northwest Lab., Richland, WA (United States)

    1992-03-19

    The reactions of multiply protonated melittin molecular ions of various charge states produced from an electrospray ionization source have been studied. The flow of ions entrained in gas through a heated metal capillary inlet serves as a reaction vessel for gas-phase measurements of molecular ion reaction rates using mass spectrometry. Activation energies for the unimolecular dissociation reactions are calculated from the temperature dependence of the reaction kinetics. The differences in activation energies for the reactions of the different charge states are attributed to the destabilizing effect of Coulombic repulsion for high charged ions. 18 refs., 3 figs., 1 tab.

  13. Energy-dependent branching between fluorescence and singlet exciton dissociation in sexithienyl thin films

    Science.gov (United States)

    Dippel, O.; Brandl, V.; Bässler, H.; Danieli, R.; Zamboni, R.; Taliani, C.

    1993-12-01

    The fluorescence yield of thin films of sexithienyl drops rapidly above the S 1←S 0 absorption edge while the yield of photocarrier generation increases simultaneously. This unusual behavior of a molecular solid is interpreted in terms of an energy-dependent branching between fluorescence and dissociation of a singlet excitation into a weakly bound electron—hole pair. This is shown to be a characteristic feature of a disordered system in which the energy levels of both neutral and charged excitations are subject to inhomogeneous broadening. In T6 the latter arises from torsional displacement of the thienylene moities.

  14. Dissociative double-photoionization of butadiene in the 25-45 eV energy range using 3-D multi-coincidence ion momentum imaging spectrometry

    International Nuclear Information System (INIS)

    Dissociative double-photoionization of butadiene in the 25-45 eV energy range has been studied with tunable synchrotron radiation using full three-dimensional ion momentum imaging. Using ab initio calculations, the electronic states of the molecular dication below 33 eV are identified. The results of the measurement and calculation show that double ionization from π orbitals selectively triggers twisting about the terminal or central C–C bonds. We show that this conformational rearrangement depends upon the dication electronic state, which effectively acts as a gateway for the dissociation reaction pathway. For photon energies above 33 eV, three-body dissociation channels where neutral H-atom evaporation precedes C–C charge-separation in the dication species appear in the correlation map. The fragment angular distributions support a model where the dication species is initially aligned with the molecular backbone parallel to the polarization vector of the light, indicating a high probability for double-ionization to the “gateway states” for molecules with this orientation

  15. Dissociative double-photoionization of butadiene in the 25-45 eV energy range using 3-D multi-coincidence ion momentum imaging spectrometry.

    Science.gov (United States)

    Oghbaie, Shabnam; Gisselbrecht, Mathieu; Laksman, Joakim; Månsson, Erik P; Sankari, Anna; Sorensen, Stacey L

    2015-09-21

    Dissociative double-photoionization of butadiene in the 25-45 eV energy range has been studied with tunable synchrotron radiation using full three-dimensional ion momentum imaging. Using ab initio calculations, the electronic states of the molecular dication below 33 eV are identified. The results of the measurement and calculation show that double ionization from π orbitals selectively triggers twisting about the terminal or central C-C bonds. We show that this conformational rearrangement depends upon the dication electronic state, which effectively acts as a gateway for the dissociation reaction pathway. For photon energies above 33 eV, three-body dissociation channels where neutral H-atom evaporation precedes C-C charge-separation in the dication species appear in the correlation map. The fragment angular distributions support a model where the dication species is initially aligned with the molecular backbone parallel to the polarization vector of the light, indicating a high probability for double-ionization to the "gateway states" for molecules with this orientation. PMID:26395707

  16. Estimating the energy of intramolecular hydrogen bonds in chitosan oligomers

    Science.gov (United States)

    Mikhailov, G. P.; Lazarev, V. V.

    2016-07-01

    The effect the number of chitosan monomer units CTS n ( n = 1-5), the protonation of chitosan dimers, and the interaction between CTS n ( n = 1-3) and acetate ions have on the energy of intramolecular hydrogen bonds is investigated by means of QTAIM analysis and solving the vibrational problem within the cluster-continuum model. It is established that the number of H-bonds in CTS n is 2 n - 1 and the total energy of H-bonds grows by ~20 kJ/mol. It is concluded that the hydrogen bonds between CTS and acetate ions play a major role in the stabilization of polyelectrolyte complexes in dilute acetic acid solutions of CTS.

  17. Various Carbon to Carbon Bond Lengths Inter-related via the Golden Ratio, and their Linear Dependence on Bond Energies

    CERN Document Server

    Heyrovska, Raji

    2008-01-01

    This work presents the relations between the carbon to carbon bond lengths in the single, double and triple bonds and in graphite, butadiene and benzene. The Golden ratio, which was shown to divide the Bohr radius into two parts pertaining to the charged particles, the electron and proton, and to divide inter-atomic distances into their cationic and anionic radii, also plays a role in the carbon-carbon bonds and in the ionic/polar character of those in graphite, butadiene and benzene. Further, the bond energies of the various CC bonds are shown to vary linearly with the bond lengths.

  18. Exclusive diffractive dissociation of K/sub L/ mesons at high energies

    International Nuclear Information System (INIS)

    Using the hadronic component of the Fermilab broad band neutral beam, we have observed diffractive dissociation of K/sub L/ mesons with a carbon target into the exclusive final states Ks π+π-, K*(890)+-π-+, Ks rho0, Ks ω0, and Ks phi, but not Ks psi. The diffractive production cross section for these states is not strongly dependent on incident energy varying at most by 30% between 75 and 150 GeV. The shapes of the mass distributions do not change appreciably as a function of lab energy. The ratio of the diffractive mass threshold production of K*(890)+-π-+, Ks rho0, Ks ω0 and Ks phi is compared with results of two other experiments at lower lab energies with charged kaon beams on a hydrogen target

  19. Collision-induced dissociation of fatty acid [M - 2H + Na]- ions: charge-directed fragmentation and assignment of double bond position.

    Science.gov (United States)

    Thomas, Michael C; Altvater, Jens; Gallagher, Thomas J; Nette, Geoffrey W

    2014-11-01

    The collision-induced dissociation (CID) of cationic fatty acid-metal ion complexes has been extensively studied and, in general, provides rich structural information. In particular, charge-remote fragmentation processes are commonly observed allowing the assignment of double bond position. In a previous manuscript, we presented two methods to doubly deprotonate polyunsaturated fatty acids to form anionic fatty acid-sodium ion complexes, referred to as [M - 2H + Na] (-) ions. In the current manuscript, the CID behavior of these [M - 2H + Na] (-) ions is investigated for the first time. Significantly, we also present a deuterium-labeling experiment, which excludes the possibility that deprotonation occurs predominately at the α-carbon in the formation of fatty acid [M - H + NaF](-) ions. This supports our original proposal where deprotonation occurs at the bis-allylic positions of polyunsaturated fatty acids. CID spectra of polyunsaturated fatty acid [M - 2H + Na](-) ions display abundant product ions arising from acyl chain cleavages. Through the examination of fatty acid isomers, it is demonstrated that double bond position may be unequivocally determined for methylene-interrupted polyunsaturated fatty acids with three or more carbon-carbon double bonds. In addition, CID of [M - 2H + Na](-) ions was applied to 18:3 isomers of Nannochloropsis oculata and three isomers were tentatively identified: ∆(9,12,15)18:3, ∆(6,9,12)18:3, and ∆(5,8,11)18:3. We propose that structurally-informative product ions are formed via charge-driven fragmentation processes at the site of the resonance-stabilized carbanion as opposed to charge-remote fragmentation processes, which could be inferred if deprotonation occurred predominately at the α-carbon. PMID:25142324

  20. Students' Interdisciplinary Reasoning about "High-Energy Bonds" and ATP

    CERN Document Server

    Dreyfus, Benjamin W; Sawtelle, Vashti; Svoboda, Julia; Turpen, Chandra; Redish, Edward F

    2012-01-01

    Students' sometimes contradictory ideas about ATP (adenosine triphosphate) and the nature of chemical bonds have been studied in the biology and chemistry education literatures, but these topics are rarely part of the introductory physics curriculum. We present qualitative data from an introductory physics course for undergraduate biology majors that seeks to build greater interdisciplinary coherence and therefore includes these topics. In these data, students grapple with the apparent contradiction between the energy released when the phosphate bond in ATP is broken and the idea that an energy input is required to break a bond. We see that students' perceptions of how each scientific discipline bounds the system of interest can influence how they justify their reasoning about a topic that crosses disciplines. This has consequences for a vision of interdisciplinary education that respects disciplinary perspectives while bringing them into interaction in ways that demonstrate consistency amongst the perspectiv...

  1. EOMCC over excited state Hartree-Fock solutions (ESHF-EOMCC: An efficient approach for the entire ground state potential energy curves of higher-order bonds

    Directory of Open Access Journals (Sweden)

    Y. Sajeev

    2015-08-01

    Full Text Available The equation-of-motion coupled cluster (EOMCC method based on the excited state Hartree-Fock (ESHF solutions is shown to be appropriate for computing the entire ground state potential energy curves of strongly correlated higher-order bonds. The new approach is best illustrated for the homolytic dissociation of higher-order bonds in molecules. The required multireference character of the true ground state wavefunction is introduced through the linear excitation operator of the EOMCC method. Even at the singles and doubles level of cluster excitation truncation, the nonparallelity error of the ground state potential energy curve from the ESHF based EOMCC method is small.

  2. Compact two-electron wave function for bond dissociation and Van der Waals interactions: A natural amplitude assessment

    International Nuclear Information System (INIS)

    Electron correlations in molecules can be divided in short range dynamical correlations, long range Van der Waals type interactions, and near degeneracy static correlations. In this work, we analyze for a one-dimensional model of a two-electron system how these three types of correlations can be incorporated in a simple wave function of restricted functional form consisting of an orbital product multiplied by a single correlation function f (r12) depending on the interelectronic distance r12. Since the three types of correlations mentioned lead to different signatures in terms of the natural orbital (NO) amplitudes in two-electron systems, we make an analysis of the wave function in terms of the NO amplitudes for a model system of a diatomic molecule. In our numerical implementation, we fully optimize the orbitals and the correlation function on a spatial grid without restrictions on their functional form. Due to this particular form of the wave function, we can prove that none of the amplitudes vanishes and moreover that it displays a distinct sign pattern and a series of avoided crossings as a function of the bond distance in agreement with the exact solution. This shows that the wave function ansatz correctly incorporates the long range Van der Waals interactions. We further show that the approximate wave function gives an excellent binding curve and is able to describe static correlations. We show that in order to do this the correlation function f (r12) needs to diverge for large r12 at large internuclear distances while for shorter bond distances it increases as a function of r12 to a maximum value after which it decays exponentially. We further give a physical interpretation of this behavior

  3. Energy dependence of dissociative $\\mathrm{J/}\\psi$ photoproduction as a signature of gluon saturation at the LHC

    CERN Document Server

    Cepila, J; Takaki, J D Tapia

    2016-01-01

    We have developed a model in which the quantum fluctuations of the proton structure are characterised by hot spots, whose number grows with decreasing Bjorken-$x$. Our model reproduces the $F_2(x,Q^2)$ data from HERA at the relevant scale, as well as the exclusive and dissociative $\\mathrm{J/}\\psi$ photoproduction data from H1 and ALICE. Our model predicts that for $W_{\\gamma\\mathrm{p}} \\approx 500$ GeV, the dissociative $\\mathrm{J/}\\psi$ cross section reaches a maximum and then decreases steeply with energy, which is in qualitatively good agreement to a recent observation that the dissociative $\\mathrm{J/}\\psi$ background in the exclusive $\\mathrm{J/}\\psi$ sample measured in photoproduction by ALICE decreases as energy increases. Our prediction provides a clear signature for gluon saturation at LHC energies.

  4. The elastic properties, generalized stacking fault energy and dissociated dislocations in MgB2 under different pressure

    KAUST Repository

    Feng, Huifang

    2013-05-31

    The 〈112̄0〉 perfect dislocation in MgB2 is suggested to dissociate into two partial dislocations in an energy favorable way 〈112̄0〉 → 1/2 〈112̄0〉 + SF + 1/2 〈112̄0〉. This dissociation style is a correction of the previous dissociation 〈1000〉 → 1/3 〈11̄00〉 SF + 1/3 〈 2100〉proposed by Zhu et al. to model the partial dislocations and stacking fault observed by transmission electron microscopy. The latter dissociation results in a maximal stacking fault energy rather than a minimal one according to the generalized stacking fault energy calculated from first-principles methods. Furthermore, the elastic constants and anisotropy of MgB2 under different pressure are investigated. The core structures and mobilities of the 〈112̄0〉 dissociated dislocations are studied within the modified Peierls-Nabarro (P-N) dislocation theory. The variational method is used to solve the modified P-N dislocation equation and the Peierls stress is also determined under different pressure. High pressure effects on elastic anisotropy, core structure and Peierls stress are also presented. © 2013 Springer Science+Business Media New York.

  5. Cross Sections for the Dissociation of J/psi and psi' by pi and rho at low energies

    OpenAIRE

    Wong, Cheuk-Yin; Swanson, E. S.; Barnes, T.

    2000-01-01

    Using the quark-interchange model of Barnes and Swanson, we evaluate the dissociation cross sections for $J/\\psi$ and $\\psi'$ by $\\pi$ and $\\rho$ at low collision energies. In collisions with $\\pi$ mesons near threshold the $\\pi + J/\\psi$ dissociation cross section is predicted to be small, but the $\\pi +\\psi'$ cross section is found to be quite large, in qualitative agreement with experimental data on $J/\\psi$ and $\\psi'$ production in high-energy heavy-ion collisions. The $\\rho + J/\\psi$ an...

  6. Dissociation of acetaldehyde in intense laser field: Coulomb explosion or field-assisted dissociation?

    International Nuclear Information System (INIS)

    Dissociation of acetaldehyde in moderate strong laser field of 1013-1014 W/cm2 was investigated. Singly charged parent ion CH3CHO+ and fragmental ions CH3+, CHO+, C2H4+, O+, CH2CHO+, and H+ were produced by 800 nm laser of 100 fs pulse duration and recorded by time-of-flight mass spectrometer. The CH3+ fragment further dissociated to CH2+, CH+, and C+ ions at higher intensity. Ab initio calculated results show that the singly-, doubly-, and triply charged parent ions are stable. So, the dissociation mechanism was not due to Coulomb explosion of multicharged ion. A field-assisted dissociation (FAD) theory, which assumes that only one bond undergoes dissociation while the rest of the molecular geometry stays unchanged, was employed to treat the dissociation dynamics. Accordingly, the dressed potential energy surfaces of the ground state for the parent and the fragment ions were calculated. Corresponding quasiclassical trajectory calculations show that the bond ruptures take place in the order of C-C, C-O, and C-H, agreeing with the observation. The observed angular dependence and charge distribution of the product ions can also be interpreted by the FAD theory

  7. Dissociation of acetaldehyde in intense laser field: Coulomb explosion or field-assisted dissociation?

    Science.gov (United States)

    Elshakre, Mohamed E.; Gao, Lirong; Tang, Xiaoping; Wang, Sufan; Shu, Yafei; Kong, Fanao

    2003-09-01

    Dissociation of acetaldehyde in moderate strong laser field of 1013-1014W/cm2 was investigated. Singly charged parent ion CH3CHO+ and fragmental ions CH3+, CHO+, C2H4+, O+, CH2CHO+, and H+ were produced by 800 nm laser of 100 fs pulse duration and recorded by time-of-flight mass spectrometer. The CH3+ fragment further dissociated to CH2+, CH+, and C+ ions at higher intensity. Ab initio calculated results show that the singly-, doubly-, and triply charged parent ions are stable. So, the dissociation mechanism was not due to Coulomb explosion of multicharged ion. A field-assisted dissociation (FAD) theory, which assumes that only one bond undergoes dissociation while the rest of the molecular geometry stays unchanged, was employed to treat the dissociation dynamics. Accordingly, the dressed potential energy surfaces of the ground state for the parent and the fragment ions were calculated. Corresponding quasiclassical trajectory calculations show that the bond ruptures take place in the order of C-C, C-O, and C-H, agreeing with the observation. The observed angular dependence and charge distribution of the product ions can also be interpreted by the FAD theory.

  8. Estimating the value of the metal-ligand bond dissociation enthalpy (M-L for adducts using empirical equations supported by TG data

    Directory of Open Access Journals (Sweden)

    Farias Robson Fernandes

    1999-01-01

    Full Text Available In this work is presented and tested (for 106 adducts, mainly of the zinc group halides two empirical equations supported in TG data to estimate the value of the metal-ligand bond dissociation enthalpy for adducts: (M-O = t i / g if t i < 420 K and (M-O = (t i / g - 7,75 . 10-2 . t i if t i > 420 K. In this empirical equations, t i is the thermodynamic temperature of the beginning of the thermal decomposition of the adduct, as determined by thermogravimetry, andg is a constant factor that is function of the metal halide considered and of the number of ligands, but is not dependant of the ligand itself. To half of the tested adducts the difference between experimental and calculated values was less than 5%. To about 80% of the tested adducts, the difference between the experimental (calorimetric and the calculated (using the proposed equations values are less than 15%.

  9. Dissociation energies of Ag–RG (RG = Ar, Kr, Xe) and AgO molecules from velocity map imaging studies

    International Nuclear Information System (INIS)

    The near ultraviolet photodissociation dynamics of silver atom—rare gas dimers have been studied by velocity map imaging. Ag–RG (RG = Ar, Kr, Xe) species generated by laser ablation are excited in the region of the C (2Σ+)←X (2Σ+) continuum leading to direct, near-threshold dissociation generating Ag* (2P3/2) + RG (1S0) products. Images recorded at excitation wavelengths throughout the C (2Σ+)←X (2Σ+) continuum, coupled with known atomic energy levels, permit determination of the ground X (2Σ+) state dissociation energies of 85.9 ± 23.4 cm−1 (Ag–Ar), 149.3 ± 22.4 cm−1 (Ag–Kr), and 256.3 ± 16.0 cm−1 (Ag–Xe). Three additional photolysis processes, each yielding Ag atom photoproducts, are observed in the same spectral region. Two of these are markedly enhanced in intensity upon seeding the molecular beam with nitrous oxide, and are assigned to photodissociation of AgO at the two-photon level. These features yield an improved ground state dissociation energy for AgO of 15 965 ± 81 cm−1, which is in good agreement with high level calculations. The third process results in Ag atom fragments whose kinetic energy shows anomalously weak photon energy dependence and is assigned tentatively to dissociative ionization of the silver dimer Ag2

  10. Multidimensional Potential Energy Surface for H2 Dissociation over Cu(111)

    DEFF Research Database (Denmark)

    Hammer, Bjørk; Scheffler, Matthias; Jacobsen, Karsten Wedel;

    1994-01-01

    We present ab initio density functional calculations within the generalized gradient approximation for H-2 dissociating over Cu(111). The minimum barrier for dissociation is 0.5 eV and shows large corrugation within the unit cell and a strong dependence on the molecular orientation. Dissociation ...... predicted to depend strongly on translational, vibrational, and rotational degrees of freedom in accordance with experiment. We show that even for a noble metal, the d electrons are important for the molecule-surface interaction....

  11. The Free Energy of Dissociation of Oligomeric Structure in Phycocyanin is not Linear with Denaturant†

    OpenAIRE

    Thoren, Katie L.; Connell, Katelyn B.; Robinson, Taylor E.; Shellhamer, David D.; Tammaro, Margaret S.; Gindt, Yvonne M.

    2006-01-01

    Using SEC HPLC and fluorescence anisotropy, absorption spectra were assigned to the specific oligomeric structures found with phycocyanin. The absorption spectra were used to quantify the population of each oligomeric form of the protein as a function of both urea concentration and temperature. Phycocyanin hexamer dissociate to trimers with equilibrium constants of 10−6 to 10−5. Phycocyanin trimers dissociate to monomers with equilibrium constants of 10−15 to 10−12. Both dissociation constant...

  12. IR Spectra and Bond Energies Computed Using DFT

    Science.gov (United States)

    Bauschlicher, Charles; Andrews, Lester; Arnold, James (Technical Monitor)

    2000-01-01

    The combination of density functional theory (DFT) frequencies and infrared (IR) intensities and experimental spectra is a very powerful tool in the identification of molecules and ions. The computed and measured isotopic ratios make the identification much more secure than frequencies and intensities alone. This will be illustrated using several examples, such as Mn(CO)n and Mn(CO)n-. The accuracy of DFT metal-ligand bond energies will also be discussed.

  13. Projectile energy dependence in the molecular excitation of th H3+, D3+ molecular ions in their polar dissociation

    Energy Technology Data Exchange (ETDEWEB)

    Yousif, F.B.; Hinojosa, G.; Dominguez, I. [IFUNAM, Cuernavaca (Mexico)] [and others

    1996-05-01

    The laboratory energy distributions of H{sup +} and D{sup +} in coincidence with H{sup {minus}} and D{sup {minus}} ions, resulting from the collision-induced-dissociation of H{sup 3+} and D{sup 3+} on He target for incoming beam energies ranging from 2.5 to 9.0 keV has been measured. The energy-analyzed-spectra of ionic fragments were measured both independently and in coincidence with each other. From these, the energy absorbed by the dissociating molecular ions in the excitation process induced by the collision with He prior to its breakup, was evaluated as a function of the projectile energy and it was found that it is not constant but it is consistent with the identified H{sup 3+} excited states which have adiabatic Born-Oppenheimer energies of 21-50 eV above the H{sup 3+} ground state.

  14. Projectile energy dependence in the molecular excitation of th H3+, D3+ molecular ions in their polar dissociation

    International Nuclear Information System (INIS)

    The laboratory energy distributions of H+ and D+ in coincidence with H- and D- ions, resulting from the collision-induced-dissociation of H3+ and D3+ on He target for incoming beam energies ranging from 2.5 to 9.0 keV has been measured. The energy-analyzed-spectra of ionic fragments were measured both independently and in coincidence with each other. From these, the energy absorbed by the dissociating molecular ions in the excitation process induced by the collision with He prior to its breakup, was evaluated as a function of the projectile energy and it was found that it is not constant but it is consistent with the identified H3+ excited states which have adiabatic Born-Oppenheimer energies of 21-50 eV above the H3+ ground state

  15. Determination of the collisional energy transfer distribution responsible for the collision-induced dissociation of NO2 with Ar

    Science.gov (United States)

    Steill, Jeffrey D.; Jasper, Ahren W.; Chandler, David W.

    2015-09-01

    Collisional energy transfer is an essential aspect of chemical reactivity and maintenance of thermal equilibrium. Here we report the shape (energy-dependence) of the collisional energy transfer probability function for collisions of vibrationally excited NO2 entrained in a molecular beam and photoexcited to within 40 cm-1 of its dissociation threshold. The internally excited molecules undergo collisions with Ar atoms in a crossed beam apparatus. Dissociative collisions rapidly produce the NO(J) fragment, which is observed by velocity-mapped ion imaging and REMPI techniques. The measured collisional energy transfer function is obtained via energy conservation and is compared with the results of classical trajectory calculations. Good agreement between the theory and experiment is found for collisions that transfer small amounts of energy, but the theory predicts a higher likelihood of energetic collisions than is observed experimentally. We explore possible explanations for this discrepancy in the dynamics of the collision excitation process.

  16. Anchor Points Reactive Potential for Bond-Breaking Reactions.

    Science.gov (United States)

    Yang, Ke R; Xu, Xuefei; Truhlar, Donald G

    2014-03-11

    We present a new method for fitting potential energy surfaces in molecular-mechanics-like internal coordinates based on data from electronic structure calculations. The method should be applicable to chemical reactions involving either bond dissociation or isomerization and is illustrated here for bond dissociation, in particular the breaking of an O-H bond in methanol and the breaking of an N-H bond in dimethylamine. As compared to previously available systematic methods for fitting global potential energy surfaces, it extends the maximum size of the system than can be treated by at least an order of magnitude. PMID:26580172

  17. Ion Translational Energy Distributions from Inner-shell Dissociative ionization of N2O, NH3 and SF6.

    OpenAIRE

    Locht, Robert; Leyh, Bernard; Jochims, H.W.; Denzer, W.; Baumgärtel, H.

    1992-01-01

    The IRPD method is applied to the dissociative ionization in the inner-shell ionization region for NO+, N2+, O+, N+ and N++/N2O. Particular attention has been focussed on the production and ion kientic energy distribution of H+/NH3.

  18. Electron-impact dissociative double ionization of N2 and CO: Dependence of transition probability on impact energy

    Science.gov (United States)

    Pandey, A.; Kumar, P.; Banerjee, S. B.; Subramanian, K. P.; Bapat, B.

    2016-04-01

    We present an experimental and computational analysis of dissociative double ionization of N2 and CO molecules under electron impact. Experiments are performed at three energies, viz. 1, 3, and 5 keV, in order to observe the effect of impact energy on the dissociative ionization kinematics. We compare the kinetic energy release (KER) distributions of the charge symmetric dissociation channels of N22 + and CO2 + at these impact energies. An approximately linear trend between the transition energy and the expected KER values is inferred on the basis of the calculated potential energy curves of the dications. Experimentally, the normalized differential KER cross sections for these channels show an increasing trend in the low KER range and a decreasing trend in the high KER range as the electron-impact energy is increased. This observation indicates that the transition probability for excitation to different molecular ion states is not only a function of energy difference between the ground and excited states, but also a complicated function of the impact energy. In addition, nature of the observed trend in the differential KER cross sections differs significantly from their differential transition probability, which are calculated using inelastic collision model for fast-electron-impact case.

  19. Low energy electron induced cytosine base release in 2′-deoxycytidine-3′-monophosphate via glycosidic bond cleavage: A time-dependent wavepacket study

    International Nuclear Information System (INIS)

    Low energy electron (LEE) induced cytosine base release in a selected pyrimidine nucleotide, viz., 2′-deoxycytidine-3′-monophosphate is investigated using ab initio electronic structure methods and time dependent quantum mechanical calculations. It has been noted that the cytosine base scission is comparatively difficult process than the 3′ C–O bond cleavage from the lowest π* shape resonance in energy region * orbital of the base to the σ* orbital of the glycosidic N–C bond. In addition, the metastable state formed after impinging LEE (0–1 eV) has very short lifetime (10 fs) which may decay in either of the two competing auto-detachment or dissociation process simultaneously. On the other hand, the selected N–C mode may cleave to form the cytosine base anion at higher energy regions (>2 eV) via tunneling of the glycosidic bond. Resonance states generated within this energy regime will exist for a duration of ∼35–55 fs. Comparison of salient features of the two dissociation events, i.e., 3′ C–O single strand break and glycosidic N–C bond cleavage in 3′-dCMPH molecule are also provided

  20. Infrared multiphoton dissociation processes of some halogenated hydrocarbons

    International Nuclear Information System (INIS)

    We review our studies on mechanisms and dynamics of infrared multiphoton dissociation of CF3CHClF, C2HCl3, CBrF2CHClF, CBrF2CHBrF, CBrF2CBrClF, and c-C4F8 using a photofragmentation translational spectroscopy and ab initio MO calculations. In the case of CF3CHClF, three-centered HCl elimination and C-Cl bond rupture occurred competitively as primary dissociation processes. The center-of-mass translational energy distribution of the products produced by the HCl elimination indicates that an exit barrier of several kcal/mol exists in the potential energy surface of the reaction. In the case of C2HCl3, three- and four-centered eliminations of HCl occurred competitively. Halogenated ethanes containing bromine atoms dissociated through a C-Br bond rupture channel. The halogenated ethyl radicals produced by the C-Br bond ruptures subsequently dissociated through a C-halogen bond rupture channel. The translational energy distributions for the C-halogen bond ruptures observed are almost consistent with those calculated by RRKM theory. In the case of c-C4F8, dissociation of c-C4F8 to two C2F4 molecules was observed as a primary process. About 30% of the exit barrier for this reaction is converted to the translational energy of the products. This indicates that the dissociation proceeds through a loose transition state. This conclusion is supported by the transition state structure calculated by an ab initio MO method. (author)

  1. Bond length and local energy density property connections for non-transition-metal oxide-bonded interactions.

    Science.gov (United States)

    Gibbs, G V; Spackman, M A; Jayatilaka, D; Rosso, K M; Cox, D F

    2006-11-01

    For a variety of molecules and earth materials, the theoretical local kinetic energy density, G(r(c)), increases and the local potential energy density, V(r(c)), decreases as the M-O bond lengths (M = first- and second-row metal atoms bonded to O) decrease and the electron density, rho(r(c)), accumulates at the bond critical points, r(c). Despite the claim that the local kinetic energy density per electronic charge, G(r(c))/rho(r(c)), classifies bonded interactions as shared interactions when less than unity and closed-shell when greater, the ratio was found to increase from 0.5 to 2.5 au as the local electronic energy density, H(r(c)) = G(r(c)) + V(r(c)), decreases and becomes progressively more negative. The ratio appears to be a measure of the character of a given M-O bonded interaction, the greater the ratio, the larger the value of rho(r(c)), the smaller the coordination number of the M atom and the more shared the bonded interaction. H(r(c))/rho(r(c)) versus G(r(c))/rho(r(c)) scatter diagrams categorize the M-O bonded interactions into domains with the local electronic energy density per electron charge, H(r(c))/rho(r(c)), tending to decrease as the electronegativity differences for the bonded pairs of atoms decrease. The values of G(r(c)) and V(r(c)), estimated with a gradient-corrected electron gas theory expression and the local virial theorem, are in good agreement with theoretical values, particularly for the bonded interactions involving second-row M atoms. The agreement is poorer for shared C-O and N-O bonded interactions. PMID:17078623

  2. High-energy collision-induced dissociation of [M+Na]+ ions desorbed by fast atom bombardment of ceramides isolated from the starfish Distolasterias nipon.

    Science.gov (United States)

    Yoo, Ji Sun; Park, Taeseong; Bang, Geul; Lee, Chulhyun; Rho, Jung-Rae; Kim, Young Hwan

    2013-02-01

    Ten ceramides and four cerebrosides were extracted from the starfish Distolasterias nipon by solvent extraction, silica gel column chromatography and reversed-phase high-performance liquid chromatography. Structural identification was conducted using tandem mass spectrometry of monosodiated ions desorbed by fast atom bombardment. The complete structures of four cerebrosides were determined by a previously reported method. The high-energy collision-induced dissociation (CID) spectral characteristics of ceramides with various structures depend on the number and positions of double bonds on both the N-acyl and sphingoid chains, the presence of a hydroxyl group or a double bond at the C-4 position of the sphingoid chain and the presence of an α-hydroxy group on the N-acyl chain. The high-energy CID of the monosodiated ion, [M+Na](+), of each ceramide molecular species generated abundant ions, providing information on the composition of the fatty acyl chains and sphingoid long-chain bases. Each homologous ion series along the fatty acyl group and aliphatic chain of the sphingoid base was used for locating the double-bond positions of both chains and hydroxyl groups on the sphingoid base chain. The double-bond positions were also confirmed by the m/z values of abundant allylic even- and odd-electron ions, and the intensity ratio of the T ion peak relative to the O ion peak. This technique could determine the complete structures of ceramides and cerebrosides in an extract mixture and has great potential for determining other sphingolipids isolated from various biological sources. PMID:23378088

  3. Vibrational energy transfer near a dissociative adsorption transition state: State-to-state study of HCl collisions at Au(111)

    Science.gov (United States)

    Geweke, Jan; Shirhatti, Pranav R.; Rahinov, Igor; Bartels, Christof; Wodtke, Alec M.

    2016-08-01

    In this work we seek to examine the nature of collisional energy transfer between HCl and Au(111) for nonreactive scattering events that sample geometries near the transition state for dissociative adsorption by varying both the vibrational and translational energy of the incident HCl molecules in the range near the dissociation barrier. Specifically, we report absolute vibrational excitation probabilities for HCl(v = 0 → 1) and HCl(v = 1 → 2) scattering from clean Au(111) as a function of surface temperature and incidence translational energy. The HCl(v = 2 → 3) channel could not be observed—presumably due to the onset of dissociation. The excitation probabilities can be decomposed into adiabatic and nonadiabatic contributions. We find that both contributions strongly increase with incidence vibrational state by a factor of 24 and 9, respectively. This suggests that V-T as well as V-EHP coupling can be enhanced near the transition state for dissociative adsorption at a metal surface. We also show that previously reported HCl(v = 0 → 1) excitation probabilities [Q. Ran et al., Phys. Rev. Lett. 98, 237601 (2007)]—50 times smaller than those reported here—were influenced by erroneous assignment of spectroscopic lines used in the data analysis.

  4. I. Dissociation free energies in drug-receptor systems via non equilibrium alchemical simulations: theoretical framework

    CERN Document Server

    Procacci, Piero

    2016-01-01

    In this contribution I critically revise the alchemical reversible approach in the context of the statistical mechanics theory of non covalent bonding in drug receptor systems. I show that most of the pitfalls and entanglements for the binding free energies evaluation in computer simulations are rooted in the equilibrium assumption that is implicit in the reversible method. These critical issues can be resolved by using a non-equilibrium variant of the alchemical method in molecular dynamics simulations, relying on the production of many independent trajectories with a continuous dynamical evolution of an externally driven alchemical coordinate, completing the decoupling of the ligand in a matter of few tens of picoseconds rather than nanoseconds. The absolute binding free energy can be recovered from the annihilation work distributions by applying an unbiased unidirectional free energy estimate, on the assumption that any observed work distribution is given by a mixture of normal distributions, whose compone...

  5. Mass spectrometric determination of the dissociation energy of TcC(g)

    International Nuclear Information System (INIS)

    The TcC(g) molecule is observed above a liquid technetium carbide phase of unknown composition by using Knudsen effusion mass spectrometry. Intensity data for Tc(g) between 2229 and 25600K and for TcC(g) between 2393 and 23950K give a third-law bond energy of D00 = (134 +- 7) kcal mol-1 for TcC(g). A value of D00 = (140 +- 2) kcal mol-1 is obtained by the second-law method. 2 figures

  6. Catalytic methanol dissociation

    International Nuclear Information System (INIS)

    Results of the methanol dissociation study on copper/potassium catalyst with alumina support at various temperatures are presented. The following gaseous and liquid products at. The catalytic methanol dissociation is obtained: hydrogen, carbon monoxide, carbon dioxide, methane, and dimethyl ether. Formation rates of these products are discussed. Activation energies of corresponding reactions are calculated

  7. Comparative anti-inflammatory activities of curcumin and tetrahydrocurcumin based on the phenolic O-H bond dissociation enthalpy, ionization potential and quantum chemical descriptor.

    Science.gov (United States)

    Murakami, Yukio; Ishii, Hiroaki; Takada, Naoki; Tanaka, Shoji; Machino, Mamoru; Ito, Shigeru; Fujisawa, Seiichiro

    2008-01-01

    Curcumin and its reduced derivative tetrahydrocurcumin have been shown to exhibit chemopreventive activity. Cyclooxygenase-2 (COX-2) inhibition in lipopolysaccharide (LPS)- or Porphyromonas gingivalis fimbria-stimulated RAW 264.7 cells was investigated using Northern blot analysis. The fimbria-stimulated expression of the COX-2 gene was inhibited by curcumin but not by tetrahydrocurcumin. LPS-stimulated COX-2 gene expression was completely inhibited by curcumin, but an increase in the concentration of tetrahydrocurcumin did not cause complete inhibition of COX-2 expression. The inhibitory effect of curcumin on nuclear factor kappa B (NF-kappaB) activation in the cells was clearly observed, but that of tetrahydrocurcumin was incomplete even at a concentration of 20 microM. To explain the difference in effect between the two compounds, analysis of the frontier orbital was performed using ab initio 6-31G* wave function. The calculated chemical hardness (eta) for curcumin was clearly smaller, whereas its electronegativity (chi) and electrophilicity (omega) were clearly greater than the corresponding values for the curcumin-related compounds tetrahydrocurcumin, isoeugenol and eugenol. This suggested that the anti-inflammatory activities of curcumin may be related to eta-, chi- and/or omega-controlled enzymes. In addition, the bond dissociation enthalpy (BDE) of the phenolic OH was calculated using the density function theory (DFT)/B3LY. The total BDE values of curcumin and tetrahydrocurcumin were almost identical, but the BDE of one-electron oxidation and ionization potential (IP) for curcumin were lower than those for tetrahydrocurcumin, suggesting the highly pro-oxidative activity of curcumin. Curcumin has both oxidant and antioxidant properties. A causal link between the anti-inflammatory activities and molecular properties of phenolic antioxidants is suggested. PMID:18507010

  8. A novel photo-thermochemical cycle for the dissociation of CO2 using solar energy

    International Nuclear Information System (INIS)

    Highlights: • A novel photo-thermochemical cycle for CO2 splitting vie solar energy has been proposed. • Experiments of several successive cycles are performed to validate the feasibility. • Mechanism of reactions has been investigated using characterization methods. • An optional method for the charge transfer mechanism was conjectured in this study. - Abstract: To dissociate carbon dioxide (CO2) using solar energy, a novel photo-thermochemical cycle combining photochemistry with thermochemistry is proposed in this paper. After illuminating titanium dioxide (TiO2) in a helium (He) atmosphere by ultraviolet (UV) irradiation, CO2 was input and converted to carbon monoxide (CO) under heating in an enclosed cavity. To determine the optimal heating temperature, sets of four consecutive cycles were performed at temperatures from 573 K to 873 K. The preferred temperature was found to be 773 K. CO was stably produced in five successive cycles at 773 K, demonstrating the method’s possibility. Scanning electron microscopy (SEM), high-resolution transmission electron microscopy (HRTEM) and X-ray diffraction (XRD) were employed to assess the crystal structure and morphology. X-ray photoelectron spectroscopy (XPS) and photoluminescence (PL) analyses were also conducted to investigate the charge transfer and reaction mechanisms on the TiO2 surface. Finally, a charge transfer mechanism is tentatively proposed

  9. The investigation of photo-dissociation by time dependent quantum method

    International Nuclear Information System (INIS)

    The fragmentation of a bound molecule through absorption of one or more photons is called photo-dissociation. The electromagnetic energy of the light beam is converted into internal energy of the molecule and if the transferred energy exceeds the binding energy of the weakest bond, the molecule will irreversible break apart. Let us, as an example, consider the dissociation of a parent molecule AB into products A and B, where A and B represent either structureless atoms or molecules with internal degrees of freedom of their own. Formally we write a photo-dissociation process as, AB+Nphotonℎω→(AB)*→A(α)+B(β) Photo-dissociation can be roughly classified as either direct or indirect dissociation. In a direct process the parent molecule dissociates immediately after the photon has promoted it to the upper electronic state. No well or other dynamical constraint hinders the fragmentation and the 'lifetime' of the excited complex is very short, less than a vibrational period within the complex. In indirect photo-fragmentation, on the other hand, a potential well or some other dynamical force hinders direct fragmentation of the excited complex and the lifetime amounts to at least several internal vibrational periods. Photo-dissociation is one of the important topics of quantum chemistry. The basic principles of photo-dissociation and the time dependent quantum wave packet method, which is one of the methods developed to investigate dissociation have been applied to this study, which the dissociations of NH+ and HCl molecules.

  10. Dissociative ionization cross sections of CO2 at electron impact energy of 5 keV

    International Nuclear Information System (INIS)

    The dissociative ionization of CO2 induced by 5 keV electrons in two-body and three-body dissociative channels of CO22+ and CO23+ is identified by the ion—ion coincidence- method using a momentum imaging spectrometer. The partial ionization cross sections (PICSs) of different ionic fragments are measured and the results generally agree with the calculations made by a semi-empirical approach. Furthermore, the PICSs of the dissociative channels are also obtained by carefully considering the detection efficiency of the micro-channel plates and the total transmission efficiency of the time of flight system. (atomic and molecular physics)

  11. Six-dimensional potential energy surface of the dissociative chemisorption of HCl on Au(111) using neural networks

    Institute of Scientific and Technical Information of China (English)

    LIU TianHui; FU BiNa; ZHANG Dong H

    2014-01-01

    We constructed a six-dimensional potential energy surface(PES)for the dissociative chemisorption of HCl on Au(111)using the neural networks method based on roughly 70000 energies obtained from extensive density functional theory(DFT)calculations.The resulting PES is accurate and smooth,based on the small fitting errors and good agreement between the fitted PES and the direct DFT calculations.Time-dependent wave packet calculations show that the potential energy surface is very well converged with respect to the number of DFT data points,as well as to the fitting process.The dissociation probabilities of HCl initially in the ground rovibrational state from six-dimensional quantum dynamical calculations are quite diferent from the four-dimensional fixed-site calculations,indicating it is essential to perform full-dimensional quantum dynamical studies for the title molecule-surface interaction system.

  12. Low-energy collisionally activated dissociation of pentose-borate complexes

    Science.gov (United States)

    Pepi, Federico; Garzoli, Stefania; Tata, Alessandra; Giacomello, Pierluigi

    2010-01-01

    Pentose-borate 1:1 complexes were generated in the ESI source of a triple quadrupole and ion trap mass spectrometer by electrospray ionization of Na2B4O7 and pentose (arabinose, lyxose, ribose, xylose) 2:1 solution in CH3CN/H2O. The study of their low-energy collisionally activated dissociation (CAD) demonstrated that ribose and lyxose are preferentially complexed at the C2-C3 cis-diol function whereas arabinose and xylose are esterified at the C1-C2 hydroxyl groups. No evidence was found of the stronger affinity for ribose to borate. The ribose probiotic rule can be explained by considering its peculiar capability, among the investigated pentoses, to almost totally complex the borate anion at the C2-C3 hydroxyl group, thus enabling the subsequent stages of nucleotide assembly, such as phosphorylation and linkage to the nucleobases. Finally, the differences observed in the pentose-borate complex CAD spectra can be used for the mass spectrometric discrimination of isomeric pentoses in complex mixtures.

  13. A revised set of values of single-bond radii derived from the observed interatomic distances in metals by correction for bond number and resonance energy

    OpenAIRE

    Pauling, Linus; Kamb, Barclay

    1986-01-01

    An earlier discussion [Pauling, L. (1947) J. Am. Chem. Soc. 69, 542] of observed bond lengths in elemental metals with correction for bond number and resonance energy led to a set of single-bond metallic radii with values usually somewhat less than the corresponding values obtained from molecules and complex ions. A theory of resonating covalent bonds has now been developed that permits calculation of the number of resonance structures per atom and of the effective resonance energy per bond. ...

  14. Feasibility of large-scale phosphoproteomics with higher energy collisional dissociation fragmentation

    DEFF Research Database (Denmark)

    Nagaraj, Nagarjuna; D'Souza, Rochelle C J; Cox, Juergen;

    2010-01-01

    Mass spectrometry (MS)-based proteomics now enables the analysis of thousands of phosphorylation sites in single projects. Among a wide range of analytical approaches, the combination of high resolution MS scans in an Orbitrap analyzer with low resolution MS/MS scans in a linear ion trap has prov...... large-scale phosphoproteome analysis alongside collisional induced dissociation, (CID) and electron capture/transfer dissociation (ECD/ETD)....

  15. The Trouble with Chemical Energy: Why Understanding Bond Energies Requires an Interdisciplinary Systems Approach

    OpenAIRE

    Cooper, Melanie M.; Klymkowsky, Michael W.

    2013-01-01

    Helping students understand “chemical energy” is notoriously difficult. Many hold inconsistent ideas about what energy is, how and why it changes during the course of a chemical reaction, and how these changes are related to bond energies and reaction dynamics. There are (at least) three major sources for this problem: 1) the way biologists talk about chemical energy (which is also the way we talk about energy in everyday life); 2) the macroscopic approach to energy concepts that is common in...

  16. Dissociation energies of Ag–RG (RG = Ar, Kr, Xe) and AgO molecules from velocity map imaging studies

    Energy Technology Data Exchange (ETDEWEB)

    Cooper, Graham A.; Gentleman, Alexander S.; Iskra, Andreas; Wijk, Robert van; Mackenzie, Stuart R., E-mail: stuart.mackenzie@chem.ox.ac.uk [Physical and Theoretical Chemistry Laboratory, Oxford Chemistry, South Parks Road, Oxford OX1 3QZ (United Kingdom); Kartouzian, Aras [Physical and Theoretical Chemistry Laboratory, Oxford Chemistry, South Parks Road, Oxford OX1 3QZ (United Kingdom); Department of Physical Chemistry, Catalysis Research Center, Technische Universität München, Lichtenbergstr. 4, 85748 Garching (Germany)

    2015-09-28

    The near ultraviolet photodissociation dynamics of silver atom—rare gas dimers have been studied by velocity map imaging. Ag–RG (RG = Ar, Kr, Xe) species generated by laser ablation are excited in the region of the C ({sup 2}Σ{sup +})←X ({sup 2}Σ{sup +}) continuum leading to direct, near-threshold dissociation generating Ag* ({sup 2}P{sub 3/2}) + RG ({sup 1}S{sub 0}) products. Images recorded at excitation wavelengths throughout the C ({sup 2}Σ{sup +})←X ({sup 2}Σ{sup +}) continuum, coupled with known atomic energy levels, permit determination of the ground X ({sup 2}Σ{sup +}) state dissociation energies of 85.9 ± 23.4 cm{sup −1} (Ag–Ar), 149.3 ± 22.4 cm{sup −1} (Ag–Kr), and 256.3 ± 16.0 cm{sup −1} (Ag–Xe). Three additional photolysis processes, each yielding Ag atom photoproducts, are observed in the same spectral region. Two of these are markedly enhanced in intensity upon seeding the molecular beam with nitrous oxide, and are assigned to photodissociation of AgO at the two-photon level. These features yield an improved ground state dissociation energy for AgO of 15 965 ± 81 cm{sup −1}, which is in good agreement with high level calculations. The third process results in Ag atom fragments whose kinetic energy shows anomalously weak photon energy dependence and is assigned tentatively to dissociative ionization of the silver dimer Ag{sub 2}.

  17. Theoretical Electron Density Distributions for Fe- and Cu-Sulfide Earth Materials: A Connection between Bond Length, Bond Critical Point Properties, Local Energy Densities, and Bonded Interactions

    Energy Technology Data Exchange (ETDEWEB)

    Gibbs, Gerald V.; Cox, David F.; Rosso, Kevin M.; Ross, Nancy L.; Downs, R. T.; Spackman, M. A.

    2007-03-01

    Bond critical point and local energy density properties together with net atomic charges were calculated for theoretical electron density distributions, F(r), generated for a variety of Fe and Cu metal-sulfide materials with high- and low-spin Fe atoms in octahedral coordination and high-spin Fe atoms in tetrahedral coordination. The electron density, F(rc), the Laplacian, 32F(rc), the local kinetic energy, G(rc), and the oxidation state of Fe increase as the local potential energy density, V(rc), the Fe-S bond lengths, and the coordination numbers of the Fe atoms decrease. The properties of the bonded interactions for the octahedrally coordinated low-spin Fe atoms for pyrite and marcasite are distinct from those for high-spin Fe atoms for troilite, smythite, and greigite. The Fe-S bond lengths are shorter and the values of F(rc) and 32F(rc) are larger for pyrite and marcasite, indicating that the accumulation and local concentration of F(r) in the internuclear region are greater than those involving the longer, high-spin Fe-S bonded interactions. The net atomic charges and the bonded radii calculated for the Fe and S atoms in pyrite and marcasite are also smaller than those for sulfides with high-spin octahedrally coordinated Fe atoms. Collectively, the Fe-S interactions are indicated to be intermediate in character with the low-spin Fe-S interactions having greater shared character than the highspin interactions. The bond lengths observed for chalcopyrite together with the calculated bond critical point properties are consistent with the formula Cu+Fe3+S2. The bond length is shorter and the F(rc) value is larger for the FeS4 tetrahedron displayed by metastable greigite than those displayed by chalcopyrite and cubanite, consistent with a proposal that the Fe atom in greigite is tetravalent. S-S bond paths exist between each of the surface S atoms of adjacent slabs of FeS6 octahedra comprising the layer sulfide smythite, suggesting that the neutral Fe3S4 slabs are

  18. Theoretical electron density distributions for Fe- and Cu-sulfide earth materials: a connection between bond length, bond critical point properties, local energy densities, and bonded interactions.

    Science.gov (United States)

    Gibbs, G V; Cox, D F; Rosso, K M; Ross, N L; Downs, R T; Spackman, M A

    2007-03-01

    Bond critical point and local energy density properties together with net atomic charges were calculated for theoretical electron density distributions, rho(r), generated for a variety of Fe and Cu metal-sulfide materials with high- and low-spin Fe atoms in octahedral coordination and high-spin Fe atoms in tetrahedral coordination. The electron density, rho(rc), the Laplacian, triangle down2rho(rc), the local kinetic energy, G(rc), and the oxidation state of Fe increase as the local potential energy density, V(rc), the Fe-S bond lengths, and the coordination numbers of the Fe atoms decrease. The properties of the bonded interactions for the octahedrally coordinated low-spin Fe atoms for pyrite and marcasite are distinct from those for high-spin Fe atoms for troilite, smythite, and greigite. The Fe-S bond lengths are shorter and the values of rho(rc) and triangle down2rho(rc) are larger for pyrite and marcasite, indicating that the accumulation and local concentration of rho(r) in the internuclear region are greater than those involving the longer, high-spin Fe-S bonded interactions. The net atomic charges and the bonded radii calculated for the Fe and S atoms in pyrite and marcasite are also smaller than those for sulfides with high-spin octahedrally coordinated Fe atoms. Collectively, the Fe-S interactions are indicated to be intermediate in character with the low-spin Fe-S interactions having greater shared character than the high-spin interactions. The bond lengths observed for chalcopyrite together with the calculated bond critical point properties are consistent with the formula Cu+Fe3+S2. The bond length is shorter and the rho(rc) value is larger for the FeS4 tetrahedron displayed by metastable greigite than those displayed by chalcopyrite and cubanite, consistent with a proposal that the Fe atom in greigite is tetravalent. S-S bond paths exist between each of the surface S atoms of adjacent slabs of FeS6 octahedra comprising the layer sulfide smythite

  19. Dissociative charge exchange of H2+

    International Nuclear Information System (INIS)

    This thesis is devoted to molecular dissociation, in particular the dissociation of the hydrogen molecule H2 arising from electron capture of its ion H2+ in a collision. Thereby the important practical question how a chemical bond can be broken is implicitly addressed. This thesis opens (chapter I) with an overview of the available experimental approaches in molecular physics. Further the simple Demkov model for NRCE is described. In chapter II a novel experimental technique for measurements on dissociative processes is introduced which combines a high efficiency with a high energy resolution. A detailed description of the techniques applied in the detector, which has a high spatial and timing resolution with 30 μm and 350 psec FWHM respectively for the detection of one particle, is given in chapter III. A semi-classical theory for NRCE in the medium energy range between a diatomic molecular ion and an atom is developed in chapter IV. The experiments on dissociative charge exchange of H2+ with Ar, Mg, Na and Cs targets at keV energies are described in Chapter V. The predissociation of the c3PIsub(u)-state of H2 populated after charge exchange of H2 with several targets at keV energies; is the subject of chapter VI. In chapter VII, orientational oscillations in the cross section for charge exchange of H2+ with alkali targets are discussed. The last chapter deals with predissociation of highly excited states in H2. (Auth.)

  20. Exact electronic and nuclear time-dependent potential energy surfaces for attosecond electron localization in the dissociation of H2+

    International Nuclear Information System (INIS)

    We study the electron localization dynamics in the dissociation of H2+ using a 1D model Hamiltonian. To this end we calculate the exact time-dependent potential energy surfaces (TDPES) both for the electron and for the nuclei. The exact electronic TDPES shows that the final electron localization is determined when the interatomic barrier becomes large and prohibits electron tunneling. The exact nuclear TDPES shows the mechanism of slowdown of the dissociation. It is found that the nuclear potential cannot be approximated by the weighted average of the quasi-static state potential energy surfaces, but can be approximated well by the transition between them. We show these two time-dependent potentials are the exact potential functionals of the time-dependent multicomponent density functional theory and can reproduce the whole phenomena of electron localization dynamics.

  1. An isomer-specific high-energy collision-induced dissociation MS/MS database for forensic applications: a proof-of-concept on chemical warfare agent markers.

    Science.gov (United States)

    Subramaniam, Raja; Östin, Anders; Nygren, Yvonne; Juhlin, Lars; Nilsson, Calle; Åstot, Crister

    2011-09-01

    Spectra database search has become the most popular technique for the identification of unknown chemicals, minimizing the need for authentic reference chemicals. In the present study, an isomer-specific high-energy collision-induced dissociation (CID) MS/MS spectra database of 12 isomeric O-hexyl methylphosphonic acids (degradation markers of nerve agents) was created. Phosphonate anions were produced by the electrospray ionization of phosphonic acids or negative-ion chemical ionization of their fluorinated derivatives and were analysed in a hybrid magnetic-sector-time-of-flight tandem mass spectrometer. A centre-of-mass energy (E(com)) of 65 eV led to an optimal sequential carbon-carbon bond breakage, which was interpreted in terms of charge remote fragmentation. The proposed mechanism is discussed in comparison with the routinely used low-energy CID MS/MS. Even-mass (odd-electron) charge remote fragmentation ion series were diagnostic of the O-alkyl chain structure and can be used to interpret unknown spectra. Together with the odd-mass ion series, they formed highly reproducible, isomer-specific spectra that gave significantly higher database matches and probability factors (by 1.5 times) than did the EI MS spectra of the trimethylsilyl derivatives of the same isomers. In addition, ionization by negative-ion chemical ionization and electrospray ionization resulted in similar spectra, which further highlights the general potential of the high-energy CID MS/MS technique. PMID:21915956

  2. Dynamics of Hyperthermal Energy Ion-Surface Collisions: Dissociative and non-dissociative Scattering of Ethanol cations from a Self-Assembled Monolayer Surface of Fluorinated Alkyl Thiol on Au (111)

    International Nuclear Information System (INIS)

    Dissociation and inelastic scattering of ethanol molecular ions from self-assembled monolayers (SAM) surface of fluorinated alkyl thiol on an Au (111) monocrystal have been studied at 28.9 and 52.9 eV collision energies. A single dynamics mechanism for quasi0inelastic scattering was found at both energies. Ions recoil nearly parallel to the surface with very small kinetic energy losses of the order of < 2 eV. Dissociation dynamics features for the main dissociation channel, loss of methyl radical, are dramatically different from that of inelastically scattered primary ions and are different at the two collision energies studies. At 28.9 eV two energetically and angularly resolved features are observed, one corresponding to the loss of very large amounts (nearly all) of ions translational energy and the other appearing to gain energy (superelastic scattering). This implies a lifetime of such excited ions of more than 5s. The same dynamics features are observed at 52.9 eV ion energy except that a second inelastic process begins to compete with the nearly fully inelastic process. Moreover, at this energy the delayed ion dissociation mechanism is the dominant mechanism. The hypothesis that collision of ethanol cations useful rationale for the observed dynamics. Support for this hypotheses is provided by Newton diagrams, which summarize momentum conservation relationships in terms of a common center-of-mass, cmeff, which provides a basis for describing different ion-surface interactions contributing to surface-induced dissociation of ethanol ions. Preliminary experiments with Ar+ scattered from the same surface exhibit very similar dynamics features to the observed for ethanol cations. Finally, we note that intensities of scattered primary or fragment ions never approach the specular angle at the energies investigated here

  3. Dissociation energies of AgRG (RG = Ar, Kr, Xe) and AgO molecules from velocity map imaging studies

    CERN Document Server

    Cooper, Graham A; Gentleman, Alexander S; Iskra, Andreas; van Wijk, Robert; Mackenzie, Stuart R

    2015-01-01

    The near ultraviolet photodissociation dynamics of silver atom rare gas dimers have been studied by velocity map imaging. AgRG (RG = Ar, Kr, Xe) species generated by laser ablation are excited in the region of the C <- X continuum leading to direct, near threshold dissociation generating Ag* (2P3/2) + RG (1S0) products. Images recorded at excitation wavelengths throughout the C <- X continuum, coupled with known atomic energy levels, permit determination of the ground X (2SIGMA+) state dissociation energies of 85.9 +/- 23.4 cm-1 (AgAr), 149.3 +/- 22.4 cm-1 (AgKr) and 256.3 +/- 16.0 cm-1 (AgXe). Three additional photolysis processes, each yielding Ag atom photoproducts, are observed in the same spectral region. Two of these are markedly enhanced in intensity upon seeding the molecular beam with nitrous oxide, and are assigned to photodissociation of AgO at the two photon level. These features yield an improved ground state dissociation energy for AgO of 15965 +/- 81 cm-1, which is in good agreement with ...

  4. The dynamic Auger Doppler effect in HF and DF: control of fragment velocities in femtosecond dissociation through photon energy detuning

    Science.gov (United States)

    Wiesner, K.; Naves de Brito, A.; Sorensen, S. L.; Burmeister, F.; Gisselbrecht, M.; Svensson, S.; Björneholm, O.

    2002-03-01

    The Auger-Doppler effect in the experimental spectra of HF and DF is presented, and the dynamics of ultra-fast dissociation in the core-excited state are discussed. The Doppler splitting of the atomic Auger peak is calculated and simulated using a classical model and a very good agreement is found between experiment and simulation. It is shown that the difference in photon energy relative to the resonance is transferred completely into the kinetic energy release (KER). This is expected to be a general phenomenon, but is clearly illuminated in the HF/DF case. Thus the fragment velocity can be controlled through photon energy detuning.

  5. Bond Rupture following C14 and T3 Beta Decay

    International Nuclear Information System (INIS)

    As a result of nuclear transformations an atom acquires a recoil energy, and a portion of this energy becomes associated with the chemical bond or bonds joining the activated atom to the molecule. Usually sufficient energy is deposited in these bonds to permit the activated atom to dissociate from the remainder of the molecule. Bond-rupture, however, usually does not occur with 100% efficiency. Momentum transfer to an atom in a molecule (internal excitation and bond-rupture) have been discussed recently with reference to activation of atoms joined to a molecule by only one bond. Additional molecules are considered in the present paper, and data presented on the net recoil energy required for bond- rupture, the rotational and vibrational excitation energies received by the rupturing bond, the internal energy of the radical originally bonded to the activated atom, and the kinetic energy of the radicals. It is shown that, on the average, the recoil energy that must be acquired by the activated atom in order to rupture from the molecule is about 25% greater than that calculated assuming a pseudo-diatomic molecule. Data are also presented for certain C14 and T3 beta-decay recoil processes. For C14O2 it is calculated that a net N14 recoil energy s 1.92 times the ON-O+ bond dissociation energy is required for bond-rupture. Since the NO+2 product may possess about 0.6 to 1.0 eV of electronic excitation energy, the ON-O+ bond dissociation energy is not uniquely defined. The calculated value of non-bond-rupture is 73 - 87% in good agreement with the reported experimental value of 81%. Similar data are also presented for such molecules as CH3T, C2H5T, C3H7T, and C142H6. (author)

  6. Dissociative scattering of low-energy SiF{sub 3}{sup +} and SiF{sup +} ions (5-200 eV) on Cu(100) surface

    Energy Technology Data Exchange (ETDEWEB)

    Yamamoto, Hiroyuki; Baba, Yuji; Sasaki, T.A. [Japan Atomic Energy Research Inst., Tokai, Ibaraki (Japan). Tokai Research Establishment

    1997-03-01

    Dissociative scattering of molecular SiF{sub 3}{sup +} and SiF{sup +} ions from a Cu(100) single crystal surface has been investigated in the incident energy range from 5 eV to 200 eV with a scattering angle of 77deg. The scattered ion intensity of dissociative ions and parent molecular ions were measured as a function of incident ion energy. The observed data show that onset energies of dissociation for SiF{sub 3}{sup +} and SiF{sup +} ions are 30 eV and 40 eV, respectively. The obtained threshold energies are consistent with a impulsive collision model where the dissociation of incident ion is caused by vibrational excitation during collision. (author)

  7. Thermochemistry of 2,2'-dipyridil N-oxide and 2,2'-dipyridil N,N'-dioxide. The dissociation enthalpies of the N-O bonds

    Energy Technology Data Exchange (ETDEWEB)

    Santos, Ana Filipa L.O.M.; Monteiro, Andre R.; Goncalves, Jorge M. [Centro de Investigacao em Quimica, Department of Chemistry and Biochemistry, Faculty of Science, University of Porto, Rua do Campo Alegre, 687, P-4169-007 Porto (Portugal); Acree, William E. [Department of Chemistry, University of North Texas, Denton, TX 76203-5070 (United States); Ribeiro da Silva, Maria D.M.C., E-mail: mdsilva@fc.up.pt [Centro de Investigacao em Quimica, Department of Chemistry and Biochemistry, Faculty of Science, University of Porto, Rua do Campo Alegre, 687, P-4169-007 Porto (Portugal)

    2011-07-15

    Research highlights: > The standard enthalpies of formation of two crystalline 2,2'-dipyridil N-oxides were measured by combustion calorimetry. > The standard enthalpies of sublimation of two 2,2'-dipyridil N-oxides were derived from Knudsen effusion experiments. > First, second and mean (N-O) bond dissociation enthalpies (BDEs) for 2,2'-dipyridil N,N'-dioxide were derived. > The (N-O) bond dissociation enthalpy (BDE) for 2,2'-dipyridil N-oxide was calculated. - Abstract: In this paper, the first, second and mean (N-O) bond dissociation enthalpies (BDEs) were derived from the standard (p{sup o} = 0.1 MPa) molar enthalpies of formation, in the gaseous phase, {Delta}{sub f}H{sub m}{sup 0}(g), at T = 298.15 K, of 2,2'-dipyridil N-oxide and 2,2'-dipyridil N,N'-dioxide. These values were calculated from experimental thermodynamic parameters, namely from the standard (p{sup o} = 0.1 MPa) molar enthalpies of formation, in the crystalline phase, {Delta}{sub f}H{sub m}{sup 0}(cr), at T = 298.15 K, obtained from the standard molar enthalpies of combustion, {Delta}{sub c}H{sub m}{sup 0}, measured by static bomb combustion calorimetry, and from the standard molar enthalpies of sublimation, at T = 298.15 K, determined from Knudsen mass-loss effusion method.

  8. Two photon dissociation of benzene, phenylacetylene, and benzaldehyde at 243 nm: translational energy releases in the H atom channel

    International Nuclear Information System (INIS)

    Hydrogen atom production channels from photodissociation of benzene, phenylacetylene, and benzaldehyde at 243 nm have been investigated by detecting H atoms using two photon absorption at 243.2 nm and induced fluorescence at 121.6 nm. Translational energies of the H atoms were measured by Doppler broadened H atom spectra. By absorption of two photons at 243 nm, the H atoms are statistically produced from benzene and phenylacetylene whereas the H atoms from the aldehyde group in benzaldehyde are produced from different pathways. The possible dissociation mechanisms are discussed from the measured translational energy releases

  9. Orbital entanglement in bond-formation processes

    CERN Document Server

    Boguslawski, Katharina; Barcza, Gergely; Legeza, Ors; Reiher, Markus

    2013-01-01

    The accurate calculation of the (differential) correlation energy is central to the quantum chemical description of bond-formation and bond-dissociation processes. In order to estimate the quality of single- and multi-reference approaches for this purpose, various diagnostic tools have been developed. In this work, we elaborate on our previous observation [J. Phys. Chem. Lett. 3, 3129 (2012)] that one- and two-orbital-based entanglement measures provide quantitative means for the assessment and classification of electron correlation effects among molecular orbitals. The dissociation behavior of some prototypical diatomic molecules features all types of correlation effects relevant for chemical bonding. We demonstrate that our entanglement analysis is convenient to dissect these electron correlation effects and to provide a conceptual understanding of bond-forming and bond-breaking processes from the point of view of quantum information theory.

  10. Estimation of Intramolecular Hydrogen-bonding Energy via the Substitution Method

    Institute of Scientific and Technical Information of China (English)

    2008-01-01

    The intramolecular hydrogen-bonding energies for eighteen molecules were calculated based on the substitution method, and compared with those predicted by the cis-trans method.The energy values obtained from two methods are close to each other with a correlation coefficient of 0.96.Furthermore, the hydrogen-bonding energies based on the substitution method are consistent with the geometrical features of intramolecular hydrogen bonds.Both of them demonstrate that the substitution method is capable of providing a good estimation of intramolecular hydrogen-bonding energy.

  11. Energy redistribution in the dissociation of low Rydberg states of HeH and 02

    International Nuclear Information System (INIS)

    In this thesis the dissocation process is studied of the diatomic molecules, heliumhydride and molecular oxygen. In ch.'s 2-4 results on the spectroscopy and dissociative decay of the excited states of heliumhydride (HeH) are explained. The positions and dissociation pathways of the A2Σ+ and B2Π states are determined and a theoretical description of the decay of these states are given. An isotope dependent dissociation behaviour of the C2/σ+ Rydberg state is reported which explained with this theory. In ch.'s 5-7 observations are presented regarding the first Rydberg states of molecular oxygen. The spectroscopy of the (3sσ)d 1Πg and C3Πg states is treated, and the stability and decay of these Rydberg states is discussed qualitatively. An experimental study is described of the (3sσ)d 1Πg , v=4-8 states. By isotope studies and resolving rotational lines and the measurements of natural linewidths quantitative estimates have been acquired on coupling strengths, positions of repulsive valence states and perturbations reported in literature from REMPI experiments. The electronic coupling strengths between the C3Πg state and the 3Πg valence state has been established. Observed spin-orbit interactions have been quantified and the dissociation of the multiplet states (C3Πg,ω=0-2 has been correlated with the multiplet states of the fragment O3P J=0-2. The spectroscopy of the (3sσ3) Rydberg states which con- verge to and are formed in collisions with the O+2, a4Π μ ion state, is treated. The (3sσ)5/π μ state competition between auto-ionizations and (pre-)dissociation has been observed. 207 refs.; 36 figs.; 18 tabs

  12. Measurements of the charge exchange and dissociation cross-sections of the H2+ ion in a wide energy range

    International Nuclear Information System (INIS)

    The dissociation, ionisation, and charge exchange cross-sections of molecular hydrogen ions H2+ passing through various gases, have been measured as a function of the energy of the ions. The energy range studied was from 25 to 250 keV. The reaction products, analysed by a magnetic field according to their e/m ratio, are collected on scintillation detectors. Two methods have made it possible to separate the various reactions leading to the formation of particles having the same e/m ratio. The first separates the particles according to their energy, the other selects those arriving simultaneously on two different detectors. The results show a large variation in the charge exchange cross-section with the energy of the H2+ ions. The variations in the dissociation and ionisation cross-sections are less pronounced. For a given energy, the values of the cross-sections increase with the atomic weight of the target particles. These measurements have been extended to the case of H2+ ions passing through a target of charged particles. Preliminary results show an increase in the cross-sections as compared to the preceding case. Finally the scattering of the reaction products has been studied; this scattering is due to the fact that the molecules formed during a reaction are in an unstable state and the nuclei or atoms diverge from each other. (author)

  13. Structures, bonding and energies of N 6 isomers

    Science.gov (United States)

    Glukhovtsev, Mikhail N.; von Ragué Schleyer, Paul

    1992-10-01

    The most stable N 6 isomer, a twisted open-chain C 2 structure, is 188.3 kcal/mol (MP4SDTQ/6-31G(d)//MP2(full)/6-31 G(d) + ZPE(MP2/6-31 G(d))) higher in energy than three N 2 molecules. In contrast to benzene, hexazine, N 6, prefers a non-planar twist-boat D 2 structure, but this is 26.0 kcal/mol less stable than the C 2 form. The D 6h altenative is a second-order saddle point at MP2 (full)/6-31G(d) 2.1 kcal/mol higher in energy at MP4SDTQ/6-311 (+s)G(d)//MP2(full)/6-311 (+s)G(2d) + ZPE (MP2/6-31G(d)). The homodesmotic and hyperhomodesmotic reaction energies indicate that the D 6h structure is destabilized (-17.6 and -10.4 kcal/mol, respectively), in contrast to the stabilization of benzene (23.9 and 20.3 kcal/mol, respectively, MP4SDTQ/6-31 G(d, p)//MP2(full)/6-31 G(d, p)). NBO analysis shows that none of the N atoms in the N 6 open-chain structures forms more than four covalent bonds. The other N 6 valence isomers, hexaaza-Dewar-benzene, hexaazabicyclopropenyl, and hexaazaprismane are higher in energy than hexazine (33.9, 29.6 and 115.8 kcal/mol, respectively) at MP4SDTQ(fc)/6-31 G(d)/MP2(full)/6-31 G(d) + ZPE(HF/6-31 G(d)).

  14. Multiphoton dissociation of polyatomic molecules

    International Nuclear Information System (INIS)

    The dynamics of infrared multiphoton excitation and dissociation of SF6 was investigated under collision free conditions by a crossed laser-molecular beam method. In order to understand the excitation mechanism and to elucidate the requirements of laser intensity and energy fluence, a series of experiments were carried out to measure the dissociation yield dependences on energy fluence, vibrational temperature of SF6, the pulse duration of the CO2 laser and the frequency in both one and two laser experiments. Translational energy distributions of the SF5 dissociation product measured by time of flight and angular distributions and the dissociation lifetime of excited SF6 as inferred from the observation of secondary dissociation of SF5 into SF4 and F during the laser pulse suggest that the dynamics of dissociation of excited molecules is dominated by complete energy randomization and rapid intramolecular energy transfer on a nanosecond timescale, and can be adequately described by RRKM theory. An improved phenomenological model including the initial intensity dependent excitation, a rate equation describing the absorption and stimulated emission of single photons, and the unimolecular dissociation of excited molecules is constructed based on available experimental results. The model shows that the energy fluence of the laser determines the excitation of molecules in the quasi-continuum and the excess energy with which molecules dissociate after the laser pulse. The role played by the laser intensity in multiphoton dissociation is more significant than just that of overcoming the intensity dependent absorption in the lowest levels. 63 references

  15. Ab initio calculation of accurate dissociation energy,potential energy curve and dipole moment function for the A1∑+ state 7LiH molecule

    Institute of Scientific and Technical Information of China (English)

    Shi De-Heng; Liu Yu-Fang; Sun Jin-Feng; Yang Xiang-Dong; Zhu Zun-Lue

    2006-01-01

    The reasonable dissociation limit of the A1∑+ state 7LiH molecule is obtained. The accurate dissociation energy and the equilibrium geometry of this state are calculated using a symmetry-adapted-cluster configuration-interaction method in complete active space for the first time. The whole potential energy curve and the dipole moment function for the A1∑+ state are calculated over a wide internuclear separation range from about 0.1 to 1.4 nm. The calculated equilibrium geometry and dissociation energy of this potential energy curve are of Re=0.2487 nm and De=1.064 eV,respectively. The unusual negative values of the anharmonicity constant and the vibration-rotational coupling constant are of wexe=-4.7158cm-1 and αe=-0.08649cm-1, respectively. The vertical excitation energy from the ground to the A1∑+ state is calculated and the value is of 3.613eV at 0.15875nm (the equilibrium position of the ground state).The highly anomalous shape of this potential energy curve, which is exceptionally flat over a wide radial range around the equilibrium position, is discussed in detail. The harmonic frequency value of 502.47cm-1 about this state is approximately estimated. Careful comparison of the theoretical determinations with those obtained by previous theories about the A1∑+ state dissociation energy clearly shows that the present calculations are much closer to the experiments than previous theories, thus represents an improvement.

  16. Orbital entanglement in bond-formation processes

    OpenAIRE

    Boguslawski, Katharina; Tecmer, Pawel; Barcza, Gergely; Legeza, Ors; Reiher, Markus

    2013-01-01

    The accurate calculation of the (differential) correlation energy is central to the quantum chemical description of bond-formation and bond-dissociation processes. In order to estimate the quality of single- and multi-reference approaches for this purpose, various diagnostic tools have been developed. In this work, we elaborate on our previous observation [J. Phys. Chem. Lett. 3, 3129 (2012)] that one- and two-orbital-based entanglement measures provide quantitative means for the assessment a...

  17. Ab initio calculations of accurate dissociation energy and analytic potential energy function for the second excited state B1П of 7LiH

    Institute of Scientific and Technical Information of China (English)

    Shi De-Heng; Liu Yu-Fang; Sun Jin-Feng; Zhu Zun-Lùe; Yang Xiang-Dong

    2006-01-01

    The reasonable dissociation limit of the second excited singlet state B1П of 7LiH molecule is obtained. The obtained over the internuclear distance ranging from about 0.10 nm to 0.54 nm, and has a least-square fit to the analytic compared with previous theoretical results. The equilibrium internuclear distance obtained by geometry optimization is found to be quite different from that obtained by single-point energy scanning under the same calculation condition.comparison of the theoretical calculations of dissociation energies, equilibrium interatomic distances and the analytic potential energy function with those obtained by previous theoretical results clearly shows that the present work is more theories.

  18. Size-dependent stability toward dissociation and ligand binding energies of phosphine-ligated gold cluster ions

    Energy Technology Data Exchange (ETDEWEB)

    Johnson, Grant E.; Priest, Thomas A.; Laskin, Julia

    2014-01-01

    The stability of sub-nanometer size gold clusters ligated with organic molecules is of paramount importance to the scalable synthesis of monodisperse size-selected metal clusters with highly tunable chemical and physical properties. For the first time, a Fourier transform ion cyclotron resonance mass spectrometer (FT-ICR-MS) equipped with surface induced dissociation (SID) has been employed to investigate the time and collision energy resolved fragmentation behavior of cationic doubly charged gold clusters containing 7-9 gold atoms and 6-7 triphenylphosphine (TPP) ligands prepared by reduction synthesis in solution. The TPP ligated gold clusters are demonstrated to fragment through three primary dissociation pathways: (1) Loss of a neutral TPP ligand from the precursor gold cluster, (2) asymmetric fission and (3) symmetric fission and charge separation of the gold core resulting in formation of complementary pairs of singly charged fragment ions. Threshold energies and activation entropies of these fragmentation pathways have been determined employing Rice-Ramsperger-Kassel-Marcus (RRKM) modeling of the experimental SID data. It is demonstrated that the doubly charged cluster ion containing eight gold atoms and six TPP ligands, (8,6)2+, exhibits exceptional stability compared to the other cationic gold clusters examined in this study due to its large ligand binding energy of 1.76 eV. Our findings demonstrate the dramatic effect of the size and extent of ligation on the gas-phase stability and preferred fragmentation pathways of small TPP-ligated gold clusters.

  19. Atomistic spectrometrics of local bond-electron-energy pertaining to Na and K clusters

    Energy Technology Data Exchange (ETDEWEB)

    Bo, Maolin [Key Laboratory of Low-Dimensional Materials and Application Technologies, Ministry of Education, Xiangtan University, Hunan 411105 (China); Wang, Yan, E-mail: YWang8@hnust.edu.cn [School of Information and Electronic Engineering, Hunan University of Science and Technology, Hunan 411201 (China); Huang, Yongli; Liu, Yonghui [Key Laboratory of Low-Dimensional Materials and Application Technologies, Ministry of Education, Xiangtan University, Hunan 411105 (China); Li, Can [Center for Coordination Bond Engineering, School of Materials Science and Engineering, China Jiliang University, Hangzhou 330018 (China); Sun, Chang Q., E-mail: ecqsun@ntu.edu.sg [NOVITAS, School of Electrical and Electronic Engineering, Nanyang Technological University, Singapore 639798 (Singapore)

    2015-01-15

    Graphical abstract: - Highlights: • Coordination environment resolves electron binding-energy shift of Na and K clusters. • Cohesive energy of the representative bond determines the core-level shift. • XPS derives the energy level of an isolated atom and its bulk shift. • XPS derives the local bond length, bond energy, binding energy density. - Abstract: Consistency between density functional theory calculations and photoelectron spectroscopy measurements confirmed our predications on the undercoordination-induced local bond relaxation and core level shift of Na and K clusters. It is clarified that the shorter and stronger bonds between under-coordinated atoms cause local densification and local potential well depression and shift the electron binding-energy accordingly. Numerical consistency turns out the energy levels for an isolated Na (E{sub 2p} = 31.167 eV) and K (E{sub 3p} = 18.034 eV) atoms and their respective bulk shifts of 2.401 eV and 2.754 eV, which is beyond the scope of conventional approaches. This strategy has also resulted in quantification of the local bond length, bond energy, binding energy density, and atomic cohesive energy associated with the undercoordinated atoms.

  20. Seniority number description of potential energy surfaces: Symmetric dissociation of water, N2, C2, and Be2.

    Science.gov (United States)

    Bytautas, Laimutis; Scuseria, Gustavo E; Ruedenberg, Klaus

    2015-09-01

    The present study further explores the concept of the seniority number (Ω) by examining different configuration interaction (CI) truncation strategies in generating compact wave functions in a systematic way. While the role of Ω in addressing static (strong) correlation problem has been addressed in numerous previous studies, the usefulness of seniority number in describing weak (dynamic) correlation has not been investigated in a systematic way. Thus, the overall objective in the present work is to investigate the role of Ω in addressing also dynamic electron correlation in addition to the static correlation. Two systematic CI truncation strategies are compared beyond minimal basis sets and full valence active spaces. One approach is based on the seniority number (defined as the total number of singly occupied orbitals in a determinant) and another is based on an excitation-level limitation. In addition, molecular orbitals are energy-optimized using multiconfigurational-self-consistent-field procedure for all these wave functions. The test cases include the symmetric dissociation of water (6-31G), N2 (6-31G), C2 (6-31G), and Be2 (cc-pVTZ). We find that the potential energy profile for H2O dissociation can be reasonably well described using only the Ω = 0 sector of the CI wave function. For the Be2 case, we show that the full CI potential energy curve (cc-pVTZ) is almost exactly reproduced using either Ω-based (including configurations having up to Ω = 2 in the virtual-orbital-space) or excitation-based (up to single-plus-double-substitutions) selection methods, both out of a full-valence-reference function. Finally, in dissociation cases of N2 and C2, we shall also consider novel hybrid wave functions obtained by a union of a set of CI configurations representing the full valence space and a set of CI configurations where seniority-number restriction is imposed for a complete set (full-valence-space and virtual) of correlated molecular orbitals

  1. Seniority number description of potential energy surfaces: Symmetric dissociation of water, N2, C2, and Be2

    International Nuclear Information System (INIS)

    The present study further explores the concept of the seniority number (Ω) by examining different configuration interaction (CI) truncation strategies in generating compact wave functions in a systematic way. While the role of Ω in addressing static (strong) correlation problem has been addressed in numerous previous studies, the usefulness of seniority number in describing weak (dynamic) correlation has not been investigated in a systematic way. Thus, the overall objective in the present work is to investigate the role of Ω in addressing also dynamic electron correlation in addition to the static correlation. Two systematic CI truncation strategies are compared beyond minimal basis sets and full valence active spaces. One approach is based on the seniority number (defined as the total number of singly occupied orbitals in a determinant) and another is based on an excitation-level limitation. In addition, molecular orbitals are energy-optimized using multiconfigurational-self-consistent-field procedure for all these wave functions. The test cases include the symmetric dissociation of water (6-31G), N2 (6-31G), C2 (6-31G), and Be2 (cc-pVTZ). We find that the potential energy profile for H2O dissociation can be reasonably well described using only the Ω = 0 sector of the CI wave function. For the Be2 case, we show that the full CI potential energy curve (cc-pVTZ) is almost exactly reproduced using either Ω-based (including configurations having up to Ω = 2 in the virtual-orbital-space) or excitation-based (up to single-plus-double-substitutions) selection methods, both out of a full-valence-reference function. Finally, in dissociation cases of N2 and C2, we shall also consider novel hybrid wave functions obtained by a union of a set of CI configurations representing the full valence space and a set of CI configurations where seniority-number restriction is imposed for a complete set (full-valence-space and virtual) of correlated molecular orbitals

  2. Characterizing changes in the rate of protein-protein dissociation upon interface mutation using hotspot energy and organization.

    Directory of Open Access Journals (Sweden)

    Rudi Agius

    Full Text Available Predicting the effects of mutations on the kinetic rate constants of protein-protein interactions is central to both the modeling of complex diseases and the design of effective peptide drug inhibitors. However, while most studies have concentrated on the determination of association rate constants, dissociation rates have received less attention. In this work we take a novel approach by relating the changes in dissociation rates upon mutation to the energetics and architecture of hotspots and hotregions, by performing alanine scans pre- and post-mutation. From these scans, we design a set of descriptors that capture the change in hotspot energy and distribution. The method is benchmarked on 713 kinetically characterized mutations from the SKEMPI database. Our investigations show that, with the use of hotspot descriptors, energies from single-point alanine mutations may be used for the estimation of off-rate mutations to any residue type and also multi-point mutations. A number of machine learning models are built from a combination of molecular and hotspot descriptors, with the best models achieving a Pearson's Correlation Coefficient of 0.79 with experimental off-rates and a Matthew's Correlation Coefficient of 0.6 in the detection of rare stabilizing mutations. Using specialized feature selection models we identify descriptors that are highly specific and, conversely, broadly important to predicting the effects of different classes of mutations, interface regions and complexes. Our results also indicate that the distribution of the critical stability regions across protein-protein interfaces is a function of complex size more strongly than interface area. In addition, mutations at the rim are critical for the stability of small complexes, but consistently harder to characterize. The relationship between hotregion size and the dissociation rate is also investigated and, using hotspot descriptors which model cooperative effects within

  3. Evaluation of the individual hydrogen bonding energies in N-methylacetamide chains

    Institute of Scientific and Technical Information of China (English)

    2010-01-01

    The individual hydrogen bonding energies in N-methylacetamide chains were evaluated at the MP2/6-31+G** level including BSSE correction and at the B3LYP/6-311++G(3df,2pd) level including BSSE and van der Waals correction.The calculation results indicate that compared with MP2 results,B3LYP calculations without van der Waals correction underestimate the individual hydrogen bonding energies about 5.4 kJ m ol-1 for both the terminal and central hydrogen bonds,whereas B3LYP calculations with van der Waals correction produce almost the same individual hydrogen bonding energies as MP2 does for those terminal hydrogen bonds,but still underestimate the individual hydrogen bonding energies about 2.5 kJ mol-1 for the hydrogen bonds near the center.Our calculation results show that the individual hydrogen bonding energy becomes more negative (more attractive) as the chain becomes longer and that the hydrogen bonds close to the interior of the chain are stronger than those near the ends.The weakest individual hydrogen bonding energy is about-29.0 kJ m ol-1 found in the dimer,whereas with the growth of the N-methylacetamide chain the individual hydrogen bonding energy was estimated to be as large as-62.5 kJ mol-1 found in the N-methylacetamide decamer,showing that there is a significant hydrogen bond cooperative effect in N-methylacetamide chains.The natural bond orbital analysis indicates that a stronger hydrogen bond corresponds to a larger positive charge for the H atom and a larger negative charge for the O atom in the N-H···O=C bond,corresponds to a stronger second-order stabilization energy between the oxygen lone pair and the N-H antibonding orbital,and corresponds to more charge transfer between the hydrogen bonded donor and acceptor molecules.

  4. A novel thermochemical cycle for the dissociation of CO2 and H2O using sustainable energy sources

    International Nuclear Information System (INIS)

    Highlights: • A novel thermochemical CO2 and H2O splitting cycle has been proposed. • The approach can alleviate the greenhouse effect and produce the syngas. • The experiments are performed to validate the cycle effectiveness. • The maximum theoretical energy conversion efficiency of the cycle reaches 43.5%. - Abstract: A novel thermochemical cycle, which uses alternative energy sources (such as solar, geothermal, and safe nuclear) to dissociate CO2 and H2O, is proposed. The cycle can effectively reduce CO2 emission from the combustion of fossil fuels. The products of the cycle include carbon monoxide, hydrogen and oxygen. Carbon monoxide and hydrogen can be used to synthesize hydrocarbons and liquid fuels. Oxygen can be used in oxy-fuel combustion. The proposed chemical reactions are performed to validate the cycle effectiveness and superiority. Experiments are conducted to investigate and characterize the reactive chemical systems. The maximum theoretical energy conversion efficiency of the cycle reaches 43.5%

  5. First-principles study of molecular NO dissociation on Ir(100) surface

    Science.gov (United States)

    Erikat, I. A.; Hamad, B. A.; Khalifeh, J. M.

    2014-02-01

    The dissociation of NO on Ir(100) surface is investigated using density functional theory (DFT). The pathway and transition state (TS) of the dissociation of NO molecule are determined using climbing image nudge elastic band (CI-NEB). The prerequisite state of NO dissociation is determining the most stable sites of the reactant and products. We found that the most energetically stable sites are the hollow for N atom and the bridge for NO molecule as well as O atom. We found that the bending of NO is the first step of the dissociation reaction due to the increase of the back-donation from the d-band of Ir to 2 π ∗ orbital of NO, which causes the weakening of NO bond. The dissociation energy barrier of NO molecule on Ir(100) surface is 0.49 eV.

  6. Three-body dissociations: The photodissociation of dimethyl sulfoxide at 193 nm

    Energy Technology Data Exchange (ETDEWEB)

    Blank, D.A.; North, S.W.; Stranges, D. [Lawrence Berkeley National Lab., CA (United States)] [and others

    1997-04-01

    When a molecule with two equivalent chemical bonds is excited above the threshold for dissociation of both bonds, how the rupture of the two bonds is temporally coupled becomes a salient question. Following absorption at 193 nm dimethyl sulfoxide (CH{sub 3}SOCH{sub 3}) contains enough energy to rupture both C-S bonds. This can happen in a stepwise (reaction 1) or concerted (reaction 2) fashion where the authors use rotation of the SOCH{sub 3} intermediate prior to dissociation to define a stepwise dissociation: (1) CH{sub 3}SOCH{sub 3} {r_arrow} 2CH{sub 3} + SO; (2a) CH{sub 3}SOCH{sub 3} {r_arrow} CH{sub 3} + SOCH{sub 3}; and (2b) SOCH{sub 3} {r_arrow} SO + CH{sub 3}. Recently, the dissociation of dimethyl sulfoxide following absorption at 193 nm was suggested to involve simultaneous cleavage of both C-S bonds on an excited electronic surface. This conclusion was inferred from laser induced fluorescence (LIF) and resonant multiphoton ionization (2+1 REMPI) measurements of the internal energy content in the CH{sub 3} and SO photoproducts and a near unity quantum yield measured for SO. Since this type of concerted three body dissociation is very interesting and a rather rare event in photodissociation dynamics, the authors chose to investigate this system using the technique of photofragment translational spectroscopy at beamline 9.0.2.1. The soft photoionization provided by the VUV undulator radiation allowed the authors to probe the SOCH{sub 3} intermediate which had not been previously observed and provided good evidence that the dissociation of dimethyl sulfoxide primarily proceeds via a two step dissociation, reaction 2.

  7. Dissociation of gaseous zwitterion glycine-betaine by slow electrons.

    Science.gov (United States)

    Kopyra, J; Abdoul-Carime, H

    2010-05-28

    In this work, we investigate dissociation processes induced by low-energy electrons to gas phase N,N,N-trimethylglycine [glycine-betaine, (CH(3))(3)N(+)CH(2)COO(-)] molecules. Glycine-betaine represents a model system for zwitterions. All negative fragments are observed to be produced only at subelectronic excitation energies (<4 eV). With the exception of the loss of a neutral H atom that could arise from any C[Single Bond]H bond breaking, we tentatively suggest that the zwitterion dissociates exclusively from the fragmentation of the cation site of the molecule, subsequent to the attachment of the excess electron. Within the context of radiation induced damage to biological systems, the present findings contribute to a more complete description of the fragmentation mechanism occurring to amino acids, peptides, and proteins since they adopt usually a zwitterion structure. PMID:20515090

  8. Dissociative Ionization Mechanism and Appearance Energies in Adipic Acid Revealed by Imaging Photoelectron Photoion Coincidence, Selective Deuteration, and Calculations.

    Science.gov (United States)

    Heringa, Maarten F; Slowik, Jay G; Prévôt, André S H; Baltensperger, Urs; Hemberger, Patrick; Bodi, Andras

    2016-05-26

    Adipic acid, a model compound for oxygenated organic aerosol, has been studied at the VUV beamline of the Swiss Light Source. Internal energy selected cations were prepared by threshold photoionization using vacuum ultraviolet synchrotron radiation and imaging photoelectron photoion coincidence spectroscopy (iPEPICO). The threshold photoelectron spectrum yields a vertical ionization energy (IE) of 10.5 eV, significantly above the calculated adiabatic IE of 8.6 eV. The cationic minimum is accessible after vertical ionization by H-transfer from one of the γ-carbons to a carbonyl oxygen and is sufficiently energetic to decay by water loss at the ionization onset. The slope of the breakdown curves, quantum chemical calculations, and selective deuteration of the carboxylic hydrogens establish the dissociative photoionization mechanism. After ionization, one γ-methylene hydrogen and the two carboxylic hydrogens are randomized prior to H2O loss. On the basis of the deuteration degree in the H2O + CO-loss product at higher energies, a direct water-loss channel without complete randomization also exists. The breakdown diagram and center of gravity of the H2O + CO-loss peak were modeled to obtain 0 K appearance energies of 10.77, 10.32, and 11.53 eV for H2O + CO loss, CH2COOH loss, and H2O + CH2COOH loss from adipic acid. These agree well with the CBS-QB3 calculated values of 10.68, 10.45, and 11.57 eV, respectively, which shows that threshold photoionization can yield energetics data as long as the dissociation is statistical, even when the parent ion cannot be observed. The results can be used as a starting point for a deeper understanding of the ionization and low-energy fragmentation of organic aerosol components. PMID:27100102

  9. Influence of Electron Molecule Resonant Vibrational Collisions over the Symmetric Mode and Direct Excitation-Dissociation Cross Sections of CO2 on the Electron Energy Distribution Function and Dissociation Mechanisms in Cold Pure CO2 Plasmas.

    Science.gov (United States)

    Pietanza, L D; Colonna, G; Laporta, V; Celiberto, R; D'Ammando, G; Laricchiuta, A; Capitelli, M

    2016-05-01

    A new set of electron-vibrational (e-V) processes linking the first 10 vibrational levels of the symmetric mode of CO2 is derived by using a decoupled vibrational model and inserted in the Boltzmann equation for the electron energy distribution function (eedf). The new eedf and dissociation rates are in satisfactory agreement with the corresponding ones obtained by using the e-V cross sections reported in the database of Hake and Phelps (H-P). Large differences are, on the contrary, found when the experimental dissociation cross sections of Cosby and Helm are inserted in the Boltzman equation. Comparison of the corresponding rates with those obtained by using the low-energy threshold energy, reported in the H-P database, shows differences up to orders of magnitude, which decrease with the increasing of the reduced electric field. In all cases, we show the importance of superelastic vibrational collisions in affecting eedf and dissociation rates either in the direct electron impact mechanism or in the pure vibrational mechanism. PMID:27064438

  10. Modeling of Covalent Bonding in Solids by Inversion of Cohesive Energy Curves

    OpenAIRE

    Bazant, Martin Z.; Kaxiras, Efthimios

    1996-01-01

    We provide a systematic test of empirical theories of covalent bonding in solids using an exact procedure to invert ab initio cohesive energy curves. By considering multiple structures of the same material, it is possible for the first time to test competing angular functions, expose inconsistencies in the basic assumption of a cluster expansion, and extract general features of covalent bonding. We test our methods on silicon, and provide the direct evidence that the Tersoff-type bond order f...

  11. Infrared multiphoton dissociation mechanism of 1,2-dichlorotrifluoroethane in a molecular beam

    International Nuclear Information System (INIS)

    The mechanism of the infrared multiphoton dissociation of the title molecule has been studied using photofragmentation translational spectroscopy. The HCl elimination and the C-Cl bond rupture occurred competitively as primary dissociation channels. The HCl elimination reaction accounts for 66-9+5% of the total primary dissociation yields at 16±3 Jcm-2. This is consistent with the branching ratio calculated by RRKM theory. A C=C bond rupture of the CF2CFCl molecules and C-Cl bond rupture of C2HF3Cl radicals were also observed as secondary photodissociation processes. The average excitation energy of the dissociating 1,2-dichlorotrifluoroethane molecules was found to be 14-36 kcal mol-1 (1 kcal mol-1 = 4.184 kJ mol-1) above the C-Cl dissociation threshold of the molecules by comparing the observed center-of-mass translational energy distribution for the C-Cl bond rupture with that calculated by Rice-Ramsperger-Kassel-Marcus (RRKM) theory. (author)

  12. Quantum Chemistry Study on Dissociation of Oxalyl Bromide

    Institute of Scientific and Technical Information of China (English)

    2005-01-01

    The multi-bond dissociation dynamics of oxalyl bromide ((BrCO)2) has been investigated by DFT and CIS calculations. Upon the results, conclusion could be drawn that dissociation of C-Br bond of oxalyl bromide at the ground state (S0) is of barrierless. After the absorption of a photon, (BrCO)2 is excited to the first excited state and one of its C-Br bonds is broken to yield dissociate.

  13. Axial spatial distribution focusing: improving MALDI-TOF/RTOF mass spectrometric performance for high-energy collision-induced dissociation of biomolecules

    Science.gov (United States)

    Belgacem, O; Pittenauer, E; Openshaw, M E; Hart, P J; Bowdler, A; Allmaier, G

    2016-01-01

    Rationale For the last two decades, curved field reflectron technology has been used in matrix-assisted laser desorption/ionization time-of-flight (MALDI-TOF) mass spectrometers, assisting in the generation of post-source-decay (PSD) or collision-induced dissociation (CID) without decelerating precursor ions, producing true high-energy CID spectra. The result was the generation of product ion mass spectra with product ions typical of high-energy (10 keV and beyond) collision processes. The disadvantage of this approach was the lack of resolution in CID spectra resulting from the excess laser energy deposition used to generate those MS/MS spectra. The work presented in this study overcomes this limitation and includes comprehensive examples of high-energy and high-resolution CID MALDI-MS/MS spectra of biomolecules. Methods The devices used in this study are TOF/RTOF instruments equipped with a high-vacuum MALDI ion source. High-resolution and high-energy CID spectra result from the use of axial spatial distribution focusing (ASDF) in combination with curved field reflectron technology. Results A CID spectrum of the P14R1 peptide exhibits product ion resolution in excess of 10,000 (FWHM) but at the same time yields typical high-energy product ions such as w- and [y–2]-type ion series. High-energy CID spectra of lipids, exemplified by a glycerophospholipid and triglyceride, demonstrate C–C backbone fragmentation elucidating the presence of a hydroxyl group in addition to double-bond positioning. A complex high mannose carbohydrate (Man)8(GlcNAc)2 was also studied at 20 keV collision energy and revealed further high-energy product ions with very high resolution, allowing unambiguous detection and characterization of cross-ring cleavage-related ions. Conclusions This is the first comprehensive study using a MALDI-TOF/RTOF instrument equipped with a curved field reflectron and an ASDF device prior to the reflectron. © 2015 The Authors. Rapid Communications in

  14. Bond Energy Sums in Benzene, Cyclohexatriene and Cyclohexane Prove Resonance Unnecessary

    CERN Document Server

    Heyrovska, Raji

    2008-01-01

    The recent new structure of benzene shows that it consists of three C atoms of radii as in graphite alternating with three C atoms with double bond radii. This is different from the hypothetical cyclohexatriene (Kekule structure) involving alternate double and single bonds. It was shown that the difference in the bond energy sum of the atomic structure of benzene from that of the Kekule structure is the energy (erroneously) assumed to be due to resonance. Here it is shown that the present structure of benzene also explains the energy of hydrogenation into cyclohexane and its difference from that of cyclohexatriene.

  15. Partial dissociation of water on Fe$_{3}$O$_{4}$(001): adsorbate induced charge and orbital order

    OpenAIRE

    Mulakaluri, N.; Pentcheva, R.; Wieland, M.; Moritz, W.; Scheffler, M.

    2009-01-01

    The interaction of water with Fe$_3$O$_4$(001) is studied by density functional theory (DFT) calculations including an on-site Coulomb term. For isolated molecules dissociative adsorption is strongly promoted at surface defect sites, while at higher coverages a hydrogen-bonded network forms with alternating molecular and dissociated species. This mixed adsorption mode and a suppression of the $(\\sqrt{2}\\times \\sqrt{2})R45^{\\circ}$-reconstruction are confirmed by a quantitative low energy elec...

  16. Free Energy Diagram for the Heterogeneous Enzymatic Hydrolysis of Glycosidic Bonds in Cellulose.

    Science.gov (United States)

    Sørensen, Trine Holst; Cruys-Bagger, Nicolaj; Borch, Kim; Westh, Peter

    2015-09-01

    Kinetic and thermodynamic data have been analyzed according to transition state theory and a simplified reaction scheme for the enzymatic hydrolysis of insoluble cellulose. For the cellobiohydrolase Cel7A from Hypocrea jecorina (Trichoderma reesei), we were able to measure or collect relevant values for all stable and activated complexes defined by the reaction scheme and hence propose a free energy diagram for the full heterogeneous process. For other Cel7A enzymes, including variants with and without carbohydrate binding module (CBM), we obtained activation parameters for the association and dissociation of the enzyme-substrate complex. The results showed that the kinetics of enzyme-substrate association (i.e. formation of the Michaelis complex) was almost entirely entropy-controlled and that the activation entropy corresponded approximately to the loss of translational and rotational degrees of freedom of the dissolved enzyme. This implied that the transition state occurred early in the path where the enzyme has lost these degrees of freedom but not yet established extensive contact interactions in the binding tunnel. For dissociation, a similar analysis suggested that the transition state was late in the path where most enzyme-substrate contacts were broken. Activation enthalpies revealed that the rate of dissociation was far more temperature-sensitive than the rates of both association and the inner catalytic cycle. Comparisons of one- and two-domain variants showed that the CBM had no influence on the transition state for association but increased the free energy barrier for dissociation. Hence, the CBM appeared to promote the stability of the complex by delaying dissociation rather than accelerating association. PMID:26183776

  17. Bond Energy Sums in Benzene, Cyclohexatriene and Cyclohexane Prove Resonance Unnecessary

    OpenAIRE

    Heyrovska, Raji

    2008-01-01

    The recent new structure of benzene shows that it consists of three C atoms of radii as in graphite alternating with three C atoms with double bond radii. This is different from the hypothetical cyclohexatriene (Kekule structure) involving alternate double and single bonds. It was shown that the difference in the bond energy sum of the atomic structure of benzene from that of the Kekule structure is the energy (erroneously) assumed to be due to resonance. Here it is shown that the present str...

  18. Students' Interdisciplinary Reasoning about "High-Energy Bonds" and ATP

    OpenAIRE

    Dreyfus, Benjamin W.; Geller, Benjamin D.; Sawtelle, Vashti; Svoboda, Julia; Turpen, Chandra; Redish, Edward F.

    2012-01-01

    Students' sometimes contradictory ideas about ATP (adenosine triphosphate) and the nature of chemical bonds have been studied in the biology and chemistry education literatures, but these topics are rarely part of the introductory physics curriculum. We present qualitative data from an introductory physics course for undergraduate biology majors that seeks to build greater interdisciplinary coherence and therefore includes these topics. In these data, students grapple with the apparent contra...

  19. Hypovalency--a kinetic-energy density description of a 4c-2e bond.

    Science.gov (United States)

    Jacobsen, Heiko

    2009-06-01

    A bond descriptor based on the kinetic energy density, the localized-orbital locator (LOL), is used to characterize the nature of the chemical bond in electron deficient multi-center bonds. The boranes B(2)H(6), B(4)H(4), B(4)H(10), [B(6)H(6)](2-), and [B(6)H(7)](-) serve as prototypical examples of hypovalent 3c-2e and 4c-2e bonding. The kinetic energy density is derived from a set of Kohn-Sham orbitals obtained from pure density functional calculations (PBE/TZVP), and the topology of LOL is analyzed in terms of (3,-3) attractors (Gamma). The B-B-B and B-H-B 3c-2e, and the B-B-H-B 4c-2e bonding situations are defined by their own characteristic LOL profiles. The presence of one attractor in relation to the three or four atoms that are engaged in electron deficient bonding provides sufficient indication of the type of 3c-2e or 4c-2e bond present. For the 4c-2e bond in [B(6)H(7)](-) the LOL analysis is compared to results from an experimental QTAIM study. PMID:19452076

  20. II. Dissociation free energies in drug-receptor systems via nonequilibrium alchemical simulations: application to the FK506-related immunophilin ligands.

    Science.gov (United States)

    Nerattini, Francesca; Chelli, Riccardo; Procacci, Piero

    2016-06-01

    The recently proposed fast switching double annihilation (FS-DAM) [Cardelli et al., J. Chem. Theory Comput., 2015, 11, 423] is aimed at computing the absolute standard dissociation free energies for the chemical equilibrium RL ⇌ R + L occurring in solution through molecular dynamics (MD) simulations at the atomistic level. The technique is based on the production of fast nonequilibrium annihilation trajectories of one of the species (the ligand) in the solvated RL complex and in the bulk solvent. As detailed in the companion theoretical paper, the free energies of these two nonequilibrium annihilation processes are recovered by using an unbiased unidirectional estimate derived from the Crooks theorem exploiting the inherent Gaussian nature of the annihilation work. The FS-DAM technique was successfully applied to the evaluation of the dissociation free energy of the complexes of Zn(ii) cations with an inhibitor of the Tumor Necrosis Factor α converting enzyme. Here we apply the technique to a real drug-receptor system, by satisfactorily reproducing the experimental dissociation free energies of FK506-related bulky ligands towards the native FKBP12 enzyme and by predicting the dissociation constants for the same ligands towards the mutant I56D. The effect of such mutations on the binding affinity of FK506-related ligands is relevant for assessing the thermodynamic forces regulating molecular recognition in FKBP12 inhibition. PMID:27193181

  1. Dissociation of 10C nuclei in a track nuclear emulsion at an energy of 1.2 GeV per nucleon

    International Nuclear Information System (INIS)

    The charge topology in the fragmentation of 10C nuclei in a track nuclear emulsion at an energy of 1.2 GeV per nucleon is studied. In the coherent dissociation of 10C nuclei, about 82% of events are associated with the channel 10C → 2α+ 2p. The angular distributions and correlations of product fragments are presented for this channel. It is found that among 10C → 2α+ 2p events, about 30% are associated with the process in which dissociation through the ground state of the unstable 9Beg.s. nucleus is followed by 8Beg.s. + p decays

  2. Statistical characterization of the charge state and residue dependence of low-energy CID peptide dissociation patterns.

    Science.gov (United States)

    Huang, Yingying; Triscari, Joseph M; Tseng, George C; Pasa-Tolic, Ljiljana; Lipton, Mary S; Smith, Richard D; Wysocki, Vicki H

    2005-09-15

    Data mining was performed on 28 330 unique peptide tandem mass spectra for which sequences were assigned with high confidence. By dividing the spectra into different sets based on structural features and charge states of the corresponding peptides, chemical interactions involved in promoting specific cleavage patterns in gas-phase peptides were characterized. Pairwise fragmentation maps describing cleavages at all Xxx-Zzz residue combinations for b and y ions reveal that the difference in basicity between Arg and Lys results in different dissociation patterns for singly charged Arg- and Lys-ending tryptic peptides. While one dominant protonation form (proton localized) exists for Arg-ending peptides, a heterogeneous population of different protonated forms or more facile interconversion of protonated forms (proton partially mobile) exists for Lys-ending peptides. Cleavage C-terminal to acidic residues dominates spectra from singly charged peptides that have a localized proton and cleavage N-terminal to Pro dominates those that have a mobile or partially mobile proton. When Pro is absent from peptides that have a mobile or partially mobile proton, cleavage at each peptide bond becomes much more prominent. Whether the above patterns can be found in b ions, y ions, or both depends on the location of the proton holder(s) in multiply protonated peptides. Enhanced cleavages C-terminal to branched aliphatic residues (Ile, Val, Leu) are observed in both b and y ions from peptides that have a mobile proton, as well as in y ions from peptides that have a partially mobile proton; enhanced cleavages N-terminal to these residues are observed in b ions from peptides that have a partially mobile proton. Statistical tools have been designed to visualize the fragmentation maps and measure the similarity between them. The pairwise cleavage patterns observed expand our knowledge of peptide gas-phase fragmentation behaviors and may be useful in algorithm development that employs

  3. Validity of the site-averaging approximation for modeling the dissociative chemisorption of H2 on Cu(111) surface: A quantum dynamics study on two potential energy surfaces

    International Nuclear Information System (INIS)

    A new finding of the site-averaging approximation was recently reported on the dissociative chemisorption of the HCl/DCl+Au(111) surface reaction [T. Liu, B. Fu, and D. H. Zhang, J. Chem. Phys. 139, 184705 (2013); T. Liu, B. Fu, and D. H. Zhang, J. Chem. Phys. 140, 144701 (2014)]. Here, in order to investigate the dependence of new site-averaging approximation on the initial vibrational state of H2 as well as the PES for the dissociative chemisorption of H2 on Cu(111) surface at normal incidence, we carried out six-dimensional quantum dynamics calculations using the initial state-selected time-dependent wave packet approach, with H2 initially in its ground vibrational state and the first vibrational excited state. The corresponding four-dimensional site-specific dissociation probabilities are also calculated with H2 fixed at bridge, center, and top sites. These calculations are all performed based on two different potential energy surfaces (PESs). It is found that the site-averaging dissociation probability over 15 fixed sites obtained from four-dimensional quantum dynamics calculations can accurately reproduce the six-dimensional dissociation probability for H2 (v = 0) and (v = 1) on the two PESs

  4. Bond graph modeling and validation of an energy regenerative system for emulsion pump tests.

    Science.gov (United States)

    Li, Yilei; Zhu, Zhencai; Chen, Guoan

    2014-01-01

    The test system for emulsion pump is facing serious challenges due to its huge energy consumption and waste nowadays. To settle this energy issue, a novel energy regenerative system (ERS) for emulsion pump tests is briefly introduced at first. Modeling such an ERS of multienergy domains needs a unified and systematic approach. Bond graph modeling is well suited for this task. The bond graph model of this ERS is developed by first considering the separate components before assembling them together and so is the state-space equation. Both numerical simulation and experiments are carried out to validate the bond graph model of this ERS. Moreover the simulation and experiments results show that this ERS not only satisfies the test requirements, but also could save at least 25% of energy consumption as compared to the original test system, demonstrating that it is a promising method of energy regeneration for emulsion pump tests. PMID:24967428

  5. Bond Graph Modeling and Validation of an Energy Regenerative System for Emulsion Pump Tests

    Directory of Open Access Journals (Sweden)

    Yilei Li

    2014-01-01

    Full Text Available The test system for emulsion pump is facing serious challenges due to its huge energy consumption and waste nowadays. To settle this energy issue, a novel energy regenerative system (ERS for emulsion pump tests is briefly introduced at first. Modeling such an ERS of multienergy domains needs a unified and systematic approach. Bond graph modeling is well suited for this task. The bond graph model of this ERS is developed by first considering the separate components before assembling them together and so is the state-space equation. Both numerical simulation and experiments are carried out to validate the bond graph model of this ERS. Moreover the simulation and experiments results show that this ERS not only satisfies the test requirements, but also could save at least 25% of energy consumption as compared to the original test system, demonstrating that it is a promising method of energy regeneration for emulsion pump tests.

  6. Photofragment translational spectroscopy of three body dissociations and free radicals

    Energy Technology Data Exchange (ETDEWEB)

    North, S.W.

    1995-04-01

    This dissertation describes several three-body dissociations and the photodissociation of methyl radicals studied using photofragment translational spectroscopy. The first chapter provides an introduction to three body dissociation, examines current experimental methodology, and includes a discussion on the treatment of photofragment translational spectroscopy data arising from three-body fragmentation. The ultraviolet photodissociation of azomethane into two methyl radicals and nitrogen is discussed in chapter 2. Chapter 3 describes the photodissociation of acetone at 248 nm and 193 nm. At 248 nm the translational energy release from the initial C-C bond cleavage matches the exit barrier height and a comparison with results at 266 nm suggests that is invariant to the available energy. A fraction of the nascent CH{sub 3}CO radicals spontaneously dissociate following rotational averaging. The for the second C-C bond cleavage also matches the exit barrier height. At 193 nm the experimental data can be successfully fit assuming that the dynamics are analogous to those at 248 nm. A simplified model of energy partitioning which adequately describes the experimental results is discussed. Experiments on acetyl halides provide additional evidence to support the proposed acetone dissociation mechanism. A value of 17.0{+-}1.0 kcal/mole for the barrier height, CH{sub 3}CO decomposition has been determined. The photodissociation of methyl radical at 193 nm and 212.8 nm is discussed in the chapter 5. The formation of CH{sub 2} ({sup 1}A{sub l}) and H ({sup 2}S) was the only single photon dissociation pathway observed at both wavelengths.

  7. Guided ion-beam studies of the reactions of Con+ (n=2-20) with O2: Cobalt cluster-oxide and -dioxide bond energies

    International Nuclear Information System (INIS)

    The kinetic-energy dependence for the reactions of Con+ (n=2-20) with O2 is measured as a function of kinetic energy over a range of 0 to 10 eV in a guided ion-beam tandem mass spectrometer. A variety of Com+, ComO+, and ComO2+ (m≤n) product ions is observed, with the dioxide cluster ions dominating the products for all larger clusters. Reaction efficiencies of Con+ cations with O2 are near unity for all but the dimer. Bond dissociation energies for both cobalt cluster oxides and dioxides are derived from threshold analysis of the energy dependence of the endothermic reactions using several different methods. These values show little dependence on cluster size for clusters larger than three atoms. The trends in this thermochemistry and the stabilities of oxygenated cobalt clusters are discussed. The bond energies of Con+-O for larger clusters are found to be very close to the value for desorption of atomic oxygen from bulk-phase cobalt. Rate constants for O2 chemisorption on the cationic clusters are compared with results from previous work on cationic, anionic, and neutral cobalt clusters

  8. Vibrational Energies of the Hydrogen Bonds of H_3O_2^- and H_5O_2^+

    OpenAIRE

    Gamble, Stephanie Nicole

    2016-01-01

    We approximate the vibrational energies of the symmetric and asymmetric stretches of the hydrogen bonds of the molecules H_3O_2^- and H_5O_2^+ by applying an improvement to the standard time-independent Born-Oppenheimer approximation. These two molecules are symmetric around a central hydrogen which participates in hydrogen bonding. Unlike the standard Born-Oppenheimer approximation, this approximation appropriately scales the hydrogen nuclei differently than the heavier oxygen nuclei. This r...

  9. Targeted energy transfer between a Rotor and a Morse oscillator: A model for selective chemical dissociation

    OpenAIRE

    Memboeuf, Antony; Aubry, Serge

    2005-01-01

    Standard Kramers theory of chemical reactions involves a coupling with a Langevin thermal bath which intrinsically forbids the possible existence of Discrete Breathers (DBs) (i.e. local modes). However, it is now known that in complex systems, that energy may focus for long time as Discrete Breathers (local mode). In very special systems, targeted energy transfer may occur subsequently to another selected site and induces an ultraselective chemical reaction operating at low temperature. The d...

  10. Financing renewable energy infrastructure: Formulation, pricing and impact of a carbon revenue bond

    International Nuclear Information System (INIS)

    Renewable energy systems depend on large financial incentives to compete with conventional generation methods. Market-based incentives, including state-level REC markets and international carbon markets have been proposed as solutions to increase renewable energy investment. In this paper we introduce and formulate a carbon revenue bond, a financing tool to complement environmental credit markets to encourage renewable energy investment. To illustrate its use, we value the bond by predicting future revenue using stochastic processes after analyzing historical price data. Three illustrative examples are presented for renewable energy development in three different markets: Europe, Australia and New Jersey. Our findings reveal that the sale of a carbon revenue bond with a ten year maturity can finance a significant portion of a project's initial cost. - Highlights: ► Current financial incentives for renewable energy in the US are inadequate. ► We introduce and structure a “carbon revenue bond” as an innovative financing tool. ► Stochastic models of environmental credit prices are used to illustrate bond pricing. ► Three examples illustrate revenue bond impact on initial cost of infrastructure.

  11. Isotope dependent, temperature regulated, energy repartitioning in a low-barrier, short-strong hydrogen bonded cluster

    International Nuclear Information System (INIS)

    We investigate and analyze the vibrational properties, including hydrogen/deuterium isotope effects, in a fundamental organic hydrogen bonded system using multiple experimental (infrared multiple photon dissociation and argon-tagged action spectroscopy) and computational techniques. We note a qualitative difference between the two experimental results discussed here and employ ab initio molecular dynamics simulations to explain these results. A deeper understanding of the differences between the isotopically labeled systems arises from an analysis of the simulated cluster spectroscopy and leads to a system-bath coupling interpretation. Specifically, when a few active modes, involving the shared hydrogen/deuterium stretch, are identified and labeled as “system,” with all other molecular vibrational modes being identified as “bath” modes, we find critical differences in the coupling between the system modes for the shared proton and shared deuteron cases. These differences affect the energy repartitioning between these modes resulting in a complex spectral evolution as a function of temperature. Furthermore, intensity borrowing across modes that are widely distributed in the frequency domain plays an important role on the simulated spectra

  12. A Novel Method to Quantify Soil Aggregate Stability by Measuring Aggregate Bond Energies

    Science.gov (United States)

    Efrat, Rachel; Rawlins, Barry G.; Quinton, John N.; Watts, Chris W.; Whitmore, Andy P.

    2016-04-01

    Soil aggregate stability is a key indicator of soil quality because it controls physical, biological and chemical functions important in cultivated soils. Micro-aggregates are responsible for the long term sequestration of carbon in soil, therefore determine soils role in the carbon cycle. It is thus vital that techniques to measure aggregate stability are accurate, consistent and reliable, in order to appropriately manage and monitor soil quality, and to develop our understanding and estimates of soil as a carbon store to appropriately incorporate in carbon cycle models. Practices used to assess the stability of aggregates vary in sample preparation, operational technique and unit of results. They use proxies and lack quantification. Conflicting results are therefore drawn between projects that do not provide methodological or resultant comparability. Typical modern stability tests suspend aggregates in water and monitor fragmentation upon exposure to an un-quantified amount of ultrasonic energy, utilising a laser granulometer to measure the change in mean weight diameter. In this project a novel approach has been developed based on that of Zhu et al., (2009), to accurately quantify the stability of aggregates by specifically measuring their bond energies. The bond energies are measured operating a combination of calorimetry and a high powered ultrasonic probe, with computable output function. Temperature change during sonication is monitored by an array of probes which enables calculation of the energy spent heating the system (Ph). Our novel technique suspends aggregates in heavy liquid lithium heteropolytungstate, as opposed to water, to avoid exposing aggregates to an immeasurable disruptive energy source, due to cavitation, collisions and clay swelling. Mean weight diameter is measured by a laser granulometer to monitor aggregate breakdown after successive periods of calculated ultrasonic energy input (Pi), until complete dispersion is achieved and bond

  13. Energy-resolved collision-induced dissociation of non-covalent ions: charge- and guest-dependence of decomplexation reaction efficiencies.

    Science.gov (United States)

    Carroy, Glenn; Lemaur, Vincent; De Winter, Julien; Isaacs, Lyle; De Pauw, Edwin; Cornil, Jérôme; Gerbaux, Pascal

    2016-05-14

    Supramolecular chemistry, and especially host-guest chemistry, has been the subject of great interest in the past few decades leading to the synthesis of host cage molecules such as calixarenes, cyclodextrins and more recently cucurbiturils. Mass spectrometry methods are increasingly used to decipher at the molecular level the non-covalent interactions between the different associated molecules. The present article illustrates that the association between mass spectrometry and computational chemistry techniques proves very complementary to depict the gas-phase dissociation processes of ionic non-covalent complexes when subjected to collisional activation. The selected system associates a nor-seco-cucurbit[10]uril bitopic receptor with different amino compounds (adamantylamine, para-xylylenediamine, and para-phenylenediamine). When subjected to CID experiments, the ternary complexes undergo fragmentation via dissociation of non-covalently bound partners. Interestingly, depending on their charge state, the collisionally excited complexes can selectively expel either a neutral guest molecule or a protonated guest molecule. Moreover, based on energy-resolved CID experiments, it is possible to evaluate the guest molecule dependence on the gas phase dissociation efficiency. We observed that the relative order of gas phase dissociation is charge state dependent, with the adamantylamine-containing complexes being the weakest when triply charged and the strongest when doubly charged. The energetics of the gas-phase dissociation reactions have been estimated by density functional theory (DFT) calculations. We succeeded in theoretically rationalizing the experimental collision-induced dissociation results with a special emphasis on: (i) the charge state of the expelled guest molecule and (ii) the nature of the guest molecule. PMID:27086657

  14. Energetics of the ruthenium-halide bond in olefin metathesis (pre)catalysts

    KAUST Repository

    Falivene, Laura

    2013-01-01

    A DFT analysis of the strength of the Ru-halide bond in a series of typical olefin metathesis (pre)catalysts is presented. The calculated Ru-halide bond energies span the rather broad window of 25-43 kcal mol-1. This indicates that in many systems dissociation of the Ru-halide bond is possible and is actually competitive with dissociation of the labile ligand generating the 14e active species. Consequently, formation of cationic Ru species in solution should be considered as a possible event. © 2013 The Royal Society of Chemistry.

  15. Dissociation dynamics of ethylene molecules on a Ni cluster using ab initio molecular dynamics simulations

    Science.gov (United States)

    Shimamura, K.; Shibuta, Y.; Ohmura, S.; Arifin, R.; Shimojo, F.

    2016-04-01

    The atomistic mechanism of dissociative adsorption of ethylene molecules on a Ni cluster is investigated by ab initio molecular-dynamics simulations. The activation free energy to dehydrogenate an ethylene molecule on the Ni cluster and the corresponding reaction rate is estimated. A remarkable finding is that the adsorption energy of ethylene molecules on the Ni cluster is considerably larger than the activation free energy, which explains why the actual reaction rate is faster than the value estimated based on only the activation free energy. It is also found from the dynamic simulations that hydrogen molecules and an ethane molecule are formed from the dissociated hydrogen atoms, whereas some exist as single atoms on the surface or in the interior of the Ni cluster. On the other hand, the dissociation of the C-C bonds of ethylene molecules is not observed. On the basis of these simulation results, the nature of the initial stage of carbon nanotube growth is discussed.

  16. Dissociation dynamics of ethylene molecules on a Ni cluster using ab initio molecular dynamics simulations

    International Nuclear Information System (INIS)

    The atomistic mechanism of dissociative adsorption of ethylene molecules on a Ni cluster is investigated by ab initio molecular-dynamics simulations. The activation free energy to dehydrogenate an ethylene molecule on the Ni cluster and the corresponding reaction rate is estimated. A remarkable finding is that the adsorption energy of ethylene molecules on the Ni cluster is considerably larger than the activation free energy, which explains why the actual reaction rate is faster than the value estimated based on only the activation free energy. It is also found from the dynamic simulations that hydrogen molecules and an ethane molecule are formed from the dissociated hydrogen atoms, whereas some exist as single atoms on the surface or in the interior of the Ni cluster. On the other hand, the dissociation of the C-C bonds of ethylene molecules is not observed. On the basis of these simulation results, the nature of the initial stage of carbon nanotube growth is discussed. (paper)

  17. Atom probe tomography simulations and density functional theory calculations of bonding energies in Cu3Au

    KAUST Repository

    Boll, Torben

    2012-10-01

    In this article the Cu-Au binding energy in Cu3Au is determined by comparing experimental atom probe tomography (APT) results to simulations. The resulting bonding energy is supported by density functional theory calculations. The APT simulations are based on the Müller-Schottky equation, which is modified to include different atomic neighborhoods and their characteristic bonds. The local environment is considered up to the fifth next nearest neighbors. To compare the experimental with simulated APT data, the AtomVicinity algorithm, which provides statistical information about the positions of the neighboring atoms, is applied. The quality of this information is influenced by the field evaporation behavior of the different species, which is connected to the bonding energies. © Microscopy Society of America 2012.

  18. A Vision of Interdisciplinary Education: Students' Reasoning about "High-Energy Bonds" and ATP

    CERN Document Server

    Dreyfus, Benjamin W; Turpen, Chandra; Gouvea, Julia; Redish, Edward F

    2014-01-01

    As interdisciplinary courses are developed, instructors and researchers have to grapple with questions of how students should make connections across disciplines. We explore the issue of interdisciplinary reconciliation (IDR): how students reconcile seemingly contradictory ideas from different disciplines. While IDR has elements in common with other frameworks for the reconciliation of ideas across contexts, it differs in that each disciplinary idea is considered canonically correct within its own discipline. The setting for the research is an introductory physics course for biology majors that seeks to build greater interdisciplinary coherence and therefore includes biologically relevant topics such as ATP and chemical bond energy. In our case-study data, students grapple with the apparent contradiction between the energy released when the phosphate bond in ATP is broken and the idea that an energy input is required to break a bond. We see students justifying context-dependent modeling choices, showing nuanc...

  19. Modeling of Covalent Bonding in Solids by Inversion of Cohesive Energy Curves

    CERN Document Server

    Bazant, M Z; Bazant, Martin Z.; Kaxiras, Efthimios

    1996-01-01

    We provide a systematic test of empirical theories of covalent bonding in solids using an exact procedure to invert ab initio cohesive energy curves. By considering multiple structures of the same material, it is possible for the first time to test competing angular functions, expose inconsistencies in the basic assumption of a cluster expansion, and extract general features of covalent bonding. We test our methods on silicon, and provide the direct evidence that the Tersoff-type bond order formalism correctly describes coordination dependence. For bond-bending forces, we obtain skewed angular functions that favor small angles, unlike existing models. As a proof-of-principle demonstration, we derive a Si interatomic potential which exhibits comparable accuracy to existing models.

  20. A comparison of ab initio quantum-mechanical and experimental D0 binding energies of eleven H-bonded and eleven dispersion-bound complexes.

    Science.gov (United States)

    Haldar, Susanta; Gnanasekaran, Ramachandran; Hobza, Pavel

    2015-10-28

    Dissociation energies (D0) of 11 H-bonded and 11 dispersion-bound complexes were calculated as the sum of interaction energies and the change of zero-point vibrational energies (ΔZPVE). The structures of H-bonded complexes were optimized at the RI-MP2/cc-pVTZ level, at which deformation and harmonic ΔZPVE energies were also calculated. The structures of dispersion-bound complexes were optimized at the DFT-D3 level, and harmonic ΔZPVE energies were determined at the same level as well. For comparison, CCSD(T)/CBS D0 energies were also evaluated for both types of complexes. The CCSD(T)/CBS interaction energy was constructed as the sum of MP2/CBS interaction energy, extrapolated from aug-cc-pVTZ and aug-cc-pVQZ basis sets, and ΔCCSD(T) correction, determined with the aug-cc-pVDZ basis set. The ΔZPVE energies were determined for all complexes at the harmonic level and for selected complexes, these energies were also calculated using second-order vibration perturbation (VPT2) theory. For H-bonded complexes, the harmonic CCSD(T)/CBS D0 energies were in better agreement with the experimental values (with a mean relative error (MRE) of 6.2%) than the RI-MP2/cc-pVTZ D0 (a MRE of 12.3%). The same trend was found for dispersion-bound complexes (6.2% (MRE) at CCSD(T)/CBS and 7.7% (MRE) at the DFT-D3 level). When the anharmonic ΔZPVE term was included instead of harmonic one, the agreement between theoretical and experimental D0 deteriorated for H-bonded as well as dispersion-bound complexes. Finally, the applicability of "diagonal approximation" for determining the anharmonic ΔZPVE was shown. For the phenolH2O complex, the ΔZPVE energy calculated at the VPT2 level and on the basis of "diagonal approximation" differed by less than 0.1 kcal mol(-1). PMID:26392236

  1. I. Dissociation free energies of drug-receptor systems via non-equilibrium alchemical simulations: a theoretical framework.

    Science.gov (United States)

    Procacci, Piero

    2016-06-01

    In this contribution I critically revise the alchemical reversible approach in the context of the statistical mechanics theory of non-covalent bonding in drug-receptor systems. I show that most of the pitfalls and entanglements for the binding free energy evaluation in computer simulations are rooted in the equilibrium assumption that is implicit in the reversible method. These critical issues can be resolved by using a non-equilibrium variant of the alchemical method in molecular dynamics simulations, relying on the production of many independent trajectories with a continuous dynamical evolution of an externally driven alchemical coordinate, completing the decoupling of the ligand in a matter of a few tens of picoseconds rather than nanoseconds. The absolute binding free energy can be recovered from the annihilation work distributions by applying an unbiased unidirectional free energy estimate, on the assumption that any observed work distribution is given by a mixture of normal distributions, whose components are identical in either direction of the non-equilibrium process, with weights regulated by the Crooks theorem. I finally show that the inherent reliability and accuracy of the unidirectional estimate of the decoupling free energies, based on the production of a few hundreds of non-equilibrium independent sub-nanosecond unrestrained alchemical annihilation processes, is a direct consequence of the funnel-like shape of the free energy surface in molecular recognition. An application of the technique to a real drug-receptor system is presented in the companion paper. PMID:27193067

  2. Towards simple orbital-dependent density functionals for molecular dissociation

    Science.gov (United States)

    Zhang, Igor Ying; Richter, Patrick; Scheffler, Matthias

    2015-03-01

    Density functional theory (DFT) is one of the leading first-principles electronic-structure theories. However, molecular dissociation remains a challenge, because it requires a well-balanced description of the drastically different electronic structure at different bond lengths. One typical and well-documented case is the dissociation of both H2+ and H2, for which all popular DFT functionals fail. We start from the Bethe-Goldstone equation to propose a simple orbital-dependent correlation functional which generalizes the linear adiabatic connection approach. The resulting scheme is based on second-order perturbation theory (PT2), but includes the self-consistent coupling of electron-hole pairs, which ensures the correct H2 dissociation limit and gives a finite correlation energy for systems with a (near)-degenerate energy gap. This coupling PT2-like (CPT2) approximation delivers a significant improvement over all existing functionals for both H2 and H2+ dissociation. We will demonstrate the reason for this improvement analytically for H2 in a minimal basis.

  3. Chemical bond as a test of density-gradient expansions for kinetic and exchange energies

    International Nuclear Information System (INIS)

    Errors in kinetic and exchange contributions to the molecular bonding energy are assessed for approximate density functionals by reference to near-exact Hartree-Fock values. From the molecular calculations of Allan et al. and of Lee and Ghosh, it is demonstrated that the density-gradient expansion does not accurately describe the noninteracting kinetic contribution to the bonding energy, even when this expansion is carried to fourth order and applied in its spin-density-functional form to accurate Hartree-Fock densities. In a related study, it is demonstrated that the overbinding of molecules such as N2 and F2, which occurs in the local-spin-density (LSD) approximation for the exchange-correlation energy, is not attributable to errors in the self-consistent LSD densities. Contrary to expectations based upon the Gunnarsson-Jones nodality argument, it is found that the LSD approximation for the exchange energy can seriously overbind a molecule even when bonding does not create additional nodes in the occupied valence orbitals. LSD and exact values for the exchange contribution to the bonding energy are displayed and discussed for several molecules

  4. Electronic structure, molecular bonding and potential energy surfaces

    Energy Technology Data Exchange (ETDEWEB)

    Ruedenberg, K. [Ames Laboratory, IA (United States)

    1993-12-01

    By virtue of the universal validity of the generalized Born-Oppenheimer separation, potential energy surfaces (PES`) represent the central conceptual as well as quantitative entities of chemical physics and provide the basis for the understanding of most physicochemical phenomena in many diverse fields. The research in this group deals with the elucidation of general properties of PES` as well as with the quantitative determination of PES` for concrete systems, in particular pertaining to reactions involving carbon, oxygen, nitrogen and hydrogen molecules.

  5. Exact electronic and nuclear time-dependent potential energy surfaces for attosecond electron localization in the dissociation of H{sub 2}{sup +}

    Energy Technology Data Exchange (ETDEWEB)

    Suzuki, Yasumitsu; Abedi, Ali; Gross, Eberhard K.U. [Max Planck Institute of Microstructure Physics, Weinberg 2, D-06120 Halle (Germany); Maitra, Neepa T. [Department of Physics and Astronomy, Hunter College and the City University of New York, 695 Park Avenue, New York, New York 10065 (United States); Yamashita, Koichi [Department of Chemical System Engineering, School of Engineering, The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-8656 (Japan)

    2013-07-01

    We study the electron localization dynamics in the dissociation of H2+ using a 1D model Hamiltonian. To this end we calculate the exact time-dependent potential energy surfaces (TDPES) both for the electron and for the nuclei. The exact electronic TDPES shows that the final electron localization is determined when the interatomic barrier becomes large and prohibits electron tunneling. The exact nuclear TDPES shows the mechanism of slowdown of the dissociation. It is found that the nuclear potential cannot be approximated by the weighted average of the quasi-static state potential energy surfaces, but can be approximated well by the transition between them. We show these two time-dependent potentials are the exact potential functionals of the time-dependent multicomponent density functional theory and can reproduce the whole phenomena of electron localization dynamics.

  6. A periodic energy decomposition analysis method for the investigation of chemical bonding in extended systems

    International Nuclear Information System (INIS)

    The development and first applications of a new periodic energy decomposition analysis (pEDA) scheme for extended systems based on the Kohn-Sham approach to density functional theory are described. The pEDA decomposes the bonding energy between two fragments (e.g., the adsorption energy of a molecule on a surface) into several well-defined terms: preparation, electrostatic, Pauli repulsion, and orbital relaxation energies. This is complemented by consideration of dispersion interactions via a pairwise scheme. One major extension toward a previous implementation [Philipsen and Baerends, J. Phys. Chem. B 110, 12470 (2006)] lies in the separate discussion of electrostatic and Pauli and the addition of a dispersion term. The pEDA presented here for an implementation based on atomic orbitals can handle restricted and unrestricted fragments for 0D to 3D systems considering periodic boundary conditions with and without the determination of fragment occupations. For the latter case, reciprocal space sampling is enabled. The new method gives comparable results to established schemes for molecular systems and shows good convergence with respect to the basis set (TZ2P), the integration accuracy, and k-space sampling. Four typical bonding scenarios for surface-adsorbate complexes were chosen to highlight the performance of the method representing insulating (CO on MgO(001)), metallic (H2 on M(001), M = Pd, Cu), and semiconducting (CO and C2H2 on Si(001)) substrates. These examples cover diverse substrates as well as bonding scenarios ranging from weakly interacting to covalent (shared electron and donor acceptor) bonding. The results presented lend confidence that the pEDA will be a powerful tool for the analysis of surface-adsorbate bonding in the future, enabling the transfer of concepts like ionic and covalent bonding, donor-acceptor interaction, steric repulsion, and others to extended systems

  7. A periodic energy decomposition analysis method for the investigation of chemical bonding in extended systems

    Energy Technology Data Exchange (ETDEWEB)

    Raupach, Marc; Tonner, Ralf, E-mail: tonner@chemie.uni-marburg.de [Fachbereich Chemie, Philipps-Universität Marburg, Hans-Meerwein-Straße, 35032 Marburg (Germany)

    2015-05-21

    The development and first applications of a new periodic energy decomposition analysis (pEDA) scheme for extended systems based on the Kohn-Sham approach to density functional theory are described. The pEDA decomposes the bonding energy between two fragments (e.g., the adsorption energy of a molecule on a surface) into several well-defined terms: preparation, electrostatic, Pauli repulsion, and orbital relaxation energies. This is complemented by consideration of dispersion interactions via a pairwise scheme. One major extension toward a previous implementation [Philipsen and Baerends, J. Phys. Chem. B 110, 12470 (2006)] lies in the separate discussion of electrostatic and Pauli and the addition of a dispersion term. The pEDA presented here for an implementation based on atomic orbitals can handle restricted and unrestricted fragments for 0D to 3D systems considering periodic boundary conditions with and without the determination of fragment occupations. For the latter case, reciprocal space sampling is enabled. The new method gives comparable results to established schemes for molecular systems and shows good convergence with respect to the basis set (TZ2P), the integration accuracy, and k-space sampling. Four typical bonding scenarios for surface-adsorbate complexes were chosen to highlight the performance of the method representing insulating (CO on MgO(001)), metallic (H{sub 2} on M(001), M = Pd, Cu), and semiconducting (CO and C{sub 2}H{sub 2} on Si(001)) substrates. These examples cover diverse substrates as well as bonding scenarios ranging from weakly interacting to covalent (shared electron and donor acceptor) bonding. The results presented lend confidence that the pEDA will be a powerful tool for the analysis of surface-adsorbate bonding in the future, enabling the transfer of concepts like ionic and covalent bonding, donor-acceptor interaction, steric repulsion, and others to extended systems.

  8. Breaking energy bonds: micro hydro in Sri Lanka

    Energy Technology Data Exchange (ETDEWEB)

    Lahiru Perera, M.A.; Karunaratne, T.W. [ITDG (Sri Lanka)

    2001-08-01

    The article discusses the need to provide electrical power through mini hydroelectric power systems for disadvantaged rural communities in Sri Lanka. The objective of the country's Electricity Consumers' Society is to enable communities to have their own renewable energy sources over which they will have total control. The Society's strategy is discussed in detail. At present, mineral oil is still widely used in bottle lamps but a new era of empowerment appears to have dawned and will be completed when the 'powerless' 46% of the population has access to efficient, environmentally friendly electrical power.

  9. Geometrical structures and probable dissociation channels of CrPm+ (m=2, 4, 6, 8) clusters

    International Nuclear Information System (INIS)

    A density functional theory study on the geometrical structures and probable dissociation channels of CrPm+ (m=2, 4, 6, 8) clusters has been performed. Our results reveal that the tetrahedral P4 structure and linear P2 structure are two stable units in CrPm+ clusters relatively. The lowest energy structures of CrPm+ clusters are constructed by bonding Cr with P4 unit or P2 unit. The bond between Cr and P4 unit or P2 unit is much weaker than the bond between P atoms in P4 or P2 unit. The most probable dissociation channel for CrP8+ cluster is the detachment of P4 unit or P2 unit. Our conclusions are consistent with the previous laser photodissociation experiments.

  10. Covalent bonding effect on the mean excitation energy of H2 with the local plasma model

    Science.gov (United States)

    Kamaratos, E.

    1984-01-01

    Chemical bonding is taken into account explicitly in the determination of the mean excitation energy (I) for stopping power of H2 with the local plasma approximation by employing molecular electronic wave functions for H2 for the first time. This procedure leads to a new value for IH2 that is higher than all accepted experimental and theoretical values.

  11. Unified description of hydrogen bonding by a two-state effective Hamiltonian

    CERN Document Server

    McKenzie, Ross H

    2011-01-01

    An effective Hamiltonian is considered for hydrogen bonding between two molecules due to the quantum mechanical interaction between the orbitals of the H-atom and the donor and acceptor atoms in the molecules. The Hamiltonian acts on two diabatic states and has a simple chemically motivated form for its matrix elements. The model gives insight into the "H-bond puzzle", describes different classes of bonds, and empirical correlations between the donor-acceptor distance $R$ and binding energies, bond lengths, and the softening of vibrational frequencies. A key prediction is the UV photo-dissociation of H-bonded complexes via an excited electronic state with an exalted vibrational frequency.

  12. Average bond energies between boron and elements of the fourth, fifth, sixth, and seventh groups of the periodic table

    Science.gov (United States)

    Altshuller, Aubrey P

    1955-01-01

    The average bond energies D(gm)(B-Z) for boron-containing molecules have been calculated by the Pauling geometric-mean equation. These calculated bond energies are compared with the average bond energies D(exp)(B-Z) obtained from experimental data. The higher values of D(exp)(B-Z) in comparison with D(gm)(B-Z) when Z is an element in the fifth, sixth, or seventh periodic group may be attributed to resonance stabilization or double-bond character.

  13. On the photostability of peptides after selective photoexcitation of the backbone: Prompt versus slow dissociation

    DEFF Research Database (Denmark)

    Byskov, Camilla Skinnerup; Jensen, Frank; Jørgensen, Thomas J D;

    2014-01-01

    , which is remote from the initial site of excitation. Hence loss of CE serves as direct proof that energy has reached the charge-site end, leaving the backbone intact. Our work demonstrates that excitation of tertiary amide moieties (proline linkages) results in both prompt dissociation and statistical...... present a protocol to disentangle slow and non-hazardous statistical dissociation from prompt cleavage of peptide bonds by 210 nm light based on experiments on protonated peptides isolated in vacuo and tagged by 18-crown-6 ether (CE). The weakest link in the system is between the charged site and CE...

  14. Mathematical Simulation of Graphene With Modified c-c Bond Length and Transfer Energy

    Directory of Open Access Journals (Sweden)

    P.A. Alvi

    2011-01-01

    Full Text Available In nanotechnology research, allotropes of carbon like Graphene, Fullerene (Buckyball and Carbon nanotubes are widely used due to their remarkable properties. Electrical and mechanical properties of those allotropes vary with their molecular geometry. This paper is specially based on modeling and simulation of graphene in order to calculate energy band structure in k space with varying the C-C bond length and C-C transfer energy. Significant changes have been observed in the energy band structure of graphene due to variation in C-C bond length and C-C transfer energy. In particular, this paper focuses over the electronic structure of graphene within the frame work of tight binding approximation. It has been reported that conduction and valence states in graphene only meet at two points in k-space and that dispersion around these special points is conical.

  15. The ground and excited state potential energy surfaces of nitromethane related to its dissociation dynamics after excitation at 193 nm

    International Nuclear Information System (INIS)

    The relevant low-lying singlet and triplet potential energy surfaces in the photolysis of nitromethane have been studied by using the multistate extension of the multiconfigurational second-order perturbation theory in conjunction with large atomic natural orbital-type basis sets. The proposed mechanism for the photolytic decomposition of CH3NO2 provides a consistent and reinterpreted picture of the available experimental results. Two reaction paths are found in the photolysis of nitromethane after excitation at 193 nm: (1) Major Channel, CH3NO2(1A')+hν(193 nm)→CH3NO2(2A'')→(lim(lu-tag)lu-tag(bu(IC))))CH3NO2(2A')→CH3(1A1')+NO2(1 2B1)→(lim(lu-tag(-hν')lu-tag(bu(IC))))CH3(1A1')+NO2(1 2A1)→(lim(lu-tag(193 nm)lu-tag(bu(hν))))CH3(1A1')+NO(A 2Σ+)+αO(3P)+βO(1D). (2) Minor Channel, CH3NO2(1A')+hν(193 nm)→CH3NO2(2A'')→CH3(1A1')+NO2(1 2A2)→CH3(1A1')+NO(X 2Π)+αO(3P)+βO(1D), being α and β fractional numbers. No ionic species are found in any dissociation path. Additionally, the respective low-lying Rydberg states of nitromethane and nitrogen dioxide have been studied too.

  16. Density functional for van der Waals forces accounts for hydrogen bond in benchmark set of water hexamers

    OpenAIRE

    Kelkkanen, Kari André; Lundqvist, Bengt; Nørskov, Jens Kehlet

    2009-01-01

    A recent extensive study has investigated how various exchange-correlation (XC) functionals treat hydrogen bonds in water hexamers and has shown traditional generalized gradient approximation and hybrid functionals used in density-functional (DF) theory to give the wrong dissociation-energy trend of low-lying isomers and van der Waals (vdW) dispersion forces to give key contributions to the dissociation energy. The question raised whether functionals that incorporate vdW forces implicitly int...

  17. Fabrication and Characterization of a Lead Zirconate Titanate Micro Energy Harvester Based on Eutectic Bonding

    Science.gov (United States)

    Li, Yi-Gui; Sun, Jian; Yang, Chun-Sheng; Liu, Jing-Quan; Sugiyama, Susumu; Tanaka, Katsuhiko

    2011-06-01

    A lead zirconate titanate(PZT)-Si energy harvester cantilever with PZT bulk ceramics is fabricated by eutectic bonding, polishing and dicing processes. The feasibility of this process is studied using a successful operation of the cantilever in both actuation and harvesting modes. The first prototype made from a PZT-Au-Si cantiliever is tested. The testing results show the voltage output of 632 mV at the frequency of 815 Hz when the excitation acceleration is 0.5 g. The PZT and silicon layers are bonded together to form a sandwiched structure using a gold layer as an intermediate layer.

  18. Using Qualified Energy Conservation Bonds for Public Building Upgrades. Reducing Energy Bills in the City of Philadelphia

    Energy Technology Data Exchange (ETDEWEB)

    Zimring, Mark [Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States)

    2012-07-18

    Qualified Energy Conservation Bonds (QECBs) are federally-subsidized bonds that enable state, tribal, and local government issuers to borrow money to fund a range of energy conservation projects, including public building upgrades that reduce energy use by at least 20 percent, at very attractive borrowing rates and long terms. As part of the American Recovery and Reinvestment Act (ARRA), the City of Philadelphia received a $15 million QECB award from the U.S. Department of the Treasury (Treasury). The city leveraged $6.25 million of its QECB allocation to finance half of a $12.6 million initiative to upgrade the energy efficiency of City buildings. The upgrades to four city facilities are expected to deliver over $10 million of net savings, and are a major step towards achieving the city’s goal of reducing government energy consumption by 30 percent by 2015.

  19. Interlayer bonding energy of layered minerals: Implication for the relationship with friction coefficient

    Science.gov (United States)

    Sakuma, Hiroshi; Suehara, Shigeru

    2015-04-01

    The frictional strength of layered minerals is an important component of fault slip physics. A low-friction coefficient of these minerals has been attributed to the interlayer bonding energy (ILBE) of their weak interlayer bonding. The ILBE used for discussing the friction coefficient is based on a simple electrostatic calculation; however, the values should be revisited by precise calculations based on quantum mechanics. In this study, the ILBEs of layered minerals were calculated by using the density functional theory (DFT) method with van der Waals correction. The ILBEs calculated by the simple electrostatic method for hydrogen-bonding minerals such as kaolinite, lizardite, gibbsite, and brucite strongly overestimated the reliable energies calculated by the DFT method. This result should be ascribed to the inaccurate approximation of the point charges at the basal plane. A linear relationship between the experimentally measured friction coefficients of layered minerals and the ILBEs determined by the simple method was not confirmed by using the reliable ILBEs calculated by our DFT method. The results, however, do not remove the possibility of a relationship between interlayer bonding energy and the friction coefficient because the latter, used for comparing the former, was obtained through experiments conducted under various conditions.

  20. Dissociation energies of the molecules RhTh and RhU from high temperature mass spectrometry and predicted thermodynamic stabilities of selected diatomic actinide--platinum metal intermetallic molecules

    International Nuclear Information System (INIS)

    Gaseous RhTh and RhU have been observed in a Knudsen effusion mass spectrometric investigation of a thorium--uranium-rhodium--graphite system at high temperatures (2400--2700 0K). Thermodynamic treatment of the experimental data yielded the atomization energies of RhTh and RhU as D0298(RhTh) =513 +- 21 kJ mole-1 or 122.6 +- 5 kcal mole-1 and D0298(RhU) =519 +- 17 kJ mole-1 or 124.0 +- 4 kcal mole-1. These values were derived from the third law enthalpies. The known experimental bond energies for the ligand-free gaseous intermetallic compounds between the actinides and the platinum metals have been interpretated in terms of a previously developed model based on the Brewer--Engel approach. Also, calculations are presented for the dissociation energies of certain selected actinide--platinum metal diatomic molecules which have not yet been experimentally observed

  1. Low-energy electron-induced dissociation in condensed-phase L-cysteine II: a comparative study on anion desorption from chemisorbed and physisorbed films

    Science.gov (United States)

    Alizadeh, Elahe; Massey, Sylvain; Sanche, Léon; Rowntree, Paul A.

    2016-04-01

    Due to its multifunctional structure, cysteine is becoming an ideal model molecule for investigating the complex interactions of proteins with metallic surfaces such as gold nanoparticles. We report herein the results of low-energy electron induced degradation of L-cysteine films, chemisorbed on a gold substrate via the thiol group or physisorbed into a clean gold surface. The data were recorded under ultra-high vacuum conditions at room temperature. Anion yields desorbed from these films by the impact of 0.5 to 19 eV electrons provide clear evidence of the efficient decomposition of this amino acid via dissociative electron attachment (i.e., from dissociation of intermediate transient anions located between 5 and 14 eV). The peaks in the desorbed-anion yield functions, associated with DEA, are superimposed on a continuously rising signal attributed to dipolar dissociation. Similar to the results previously observed from physisorbed films, light anionic species, with masses lower than 35 amu, have been detected. In addition, we measured for first time fragments at 14 amu (CH2-) and 15 amu (CH3-) desorbing from physisorbed films, as well as heavier fragments of mass 45 and 46 amu desorbing from chemisorbed films. Contribution to the Topical Issue "Low-Energy Interactions related to Atmospheric and Extreme Conditions", edited by S. Ptasinska, M. Smialek-Telega, A. Milosavljevic, B. Sivaraman.

  2. Hydrogen Bonding between Metal-Ion Complexes and Noncoordinated Water: Electrostatic Potentials and Interaction Energies.

    Science.gov (United States)

    Andrić, Jelena M; Misini-Ignjatović, Majda Z; Murray, Jane S; Politzer, Peter; Zarić, Snežana D

    2016-07-01

    The hydrogen bonding of noncoordinated water molecules to each other and to water molecules that are coordinated to metal-ion complexes has been investigated by means of a search of the Cambridge Structural Database (CSD) and through quantum chemical calculations. Tetrahedral and octahedral complexes that were both charged and neutral were studied. A general conclusion is that hydrogen bonds between noncoordinated water and coordinated water are much stronger than those between noncoordinated waters, whereas hydrogen bonds of water molecule in tetrahedral complexes are stronger than in octahedral complexes. We examined the possibility of correlating the computed interaction energies with the most positive electrostatic potentials on the interacting hydrogen atoms prior to interaction and obtained very good correlation. This study illustrates the fact that electrostatic potentials computed for ground-state molecules, prior to interaction, can provide considerable insight into the interactions. PMID:26989883

  3. Dissociation of {sup 10}C nuclei in a track nuclear emulsion at an energy of 1.2 GeV per nucleon

    Energy Technology Data Exchange (ETDEWEB)

    Mamatkulov, K. Z.; Kattabekov, R. R. [Joint Institute for Nuclear Research (Russian Federation); Alikulov, S. S. [A. Kodirii Jizzakh State Pedagogical Institute (Uzbekistan); Artemenkov, D. A. [Joint Institute for Nuclear Research (Russian Federation); Bekmirzaev, R. N. [A. Kodirii Jizzakh State Pedagogical Institute (Uzbekistan); Bradnova, V.; Zarubin, P. I., E-mail: zarubin@lhe.jinr.ru; Zarubina, I. G.; Kondratieva, N. V.; Kornegrutsa, N. K.; Krivenkov, D. O.; Malakhov, A. I. [Joint Institute for Nuclear Research (Russian Federation); Olimov, K. [Uzbek Academy of Sciences, Institute for Physics and Technology (Uzbekistan); Peresadko, N. G.; Polukhina, N. G. [Russian Academy of Sciences, Lebedev Physical Institute (Russian Federation); Rukoyatkin, P. A.; Rusakova, V. V.; Stanoeva, R. [Joint Institute for Nuclear Research (Russian Federation); Kharlamov, S. P. [Russian Academy of Sciences, Lebedev Physical Institute (Russian Federation)

    2013-10-15

    The charge topology in the fragmentation of {sup 10}C nuclei in a track nuclear emulsion at an energy of 1.2 GeV per nucleon is studied. In the coherent dissociation of {sup 10}C nuclei, about 82% of events are associated with the channel {sup 10}C {yields} 2{alpha}+ 2p. The angular distributions and correlations of product fragments are presented for this channel. It is found that among {sup 10}C {yields} 2{alpha}+ 2p events, about 30% are associated with the process in which dissociation through the ground state of the unstable {sup 9}Be{sub g.s.} nucleus is followed by {sup 8}Be{sub g.s.} + p decays.

  4. Electronic bond tuning with heterocyclic carbenes

    KAUST Repository

    Falivene, Laura

    2013-01-01

    We discuss the impact of the nature of the heterocyclic carbene ring, when used as a complex forming ligand, on the relative stability of key intermediates in three typical Ru, Pd and Au promoted reactions. Results show that P-heterocyclic carbenes have a propensity to increase the bonding of the labile ligand and of the substrate in Ru-promoted olefin metathesis, whereas negligible impact is expected on the stability of the ruthenacycle intermediate. In the case of Pd cross-coupling reactions, dissociation of a P-heterocyclic carbene is easier than dissociation of the N-heterocyclic analogue. In the case of the Au-OH synthon, the Au-OH bond is weakened with the P-heterocyclic carbene ligands. A detailed energy decomposition analysis is performed to rationalize these results. © 2013 The Royal Society of Chemistry.

  5. Various Carbon to Carbon Bond Lengths Inter-related via the Golden Ratio, and their Linear Dependence on Bond Energies

    OpenAIRE

    Heyrovska, Raji

    2008-01-01

    This work presents the relations between the carbon to carbon bond lengths in the single, double and triple bonds and in graphite, butadiene and benzene. The Golden ratio, which was shown to divide the Bohr radius into two parts pertaining to the charged particles, the electron and proton, and to divide inter-atomic distances into their cationic and anionic radii, also plays a role in the carbon-carbon bonds and in the ionic/polar character of those in graphite, butadiene and benzene. Further...

  6. Ionisation and dissociation of water induced by swift multicharged ions

    International Nuclear Information System (INIS)

    Ionization and dissociation of water molecules and water clusters induced by 11.7 MeV/A Ni25+ ions were carried out by imaging techniques. Branching ratios, ionisation cross sections and Kinetic Energy Released distributions have been measured together with fragmentation dynamics studies. Multiple ionization represents approximately 30% of the ionizing events. Double ionization produces in significant way atomic oxygen, considered as a possible precursor of the large production of HO2 radical in liquid water radiolysis by ions of high Linear Energy Transfer. We evidence a strong selectivity of bond breakage in the case of ion-induced HOD fragmentation. Once the molecule doubly ionized, the breakage of the O-H bond is found 6.5 times more probable than that of the O-D bond. A semi-classical calculation simulating the fragmentation dynamics on the potential energy surface of the ground-state of di-cation H2O2+ makes possible to as well reproduce the preferential nature of the breakage of the O-H bond as the position and the shift of the kinetic energy distributions. First results concerning interaction with water clusters are also reported. Measurements in coincidence are carried out giving access to correlation, with the distributions in energy and angle of the emitted fragments. Mass spectrum points fast intra-cluster proton transfer, leading to the emission of protonated clusters. (author)

  7. Three-particle dissociation of D3 and H3 (2sa'1): energies and momentum correlation maps for selected rovibrational levels

    International Nuclear Information System (INIS)

    The short-lived 32A'(2sa'1) electronic state of the molecules D3 and H3 is studied. First we present variational results for the rovibrational energy levels up to about 10 000 cm-1, based on a recent potential energy surface and using a program adapted to the D3h symmetry point group. Three-particle fragmentation caused by non-adiabatic coupling to the dissociative ground state has been investigated by calculating diabatization angle functions and applying the semiclassical trajectory surface-hopping technique. For comparison with experiments we have constructed state resolved theoretical momentum correlation maps (Dalitz plots) for a few low-lying rovibrational levels.

  8. Fabrication and Characterization of a Lead Zirconate Titanate Micro Energy Harvester Based on Eutectic Bonding

    Institute of Scientific and Technical Information of China (English)

    LI Yi-Gui; SUN Jian; YANG Chun-Sheng; LIU Jing-Quan; SUGIYAMA Susumu; TANAKA Katsuhiko

    2011-01-01

    A lead zirconate titanate(PZT)-Si energy harvester cantilever with PZT bulk ceramics is fabricated by eutectic bonding, polishing and dicing processes. The feasibility of this process is studied using a successful operation of the cantilever in both actuation and harvesting modes. The first prototype made from a PZT-Au-Si cantiliever is tested. The testing results show the voltage output of 632mV at the frequency of 815Hz when the excitation acceleration is 0.5 g. The PZT and silicon layers are bonded together to form a sandwiched structure using a gold layer as an intermediate layer.%@@ A lead zirconate titanate(PZT)-Si energy harvester cantilever with PZT bulk ceramics is fabricated by eutectic bonding, polishing and dicing processes.The feasibility of this process is studied using a successful operation of the cantilever in both actuation and harvesting modes.The first prototype made from a PZT-Au-Si cantiliever is tested.The testing results show the voltage output of 632mV at the frequency of 815 Hz when the excitation acceleration is 0.5 g.The PZT and silicon layers are bonded together to form a sandwiched structure using a gold layer as an intermediate layer.

  9. On collisional energy transfer in recombination and dissociation reactions: A Wiener-Hopf problem and the effect of a near elastic peak.

    Science.gov (United States)

    Zhu, Zhaoyan; Marcus, R A

    2008-12-01

    The effect of the large impact parameter near-elastic peak of collisional energy transfer for unimolecular dissociation/bimolecular recombination reactions is studied. To this end, the conventional single exponential model, a biexponential model that fits the literature classical trajectory data better, a model with a singularity at zero energy transfer, and the most realistic model, a model with a near-singularity, are fitted to the trajectory data in the literature. The typical effect of the energy transfer on the recombination rate constant is maximal at low pressures and this region is the one studied here. The distribution function for the limiting dissociation rate constant k(0) at low pressures is shown to obey a Wiener-Hopf integral equation and is solved analytically for the first two models and perturbatively for the other two. For the single exponential model, this method yields the trial solution of Troe. The results are applied to the dissociation of O(3) in the presence of argon, for which classical mechanical trajectory data are available. The k(0)'s for various models are calculated and compared, the value for the near-singularity model being about ten times larger than that for the first two models. This trend reflects the contribution to the cross section from collisions with larger impact parameter. In the present study of the near-singularity model, it is found that k(0) is not sensitive to reasonable values for the lower bound. Energy transfer values DeltaE's are also calculated and compared and can be similarly understood. However, unlike the k(0) values, they are sensitive to the lower bound, and so any comparison of a classical trajectory analysis for DeltaE's with the kinetic experimental data needs particular care. PMID:19063543

  10. On collisional energy transfer in recombination and dissociation reactions: A Wiener-Hopf problem and the effect of a near elastic peak

    International Nuclear Information System (INIS)

    The effect of the large impact parameter near-elastic peak of collisional energy transfer for unimolecular dissociation/bimolecular recombination reactions is studied. To this end, the conventional single exponential model, a biexponential model that fits the literature classical trajectory data better, a model with a singularity at zero energy transfer, and the most realistic model, a model with a near-singularity, are fitted to the trajectory data in the literature. The typical effect of the energy transfer on the recombination rate constant is maximal at low pressures and this region is the one studied here. The distribution function for the limiting dissociation rate constant k0 at low pressures is shown to obey a Wiener-Hopf integral equation and is solved analytically for the first two models and perturbatively for the other two. For the single exponential model, this method yields the trial solution of Troe. The results are applied to the dissociation of O3 in the presence of argon, for which classical mechanical trajectory data are available. The k0's for various models are calculated and compared, the value for the near-singularity model being about ten times larger than that for the first two models. This trend reflects the contribution to the cross section from collisions with larger impact parameter. In the present study of the near-singularity model, it is found that k0 is not sensitive to reasonable values for the lower bound. Energy transfer values 's are also calculated and compared and can be similarly understood. However, unlike the k0 values, they are sensitive to the lower bound, and so any comparison of a classical trajectory analysis for 's with the kinetic experimental data needs particular care.

  11. Complete-active-space second-order perturbation theory (CASPT2//CASSCF) study of the dissociative electron attachment in canonical DNA nucleobases caused by low-energy electrons (0-3 eV).

    Science.gov (United States)

    Francés-Monerris, Antonio; Segarra-Martí, Javier; Merchán, Manuela; Roca-Sanjuán, Daniel

    2015-12-01

    Low-energy (0-3 eV) ballistic electrons originated during the irradiation of biological material can interact with DNA/RNA nucleobases yielding transient-anion species which undergo decompositions. Since the discovery that these reactions can eventually lead to strand breaking of the DNA chains, great efforts have been dedicated to their study. The main fragmentation at the 0-3 eV energy range is the ejection of a hydrogen atom from the specific nitrogen positions. In the present study, the methodological approach introduced in a previous work on uracil [I. González-Ramírez et al., J. Chem. Theory Comput. 8, 2769-2776 (2012)] is employed to study the DNA canonical nucleobases fragmentations of N-H bonds induced by low-energy electrons. The approach is based on minimum energy path and linear interpolation of internal coordinates computations along the N-H dissociation channels carried out at the complete-active-space self-consistent field//complete-active-space second-order perturbation theory level. On the basis of the calculated theoretical quantities, new assignations for the adenine and cytosine anion yield curves are provided. In addition, the π1 (-) and π2 (-) states of the pyrimidine nucleobases are expected to produce the temporary anions at electron energies close to 1 and 2 eV, respectively. Finally, the present theoretical results do not allow to discard neither the dipole-bound nor the valence-bound mechanisms in the range of energies explored, suggesting that both possibilities may coexist in the experiments carried out with the isolated nucleobases. PMID:26646889

  12. Complete-active-space second-order perturbation theory (CASPT2//CASSCF) study of the dissociative electron attachment in canonical DNA nucleobases caused by low-energy electrons (0-3 eV)

    Energy Technology Data Exchange (ETDEWEB)

    Francés-Monerris, Antonio; Segarra-Martí, Javier; Merchán, Manuela; Roca-Sanjuán, Daniel, E-mail: Daniel.Roca@uv.es [Instituto de Ciencia Molecular, Universitat de València, P.O. Box 22085, 46071 València (Spain)

    2015-12-07

    Low-energy (0-3 eV) ballistic electrons originated during the irradiation of biological material can interact with DNA/RNA nucleobases yielding transient-anion species which undergo decompositions. Since the discovery that these reactions can eventually lead to strand breaking of the DNA chains, great efforts have been dedicated to their study. The main fragmentation at the 0-3 eV energy range is the ejection of a hydrogen atom from the specific nitrogen positions. In the present study, the methodological approach introduced in a previous work on uracil [I. González-Ramírez et al., J. Chem. Theory Comput. 8, 2769-2776 (2012)] is employed to study the DNA canonical nucleobases fragmentations of N–H bonds induced by low-energy electrons. The approach is based on minimum energy path and linear interpolation of internal coordinates computations along the N–H dissociation channels carried out at the complete-active-space self-consistent field//complete-active-space second-order perturbation theory level. On the basis of the calculated theoretical quantities, new assignations for the adenine and cytosine anion yield curves are provided. In addition, the π{sub 1}{sup −} and π{sub 2}{sup −} states of the pyrimidine nucleobases are expected to produce the temporary anions at electron energies close to 1 and 2 eV, respectively. Finally, the present theoretical results do not allow to discard neither the dipole-bound nor the valence-bound mechanisms in the range of energies explored, suggesting that both possibilities may coexist in the experiments carried out with the isolated nucleobases.

  13. Complete-active-space second-order perturbation theory (CASPT2//CASSCF) study of the dissociative electron attachment in canonical DNA nucleobases caused by low-energy electrons (0-3 eV)

    International Nuclear Information System (INIS)

    Low-energy (0-3 eV) ballistic electrons originated during the irradiation of biological material can interact with DNA/RNA nucleobases yielding transient-anion species which undergo decompositions. Since the discovery that these reactions can eventually lead to strand breaking of the DNA chains, great efforts have been dedicated to their study. The main fragmentation at the 0-3 eV energy range is the ejection of a hydrogen atom from the specific nitrogen positions. In the present study, the methodological approach introduced in a previous work on uracil [I. González-Ramírez et al., J. Chem. Theory Comput. 8, 2769-2776 (2012)] is employed to study the DNA canonical nucleobases fragmentations of N–H bonds induced by low-energy electrons. The approach is based on minimum energy path and linear interpolation of internal coordinates computations along the N–H dissociation channels carried out at the complete-active-space self-consistent field//complete-active-space second-order perturbation theory level. On the basis of the calculated theoretical quantities, new assignations for the adenine and cytosine anion yield curves are provided. In addition, the π1− and π2− states of the pyrimidine nucleobases are expected to produce the temporary anions at electron energies close to 1 and 2 eV, respectively. Finally, the present theoretical results do not allow to discard neither the dipole-bound nor the valence-bound mechanisms in the range of energies explored, suggesting that both possibilities may coexist in the experiments carried out with the isolated nucleobases

  14. Complete-active-space second-order perturbation theory (CASPT2//CASSCF) study of the dissociative electron attachment in canonical DNA nucleobases caused by low-energy electrons (0-3 eV)

    Science.gov (United States)

    Francés-Monerris, Antonio; Segarra-Martí, Javier; Merchán, Manuela; Roca-Sanjuán, Daniel

    2015-12-01

    Low-energy (0-3 eV) ballistic electrons originated during the irradiation of biological material can interact with DNA/RNA nucleobases yielding transient-anion species which undergo decompositions. Since the discovery that these reactions can eventually lead to strand breaking of the DNA chains, great efforts have been dedicated to their study. The main fragmentation at the 0-3 eV energy range is the ejection of a hydrogen atom from the specific nitrogen positions. In the present study, the methodological approach introduced in a previous work on uracil [I. González-Ramírez et al., J. Chem. Theory Comput. 8, 2769-2776 (2012)] is employed to study the DNA canonical nucleobases fragmentations of N-H bonds induced by low-energy electrons. The approach is based on minimum energy path and linear interpolation of internal coordinates computations along the N-H dissociation channels carried out at the complete-active-space self-consistent field//complete-active-space second-order perturbation theory level. On the basis of the calculated theoretical quantities, new assignations for the adenine and cytosine anion yield curves are provided. In addition, the π1- and π2- states of the pyrimidine nucleobases are expected to produce the temporary anions at electron energies close to 1 and 2 eV, respectively. Finally, the present theoretical results do not allow to discard neither the dipole-bound nor the valence-bound mechanisms in the range of energies explored, suggesting that both possibilities may coexist in the experiments carried out with the isolated nucleobases.

  15. Electronic structure, stacking energy, partial charge, and hydrogen bonding in four periodic B-DNA models

    Science.gov (United States)

    Poudel, Lokendra; Rulis, Paul; Liang, Lei; Ching, W. Y.

    2014-08-01

    We present a theoretical study of the electronic structure of four periodic B-DNA models labeled (AT)10,(GC)10, (AT)5(GC)5, and (AT-GC)5 where A denotes adenine, T denotes thymine, G denotes guanine, and C denotes cytosine. Each model has ten base pairs with Na counterions to neutralize the negative phosphate group in the backbone. The (AT)5(GC)5 and (AT-GC)5 models contain two and five AT-GC bilayers, respectively. When compared against the average of the two pure models, we estimate the AT-GC bilayer interaction energy to be 19.015 Kcal/mol, which is comparable to the hydrogen bonding energy between base pairs obtained from the literature. Our investigation shows that the stacking of base pairs plays a vital role in the electronic structure, relative stability, bonding, and distribution of partial charges in the DNA models. All four models show a highest occupied molecular orbital (HOMO) to lowest unoccupied molecular orbital (LUMO) gap ranging from 2.14 to 3.12 eV with HOMO states residing on the PO4 + Na functional group and LUMO states originating from the bases. Our calculation implies that the electrical conductance of a DNA molecule should increase with increased base-pair mixing. Interatomic bonding effects in these models are investigated in detail by analyzing the distributions of the calculated bond order values for every pair of atoms in the four models including hydrogen bonding. The counterions significantly affect the gap width, the conductivity, and the distribution of partial charge on the DNA backbone. We also evaluate quantitatively the surface partial charge density on each functional group of the DNA models.

  16. Molecular resonant dissociation of surface-adsorbed molecules by plasmonic nanoscissors

    Science.gov (United States)

    Zhang, Zhenglong; Sheng, Shaoxiang; Zheng, Hairong; Xu, Hongxing; Sun, Mengtao

    2014-04-01

    The ability to break individual bonds or specific modes in chemical reactions is an ardently sought goal by chemists and physicists. While photochemistry based methodologies are very successful in controlling e.g. photocatalysis, photosynthesis and the degradation of plastic, it is hard to break individual molecular bonds for those molecules adsorbed on the surface because of the weak light-absorption in molecules and the redistribution of the resulting vibrational energy both inside the molecule and to its surrounding environment. Here we show how to overcome these obstacles with a plasmonic hot-electron mediated process and demonstrate a new method that allows the sensitive control of resonant dissociation of surface-adsorbed molecules by `plasmonic' scissors. To that end, we used a high-vacuum tip-enhanced Raman spectroscopy (HV-TERS) setup to dissociate resonantly excited NC2H6 fragments from Malachite green. The surface plasmons (SPs) excited at the sharp metal tip not only enhance the local electric field to harvest the light incident from the laser, but crucially supply `hot electrons' whose energy can be transferred to individual bonds. These processes are resonant Raman, which result in some active chemical bonds and then weaken these bonds, followed by dumping in lots of indiscriminant energy and breaking the weakest bond. The method allows for sensitive control of both the rate and probability of dissociation through their dependence on the density of hot electrons, which can be manipulated by tuning the laser intensity or tunneling current/bias voltage in the HV-TERS setup, respectively. The concepts of plasmonic scissors open up new versatile avenues for the deep understanding of in situ surface-catalyzed chemistry.The ability to break individual bonds or specific modes in chemical reactions is an ardently sought goal by chemists and physicists. While photochemistry based methodologies are very successful in controlling e.g. photocatalysis

  17. Students' reasoning about "high-energy bonds" and ATP: A vision of interdisciplinary education

    Science.gov (United States)

    Dreyfus, Benjamin W.; Sawtelle, Vashti; Turpen, Chandra; Gouvea, Julia; Redish, Edward F.

    2014-06-01

    As interdisciplinary courses are developed, instructors and researchers have to grapple with questions of how students should make connections across disciplines. We explore the issue of interdisciplinary reconciliation (IDR): how students reconcile seemingly contradictory ideas from different disciplines. While IDR has elements in common with other frameworks for the reconciliation of ideas across contexts, it differs in that each disciplinary idea is considered canonically correct within its own discipline. The setting for the research is an introductory physics course for biology majors that seeks to build greater interdisciplinary coherence and therefore includes biologically relevant topics such as adenosine triphosphate (ATP) and chemical bond energy. In our case-study data, students grapple with the apparent contradiction between the energy released when the phosphate bond in ATP is broken and the idea that an energy input is required to break a bond. We see students justifying context-dependent modeling choices, showing nuance in articulating how system choices may be related to disciplinary problems of interest. This represents a desired end point of IDR, in which students can build coherent connections between concepts from different disciplines while understanding each concept in its own disciplinary context. Our case study also illustrates elements of the instructional environment that play roles in the process of IDR.

  18. VUV photophysics and dissociative photoionization of pyrimidine, purine, imidazole and benzimidazole in the 7-18 eV photon energy range

    Energy Technology Data Exchange (ETDEWEB)

    Schwell, Martin [Laboratoire Interuniversitaire des Systemes Atmospheriques (LISA), CNRS-UMR 7583, Universite Paris 7 and 12, 61 Avenue du General de Gaulle, 94010 Creteil (France)], E-mail: schwell@lisa.univ-paris12.fr; Jochims, Hans-Werner; Baumgaertel, Helmut [Institut fuer Physikalische und Theoretische Chemie der Freien Universitaet Berlin, Takustr. 3, Berlin 14195 (Germany); Leach, Sydney [Laboratoire d' Etude du Rayonnement et de la Matiere en Astrophysique (LERMA), CNRS-UMR 8112, Observatoire de Paris-Meudon, 5 Place Jules-Janssen, 92195 Meudon (France)], E-mail: Sydney.Leach@obspm.fr

    2008-11-03

    Photoionization mass spectrometry is used to study ionization processes and fragmentation pathways of four prebiotic species, pyrimidine, purine, imidazole and benzimidazole, in the 7-18 eV photon energy region, with synchrotron radiation as excitation source. These molecules are possible precursors of the nucleic acid bases that occur in DNA and RNA. Ionization energies and ion appearance energies are reported. They are compared with electron impact and other studies and are discussed in terms of the electronic and nuclear structures of these species and their cations. The ion appearance energies, in conjunction with thermochemical data, were used to propose dissociative photoionization pathways, principally involving loss of HCN molecules in each of the four species. Astrophysical implications of the results concern the prospects for observation and survival of these molecules in the interstellar medium, in comets and in meteorites. Suggestions are made concerning suitable sites for radioastronomical searches for these purines and pyrimidines.

  19. Dissociation dynamics of methylal

    Energy Technology Data Exchange (ETDEWEB)

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

    1999-08-01

    The dissociation of methylal is investigated using mass spectrometry, combined with a pyrolytic radical source and femtosecond pump probe experiments. Based on preliminary results two reaction paths of methylal dissociation are proposed and discussed. (author) 4 fig., 3 refs.

  20. Direct dissociative chemisorption of alkanes on Pt(111): Influence of molecular complexity

    International Nuclear Information System (INIS)

    The direct dissociative chemisorption of ethane, propane, n-butane, isobutane, and neopentane on Pt(111) was investigated as a function of the initial translational energy, ET, polar angle of incidence, θi, initial vibrational temperature, and surface temperature using supersonic molecular beam techniques. For each alkane, the initial probability for direct dissociative chemisorption scales with the initial normal energy of the alkanes, En=ET cos2 θi, and is independent of both the surface temperature and initial vibrational energy of the alkanes under the experimental conditions employed. Above initial normal energies of approximately 125 kJ/mol, at constant En, the dissociation probability decreases with increasing chain length of the C2-C4 linear alkanes; however, the dissociation probability of neopentane is greater than that of isobutane, and both isobutane and neopentane are more reactive than n-butane. By assuming that cleavage of primary C-H bonds is the dominant reaction pathway for all of the alkanes investigated here, the trends in reactivity are best explained by considering the differences in the steric factors for primary C-H bond cleavage for these alkanes. Secondary C-H bond cleavage does appear to contribute to the reactivity of propane and n-butane but only at the highest energies examined. Additionally, the reaction probabilities of each of these alkanes were estimated using a statistical model recently proposed by Ukrainstev and Harrison [J. Chem. Phys. 101, 1564 (1994)]. Assuming cleavage of only primary C-H bonds, the trends in reactivity for ethane, propane, n-butane, and isobutane were qualitatively reproduced by the statistical model; however, except for ethane, which was used to obtain the necessary parameters for the theory, there was poor quantitative agreement, and the predictions for neopentane were significantly lower than the measured values. The model also predicts that the dissociation probability is enhanced by increasing the

  1. Chemical bond effects on the low energy electronic stopping power: theory

    International Nuclear Information System (INIS)

    We discuss the applicability of a modified version of the Firsov model to account for the low-energy electronic stopping cross section (Se) due to molecular targets. We employ floating spherical Gaussian orbitals (FSGO), which reproduce major trends in electronic and geometrical structure of molecules. Two advantages of using FSGO are: i) each localized orbital is classified as inner shell, bonding and lone-pair species, hence a natural partitioning of Se from each type of orbital is possible and ii) a simple analytical expression for the orbital contribution to Se is obtained after averaging over all molecular orientations. Our results show an explicit dependence of Se on the geometric structure of the molecule as well as on the core and bond character. (orig.)

  2. Mode specificity for the dissociative chemisorption of H2O on Cu(111): a quantum dynamics study on an accurately fitted potential energy surface.

    Science.gov (United States)

    Liu, Tianhui; Zhang, Zhaojun; Fu, Bina; Yang, Xueming; Zhang, Dong H

    2016-03-16

    The mode-specific dynamics for the dissociative chemisorption of H2O on Cu(111) is first investigated by seven-dimensional quantum dynamics calculations, based on an accurately fitted potential energy surface (PES) recently developed by neural network fitting to DFT energy points. It is indicated that excitations in all three vibrational modes have a significant impact on reactivity, which are more efficacious than increasing the translational energy in promoting the reaction, with the largest enhancement for the excitation in the asymmetric stretching mode. There is large discrepancy between the six-dimensional reactivities with fixed azimuthal angles and seven-dimensional results, revealing that the 6D "flat surface" model cannot accurately characterize the reaction dynamics. The azimuthal angle-averaging approach is validated for vibrational excited states of the reactant, where the 7D mode-specific probability can be well reproduced by averaging the 6D azimuthal angle-fixed probabilities over 18 angles. PMID:26941197

  3. Dynamics of the dissociative electron attachment in H2O and D2O: The A1 resonance and axial recoil approximation

    Indian Academy of Sciences (India)

    N Bhargava Ram; Vaibhav S Prabhudesai; E Krishnakumar

    2012-01-01

    The dynamics of the formation and decay of negative ion resonance of A1 symmetry at 8.5 eV electron energy in the dissociative electron attachment (DEA) process in H2O and D2O are investigated using the velocity slice imaging technique. While the highest energy hydride ions formed by DEA show angular distributions characteristic to the A1 symmetry, those formed with low-kinetic energy show considerably different angular distributions indicating changes in the orientation of the dissociating bond due to bending mode vibrations. Our observations are quite different from the recently reported measurements, but consistent with the fully quantum calculations.

  4. Synthesis of Novel High Energy Polyaniline Derivative Containing S-S Bond in Six-membered Cycle

    Institute of Scientific and Technical Information of China (English)

    ZHOU Lei; DENG Shi-Ren; LI Zao-Ying

    2003-01-01

    @@ A novel conducting polymer as new class of high energy storage material, [1,2] which has one six-membered cycle containing S-S bond in the moiety of aniline was synthesized. The polymer had enhanced redox progress due to an intramolecular electrocatalytic effect of polyaniline on S-S bond. The polymer has some advantages because of its high theoretical specific energy and fast kinetics when used in lithium batteries. The most promised advantage of it is that the intramolecular cleavage and recombination of the S-S bond improve the cyclicability greatly.

  5. On optimal designing of low frequency polychromatic fields for facile photo-dissociation of model diatomic molecules

    Indian Academy of Sciences (India)

    S Ghosh; K Maji; R Sharma; S P Bhattacharyya

    2009-09-01

    The dissociation of a diatomic molecule in low frequency polychromatic fields of moderate intensities is studied. Genetic Algorithm is invoked to search out a set of four optimal non-resonant frequencies (1 - 4), intensities (1 - 4) the and phase angles (1 - 4), for achieving a facile photo dissociation. Time-dependent Hellmann-Feynman theorem is used to gain insight into the frequency resolved energy absorption pattern. The ‘quantum phase space’ structures indicate occurrence of bond breaking dynamics akin to the classical one.

  6. Discovering Chemistry With Natural Bond Orbitals

    CERN Document Server

    Weinhold, Frank

    2012-01-01

    This book explores chemical bonds, their intrinsic energies, and the corresponding dissociation energies which are relevant in reactivity problems. It offers the first book on conceptual quantum chemistry, a key area for understanding chemical principles and predicting chemical properties. It presents NBO mathematical algorithms embedded in a well-tested and widely used computer program (currently, NBO 5.9). While encouraging a "look under the hood" (Appendix A), this book mainly enables students to gain proficiency in using the NBO program to re-express complex wavefunctions in terms of intui

  7. Direct dissociative chemisorption of propane on Ir(110)

    International Nuclear Information System (INIS)

    We have employed molecular beam techniques to investigate the initial probability of direct dissociative chemisorption, Pd, and the intrinsic trapping probability, ξ, of C3H8, C3D8, and (CH3)2CD2 on Ir(110) as a function of beam translational energy, Ei, from 1.5 to 59 kcal/mol. For C3H8 and (CH3)2CD2, a measurable (≥0.02) initial probability of direct dissociative chemisorption is observed above a beam energy of approximately 7 kcal/mol. For C3D8 this energy is roughly 10 kcal/mol. Above these energies the initial probability of direct chemisorption of each of the isotopomers of propane increases nearly linearly with Ei, approaching a value of approximately Pd=0.48 at Ei=52 kcal/mol for C3H8 and (CH3)2CD2, and Pd=0.44 at Ei=59 kcal/mol for C3D8. This kinetic isotope effect for the direct chemisorption of C3D8 relative to C3H8 is smaller than that expected for a mechanism of H (or D) abstraction by tunneling through an Eckart barrier, suggesting a contribution of C endash C bond cleavage to direct chemisorption. The lack of a kinetic isotope effect for the direct chemisorption of (CH3)2CD2 relative to C3H8 indicates that 1 degree C endash H bond cleavage dominates over 2 degree C endash H bond cleavage during the direct chemisorption of propane on Ir(110). The trapping behavior of each of these isotopomers of propane is approximately identical as a function of Ei, with ξ>0.9 at Ei=1.5 kcal/mol, ξ=0.3 at Ei=20 kcal/mol, and ξi=40 kcal/mol. copyright 1996 American Institute of Physics

  8. A program to calculate non-bonded interaction energy in biomolecular aggregates.

    Science.gov (United States)

    Sundaram, K; Prasad, C V

    1982-02-01

    This paper describes a program to calculate intermolecular as well as intramolecular electronic potential energy resulting from non-bonded interactions. The underlying theory is obtained by the application of Rayleigh-Schroedinger perturbation theory to non-overlap regions of a molecular system. The rigorous theoretical expressions for the energy terms are simplified by approximations consistent with those commonly employed in semi-empirical molecular orbital theories. The program is particularly suited for the study of biomolecular assemblies, and in situations where insight into contributions to total energy from various component interaction types is desired. The inclusion of the non-additive dispersion effects in this approach makes it especially interesting for the study of cooperative phenomena in the light of a recent finding [1]. PMID:7067416

  9. Cleavage of thymine N3-H bonds by low-energy electrons attached to base π* orbitals

    International Nuclear Information System (INIS)

    In this work, we extend our earlier studies on single strand break (SSB) formation in DNA to consider the possibility of cleaving a thymine N3-H bond to generate a nitrogen-centered anion and a hydrogen radical which might proceed to induce further bond cleavages. In earlier studies, we considered SSBs induced by low-energy electrons that attach to DNA bases' π* orbitals or to phosphate P=O π* orbitals to cleave sugar-phosphate C-O bonds or base-sugar N1-C bonds. We also studied the effects of base π-stacking on the rates of such bond cleavages. To date, our results suggest that sugar-phosphate C-O bonds have the lowest barriers to cleavage, that attachment of electrons with energies below 2 eV most likely occurs at the base π* orbitals, that electrons with energy above 2 eV can also attach to phosphate P=O π* orbitals, and that base π stacking has a modest but slowing effect on the rates of SSB formation. However, we had not yet examined the possibility that base N3-H bonds could rupture subsequent to base π* orbital capture. In the present work, the latter possibility is considered and it is found that the barrier to cleavage of the N3-H bond in thymine is considerably higher than for cleaving sugar-phosphate C-O bonds, so our prediction that SSB formation is dominated by C-O bond cleavage remains intact

  10. Energy and critical ionic-bond parameter of a 3D large-radius bipolaron

    International Nuclear Information System (INIS)

    A theory of a strong-coupling large-radius bipolaron has been developed. The possibility of the formation of 3D bipolarons in high-temperature superconductors is discussed. For the bipolaron energy, the lowest variational estimate has been obtained at α > 8, where α is the electron-phonon coupling constant. The critical ionic-bond parameter ηc = ε∞/ε0, where ε∞ and ε0 are the high-frequency and static dielectric constants, has been found to be ηc = 0.2496.

  11. Comparison of DFT with Traditional Methods for the Calculation of Vibrational Frequencies and Bond Energies

    Science.gov (United States)

    Bauschlicher, Charles W.; Arnold, James O. (Technical Monitor)

    1997-01-01

    The vibrational frequencies of MO2 are computed at many levels of theory, including HF, B3LYP, BP86, CASSCF, MP2, and CCSD(T). The computed results are compared with the available experimental results. Most of the methods fail for at least one state of the systems considered. The accuracy of the results and the origin of the observed failures are discussed. The B3LYP bond energies are compared with traditional methods for a variety of systems, ranging from FeCOn+ to SiCln and its positive ions. The cases where B3LYP differs from the traditional methods are discussed.

  12. Simple non-empirical procedure for spin-component-scaled MP2 methods applied to the calculation of dissociation energy curve of noncovalently-interacting systems

    CERN Document Server

    Grabowski, I; Della Sala, F

    2013-01-01

    We present a simple and non-empirical method to determine optimal scaling coefficients, within the (spin-component)-scaled MP2 approach, for calculating intermolecular potential energies of noncovalently-interacting systems. The method is based on an observed proportionality between (spin-component) MP2 and CCSD(T) energies for a wide range of intermolecular distances and allows to compute with high accuracy a large portion of the dissociation curve at the cost of a single CCSD(T) calculation. The accuracy of the present procedure is assessed for a series of noncovalently-interacting test systems: the obtained results reproduce CCSD(T) quality in all cases and definitely outperform conventional MP2, CCSD and SCS-MP2 results. The difficult case of the Beryllium dimer is also considered.

  13. Strain effect on the adsorption, diffusion, and molecular dissociation of hydrogen on Mg (0001) surface

    Energy Technology Data Exchange (ETDEWEB)

    Lei, Huaping; Wang, Caizhuang; Yao, Yongxin; Hupalo, Myron [Ames Laboratory, USDOE, Ames, Iowa 50011 (United States); Wang, Yangang [Ames Laboratory, USDOE, Ames, Iowa 50011 (United States); Supercomputing Center of Computer Network Information Center, CAS, Beijing 100190 (China); McDougall, Dan; Tringides, Michael; Ho, Kaiming [Ames Laboratory, USDOE, Ames, Iowa 50011 (United States); Department of Physics and Astronomy, Iowa State University, Ames, Iowa 50011 (United States)

    2013-12-14

    The adsorption, diffusion, and molecular dissociation of hydrogen on the biaxially strained Mg (0001) surface have been systematically investigated by the first principle calculations based on density functional theory. When the strain changes from the compressive to tensile state, the adsorption energy of H atom linearly increases while its diffusion barrier linearly decreases oppositely. The dissociation barrier of H{sub 2} molecule linearly reduces in the tensile strain region. Through the chemical bonding analysis including the charge density difference, the projected density of states and the Mulliken population, the mechanism of the strain effect on the adsorption of H atom and the dissociation of H{sub 2} molecule has been elucidated by an s-p charge transfer model. With the reduction of the orbital overlap between the surface Mg atoms upon the lattice expansion, the charge transfers from p to s states of Mg atoms, which enhances the hybridization of H s and Mg s orbitals. Therefore, the bonding interaction of H with Mg surface is strengthened and then the atomic diffusion and molecular dissociation barriers of hydrogen decrease accordingly. Our works will be helpful to understand and to estimate the influence of the lattice deformation on the performance of Mg-containing hydrogen storage materials.

  14. Strain effect on the adsorption, diffusion, and molecular dissociation of hydrogen on Mg (0001) surface.

    Science.gov (United States)

    Lei, Huaping; Wang, Caizhuang; Yao, Yongxin; Wang, Yangang; Hupalo, Myron; McDougall, Dan; Tringides, Michael; Ho, Kaiming

    2013-12-14

    The adsorption, diffusion, and molecular dissociation of hydrogen on the biaxially strained Mg (0001) surface have been systematically investigated by the first principle calculations based on density functional theory. When the strain changes from the compressive to tensile state, the adsorption energy of H atom linearly increases while its diffusion barrier linearly decreases oppositely. The dissociation barrier of H2 molecule linearly reduces in the tensile strain region. Through the chemical bonding analysis including the charge density difference, the projected density of states and the Mulliken population, the mechanism of the strain effect on the adsorption of H atom and the dissociation of H2 molecule has been elucidated by an s-p charge transfer model. With the reduction of the orbital overlap between the surface Mg atoms upon the lattice expansion, the charge transfers from p to s states of Mg atoms, which enhances the hybridization of H s and Mg s orbitals. Therefore, the bonding interaction of H with Mg surface is strengthened and then the atomic diffusion and molecular dissociation barriers of hydrogen decrease accordingly. Our works will be helpful to understand and to estimate the influence of the lattice deformation on the performance of Mg-containing hydrogen storage materials. PMID:24329077

  15. Strain effect on the adsorption, diffusion, and molecular dissociation of hydrogen on Mg (0001) surface

    International Nuclear Information System (INIS)

    The adsorption, diffusion, and molecular dissociation of hydrogen on the biaxially strained Mg (0001) surface have been systematically investigated by the first principle calculations based on density functional theory. When the strain changes from the compressive to tensile state, the adsorption energy of H atom linearly increases while its diffusion barrier linearly decreases oppositely. The dissociation barrier of H2 molecule linearly reduces in the tensile strain region. Through the chemical bonding analysis including the charge density difference, the projected density of states and the Mulliken population, the mechanism of the strain effect on the adsorption of H atom and the dissociation of H2 molecule has been elucidated by an s-p charge transfer model. With the reduction of the orbital overlap between the surface Mg atoms upon the lattice expansion, the charge transfers from p to s states of Mg atoms, which enhances the hybridization of H s and Mg s orbitals. Therefore, the bonding interaction of H with Mg surface is strengthened and then the atomic diffusion and molecular dissociation barriers of hydrogen decrease accordingly. Our works will be helpful to understand and to estimate the influence of the lattice deformation on the performance of Mg-containing hydrogen storage materials

  16. Quantum entanglement and the dissociation process of diatomic molecules

    International Nuclear Information System (INIS)

    In this work, we investigate quantum entanglement-related aspects of the dissociation process of some selected, representative homo- and heteronuclear diatomic molecules. This study is based upon high-quality ab initio calculations of the (correlated) molecular wavefunctions involved in the dissociation processes. The values of the electronic entanglement characterizing the system in the limit cases corresponding to (i) the united-atom representation and (ii) the asymptotic region when atoms dissociate are discussed in detail. It is also shown that the behaviour of the electronic entanglement as a function of the reaction coordinate R exhibits remarkable correspondences with the phenomenological description of the physically meaningful regimes comprising the processes under study. In particular, the extrema of the total energies and the electronic entanglement are shown to be associated with the main physical changes experienced by the molecular spatial electronic density, such as charge depletion and accumulation or bond cleavage regions. These structural changes are characterized by several selected descriptors of the density, such as the Laplacian of the electronic molecular distributions (LAP), the molecular electrostatic potential (MEP) and the atomic electric potentials fitted to the MEP.

  17. Quantum entanglement and the dissociation process of diatomic molecules

    Energy Technology Data Exchange (ETDEWEB)

    Esquivel, Rodolfo O; Molina-Espiritu, Moyocoyani [Departamento de Quimica, Universidad Autonoma Metropolitana, 09340-Mexico DF (Mexico); Flores-Gallegos, Nelson [Unidad Profesional Interdisciplinaria de IngenierIa, Campus Guanajuato del Instituto Politecnico Nacional, 36275-Guanajuato (Mexico); Plastino, A R; Angulo, Juan Carlos; Dehesa, Jesus S [Instituto Carlos I de Fisica Teorica y Computacional, and Departamento de Fisica Atomica, Molecular y Nuclear, Universidad de Granada, 18071-Granada (Spain); Antolin, Juan, E-mail: esquivel@xanum.uam.mx, E-mail: arplastino@ugr.es [Departamento de Fisica Aplicada, EUITIZ, Universidad de Zaragoza, 50018-Zaragoza (Spain)

    2011-09-14

    In this work, we investigate quantum entanglement-related aspects of the dissociation process of some selected, representative homo- and heteronuclear diatomic molecules. This study is based upon high-quality ab initio calculations of the (correlated) molecular wavefunctions involved in the dissociation processes. The values of the electronic entanglement characterizing the system in the limit cases corresponding to (i) the united-atom representation and (ii) the asymptotic region when atoms dissociate are discussed in detail. It is also shown that the behaviour of the electronic entanglement as a function of the reaction coordinate R exhibits remarkable correspondences with the phenomenological description of the physically meaningful regimes comprising the processes under study. In particular, the extrema of the total energies and the electronic entanglement are shown to be associated with the main physical changes experienced by the molecular spatial electronic density, such as charge depletion and accumulation or bond cleavage regions. These structural changes are characterized by several selected descriptors of the density, such as the Laplacian of the electronic molecular distributions (LAP), the molecular electrostatic potential (MEP) and the atomic electric potentials fitted to the MEP.

  18. Measurements of the dissociative recombination coefficients for O2+, NH4+, H3O+ and NO+ at thermal energies

    International Nuclear Information System (INIS)

    The dissociative recombination reactions with electrons of O2+, NH4+,NO+ and H3O+ have been studied under truly thermalised conditions over the temperature range 200-600 K using a flowing afterglow/Langmuir probe apparatus. The recombination coefficents, αsub(t), for O2+, NH4+ and NO+ were found to vary as: 1.95x1O-7 (300/T)sup(0.7), 1.35x10-6 (300/T)sup(0.6) and 4.0x10-7 (300/T)sup(0.9) cm3s-1 respectively; no significant variation with temperature was found for αsub(t)(H3O+) = 1.0x10-6 cm3s-1. (Authors)

  19. DFT study of NH 3 dissociation on Si(1 1 1)-7 × 7. The role of intermolecular interactions

    Science.gov (United States)

    Ferullo, Ricardo M.; Fuente, Silvia A.; Belelli, Patricia G.; Castellani, Norberto J.

    2007-04-01

    The adsorption of NH 3 molecule on the Si(1 1 1)-7 × 7 surface modelled with a cluster has been studied using density functional theory (DFT). The results indicate the existence of a precursor state for the non-dissociative chemisorption. The active site for the molecular chemisorption is the adatom; while the NH 3 molecule adsorbs on the Si restatom via this preadsorbed state, the adsorption on the Si adatom is produced practically without an energy barrier. The ammonia adsorption on the adatom induces an electron transfer from the dangling bond of this atom to the dangling bond of the adjacent Si restatom, hindering this site for the adsorption of a second NH 3 incoming molecule. However, this second molecule links strongly by means of two H-bonds. The dissociative chemisorption process was studied considering one and two ammonia molecules. For the dissociation of a lonely NH 3 molecule an energy barrier of ˜0.3 eV was calculated, yielding NH 2 on the adatom and H on the restatom. When two molecules are adsorbed, the NH 3-NH 3 interaction yields the weakening of a N-H bond of the ammonia molecule adsorbed closer the Si surface. As a consequence, the dissociation barrier practically disappears. Thus, the presence of a second NH 3 molecule at the adatom-restatom pair of the Si(1 1 1)-7 × 7 surface makes the dissociative reaction self-assisted, the total adsorption process elapsing with a negligible activation barrier (less than 0.01 eV).

  20. The Influence of Interatomic Bonding Potentials on Detonation Properties

    OpenAIRE

    Heim, Andrew J.; Grønbech-Jensen, Niels; Germann, Timothy C.; Kober, Edward M.; Holian, Brad Lee; Lomdahl, Peter S.

    2006-01-01

    The dependence of macroscopic detonation properties of a two-dimensional diatomic (AB) molecular system on the fundamental properties of the molecule were investigated. This includes examining the detonation velocity, reaction zone thickness, and critical width as a function of the exothermicity of the gas-phase reaction and the gas-phase dissociation energy for. Following previous work, molecular dynamics (MD) simulations with a reactive empirical bond-order potential were used to characteri...

  1. O2 Protonation Controls Threshold Behavior for N-Glycosidic Bond Cleavage of Protonated Cytosine Nucleosides.

    Science.gov (United States)

    Wu, R R; Rodgers, M T

    2016-06-01

    IRMPD action spectroscopy studies of protonated 2'-deoxycytidine and cytidine, [dCyd+H](+) and [Cyd+H](+), have established that both N3 and O2 protonated conformers coexist in the gas phase. Threshold collision-induced dissociation (CID) of [dCyd+H](+) and [Cyd+H](+) is investigated here using guided ion beam tandem mass spectrometry techniques to elucidate the mechanisms and energetics for N-glycosidic bond cleavage. N-Glycosidic bond cleavage is observed as the major dissociation pathways resulting in competitive elimination of either protonated or neutral cytosine for both protonated cytosine nucleosides. Electronic structure calculations are performed to map the potential energy surfaces (PESs) for both N-glycosidic bond cleavage pathways observed. The molecular parameters derived from theoretical calculations are employed for thermochemical analysis of the energy-dependent CID data to determine the minimum energies required to cleave the N-glycosidic bond along each pathway. B3LYP and MP2(full) computed activation energies for N-glycosidic bond cleavage associated with elimination of protonated and neutral cytosine, respectively, are compared to measured values to evaluate the efficacy of these theoretical methods in describing the dissociation mechanisms and PESs for N-glycosidic bond cleavage. The 2'-hydroxyl of [Cyd+H](+) is found to enhance the stability of the N-glycosidic bond vs that of [dCyd+H](+). O2 protonation is found to control the threshold energies for N-glycosidic bond cleavage as loss of neutral cytosine from the O2 protonated conformers is found to require ∼25 kJ/mol less energy than the N3 protonated analogues, and the activation energies and reaction enthalpies computed using B3LYP exhibit excellent agreement with the measured thresholds for the O2 protonated conformers. PMID:27159774

  2. Coordination-resolved local bond relaxation, electron binding-energy shift, and Debye temperature of Ir solid skins

    International Nuclear Information System (INIS)

    Highlights: • Cohesive energy of the representative bond determines the core-level shift. • XPS derives the energy level of an isolated atom and its bulk shift. • XPS derives the local bond length, bond energy, binding energy density. • Thermal XPS resolves the Debye temperature and atomic cohesive energy. - Abstract: Numerical reproduction of the measured 4f7/2 energy shift of Ir(1 0 0), (1 1 1), and (2 1 0) solid skins turns out the following: (i) the 4f7/2 level of an isolated Ir atom shifts from 56.367 eV to 60.332 eV by 3.965 eV upon bulk formation; (ii) the local energy density increases by up to 130% and the atomic cohesive energy decreases by 70% in the skin region compared with the bulk values. Numerical match to observation of the temperature dependent energy shift derives the Debye temperature that varies from 285.2 K (Surface) to 315.2 K (Bulk). We clarified that the shorter and stronger bonds between under-coordinated atoms cause local densification and quantum entrapment of electron binding energy, which perturbs the Hamiltonian and the core shifts in the skin region

  3. Evaluating interaction energies of weakly bonded systems using the Buckingham-Hirshfeld method

    International Nuclear Information System (INIS)

    We present the finalized Buckingham-Hirshfeld method (BHD-DFT) for the evaluation of interaction energies of non-bonded dimers with Density Functional Theory (DFT). In the method, dispersion energies are evaluated from static multipole polarizabilities, obtained on-the-fly from Coupled Perturbed Kohn-Sham calculations and partitioned into diatomic contributions using the iterative Hirshfeld partitioning method. The dispersion energy expression is distributed over four atoms and has therefore a higher delocalized character compared to the standard pairwise expressions. Additionally, full multipolar polarizability tensors are used as opposed to effective polarizabilities, allowing to retain the anisotropic character at no additional computational cost. A density dependent damping function for the BLYP, PBE, BP86, B3LYP, and PBE0 functionals has been implemented, containing two global parameters which were fitted to interaction energies and geometries of a selected number of dimers using a bi-variate RMS fit. The method is benchmarked against the S22 and S66 data sets for equilibrium geometries and the S22x5 and S66x8 data sets for interaction energies around the equilibrium geometry. Best results are achieved using the B3LYP functional with mean average deviation values of 0.30 and 0.24 kcal/mol for the S22 and S66 data sets, respectively. This situates the BHD-DFT method among the best performing dispersion inclusive DFT methods. Effect of counterpoise correction on DFT energies is discussed

  4. Distinguishing Bonds.

    Science.gov (United States)

    Rahm, Martin; Hoffmann, Roald

    2016-03-23

    The energy change per electron in a chemical or physical transformation, ΔE/n, may be expressed as Δχ̅ + Δ(VNN + ω)/n, where Δχ̅ is the average electron binding energy, a generalized electronegativity, ΔVNN is the change in nuclear repulsions, and Δω is the change in multielectron interactions in the process considered. The last term can be obtained by the difference from experimental or theoretical estimates of the first terms. Previously obtained consequences of this energy partitioning are extended here to a different analysis of bonding in a great variety of diatomics, including more or less polar ones. Arguments are presented for associating the average change in electron binding energy with covalence, and the change in multielectron interactions with electron transfer, either to, out, or within a molecule. A new descriptor Q, essentially the scaled difference between the Δχ̅ and Δ(VNN + ω)/n terms, when plotted versus the bond energy, separates nicely a wide variety of bonding types, covalent, covalent but more correlated, polar and increasingly ionic, metallogenic, electrostatic, charge-shift bonds, and dispersion interactions. Also, Q itself shows a set of interesting relations with the correlation energy of a bond. PMID:26910496

  5. Effect of stacking fault energy on nanostructure formation under accumulative roll bonding (ARB) process

    International Nuclear Information System (INIS)

    In this study, the effect of stacking fault energy on the formation of nanostructure in aluminum, copper, and brass fabricated via the accumulative roll bonding (ARB) process was investigated. Evolution of microstructure of the samples was investigated by transmission electron microscopy (TEM). Occurrence of the recrystallization (both continuous and discontinuous) in the copper and brass led to the formation of nano grains with mean sizes of 80, and 40 nm, respectively; while, the mean grain size of aluminum was 250 nm. Differences in microstructural evolution during processing of aluminum, copper, and brass was related to their stacking fault energies. In order to facilitate nanostructure formation in the commercial purity aluminum, the second phase particles (alumina) were added to aluminum matrix. In this case, the mean grain size of the aluminum changed down to 90 nm

  6. Ab-initio investigation of the covalent bond energies in the metallic covalent superconductor MgB2 and in AlB2

    OpenAIRE

    Bester, Gabriel; Fahnle, Manfred

    2001-01-01

    The contributions of the covalent bond energies of various atom pairs to the cohesive energy of MgB2 and AlB2 are analysed with a variant of our recently developed energy-partitioning scheme for the density-functional total energy. The covalent bond energies are strongest for the intralayer B-B pairs. In contrast to the general belief, there is also a considerable covalent bonding between the layers, mediated by the metal atom. The bond energies between the various atom pairs are analysed in ...

  7. Analyzing angular distributions for two-step dissociation mechanisms in velocity map imaging.

    Science.gov (United States)

    Straus, Daniel B; Butler, Lynne M; Alligood, Bridget W; Butler, Laurie J

    2013-08-15

    Increasingly, velocity map imaging is becoming the method of choice to study photoinduced molecular dissociation processes. This paper introduces an algorithm to analyze the measured net speed, P(vnet), and angular, β(vnet), distributions of the products from a two-step dissociation mechanism, where the first step but not the second is induced by absorption of linearly polarized laser light. Typically, this might be the photodissociation of a C-X bond (X = halogen or other atom) to produce an atom and a momentum-matched radical that has enough internal energy to subsequently dissociate (without the absorption of an additional photon). It is this second step, the dissociation of the unstable radicals, that one wishes to study, but the measured net velocity of the final products is the vector sum of the velocity imparted to the radical in the primary photodissociation (which is determined by taking data on the momentum-matched atomic cophotofragment) and the additional velocity vector imparted in the subsequent dissociation of the unstable radical. The algorithm allows one to determine, from the forward-convolution fitting of the net velocity distribution, the distribution of velocity vectors imparted in the second step of the mechanism. One can thus deduce the secondary velocity distribution, characterized by a speed distribution P(v1,2°) and an angular distribution I(θ2°), where θ2° is the angle between the dissociating radical's velocity vector and the additional velocity vector imparted to the product detected from the subsequent dissociation of the radical. PMID:23464815

  8. On the mean kinetic energy of the proton in strong hydrogen bonded systems

    International Nuclear Information System (INIS)

    The mean atomic kinetic energies of the proton, Ke(H), and of the deuteron, Ke(D), were calculated in moderate and strongly hydrogen bonded (HB) systems, such as the ferro-electric crystals of the KDP type (XH2PO4, X = K, Cs, Rb, Tl), the DKDP (XD2PO4, X = K, Cs, Rb) type, and the X3H(SO4)2 superprotonic conductors (X = K, Rb). All calculations utilized the simulated partial phonon density of states, deduced from density functional theory based first-principle calculations and from empirical lattice dynamics simulations in which the Coulomb, short range, covalent, and van der Waals interactions were accounted for. The presently calculated Ke(H) values for the two systems were found to be in excellent agreement with published values obtained by deep inelastic neutron scattering measurements carried out using the VESUVIO instrument of the Rutherford Laboratory, UK. The Ke(H) values of the M3H(SO4)2 compounds, in which the hydrogen bonds are centro-symmetric, are much lower than those of the KDP type crystals, in direct consistency with the oxygen-oxygen distance ROO, being a measure of the HB strength

  9. On the mean kinetic energy of the proton in strong hydrogen bonded systems

    Energy Technology Data Exchange (ETDEWEB)

    Finkelstein, Y. [Nuclear Research Center–Negev, Beer-Sheva 84190 (Israel); Moreh, R. [Physics Department, Ben-Gurion University of the Negev, Beer-Sheva 84105 (Israel); Shang, S. L.; Wang, Y.; Liu, Z. K. [Department of Materials Science and Engineering, The Pennsylvania State University, University Park, Pennsylvania 16802 (United States); Shchur, Ya. [Institute for Condensed Matter Physics, 1 Svientsitskii str., L’viv 79011 (Ukraine)

    2016-02-07

    The mean atomic kinetic energies of the proton, Ke(H), and of the deuteron, Ke(D), were calculated in moderate and strongly hydrogen bonded (HB) systems, such as the ferro-electric crystals of the KDP type (XH{sub 2}PO{sub 4}, X = K, Cs, Rb, Tl), the DKDP (XD{sub 2}PO{sub 4}, X = K, Cs, Rb) type, and the X{sub 3}H(SO{sub 4}){sub 2} superprotonic conductors (X = K, Rb). All calculations utilized the simulated partial phonon density of states, deduced from density functional theory based first-principle calculations and from empirical lattice dynamics simulations in which the Coulomb, short range, covalent, and van der Waals interactions were accounted for. The presently calculated Ke(H) values for the two systems were found to be in excellent agreement with published values obtained by deep inelastic neutron scattering measurements carried out using the VESUVIO instrument of the Rutherford Laboratory, UK. The Ke(H) values of the M{sub 3}H(SO{sub 4}){sub 2} compounds, in which the hydrogen bonds are centro-symmetric, are much lower than those of the KDP type crystals, in direct consistency with the oxygen-oxygen distance R{sub OO}, being a measure of the HB strength.

  10. Effect of aging on surface chemical bonds of PTFE irradiated by low energy Ti ion

    International Nuclear Information System (INIS)

    Polytetrafluoroethylene (PTFE) was irradiated by low energy titanium ion in a metal vapor vacuum arc (MEVVA) implanter. The samples were irradiated with 80 keV Ti ion with fluences from 5x1015 to 5x1017 Ti/cm2, respectively. Transportation of Ion in Matters (TRIM) code was employed to simulate Ti ion irradiation. The as-irradiated samples were investigated by ESCA, SEM and wettability. As increasing ion fluence, various chemical bonds and irradiation-damaged surfaces were observed. The water droplet contact angel of PTFE samples increased gradually with ion fluence. All the as-irradiated PTFE samples were aged in air for 1 year. After aging the surface-restructuring behavior was observed on the surfaces of the samples irradiated with ion fluence equal to or less than 5x1016 Ti/cm2, which resulted in decrease of the droplet contact angle of these samples. The surface roughness change of the aged samples, which were measured by atomic force microscopy (AFM), was consistent with the droplet contact angle change. The experimental results revealed that Ti ion fluence closely affected the surface chemical bond, morphology and wettability, as well as the aging stability of the as-irradiated PTFE samples

  11. Energy as a Bond. Relations with Russia in the Context of Europe and The Netherlands

    International Nuclear Information System (INIS)

    supplies to Europe. Both Russia and Europe can gain much if they are able to strengthen their mutually beneficial economic cooperation. Political conflicts are normal among countries with diverging interests, but they should not be discussed in the context of economic cooperation, especially not in the area of energy. After all, energy dependence in the case of the EU and Russia exists on both sides. Increasing economic interdependence, not only in the area of energy, will lessen fears on both sides about asymmetric dependence. This paper examines the recent policy changes in Russia, its economic development, and the state of the Russian energy sectors. To analyse EU-Russian energy relations in a much broader context, EU policies towards Russia are discussed. Further, some statements are made about Dutch-Russian energy cooperation and the importance of a bilateral approach as part of an EU member state's overall external energy policy. The findings are evaluated in the context of the trends in international energy relations focussing on the role of the state and the decreasing importance of market-oriented players. The paper argues that Russia's economic recovery and modernisation is an opportunity for further cooperation with the EU. Hence, energy should be seen as the bond that makes cooperation in many areas imperative and beneficial, following the historic vision that energy has brought about and could continue to stimulate in the wider cooperation between the peoples of Europe

  12. Ab initio and semiempirical studies of the adsorption and dissociation of water on pure, defective, and doped MgO (001) surfaces

    International Nuclear Information System (INIS)

    Ab initio and semiempirical calculations of large cluster models have been performed in order to study water adsorption and dissociation on pure, defective (vacancies) and doped (Li, Na, K, Ca, Fe) MgO (001) surfaces. The geometries of the adsorbed and dissociated molecules have been optimized preparatory to analysis of binding energies, stretching frequencies, charge transfers, preferential sites of interaction, and bond distances. We have used Mulliken, natural bond order, and electrostatic-derived atomic and overlap populations to analyze charge distributions in the clusters. We have also investigated transition structures, activation energies, energy gaps, HOMO, density of states, SCF orbital energies as well as the acid endash base properties of our cluster model. Numerical results are compared, where possible, with experiment, interpreted in the framework of various analytical models, and correlated with site coordination numbers, corner and edge site preferential locations, and direction of charge transfer. A thorough charge analysis indicates substantial charge redistribution in the magnesium oxide crystal as a result of water adsorption and dissociation in pure, defective, and doped MgO crystals. The introduction of heavier impurities and vacancies could produce substantial changes in the physical and chemical properties of the catalyst and increase the binding and dissociation energies. Some of the largest changes originate from the introduction of vacancies. Two and three-dimensional potential energy surfaces are used to investigate activation energies of hydroxylation on the MgO surface. Stretching frequencies are correlated with magnesium and oxygen coordination numbers. copyright 1998 American Institute of Physics

  13. Density functional study on positively charged six-coordinate FeO2 porphyrin complex for a trigger of O2 dissociation

    Science.gov (United States)

    Kitagawa, Naohiro; Obata, Masao; Oda, Tatsuki

    2016-01-01

    Properties on electronic structure in an Fe-porphyrin (FeP) complex with the proximal imidazole (Im) ligand, a model of active moiety of hemeprotein for analyzing bonding- and separating-processes of dioxygen molecule (O2), were studied by means of spin-polarized density functional theory. It was found that in the ionized model, the bonding stability of O2 was reduced by one order in energy compared with that of the neutral model, implying existence of the state having a large fluctuation between bonded and separated configurations. We proposed a microscopic scenario on O2 dissociation phenomenon in terms of spin-crossover and allosteric mechanism.

  14. The key role of dislocation dissociation in the plastic behaviour of single crystal nickel-based superalloy with low stacking fault energy: Three-dimensional discrete dislocation dynamics modelling

    Science.gov (United States)

    Huang, Minsheng; Li, Zhenhuan

    2013-12-01

    To model the deformation of single crystal nickel based superalloys (SCNBS) with low stacking fault energy (SFE), three-dimensional discrete dislocation dynamics (3D-DDD) is extended by incorporating dislocation dissociation mechanism. The present 3D-DDD simulations show that, consistent with the existing TEM observation, the leading partial can enter the matrix channel efficiently while the trailing partial can hardly glide into it when the dislocation dissociation is taken into account. To determine whether the dislocation dissociation can occur or not, a critical percolation stress (CPS) based criterion is suggested. According to this CPS criterion, for SCNBS there exists a critical matrix channel width. When the channel width is lower than this critical value, the dislocation tends to dissociate into an extended configuration and vice versa. To clarify the influence of dislocation dissociation on CPS, the classical Orowan formula is improved by incorporating the SFE. Moreover, the present 3D-DDD simulations also show that the yielding stress of SCNBSs with low SFE may be overestimated up to 30% if the dislocation dissociation is ignored. With dislocation dissociation being considered, the size effect due to the width of γ matrix channel and the length of γ‧ precipitates on the stress-strain responses of SCNBS can be enhanced remarkably. In addition, due to the strong constraint effect by the two-phase microstructure in SCNBS, the configuration of formed junctions is quite different from that in single phase crystals such as Cu. The present results not only provide clear understanding of the two-phase microstructure levelled microplastic mechanisms in SCNBSs with low SFE, but also help to develop new continuum-levelled constitutive laws for SCNBSs.

  15. Theoretical Investigation of the Bond Dissociation of Hydroxyl Terminated Polybutadiene Binder and Effect on Mechanical Properties%理论研究丁羟粘合剂化学键解离及其对力学性能的影响

    Institute of Scientific and Technical Information of China (English)

    武文明; 张炜; 陈敏伯; 强洪夫; 史良伟

    2012-01-01

    The binder of hydroxyl terminated polybutadiene(HTPB) cured by toluene diisocyanate(TDI) is usually used in solid propellants,in which the crucial issue involved in the storage and use is aging problem.The quantum chemistry calculation was used to analyze the relationship between homolytic bond dissociation energy(BDE) of two HTPB-TDI binder models and bond decomposition caused by aging.The computational results were proved to be reliable and suitable for comparative analysis.The BDE values of C—O bonds connected with CH2 group were calculated to be minima,suggesting that they are the weakest bonds resulting in decomposition during thermal aging.The main degradation product is CO2.In the binder formed by the reaction of allylic primary hydroxyl of HTPB and TDI,the α-C—H is the weakest X—H(X=C,N) bond,suggesting that it is vulnerable to free radical attack accompanying the hydrogen transfer.The possible mechanism of aging for the easy-cleavage C—O bonds was proposed.The calculated activation energies of C—O bonds cleavage are approximately equal to the corresponding BDE values,indicating that the formation of radicals accompanies a barrier-free release of CO2 during thermal aging.The half-life time of such aging process was described by an exponential decay function of temperature.The aging of HTPB-TDI binder accelerates with increasing temperature.The radical recombination reactions of decomposed amino radicals and alkyl radicals are supported by thermodynamic data calculated.Molecular dynamic simulations were used to analyze the variation in the network structures and effect on mechanical properties of HTPB-TDI binder models before and after aging.It is found that the density of the system decreases with release and diffusion of CO2,and the corresponding tensile modulus and shear modulus increase with aging.%异腈酸酯固化的端羟基聚丁二烯(HTPB)粘合剂常用于固体推进剂中,老化是其贮存和使用中的重要

  16. Bonding in Mercury Molecules Described by the Normalized Elimination of the Small Component and Coupled Cluster Theory

    NARCIS (Netherlands)

    Cremer, Dieter; Kraka, Elfi; Filatov, Michael

    2008-01-01

    Bond dissociation energies (BDEs) of neutral HgX and cationic HgX(+) molecules range from less than a kcal mol(-1) to as much as 60 kcal mol(-1). Using NESCICCCSD(T) [normalized elimination of the small component and coupled-cluster theory with all single and double excitations and a perturbative tr

  17. Density functional for van der Waals forces accounts for hydrogen bond in benchmark set of water hexamers

    DEFF Research Database (Denmark)

    Kelkkanen, Kari André; Lundqvist, Bengt; Nørskov, Jens Kehlet

    2009-01-01

    A recent extensive study has investigated how various exchange-correlation (XC) functionals treat hydrogen bonds in water hexamers and has shown traditional generalized gradient approximation and hybrid functionals used in density-functional (DF) theory to give the wrong dissociation-energy trend...

  18. Carbon Bonds and the saving of energy; Bonos de carbono y el ahorro de energia

    Energy Technology Data Exchange (ETDEWEB)

    Alvarez Ramirez, Alejandro [NovaEnergia (Mexico)

    2005-07-01

    This document deals with the development of the carbon bond project, the energy saving and the entry into force of the Kyoto Protocol at a world-wide level. In this project Mexico opts for a development model in which the economic growth brakes ties with the discharge of greenhouse effect gases and in which the progress does not mean more damages to our planet. [Spanish] Este documento trata sobre el desarrollo del proyecto de bonos de carbono, ahorro de energia y la entrada en vigor del Protocolo de Kyoto a nivel mundial, en el cual Mexico opta por un modelo de desarrollo en el que el crecimiento economico esta desvinculado de la emision de gases de efecto invernadero y en donde el progreso no signifique mas danos a nuestro planeta.

  19. Dissociative versus molecular adsorption of phenol on Si(100)2×1 : A first-principles calculation

    Science.gov (United States)

    Carbone, Marilena; Meloni, Simone; Caminiti, Ruggero

    2007-08-01

    We investigated the competitive adsorption of a bifunctional molecule, phenol, on Si(100)2×1 by ab initio calculations. We performed geometry optimizations of phenol adsorbed either molecularly or dissociatively, on five possible sites (top, bridge, valley bridge, cave, and pedestal), in the low coverage regime. We found that the dissociative adsorption of phenol on top of a silicon dimer is the most favorable adsorption configuration. In the group of dissociative adsorption the phenol initially placed on the bridge or the valley-bridge sites ends up as a toplike local minima. The pedestal and cave sites remain as low-adsorption energy “open” sites. In the group of molecular adsorption, a higher adsorption energy is associated to the adsorption through an addition reaction and loss of the aromatic character (bridge, valley-bridge, and pedestal sites). Standard butterfly or diagonal butterfly are the corresponding optimized geometries. Retention of aromatic character and lower adsorption energy are associated to the adsorption on the top and cave sites. The ordering of adsorption sites according to the adsorption energy shows a mixture of the dissociative and the molecular sites. In the case of adsorption on the top site, the adsorption energies after a rotation of the phenoxy fragment along the bonding axis and hydrogen migration on the surface are very similar. The bend of the phenoxy fragment on the surface, instead, is not favored (the adsorption energy is 1.004eV lower compared to the vertical position). Different electron density maps were calculated for different adsorption sites and modes. Finally, we investigated the possibility that molecularly adsorbed phenol behaves as a precursor for the dissociative one by nudged elastic band calculations. We found a barrier of the same order of magnitude of the thermodynamic energy at room temperature for the conversion of the valley-bridge molecular into the top dissociative site.

  20. Density function theory study of the adsorption and dissociation of carbon monoxide on tungsten nanoparticles.

    Science.gov (United States)

    Weng, Meng-Hsiung; Ju, Shin-Pon; Chen, Hsin-Tsung; Chen, Hui-Lung; Lu, Jian-Ming; Lin, Ken-Huang; Lin, Jenn-Sen; Hsieh, Jin-Yuan; Yang, Hsi-Wen

    2013-02-01

    The adsorption and dissociation properties of carbon monoxide (CO) molecule on tungsten W(n) (n = 10-15) nanoparticles have been investigated by density-functional theory (DFT) calculations. The lowest-energy structures for W(n) (n = 10-15) nanoparticles are found by the basin-hopping method and big-bang method with the modified tight-binding many-body potential. We calculated the corresponding adsorption energies, C-O bond lengths and dissociation barriers for adsorption of CO on nanoparticles. The electronic properties of CO on nanoparticles are studied by the analysis of density of state and charge density. The characteristic of CO on W(n) nanoparticles are also compared with that of W bulk. PMID:23646573

  1. Correlations in hadron diffraction dissociation

    International Nuclear Information System (INIS)

    Hadron diffractive dissociation reactions are studied based on three component Deck model. The correlations between the mass in dissociated particle subsystem and the dissociation angle/or partial waves) defined in gottfried-Jackson system, are interpreted. Several reactions with different spin and parity structures in dissociative verticles, are studied. The three component Deck model is extended to dissociation of light nuclei, in particular the deuteron dissociation. (M.C.K.)

  2. Force History Dependence of Receptor-Ligand Dissociation

    OpenAIRE

    Marshall, Bryan T.; Sarangapani, Krishna K.; Lou, Jizhong; McEver, Rodger P.; Zhu, Cheng

    2004-01-01

    Receptor-ligand bonds that mediate cell adhesion are often subjected to forces that regulate their dissociation via modulating off-rates. Off-rates control how long receptor-ligand bonds last and how much force they withstand. One should therefore be able to determine off-rates from either bond lifetime or unbinding force measurements. However, substantial discrepancies exist between the force dependence of off-rates derived from the two types of measurements even for the same interactions, e...

  3. Ab Initio Investigation of O-H Dissociation from the Al-OH2 Complex Using Molecular Dynamics and Neural Network Fitting.

    Science.gov (United States)

    Ho, Thi H; Pham-Tran, Nguyen-Nguyen; Kawazoe, Yoshiyuki; Le, Hung M

    2016-01-28

    The dissociation dynamics of the O-H bond in Al-OH2 is investigated on an approximated ab initio potential energy surface (PES). By adopting a dynamic sampling method, we obtain a database of 92 834 configurations. The potential energy for each point is calculated using MP2/6-311G (3df, 2p) calculations; then, a 60-neuron feed-forward neural network is utilized to fit the data to construct an analytic PES. The root-mean-square error (rmse) for the training set is reported as 0.0036 eV, while the rmse for the independent testing set is 0.0034 eV. Such excellent fitting accuracy indeed confirms the reliability of the constructed PES. Subsequently, quasi-classical molecular dynamics (MD) trajectories are performed on the constructed PES at various levels of vibrational excitation in the range of 1.03 to 2.23 eV to investigate the probability of O-H bond dissociation. The results indicate a linear relationship between reaction probability and internal energy, from which we can determine the minimum activation internal energy required for the dissociation as 0.62 eV. Moreover, the O-H bond rupture is shown to be highly correlated with the formation of Al-O bond. PMID:26741404

  4. Butanethiol adsorption and dissociation on Ag (111): A periodic DFT study

    Science.gov (United States)

    Li, Aixiao; Piquemal, Jean-Philip; Richardi, Johannes; Calatayud, Monica

    2016-04-01

    The molecular and dissociative adsorption of butanethiol (C4H9SH) on regular Ag (111) surfaces has been studied by means of periodic ab initio density functional techniques. In molecular form, butanethiol is bound to the surface only by weak polarization-induced forces with the C-S axis tilted by 38° relative to the normal surface. The S atom occupies a position between a hollow fcc and a bridge site. In the dissociative adsorption process, the S-H bond breaks leading to butanethiolate. The S atom of the thiolate also occupies a threefold position, slightly displaced to a hollow fcc site compared to the thiol adsorption case. The C-S axis of the thiolate is tilted by about 37°. The calculated adsorption energies show that the butanethiol and butanethiolate have similar adsorption ability. The computed reaction pathway for the S-H dissociation gives an activation energy of 0.98 eV indicating that the thiolate formation from thiol, although not spontaneous at room temperature, might be feasible on silver surfaces. The dissociation process induces both adsorbate and surface polarization with a significant charge transfer from the substrate to the adsorbate.

  5. Dissociation of ultracold molecules with Feshbach resonances

    OpenAIRE

    Dürr, Stephan; Volz, Thomas; Rempe, Gerhard

    2004-01-01

    Ultracold molecules are associated from an atomic Bose-Einstein condensate by ramping a magnetic field across a Feshbach resonance. The reverse ramp dissociates the molecules. The kinetic energy released in the dissociation process is used to measure the widths of 4 Feshbach resonances in 87Rb. This method to determine the width works remarkably well for narrow resonances even in the presence of significant magnetic-field noise. In addition, a quasi-mono-energetic atomic wave is created by ju...

  6. Microsolvation of methylmercury: structures, energies, bonding and NMR constants ((199)Hg, (13)C and (17)O).

    Science.gov (United States)

    Flórez, Edison; Maldonado, Alejandro F; Aucar, Gustavo A; David, Jorge; Restrepo, Albeiro

    2016-01-21

    Hartree-Fock (HF) and second order perturbation theory (MP2) calculations within the scalar and full relativistic frames were carried out in order to determine the equilibrium geometries and interaction energies between cationic methylmercury (CH3Hg(+)) and up to three water molecules. A total of nine structures were obtained. Bonding properties were analyzed using the Quantum Theory of Atoms In Molecules (QTAIM). The analyses of the topology of electron densities reveal that all structures exhibit a partially covalent HgO interaction between methylmercury and one water molecule. Consideration of additional water molecules suggests that they solvate the (CH3HgOH2)(+) unit. Nuclear magnetic shielding constants σ((199)Hg), σ((13)C) and σ((17)O), as well as indirect spin-spin coupling constants J((199)Hg-(13)C), J((199)Hg-(17)O) and J((13)C-(17)O), were calculated for each one of the geometries. Thermodynamic stability and the values of NMR constants correlate with the ability of the system to directly coordinate oxygen atoms of water molecules to the mercury atom in methylmercury and with the formation of hydrogen bonds among solvating water molecules. Relativistic effects account for 11% on σ((13)C) and 14% on σ((17)O), which is due to the presence of Hg (heavy atom on light atom, HALA effect), while the relativistic effects on σ((199)Hg) are close to 50% (heavy atom on heavy atom itself, HAHA effect). J-coupling constants are highly influenced by relativity when mercury is involved as in J((199)Hg-(13)C) and J((199)Hg-(17)O). On the other hand, our results show that the values of NMR constants for carbon and oxygen, atoms which are connected through mercury (C-HgO), are highly correlated and are greatly influenced by the presence of water molecules. Water molecules introduce additional electronic effects to the relativistic effects due to the mercury atom. PMID:26670708

  7. Measurements of internal stresses in bond coating using high energy x-rays from synchrotron radiation source

    CERN Document Server

    Suzuki, K; Akiniwa, Y; Nishio, K; Kawamura, M; Okado, H

    2002-01-01

    Thermal barrier coating (TBC) techniques enable high temperature combustion of turbines made of Ni-base alloy. TBC is made of zirconia top coating on NiCoCrAlY bond coating. The internal stresses in the bond coating play essential role in the delamination or fracture of TBC in service. With the X-rays from laboratory equipments, it is impossible to measure nondestructively the internal stress in the bond coating under the top coating. synchrotron radiations with a high energy and high brightness have a large penetration depth as compared with laboratory X-rays. Using the high energy X-rays from the synchrotron radiation, it is possible to measure the internal stress in the bond coating through the top coating. In this study, the furnace, which can heat a specimen to 1473 K, was developed for the stress measurement of the thermal barrier coatings. The internal stresses in the bond coating were measured at the room temperature, 773 K, 1073 K and 1373 K by using the 311 diffraction from Ni sub 3 Al with about 73...

  8. Mass spectrometric determination of atomization energies of inorganic molecules and their correlation by empirical models of bonding

    International Nuclear Information System (INIS)

    The application of the Knudsen effusion method combined with mass spectrometry for the measurement of atomization energies of inorganic molecules is described. Recent results with emphasis on molecular metals, intermetallic molecules and metal carbides are presented. The use and limitations of various empirica models of bonding are illustrated by comparing experimental values with those calculated by the various models

  9. Effect of ultrasonic energy on nanoscale interfacial structure in copper wire bonding on aluminium pads

    International Nuclear Information System (INIS)

    The effect of ultrasonic vibration on nanoscale interfacial structure of thermosonic copper wire bonding on aluminium pads was investigated. It was found that bonding strength was determined by the extent of fragmentation of a native aluminium oxide overlayer (5-10 nm thick) on aluminium pads, forming paths for formation of intermetallic compound CuAl2 in areas of direct contact of bonded metal surfaces. The degree of fracture of the oxide layer was strongly affected by a level of ultrasonic power.

  10. Controllable dissociations of PH3 molecules on Si(001)

    Science.gov (United States)

    Liu, Qin; Lei, Yanhua; Shao, Xiji; Ming, Fangfei; Xu, Hu; Wang, Kedong; Xiao, Xudong

    2016-04-01

    We demonstrate for the first time to our knowledge that controllable dissociation of PH3 adsorption products PH x (x = 2, 1) can be realized by STM (scanning tunneling microscope) manipulation techniques at room temperature. Five dissociative products and their geometric structures are identified via combining STM experiments and first-principle calculations and simulations. In total we realize nine kinds of controllable dissociations by applying a voltage pulse among the PH3-related structures on Si(001). The dissociation rates of the five most common reactions are measured by the I-t spectrum method as a function of voltage. The suddenly increased dissociation rate at 3.3 V indicates a transition from multivibrational excitation to single-step excitation induced by inelastic tunneling electrons. Our studies prove that selectively breaking the chemical bonds of a single molecule on semiconductor surface by STM manipulation technique is feasible.

  11. Quarkonium suppression: Gluonic dissociation vs. colour screening

    Indian Academy of Sciences (India)

    Binoy Krishna Patra; Dinesh Kumar Srivastava

    2003-05-01

    We evaluate the suppression of / production in an equilibrating quark gluon plasma for two competing mechanisms: Debye screening of colour interaction and dissociation due to energetic gluons. Results are obtained for S + S and Au + Au collisions at RHIC and LHC energies. At RHIC energies the gluonic dissociation of the charmonium is found to be equally important for both the systems while the screening of the interaction plays a significant role only for the larger systems. At LHC energies the Debye mechanism is found to dominate both the systems. While considering the suppression of directly produced $\\Upsilon$ at LHC energies, we find that only the gluonic dissociation mechanism comes into play for the initial conditions taken from the self screened parton cascade model in these studies.

  12. Benchmark binding energies of ammonium and alkyl-ammonium ions interacting with water. Are ammonium-water hydrogen bonds strong?

    Science.gov (United States)

    Vallet, Valérie; Masella, Michel

    2015-01-01

    Alkyl-ammonium ion/water interactions are investigated using high level quantum computations, yielding thermodynamics data in good agreement with gas-phase experiments. Alkylation and hydration lead to weaken the NHsbnd O hydrogen bonds. Upon complete hydration by four water molecules, their main features are close to those of the OHsbnd O bond in the isolated water dimer. Energy decomposition analyses indicate that hydration of alkyl-ammonium ions are mainly due to electrostatic/polarization effects, as for hard monoatomic cations, but with a larger effect of dispersion.

  13. The Effect of Carbon Monoxide Co-Adsorption on Ni-Catalysed Water Dissociation

    Directory of Open Access Journals (Sweden)

    Abas Mohsenzadeh

    2013-11-01

    Full Text Available The effect of carbon monoxide (CO co-adsorption on the dissociation of water on the Ni(111 surface has been studied using density functional theory. The structures of the adsorbed water molecule and of the transition state are changed by the presence of the CO molecule. The water O–H bond that is closest to the CO is lengthened compared to the structure in the absence of the CO, and the breaking O–H bond in the transition state structure has a larger imaginary frequency in the presence of CO. In addition, the distances between the Ni surface and H2O reactant and OH and H products decrease in the presence of the CO. The changes in structures and vibrational frequencies lead to a reaction energy that is 0.17 eV less exothermic in the presence of the CO, and an activation barrier that is 0.12 eV larger in the presence of the CO. At 463 K the water dissociation rate constant is an order of magnitude smaller in the presence of the CO. This reveals that far fewer water molecules will dissociate in the presence of CO under reaction conditions that are typical for the water-gas-shift reaction.

  14. Mechanisms and energetics for N-glycosidic bond cleavage of protonated adenine nucleosides: N3 protonation induces base rotation and enhances N-glycosidic bond stability.

    Science.gov (United States)

    Wu, R R; Rodgers, M T

    2016-06-21

    Our previous gas-phase infrared multiple photon dissociation action spectroscopy study of protonated 2'-deoxyadenosine and adenosine, [dAdo+H](+) and [Ado+H](+), found that both N3 and N1 protonated conformers are populated with the N3 protonated ground-state conformers predominant in the experiments. Therefore, N-glycosidic bond dissociation mechanisms of N3 and N1 protonated [dAdo+H](+) and [Ado+H](+) and the associated quantitative thermochemical values are investigated here using both experimental and theoretical approaches. Threshold collision-induced dissociation (TCID) of [dAdo+H](+) and [Ado+H](+) with Xe is studied using guided ion beam tandem mass spectrometry techniques. For both systems, N-glycosidic bond cleavage reactions are observed as the major dissociation pathways resulting in production of protonated adenine or elimination of neutral adenine. Electronic structure calculations are performed at the B3LYP/6-311+G(d,p) level of theory to probe the potential energy surfaces (PESs) for N-glycosidic bond cleavage of [dAdo+H](+) and [Ado+H](+). Relative energetics of the reactants, transition states, intermediates and products along the PESs for N-glycosidic bond cleavage are determined at the B3LYP/6-311+G(2d,2p), B3LYP-GD3BJ/6-311+G(2d,2p), and MP2(full)/6-311+G(2d,2p) levels of theory. The predicted N-glycosidic bond dissociation mechanisms for the N3 and N1 protonated species differ. Base rotation of the adenine residue enables formation of a strong N3H(+)O5' hydrogen-bonding interaction that stabilizes the N3 protonated species and its glycosidic bond. Comparison between experiment and theory indicates that the N3 protonated species determine the threshold energies, as excellent agreement between the measured and B3LYP computed activation energies (AEs) and reaction enthalpies (ΔHrxns) for N-glycosidic bond cleavage of the N3 protonated species is found. PMID:27240654

  15. Adsorption and dissociation of O2 on Ni-doped (5, 5) SWCNT: A DFT study

    Science.gov (United States)

    Li, Xiaodong; Liu, Liangliang; Wang, Mingguang; Wang, Zhu

    2016-05-01

    The effect of nickel doping on the adsorption and dissociation of the O2 molecule on a (5, 5) single-walled carbon nanotube (SWCNT) is investigated using first-principles density functional theory calculations in company with the nudged elastic band (NEB). Our calculated results show that nickel doping can make it much easier for oxygen adsorbed on the SWCNT, and the chemisorption energy is high enough to alter the O-O bond. What's more, the activation barrier for oxygen dissociation is lowered to 0.399 eV through nickel doping, which is much lower than Pt doped CNT. Our work have done here would be of help to develop platinum-free oxygen reduction reaction catalysts based on SWCNTs.

  16. Selective IR multiphoton dissociation of molecules in a pulsed gas-dynamically cooled molecular flow interacting with a solid surface as an alternative to low-energy methods of molecular laser isotope separation

    Science.gov (United States)

    Makarov, G. N.; Petin, A. N.

    2016-03-01

    We report the results of studies on the isotope-selective infrared multiphoton dissociation (IR MFD) of SF6 and CF3I molecules in a pulsed, gas-dynamically cooled molecular flow interacting with a solid surface. The productivity of this method in the conditions of a specific experiment (by the example of SF6 molecules) is evaluated. A number of low-energy methods of molecular laser isotope separation based on the use of infrared lasers for selective excitation of molecules are analysed and their productivity is estimated. The methods are compared with those of selective dissociation of molecules in the flow interacting with a surface. The advantages of this method compared to the low-energy methods of molecular laser isotope separation and the IR MPD method in the unperturbed jets and flows are shown. It is concluded that this method could be a promising alternative to the low-energy methods of molecular laser isotope separation.

  17. Financing Public Sector Projects with Clean Renewable Energy Bonds; Fact Sheet Series on Financing Renewable Energy Projects, National Renewable Energy Laboratory (NREL)

    Energy Technology Data Exchange (ETDEWEB)

    Kreycik, C.; Couglin, J.

    2009-12-01

    Clean renewable energy bonds (CREBs) present a low-cost opportunity for public entities to issue bonds to finance renewable energy projects. The federal government lowers the cost of debt by providing a tax credit to the bondholder in lieu of interest payments from the issuer. Because CREBs are theoretically interest free, they may be more attractive than traditional tax-exempt municipal bonds. In February 2009, Congress appropriated a total of $2.4 billion for the "New CREBs" program. No more than one-third of the budget may be allocated to each of the eligible entities: governmental bodies, electric cooperatives, and public power providers. Applications for this round of "New CREBs" were due to the Internal Revenue Service (IRS) on August 4, 2009. There is no indication Congress will extend the CREBs program; thus going forward, only projects that are approved under the 2009 round will be able to issue CREBs. This factsheet explains the CREBs mechanism and provides guidance on procedures related to issuing CREBs.

  18. Exceptional sensitivity of metal-aryl bond energies to ortho-fluorine substituents: influence of the metal, the coordination sphere, and the spectator ligands on M-C/H-C bond energy correlations.

    Science.gov (United States)

    Clot, Eric; Mégret, Claire; Eisenstein, Odile; Perutz, Robin N

    2009-06-10

    DFT calculations are reported of the energetics of C-H oxidative addition of benzene and fluorinated benzenes, Ar(F)H (Ar(F) = C(6)F(n)H(5-n), n = 0-5) at ZrCp(2) (Cp = eta(5)-C(5)H(5)), TaCp(2)H, TaCp(2)Cl, WCp(2), ReCp(CO)(2), ReCp(CO)(PH(3)), ReCp(PH(3))(2), RhCp(PH(3)), RhCp(CO), IrCp(PH(3)), IrCp(CO), Ni(H(2)PCH(2)CH(2)PH(2)), Pt(H(2)PCH(2)CH(2)PH(2)). The change in M-C bond energy of the products fits a linear function of the number of fluorine substituents, with different coefficients corresponding to ortho-, meta-, and para-fluorine. The values of the ortho-coefficient range from 20 to 32 kJ mol(-1), greatly exceeding the values for the meta- and para-coefficients (2.0-4.5 kJ mol(-1)). Similarly, the H-C bond energies of Ar(F)H yield ortho- and para-coefficients of 10.4 and 3.4 kJ mol(-1), respectively, and a negligible meta-coefficient. These results indicate a large increase in the M-C bond energy with ortho-fluorine substitution on the aryl ring. Plots of D(M-C) vs D(H-C) yield slopes R(M-C/H-C) that vary from 1.93 to 3.05 with metal fragment, all in excess of values of 1.1-1.3 reported with other hydrocarbyl groups. Replacement of PH(3) by CO decreases R(M-C/H-C) significantly. For a given ligand set and metals in the same group of the periodic table, the value of R(M-C/H-C) does not increase with the strength of the M-C bond. Calculations of the charge on the aryl ring show that variations in ionicity of the M-C bonds correlate with variations in M-C bond energy. This strengthening of metal-aryl bonds accounts for numerous experimental results that indicate a preference for ortho-fluorine substituents. PMID:19453181

  19. Determination of Hydrogen Bond Structure in Water versus Aprotic Environments To Test the Relationship Between Length and Stability

    Energy Technology Data Exchange (ETDEWEB)

    Sigala, Paul A.; Ruben, Eliza A.; Liu, Corey W.; Piccoli, Paula M. B.; Hohenstein, Edward G.; Martinez, Todd J.; Schultz, Arthur J.; Herschiag, Daniel

    2015-05-06

    Hydrogen bonds profoundly influence the architecture and activity of biological macromolecules. Deep appreciation of hydrogen bond contributions to biomolecular function thus requires a detailed understanding of hydrogen bond structure and energetics and the relationship between these properties. Hydrogen bond formation energies (Delta G(f)) are enormously more favorable in aprotic solvents than in water, and two classes of contributing factors have been proposed to explain this energetic difference, focusing respectively on the isolated and hydrogen-bonded species: (I) water stabilizes the dissociated donor and acceptor groups much better than aprotic solvents, thereby reducing the driving force for hydrogen bond formation; and (II) water lengthens hydrogen bonds compared to aprotic environments, thereby decreasing the potential energy within the hydrogen bond. Each model has been proposed to provide a dominant contribution to Delta G(f), but incisive tests that distinguish the importance of these contributions are lacking. Here we directly test the structural basis of model II. Neutron crystallography, NMR spectroscopy, and quantum mechanical calculations demonstrate that O-H center dot center dot center dot O hydrogen bonds in crystals, chloroform, acetone, and water have nearly identical lengths and very similar potential energy surfaces despite Delta G(f) differences >8 kcal/mol across these solvents. These results rule out a substantial contribution from solvent-dependent differences in hydrogen bond structure and potential energy after association (model II) and thus support the conclusion that differences in hydrogen bond Delta G(f) are predominantly determined by solvent interactions with the dissociated groups (model I). These findings advance our understanding of universal hydrogen-bonding interactions and have important implications for biology and engineering.

  20. Mediatorless solar energy conversion by covalently bonded thylakoid monolayer on the glassy carbon electrode.

    Science.gov (United States)

    Lee, Jinhwan; Im, Jaekyun; Kim, Sunghyun

    2016-04-01

    Light reactions of photosynthesis that take place in thylakoid membranes found in plants or cyanobacteria are among the most effective ways of utilizing light. Unlike most researches that use photosystem I or photosystem II as conversion units for converting light to electricity, we have developed a simple method in which the thylakoid monolayer was covalently immobilized on the glassy carbon electrode surface. The activity of isolated thylakoid membrane was confirmed by measuring evolving oxygen under illumination. Glassy carbon surfaces were first modified with partial or full monolayers of carboxyphenyl groups by reductive C-C coupling using 4-aminobenzoic acid and aniline and then thylakoid membrane was bioconjugated through the peptide bond between amine residues of thylakoid and carboxyl groups on the surface. Surface properties of modified surfaces were characterized by cyclic voltammetry, contact angle measurements, and electrochemical impedance spectroscopy. Photocurrent of 230 nA cm(-2) was observed when the thylakoid monolayer was formed on the mixed monolayer of 4-carboxylpheny and benzene at applied potential of 0.4V vs. Ag/AgCl. A small photocurrent resulted when the 4-carboxyphenyl full monolayer was used. This work shows the possibility of solar energy conversion by directly employing the whole thylakoid membrane through simple surface modification. PMID:26625272

  1. Improved 6-Plex Tandem Mass Tags Quantification Throughput Using a Linear Ion Trap-High-Energy Collision Induced Dissociation MS(3) Scan.

    Science.gov (United States)

    Liu, Jane M; Sweredoski, Michael J; Hess, Sonja

    2016-08-01

    The use of tandem mass tags (TMT) as an isobaric labeling strategy is a powerful method for quantitative proteomics, yet its accuracy has traditionally suffered from interference. This interference can be largely overcome by selecting MS(2) fragment precursor ions for high-energy collision induced dissociation (HCD) MS(3) analysis in an Orbitrap scan. While this approach minimizes the interference effect, sensitivity suffers due to the high AGC targets and long acquisition times associated with MS(3) Orbitrap detection. We investigated whether acquiring the MS(3) scan in a linear ion trap with its lower AGC target would increase overall quantification levels with a minimal effect on precision and accuracy. Trypsin-digested proteins from Saccharomyces cerevisiae were tagged with 6-plex TMT reagents. The sample was subjected to replicate analyses using either the Orbitrap or the linear ion trap for the HCD MS(3) scan. HCD MS(3) detection in the linear ion trap vs Orbitrap increased protein identification by 66% with minor loss in precision and accuracy. Thus, the use of a linear ion trap-HCD MS(3) scan during a 6-plex TMT experiment can improve overall identification levels while maintaining the power of multiplexed quantitative analysis. PMID:27377715

  2. The interplay between interface structure, energy level alignment and chemical bonding strength at organic-metal interfaces.

    Science.gov (United States)

    Willenbockel, M; Lüftner, D; Stadtmüller, B; Koller, G; Kumpf, C; Soubatch, S; Puschnig, P; Ramsey, M G; Tautz, F S

    2015-01-21

    What do energy level alignments at metal-organic interfaces reveal about the metal-molecule bonding strength? Is it permissible to take vertical adsorption heights as indicators of bonding strengths? In this paper we analyse 3,4,9,10-perylene-tetracarboxylic acid dianhydride (PTCDA) on the three canonical low index Ag surfaces to provide exemplary answers to these questions. Specifically, we employ angular resolved photoemission spectroscopy for a systematic study of the energy level alignments of the two uppermost frontier states in ordered monolayer phases of PTCDA. Data are analysed using the orbital tomography approach. This allows the unambiguous identification of the orbital character of these states, and also the discrimination between inequivalent species. Combining this experimental information with DFT calculations and the generic Newns-Anderson chemisorption model, we analyse the alignments of highest occupied and lowest unoccupied molecular orbitals (HOMO and LUMO) with respect to the vacuum levels of bare and molecule-covered surfaces. This reveals clear differences between the two frontier states. In particular, on all surfaces the LUMO is subject to considerable bond stabilization through the interaction between the molecular π-electron system and the metal, as a consequence of which it also becomes occupied. Moreover, we observe a larger bond stabilization for the more open surfaces. Most importantly, our analysis shows that both the orbital binding energies of the LUMO and the overall adsorption heights of the molecule are linked to the strength of the chemical interaction between the molecular π-electron system and the metal, in the sense that stronger bonding leads to shorter adsorption heights and larger orbital binding energies. PMID:25475998

  3. Adhesive-Bonded Composite Joint Analysis with Delaminated Surface Ply Using Strain-Energy Release Rate

    Science.gov (United States)

    Chadegani, Alireza; Yang, Chihdar; Smeltzer, Stanley S. III

    2012-01-01

    This paper presents an analytical model to determine the strain energy release rate due to an interlaminar crack of the surface ply in adhesively bonded composite joints subjected to axial tension. Single-lap shear-joint standard test specimen geometry with thick bondline is followed for model development. The field equations are formulated by using the first-order shear-deformation theory in laminated plates together with kinematics relations and force equilibrium conditions. The stress distributions for the adherends and adhesive are determined after the appropriate boundary and loading conditions are applied and the equations for the field displacements are solved. The system of second-order differential equations is solved to using the symbolic computation tool Maple 9.52 to provide displacements fields. The equivalent forces at the tip of the prescribed interlaminar crack are obtained based on interlaminar stress distributions. The strain energy release rate of the crack is then determined by using the crack closure method. Finite element analyses using the J integral as well as the crack closure method are performed to verify the developed analytical model. It has been shown that the results using the analytical method correlate well with the results from the finite element analyses. An attempt is made to predict the failure loads of the joints based on limited test data from the literature. The effectiveness of the inclusion of bondline thickness is justified when compared with the results obtained from the previous model in which a thin bondline and uniform adhesive stresses through the bondline thickness are assumed.

  4. Carbon monoxide dissociative attachment and resonant dissociation by electron-impact

    Science.gov (United States)

    Laporta, V.; Tennyson, J.; Celiberto, R.

    2016-02-01

    Low-energy dissociative electron attachment and resonant electron impact dissociation of CO molecule are considered. Ro-vibrationally resolved cross sections and rate coefficients for both the processes are calculated using an ab-initio model based on the low-lying \\text{X}{{}2}\\Pi resonance of CO-. Final results show that the cross sections increases very rapidly as a function of the ro-vibrational level; these cross sections should be useful for understanding kinetic dissociation of CO in strongly non-equilibrium plasmas.

  5. Theoretical Study of the Ozonolysis of C60: Primary Ozonide Formation, Dissociation, and Multiple Ozone Additions

    OpenAIRE

    Chapleski, Robert C., Jr.; Morris, John R.; Troya, Diego

    2014-01-01

    We present an investigation of the reaction of ozone with C60 fullerene using electronic structure methods. Motivated by recent experiments of ozone exposure to a C60 film, we have characterized stationary points in the potential energy surface for the reactions of O3 with C60 that include both the formation of primary ozonide and subsequent dissociation reactions of this intermediate that lead to C_C bond cleavage. We have also investigated the addition of multiple O3 molecules to the C60 ca...

  6. The stabilization energies of polyenyl radicals

    Science.gov (United States)

    Luo, Yu-Ran; Holmes, John L.

    1994-10-01

    The resonance stabilization energies, Es, of polyenyl radicals can be estimated by the equation Es( N)=-13.2+[3.95-15.8(2) -2/ n] kcal mol -1, where N is the number of C, C-π bonds in the polyenyl radicals. This correlation has been extended for predicting the weakest HC, CC and COH bond dissociation energies in vitamin A and similar compounds.

  7. Diffractive dissociation and new quarks

    International Nuclear Information System (INIS)

    We argue that the chiral limit of QCD can be identified with the strong (diffractive dissociation) coupling limit of reggeon field theory. Critical Pomeron scaling at high energy must then be directly related to an infra-red fixed-point of massless QCD and so requires a large number of flavors. This gives a direct argument that the emergence of diffraction-peak scaling, KNO scaling etc. at anti p-p colliders are evidence of a substantial quark structure still to be discovered

  8. Duality in diffraction dissociations

    International Nuclear Information System (INIS)

    Diffractive dissociations (aN→a*πN) are naturally explained and a model that accounts for the three-variable correlation (mass-transfer-Jackson angle correlation) is presented. This model takes into account the three possible exchanges: t (pion), u(a*) and s(a) channel exchanger. The physical consequences of the model are: a strong mass-slope correlation due to the zeros of the amplitude, a factorization of diffractive dissociations (factorization of the Pomeron), the possibility of extending this model to double diffractive dissociation and diffraction by nuclei. This model was applied to the NN→NπN reaction. Using the usual parameters of the Deck model, a comparison is made with experiments for all available distributions. the strong slope of the peak at 1400 MeV is naturally explained

  9. A comparison of ab initio quantum-mechanical and experimental D-0 binding energies of eleven H-bonded and eleven dispersion-bound complexes

    Czech Academy of Sciences Publication Activity Database

    Haldar, Susanta; Gnanasekaran, Ramachandran; Hobza, Pavel

    2015-01-01

    Roč. 17, č. 40 (2015), s. 26645-26652. ISSN 1463-9076 R&D Projects: GA ČR GBP208/12/G016 Institutional support: RVO:61388963 Keywords : noncovalent interactions * dissociation energy * CCSD(T) Subject RIV: CF - Physical ; Theoretical Chemistry Impact factor: 4.493, year: 2014

  10. Imaging the molecular dynamics of dissociative electron attachment to water

    Energy Technology Data Exchange (ETDEWEB)

    Adaniya, Hidihito; Rudek, B.; Osipov, Timur; Haxton, Dan; Weber, Thorsten; Rescigno, Thomas N.; McCurdy, C.W.; Belkacem, Ali

    2009-10-19

    Momentum imaging experiments on dissociative electron attachment to the water molecule are combined with ab initio theoretical calculations of the angular dependence of the quantum mechanical amplitude for electron attachment to provide a detailed picture of the molecular dynamics of dissociation attachment via the two lowest energy Feshbach resonances. The combination of momentum imaging experiments and theory can reveal dissociation dynamics for which the axial recoil approximation breaks down and thus provides a powerful reaction microscope for DEA to polyatomics.

  11. Influence of oxygen inhibition on the surface free-energy and dentin bond strength of self-etch adhesives.

    Science.gov (United States)

    Koga, Kensaku; Tsujimoto, Akimasa; Ishii, Ryo; Iino, Masayoshi; Kotaku, Mayumi; Takamizawa, Toshiki; Tsubota, Keishi; Miyazaki, Masashi

    2011-10-01

    We compared the surface free-energies and dentin bond strengths of single-step self-etch adhesives with and without an oxygen-inhibited layer. The labial dentin surfaces of bovine mandibular incisors were wet ground with #600-grit silicon carbide paper. The adhesives were applied to the ground dentin, light-irradiated, and the oxygen-inhibited layer was either retained or removed with ethanol. The surface free-energies were determined by measuring the contact angles of three test liquids placed on the cured adhesives. The dentin bond strengths of specimens with and without the oxygen-inhibited layer were measured. For all surfaces, the value of the estimated surface tension component was relatively constant at 35.5-39.8 mJ m(-2) . The value of the , Lewis acid component increased slightly when the oxygen-inhibited layer was removed, whereas that of the , Lewis base component decreased significantly. The bond strengths of the self-etch adhesives were significantly lower in specimens without an oxygen-inhibited layer (13.2-13.6 MPa) than in those with an oxygen-inhibited layer (17.5-18.4 MPa). These results indicate that the presence of an oxygen-inhibited layer in single-step self-etch adhesives with advanced photoinitiators promotes higher dentin bond strength. PMID:21896057

  12. Density functional for van der Waals forces accounts for hydrogen bond in benchmark set of water hexamers

    Science.gov (United States)

    Kelkkanen, André K.; Lundqvist, Bengt I.; Nørskov, Jens K.

    2009-07-01

    A recent extensive study has investigated how various exchange-correlation (XC) functionals treat hydrogen bonds in water hexamers and has shown traditional generalized gradient approximation and hybrid functionals used in density-functional (DF) theory to give the wrong dissociation-energy trend of low-lying isomers and van der Waals (vdW) dispersion forces to give key contributions to the dissociation energy. The question raised whether functionals that incorporate vdW forces implicitly into the XC functional predict the correct lowest-energy structure for the water hexamer and yield accurate total dissociation energy is here answered affirmatively for the vdW-DF [M. Dion et al., Phys. Rev. Lett.92, 246401 (2004)].

  13. Bond Energies and Thermochemical Properties of Ring-Opened Diradicals and Carbenes of exo-Tricyclo[5.2.1.0(2,6)]decane.

    Science.gov (United States)

    Hudzik, Jason M; Castillo, Álvaro; Bozzelli, Joseph W

    2015-09-24

    Exo-tricyclo[5.2.1.0(2,6)]decane (TCD) or exo-tetrahydrodicyclopentadiene is an interesting strained ring compound and the single-component high-energy density hydrocarbon fuel known as JP-10. Important initial reactions of TCD at high temperatures could cleave a strained carbon-carbon (C-C) bond in the ring system creating diradicals also constrained by the remaining ring system. This study determines the thermochemical properties of these diradicals (TCD-H2 mJ-nJ where m and n correspond to the cleaved carbons sites) including the carbon-carbon bond dissociation energy (C-C BDE) corresponding to the cleaved TCD site. Thermochemical properties including enthalpies (ΔH°f298), entropies (S(T)), heat capacities (Cp(T)), and C-H and C-C BDEs for the parent (TCD-H2 m-n), radical (TCD-H2 mJ-n and m-nJ), diradical (TCD-H2 mJ-nJ), and carbene (TCD-H2 mJJ-n and m-nJJ) species are determined. Structures, vibrational frequencies, moments of inertia, and internal rotor potentials are calculated at the B3LYP/6-31G(d,p) level of theory. Standard enthalpies of formation in the gas phase for the TCD-H2 m-n parent and radical species are determined using the B3LYP density functional theory and the higher level G3MP2B3 and CBS-QB3 composite methods. For singlet and triplet TCD diradicals and carbenes, M06-2X, ωB97X-D, and CCSD(T) methods are included in the analysis to determine ΔH°f298 values. The C-C BDEs are further calculated using CASMP2(2,2)/aug-cc-pvtz//CASSCF(2,2)/cc-pvtz and with the CASMP2 energies extrapolated to the complete basis set limit. The bond energies calculated with these methods are shown to be comparable to the other calculation methods. Isodesmic work reactions are used for enthalpy analysis of these compounds for effective cancelation of systematic errors arising from ring strain. C-C BDEs range from 77.4 to 84.6 kcal mol(-1) for TCD diradical singlet species. C-H BDEs for the parent TCD-H2 m-n carbon sites range from 93 to 101 kcal mol(-1) with a

  14. On the Use of a Driven Wedge Test to Acquire Dynamic Fracture Energies of Bonded Beam Specimens

    Energy Technology Data Exchange (ETDEWEB)

    Dillard, David A. [Virginia Polytechnic Institute and State University (Virginia Tech); Pohilt, David [Engineering Science and Mechanics Department, Virginia Tech, Blacksburg, VA, USA; Jacob, George Chennakattu [ORNL; Starbuck, Michael [Materials Science and Engineering Department, University of Tennessee, Knoxville, TN, USA; Rakesh, Kapania [Aerospace and Ocean Engineering Department, Virginia Tech, Blacksburg, VA, USA

    2011-01-01

    A driven wedge test is used to characterize the mode I fracture resistance of adhesively bonded composite beam specimens over a range of crosshead rates up to 1 m/s. The shorter moment arms (between wedge contact and crack tip) significantly reduce inertial effects and stored energy in the debonded adherends, when compared with conventional means of testing double cantilever beam (DCB) specimens. This permitted collecting an order of magnitude more crack initiation events per specimen than could be obtained with end-loaded DCB specimens bonded with an epoxy exhibiting significant stick-slip behavior. The localized contact of the wedge with the adherends limits the amount of both elastic and kinetic energy, significantly reduces crack advance during slip events, and facilitates higher resolution imaging of the fracture zone with high speed imaging. The method appears to work well under both quasi-static and high rate loading, consistently providing substantially more discrete fracture events for specimens exhibiting pronounced stick-slip failures. Deflections associated with beam transverse shear and root rotation for the shorter beams were not negligible, so simple beam theory was inadequate for obtaining qualitative fracture energies. Finite element analysis of the specimens, however, showed that fracture energies were in good agreement with values obtained from traditional DCB tests. The method holds promise for use in dynamic testing and for characterizing bonded or laminated materials exhibiting significant stick slip behavior, reducing the number of specimens required to characterize a sufficient number of fracture events.

  15. Chemical bonding in view of electron charge density and kinetic energy density descriptors.

    Science.gov (United States)

    Jacobsen, Heiko

    2009-05-01

    Stalke's dilemma, stating that different chemical interpretations are obtained when one and the same density is interpreted either by means of natural bond orbital (NBO) and subsequent natural resonance theory (NRT) application or by the quantum theory of atoms in molecules (QTAIM), is reinvestigated. It is shown that within the framework of QTAIM, the question as to whether for a given molecule two atoms are bonded or not is only meaningful in the context of a well-defined reference geometry. The localized-orbital-locator (LOL) is applied to map out patterns in covalent bonding interaction, and produces results that are consistent for a variety of reference geometries. Furthermore, LOL interpretations are in accord with NBO/NRT, and assist in an interpretation in terms of covalent bonding. PMID:19090572

  16. Direct non-dissociative and dissociative ionization of CO2 by positron impact

    International Nuclear Information System (INIS)

    Detailed measurements of the cross-section for non-dissociative ionization of CO2 are presented and compared with available experimental and theoretical results. An excellent agreement is found with the energy dependence of another experimental determination; however, uncertainties exist over the magnitude. Also presented are the preliminary results for the combined cross-section for direct dissociative ionization of CO2 into O+ or C+

  17. Hydrogen bonding tunes the early stage of hydrogen-atom abstracting reaction.

    Science.gov (United States)

    Yang, Yang; Liu, Lei; Chen, Junsheng; Han, Keli

    2014-09-01

    The spontaneous and collision-assisted hydrogen-atom abstracting reaction (HA) dynamics of triplet benzil are investigated through the combination of transient absorption spectroscopy with TD-DFT calculations. HA dynamics exhibit a remarkable dependence on the hydrogen donor properties. The effects of the triplet-state hydrogen bonding on the reaction dynamics are illustrated. In particular, it is experimentally observed that strengthened triplet-state hydrogen bonding could accelerate the HA, whereas weakened triplet-state hydrogen bonding would postpone the HA. The triplet-state hydrogen bonding has great influences on the early stage of the HA reaction, while the bond dissociation energy of the hydrogen donors determines the subsequent reaction pathways. Protic solvents could sustain longer lifetimes of the excited-state intermediate formed after HA than non-protic solvents by 10 μs. This investigation provides insights into the HA dynamics and guidance to improve the product efficiency of photochemical reactions. PMID:25036436

  18. The Microstructure and Chemical Bonds of β-C2S Under the High Energy Ball Grinding Function

    Institute of Scientific and Technical Information of China (English)

    2006-01-01

    Using the laser granularity survey technology, X- ray powder diffraction, scanning electron mi croscopy (SEM) and infrared spectrum analysis methods, we studied the microscopic structure and chemical bonds changes of β- C2 S monomineral under the high energy ball grinding function .The result indicates that, continuously under the mechanical power, β-C2 S crystal size would decrease, the micro strain and the effective Beff parameter would increase, and the amorphous phases would be presented. Furthermore, the mechanical power would cause Si- O bond broken and reorganized, the specific surface area would increase, the energy of micro-pow der agglomeration vibration would be enhanced and the crystal would be disordered .Finally, β- C2 S was caused to have the mechanochemical change and the activity enhancement.

  19. Covalent bonds are created by the drive of electron waves to lower their kinetic energy through expansion

    International Nuclear Information System (INIS)

    An analysis based on the variation principle shows that in the molecules H2+, H2, B2, C2, N2, O2, F2, covalent bonding is driven by the attenuation of the kinetic energy that results from the delocalization of the electronic wave function. For molecular geometries around the equilibrium distance, two features of the wave function contribute to this delocalization: (i) Superposition of atomic orbitals extends the electronic wave function from one atom to two or more atoms; (ii) intra-atomic contraction of the atomic orbitals further increases the inter-atomic delocalization. The inter-atomic kinetic energy lowering that (perhaps counter-intuitively) is a consequence of the intra-atomic contractions drives these contractions (which per se would increase the energy). Since the contractions necessarily encompass both, the intra-atomic kinetic and potential energy changes (which add to a positive total), the fact that the intra-atomic potential energy change renders the total potential binding energy negative does not alter the fact that it is the kinetic delocalization energy that drives the bond formation

  20. Is the decrease of the total electron energy density a covalence indicator in hydrogen and halogen bonds?

    Science.gov (United States)

    Angelina, Emilio L; Duarte, Darío J R; Peruchena, Nélida M

    2013-05-01

    In this work, halogen bonding (XB) and hydrogen bonding (HB) complexes were studied with the aim of analyzing the variation of the total electronic energy density H(r b ) with the interaction strengthening. The calculations were performed at the MP2/6-311++G(2d,2p) level of approximation. To explain the nature of such interactions, the atoms in molecules theory (AIM) in conjunction with reduced variational space self-consistent field (RVS) energy decomposition analysis were carried out. Based on the local virial theorem, an equation to decompose the total electronic energy density H(r b ) in two energy densities, (-G(r b )) and 1/4∇(2)ρ(r b ), was derived. These energy densities were linked with the RVS interaction energy components. Through the connection between both decomposition schemes, it was possible to conclude that the decrease in H(r b ) with the interaction strengthening observed in the HB as well as the XB complexes, is mainly due to the increase in the attractive electrostatic part of the interaction energy and in lesser extent to the increase in its covalent character, as is commonly considered. PMID:23187685

  1. Dissociative Reactions to Incest.

    Science.gov (United States)

    Hall, J. Mark

    In contrast to Freud's later and revised view of the etiology of hysterical, or dissociative, symptoms, it is now known that real, and not fantasized, sexual experiences in childhood are experienced in disociative symptomatology. It is useful to understand that incest involves both traumatic events, that is, incidents of sexual violation per se,…

  2. Dissociation by acceleration

    OpenAIRE

    Peeters, K.; Zamaklar, M.

    2008-01-01

    We show that mesons, described using rotating relativistic strings in a holographic setup, undergo dissociation when their acceleration 'a' exceeds a value which scales with the angular momentum 'J' as a_max ~ \\sqrt{T_s/J}, where 'T_s' is the string tension.

  3. Dissociation by acceleration

    OpenAIRE

    2007-01-01

    We show that mesons, described using rotating relativistic strings in a holographic setup, undergo dissociation when their acceleration 'a' exceeds a value which scales with the angular momentum 'J' as a_max ~ \\sqrt{T_s/J}, where 'T_s' is the string tension.

  4. Sexuality of dissocial persons

    Directory of Open Access Journals (Sweden)

    Marta Janus

    2016-02-01

    Full Text Available Introduction. The development of personality disorders as well as sexual disorders is defined by the common time spectrum as well as deficits and changes in such areas as biological, environmental and mental area. Dissocial (antisocial personality disorder is characterised by a pervasive pattern of disregard for, or violation of, the rights of others. The indices of the discussed disorder can be found in specific patterns of social inadequacy occurring during childhood and puberty. At the same time, characteristic indices of social functioning at a young age often indicate subsequent dysfunctions in the area of sexuality. Aim. The aim of this paper is to explain sexual functioning of persons with dissocial personality disorder (including the relation with sexual dysfunctions, and to ascertain issues that need further empirical studies. Method. As a result of analysis of available literature (matched with EBSCO database search fulfilling criteria of sample size, accuracy of examination procedure, conclusions and discussion 5 articles fulfilling criteria cited above has been found. Conclusions: Based on literature overview, it appeared to be impossible to determine one coherent way of sexual functioning of dissocial persons, and to establish causal relationship of sexual dysfunctions and dissocial personality disorder. However, it is possible to indicate group of most characteristic dysfunctional sexual behaviours. Noteworthy, available publication analyse only selected aspects of sexual behaviours in small, homogenous groups. There is a lack of review studies as well as multi-faceted studies.

  5. Bonding silicones with epoxies

    Energy Technology Data Exchange (ETDEWEB)

    Tira, J.S.

    1980-01-01

    It is shown that silicones, both room temperature vulcanizing (RTV) and millable rubber (press cured) can be successfully bonded to other materials using plasma treatment and epoxy adhesives. The plasma treatment using dry air atmosphere increases the surface energy of the silicone and thus provides a lower water contact angle. This phenomenon allows the epoxy adhesive to wet the silicone surface and ultimately bond. Bond strengths are sufficiently high to result in failures in the silicone materials rather than the adhesive bond.

  6. Total energy of deoxyguanosine bonded to N-2-acetylaminofluorene by the semiempirical modified-neglect of differential diatomic overlap method

    Science.gov (United States)

    Besson, Morgan

    2000-03-01

    We have computed the total energy surface as a function of two important torsion angles of the carcinogen N-2-acetylaminofluorene (AAF) bonded to the carbon C8 of deoxyguanosine using the semiempirical quantum mechanical method MNDO. One global minimum and one local minimum are found separated by an appreciable barrier. The equilibrium geometries show the rearrangement of AAF and the base consistent with experimental observations of DNA by previous investigators.

  7. A Study on Unobserved Structural Innovations of Oil Price: Evidence from Global Stock, Bond, Foreign Exchange, and Energy Markets

    OpenAIRE

    Jungho Baek; Ji-Yong Seo

    2015-01-01

    This study examines the effects of oil shocks by their respective causes and of volatility spillover including leverage effects. Previous studies did not analyze oil factor by categorizing it into three components (supply shock, demand shock, and market shock) as determinants of rate of return in stock markets, a key issue in finance. Results show that oil shocks determine returns in the global stock market, bond market, foreign exchange market, and energy market, and that their effects vary ...

  8. Pathological Dissociation as Measured by the Child Dissociative Checklist

    Science.gov (United States)

    Wherry, Jeffrey N.; Neil, Debra A.; Taylor, Tamara N.

    2009-01-01

    The component structure of the Child Dissociative Checklist was examined among abused children. A factor described as pathological dissociation emerged that was predicted by participants being male. There also were differences in pathological dissociation between groups of sexually abused and physically abused children. Replication of this factor…

  9. Strain-Induced Water Dissociation on Supported Ultrathin Oxide Films

    CERN Document Server

    Song, Zhenjun; Xu, Hu

    2015-01-01

    Controlling the dissociation of single water molecule on an insulating surface plays a crucial role in many catalytic reactions. In this Letter, we have identified the enhanced chemical reactivity of ultrathin MgO(100) films deposited on Mo(100) substrate that causes water dissociation. We reveal that the ability to split water on insulating surface closely depends on the lattice mismatch between ultrathin films and the underlying substrate, and substrate-induced in-plane tensile strain dramatically results in water dissociation on MgO(100). Three dissociative adsorption configurations of water with lower energy are predicted, and the structural transition going from molecular form to dissociative form is almost barrierless. Our results provide an effective avenue to achieve water dissociation at the single-molecule level and shed light on how to tune the chemical reactions of insulating surfaces by choosing the suitable substrates.

  10. Strain-induced water dissociation on supported ultrathin oxide films.

    Science.gov (United States)

    Song, Zhenjun; Fan, Jing; Xu, Hu

    2016-01-01

    Controlling the dissociation of single water molecule on an insulating surface plays a crucial role in many catalytic reactions. In this work, we have identified the enhanced chemical reactivity of ultrathin MgO(100) films deposited on Mo(100) substrate that causes water dissociation. We reveal that the ability to split water on insulating surface closely depends on the lattice mismatch between ultrathin films and the underlying substrate, and substrate-induced in-plane tensile strain dramatically results in water dissociation on MgO(100). Three dissociative adsorption configurations of water with lower energy are predicted, and the structural transition going from molecular form to dissociative form is almost barrierless. Our results provide an effective avenue to achieve water dissociation at the single-molecule level and shed light on how to tune the chemical reactions of insulating surfaces by choosing the suitable substrates. PMID:26953105

  11. Direct glycan structure determination of intact N-linked glycopeptides by low-energy collision-induced dissociation tandem mass spectrometry and predicted spectral library searching.

    Science.gov (United States)

    Pai, Pei-Jing; Hu, Yingwei; Lam, Henry

    2016-08-31

    Intact glycopeptide MS analysis to reveal site-specific protein glycosylation is an important frontier of proteomics. However, computational tools for analyzing MS/MS spectra of intact glycopeptides are still limited and not well-integrated into existing workflows. In this work, a new computational tool which combines the spectral library building/searching tool, SpectraST (Lam et al. Nat. Methods2008, 5, 873-875), and the glycopeptide fragmentation prediction tool, MassAnalyzer (Zhang et al. Anal. Chem.2010, 82, 10194-10202) for intact glycopeptide analysis has been developed. Specifically, this tool enables the determination of the glycan structure directly from low-energy collision-induced dissociation (CID) spectra of intact glycopeptides. Given a list of possible glycopeptide sequences as input, a sample-specific spectral library of MassAnalyzer-predicted spectra is built using SpectraST. Glycan identification from CID spectra is achieved by spectral library searching against this library, in which both m/z and intensity information of the possible fragmentation ions are taken into consideration for improved accuracy. We validated our method using a standard glycoprotein, human transferrin, and evaluated its potential to be used in site-specific glycosylation profiling of glycoprotein datasets from LC-MS/MS. In addition, we further applied our method to reveal, for the first time, the site-specific N-glycosylation profile of recombinant human acetylcholinesterase expressed in HEK293 cells. For maximum usability, SpectraST is developed as part of the Trans-Proteomic Pipeline (TPP), a freely available and open-source software suite for MS data analysis. PMID:27506355

  12. Accounting for the differences in the structures and relative energies of the highly homoatomic np pi-np pi (n > or = 3)-bonded S2I4 2+, the Se-I pi-bonded Se2I4 2+, and their higher-energy isomers by AIM, MO, NBO, and VB methodologies.

    Science.gov (United States)

    Brownridge, Scott; Crawford, Margaret-Jane; Du, Hongbin; Harcourt, Richard D; Knapp, Carsten; Laitinen, Risto S; Passmore, Jack; Rautiainen, J Mikko; Suontamo, Reijo J; Valkonen, Jussi

    2007-02-01

    The bonding in the highly homoatomic np pi-np pi (n > or = 3)-bonded S2I42+ (three sigma + two pi bonds), the Se-I pi-bonded Se2I42+ (four sigma + one pi bonds), and their higher-energy isomers have been studied using modern DFT and ab initio calculations and theoretical analysis methods: atoms in molecules (AIM), molecular orbital (MO), natural bond orbital (NBO), and valence bond (VB) analyses, giving their relative energies, theoretical bond orders, and atomic charges. The aim of this work was to seek theory-based answers to four main questions: (1) Are the previously proposed simple pi*-pi* bonding models valid for S2I42+ and Se2I42+? (2) What accounts for the difference in the structures of S2I42+ and Se2I42+? (3) Why are the classically bonded isolobal P2I4 and As2I4 structures not adopted? (4) Is the high experimentally observed S-S bond order supported by theoretical bond orders, and how does it relate to high bond orders between other heavier main group elements? The AIM analysis confirmed the high bond orders and established that the weak bonds observed in S2I42+ and Se2I42+ are real and the bonding in these cations is covalent in nature. The full MO analysis confirmed that S2I42+ contains three sigma and two pi bonds, that the positive charge is essentially equally distributed over all atoms, that the bonding between S2 and two I2+ units in S2I42+ is best described by two mutually perpendicular 4c2e pi*-pi* bonds, and that in Se2I42+, two SeI2+ moieties are joined by a 6c2e pi*-pi* bond, both in agreement with previously suggested models. The VB treatment provided a complementary approach to MO analysis and provided insight how the formation of the weak bonds affects the other bonds. The NBO analysis and the calculated AIM charges showed that the minimization of the electrostatic repulsion between EI2+ units (E = S, Se) and the delocalization of the positive charge are the main factors that explain why the nonclassical structures are favored for S2I42

  13. The influence of large-amplitude librational motion on the hydrogen bond energy for alcohol-water complexes.

    Science.gov (United States)

    Andersen, J; Heimdal, J; Wugt Larsen, R

    2015-10-01

    The far-infrared absorption spectra have been recorded for hydrogen-bonded complexes of water with methanol and t-butanol embedded in cryogenic neon matrices at 2.8 K. The partial isotopic substitution of individual subunits enabled by a dual inlet deposition procedure provides for the first time unambiguous assignments of the intermolecular high-frequency out-of-plane and low-frequency in-plane donor OH librational modes for mixed alcohol-water complexes. The vibrational assignments confirm directly that water acts as the hydrogen bond donor in the most stable mixed complexes and the tertiary alcohol is a superior hydrogen bond acceptor. The class of large-amplitude donor OH librational motion is shown to account for up to 5.1 kJ mol(-1) of the destabilizing change of vibrational zero-point energy upon intermolecular OHO hydrogen bond formation. The experimental findings are supported by complementary electronic structure calculations at the CCSD(T)-F12/aug-cc-pVTZ level of theory. PMID:26304774

  14. High-energy, stable and recycled molecular solar thermal storage materials using AZO/graphene hybrids by optimizing hydrogen bonds.

    Science.gov (United States)

    Luo, Wen; Feng, Yiyu; Qin, Chengqun; Li, Man; Li, Shipei; Cao, Chen; Long, Peng; Liu, Enzuo; Hu, Wenping; Yoshino, Katsumi; Feng, Wei

    2015-10-21

    An important method for establishing a high-energy, stable and recycled molecular solar heat system is by designing and preparing novel photo-isomerizable molecules with a high enthalpy and a long thermal life by controlling molecular interactions. A meta- and ortho-bis-substituted azobenzene chromophore (AZO) is covalently grafted onto reduced graphene oxide (RGO) for solar thermal storage materials. High grafting degree and close-packed molecules enable intermolecular hydrogen bonds (H-bonds) for both trans-(E) and cis-(Z) isomers of AZO on the surface of nanosheets, resulting in a dramatic increase in enthalpy and lifetime. The metastable Z-form of AZO on RGO is thermally stabilized with a half-life of 52 days by steric hindrance and intermolecular H-bonds calculated using density functional theory (DFT). The AZO-RGO fuel shows a high storage capacity of 138 Wh kg(-1) by optimizing intermolecular H-bonds with a good cycling stability for 50 cycles induced by visible light at 520 nm. Our work opens up a new method for making advanced molecular solar thermal storage materials by tuning molecular interactions on a nano-template. PMID:26289389

  15. Low-cost bump-bonding processes for high energy physics pixel detectors

    Science.gov (United States)

    Caselle, M.; Blank, T.; Colombo, F.; Dierlamm, A.; Husemann, U.; Kudella, S.; Weber, M.

    2016-01-01

    In the next generation of collider experiments detectors will be challenged by unprecedented particle fluxes. Thus large detector arrays of highly pixelated detectors with minimal dead area will be required at reasonable costs. Bump-bonding of pixel detectors has been shown to be a major cost-driver. KIT is one of five production centers of the CMS barrel pixel detector for the Phase I Upgrade. In this contribution the SnPb bump-bonding process and the production yield is reported. In parallel to the production of the new CMS pixel detector, several alternatives to the expensive photolithography electroplating/electroless metal deposition technologies are developing. Recent progress and challenges faced in the development of bump-bonding technology based on gold-stud bonding by thin (15 μm) gold wire is presented. This technique allows producing metal bumps with diameters down to 30 μm without using photolithography processes, which are typically required to provide suitable under bump metallization. The short setup time for the bumping process makes gold-stud bump-bonding highly attractive (and affordable) for the flip-chipping of single prototype ICs, which is the main limitation of the current photolithography processes.

  16. Low-cost bump-bonding processes for high energy physics pixel detectors

    International Nuclear Information System (INIS)

    In the next generation of collider experiments detectors will be challenged by unprecedented particle fluxes. Thus large detector arrays of highly pixelated detectors with minimal dead area will be required at reasonable costs. Bump-bonding of pixel detectors has been shown to be a major cost-driver. KIT is one of five production centers of the CMS barrel pixel detector for the Phase I Upgrade. In this contribution the SnPb bump-bonding process and the production yield is reported. In parallel to the production of the new CMS pixel detector, several alternatives to the expensive photolithography electroplating/electroless metal deposition technologies are developing. Recent progress and challenges faced in the development of bump-bonding technology based on gold-stud bonding by thin (15μm) gold wire is presented. This technique allows producing metal bumps with diameters down to 30μm without using photolithography processes, which are typically required to provide suitable under bump metallization. The short setup time for the bumping process makes gold-stud bump-bonding highly attractive (and affordable) for the flip-chipping of single prototype ICs, which is the main limitation of the current photolithography processes

  17. Dissociation and Decay of Ultra-cold Sodium Molecules

    OpenAIRE

    Mukaiyama, T.; Abo-Shaeer, J. R.; Xu, K.; Chin, J. K.; Ketterle, W.

    2003-01-01

    The dissociation of ultracold molecules is studied by ramping an external magnetic field through a Feshbach resonance. The observed dissociation energy shows non-linear dependence on the ramp speed and directly yields the strength of the atom-molecule coupling. In addition, inelastic molecule-molecule and molecule-atom collisions are characterized.

  18. Tubulin bond energies and microtubule biomechanics determined from nanoindentation in silico

    CERN Document Server

    Kononova, Olga; Theisen, Kelly E; Marx, Kenneth A; Dima, Ruxandra I; Ataullakhanov, Fazly I; Grishchuk, Ekaterina L; Barsegov, Valeri

    2015-01-01

    Microtubules, the primary components of the chromosome segregation machinery, are stabilized by longitudinal and lateral non-covalent bonds between the tubulin subunits. However, the thermodynamics of these bonds and the microtubule physico-chemical properties are poorly understood. Here, we explore the biomechanics of microtubule polymers using multiscale computational modeling and nanoindentations in silico of a contiguous microtubule fragment. A close match between the simulated and experimental force-deformation spectra enabled us to correlate the microtubule biomechanics with dynamic structural transitions at the nanoscale. Our mechanical testing revealed that the compressed MT behaves as a system of rigid elements interconnected through a network of lateral and longitudinal elastic bonds. The initial regime of continuous elastic deformation of the microtubule is followed by the transition regime, during which the microtubule lattice undergoes discrete structural changes, which include first the reversib...

  19. Bond Orientational Order, Molecular Motion and Free Energy of High Density DNA Mesophases

    CERN Document Server

    Podgornik, R; Gawrisch, K; Rau, D C; Rupprecht, A; Parsegian, V A

    1995-01-01

    By equilibrating condensed DNA arrays against reservoirs of known osmotic stress and examining them with several structural probes, it has been possible to achieve a detailed thermodynamic and structural characterization of the change between two distinct regions on the liquid crystalline phase digram: a higher-density hexagonally packed region with long-range bond orientational order in the plane perpendicular to the average molecular direction; and a lower-density cholesteric region with fluid-like positional order. X-rays scattering on highly ordered DNA arrays at high density and with the helical axis oriented parallel to the incoming beam showed a six-fold azimuthal modulation of the first order diffraction peak that reflects the macroscopic bond-orientational order. Transition to the less-dense cholesteric phase through osmotically controlled swelling shows the loss of this bond orientational order that had been expected from the change in optical birefringence patterns and that is consistent with a rap...

  20. A theoretical study of CH4 dissociation on pure and gold-alloyed Ni(111) surfaces

    DEFF Research Database (Denmark)

    Kratzer, P.; Hammer, Bjørk; Nørskov, Jens Kehlet

    1996-01-01

    We present a density functional theory study of the first step of CH4 adsorption on the Ni(111) surface, dissociation into adsorbed CH3 and H. The rupture of the C-H bond occurs preferentially on top of a Ni atom, with a dissociation barrier of about 100 kJ/mol (including zero point corrections)....

  1. Hydrogen Attachment/Abstraction Dissociation (HAD) of Gas-Phase Peptide Ions for Tandem Mass Spectrometry.

    Science.gov (United States)

    Takahashi, Hidenori; Sekiya, Sadanori; Nishikaze, Takashi; Kodera, Kei; Iwamoto, Shinichi; Wada, Motoi; Tanaka, Koichi

    2016-04-01

    Dissociation of gas-phase peptide ions through interaction with low-energy hydrogen (H) radical (∼0.15 eV) was observed with a quadrupole ion trap mass spectrometry. The H radical generated by thermal dissociation of H2 molecules passing through a heated tungsten capillary (∼2000 °C) was injected into the ion trap containing target peptide ions. The fragmentation spectrum showed abundant c-/z- and a-/x-type ions, attributable to H attachment/abstraction to/from peptide ion. Because the low-energy neutral H radical initiated the fragmentation, the charge state of the precursor ion was maintained during the dissociation. As a result, precursor ions of any charge state, including singly charged positive and negative ions, could be analyzed for amino acid sequence. The sequence coverage exceeding 90% was obtained for both singly protonated and singly deprotonated substance P peptide. This mass spectrometry also preserved labile post-translational modification bonds. The modification sites of triply phosphorylated peptide (kinase domain of insulin receptor) were identified with the sequence coverage exceeding 80%. PMID:27002918

  2. State-resolved imaging of CO from propenal photodissociation: Signatures of concerted three-body dissociation

    International Nuclear Information System (INIS)

    State-selected DC sliced images of propenal photodissociation show clear signatures of a novel synchronous concerted three-body dissociation of propenal recently proposed by Lee and co-workers to give C2H2 + H2 + CO [S. H. Lee, C. H. Chin, C. Chaudhuri, ChemPhysChem 12, 753 (2011)]. Unlike any prior example of a concerted 3-body dissociation event, this mechanism involves breaking three distinct bonds and yields 3 distinct molecules. DC sliced images of CO fragments were recorded for a range of rotational levels for both v = 0 and v = 1. The results show formation of two distinct CO product channels having dissimilar translational energy distributions with characteristic rovibrational state distributions. The images for CO (v = 0) show a large contribution of slower CO fragments at lower rotational levels (J = 5–25). This slow component is completely absent from the v = 1 CO images. The images for the higher rotational levels of the v = 0 and v = 1 CO are nearly identical, and this provides a basis for decomposing the two channels for v = 0. The quantum state and translational energy distributions for the slow channel are readily assigned to the 3-body dissociation based on the properties of the transition state. The faster CO fragments dominating the higher rotational levels in both v = 0 and v = 1 are attributed to formation of CH3CH + CO, also in agreement with the inferences based on previous non-state-resolved measurements with supporting theoretical calculations

  3. Nucleon-XcJ Dissociation Cross Sections

    Institute of Scientific and Technical Information of China (English)

    冯又层; 许晓明; 周代翠

    2002-01-01

    Nucleon-XcJ dissociation cross sections are calculated in a constituent interexchange model in which quark-quark potential is derived from the Buchmüller-Tye quark-anti-quark potential. These new cross sections for dominant reaction channels depend on the centre-of-mass energy of the nucleon and the charmonium.

  4. Theoretically predicted Fox-7 based new high energy density molecules

    Science.gov (United States)

    Ghanta, Susanta

    2016-08-01

    Computational investigation of CHNO based high energy density molecules (HEDM) are designed with FOX-7 (1, 1-dinitro 2, 2-diamino ethylene) skeleton. We report structures, stability and detonation properties of these new molecules. A systematic analysis is presented for the crystal density, activation energy for nitro to nitrite isomerisation and the C-NO2 bond dissociation energy of these molecules. The Atoms in molecules (AIM) calculations have been performed to interpret the intra-molecular weak H-bonding interactions and the stability of C-NO2 bonds. The structure optimization, frequency and bond dissociation energy calculations have been performed at B3LYP level of theory by using G03 quantum chemistry package. Some of the designed molecules are found to be more promising HEDM than FOX-7 molecule, and are proposed to be candidate for synthetic purpose.

  5. Chemical activation of molecules by metals: Experimental studies of electron distributions and bonding

    International Nuclear Information System (INIS)

    The formal relationship between measured molecular ionization energies and thermodynamic bond dissociation energies has been developed into a single equation which unifies the treatment of covalent bonds, ionic bonds, and partially ionic bonds. This relationship has been used to clarify the fundamental thermodynamic information relating to metal-hydrogen, metal-alkyl, and metal-metal bond energies. We have been able to obtain a direct observation and measurement of the stabilization energy provided by the agostic interaction of the C-H bond with the metal. The ionization energies have also been used to correlate the rates of carbonyl substitution reactions of (η5-C5H4X)Rh(CO)2 complexes, and to reveal the electronic factors that control the stability of the transition state. The extent that the electronic features of these bonding interactions transfer to other chemical systems is being investigated in terms of the principle of additivity of ligand electronic effects. Specific examples under study include metal- phosphines, metal-halides, and metallocenes. Especially interesting has been the recent application of these techniques to the characterization of the soccer-ball shaped C60 molecule, buckminsterfullerene, and its interaction with a metal surface. The high-resolution valence ionizations in the gas phase reveal the high symmetry of the molecule, and studies of thin films of C60 reveal weak intermolecular interactions. Scanning tunneling and atomic force microscopy reveal the arrangement of spherical molecules on gold substrates, with significant delocalization of charge from the metal surface. 21 refs

  6. \\title{Low-Cost Bump-Bonding Processes for High Energy Physics Pixel Detectors}

    CERN Document Server

    Caselle, Michele; Colombo, Fabio; Dierlamm, Alexander Hermann; Husemann, Ulrich; Kudella, Simon; Weber, M

    2015-01-01

    In the next generation of collider experiments detectors will be challenged by unprecedented particle fluxes. Thus large detector arrays of highly pixelated detectors with minimal dead area at reasonable costs are required. Bump-bonding of pixel detectors has been shown to be a major cost-driver. KIT is one of the production centers of the CMS barrel pixel detector for the Phase I Upgrade. In this contribution the SnPb bump-bonding process and the production yield is reported. In parallel to the production of the new CMS pixel detector, several alternatives to the expensive photolithography electroplating/electroless metal deposition technologies are developing. Recent progress and challenges faced in the development of bump-bonding technology based on gold-stud bonding by thin ($15\\,\\rm{\\mu m}$) gold wire is presented. This technique allows producing metal bumps with diameters down to $30\\,\\rm{\\mu m}$ without using photolithography processes, which are typically required to provide suitable under bu...

  7. Performance and Reliability of Bonded Interfaces for High-Temperature Packaging; NREL (National Renewable Energy Laboratory)

    Energy Technology Data Exchange (ETDEWEB)

    DeVoto, Douglas

    2015-06-10

    This is a technical review of the DOE VTO EDT project EDT063, Performance and Reliability of Bonded Interfaces for High-Temperature Packaging. A procedure for analyzing the reliability of sintered-silver through experimental thermal cycling and crack propagation modeling has been outlined and results have been presented.

  8. Polarization induced water molecule dissociation below the first-order electronic-phase transition temperature

    CERN Document Server

    Arulsamy, Andrew Das; Elersic, Kristina; Modic, Martina; Subramani, Uma Shankar

    2011-01-01

    Hydrogen produced from the photocatalytic splitting of water is one of the reliable alternatives to replace the polluting fossil and the radioactive nuclear fuels. Here, we provide unequivocal evidence for the existence of blue- and red-shifting O$-$H covalent bonds within a single water molecule adsorbed on MgO surface as a result of asymmetric displacement polarizabilities. The adsorbed H-O-H on MgO gives rise to one weaker H-O bond, while the other O-H covalent bond from the same adsorbed water molecule compensates this effect with a stronger bond. The weaker bond (nearest to the surface), the interlayer tunneling electrons and the silver substrate are shown to be the causes for the smallest dissociative activation energy on MgO monolayer. The origin that is responsible to initiate the splitting mechanism is proven to be due to the changes in the polarizability of an adsorbed water molecule, which are further supported by the temperature-dependent static dielectric constant measurements for water below the...

  9. Spectroscopically determined force field for water dimer: physically enhanced treatment of hydrogen bonding in molecular mechanics energy functions.

    Science.gov (United States)

    Mannfors, Berit; Palmo, Kim; Krimm, Samuel

    2008-12-11

    Our ab initio transformed spectroscopically determined force field (SDFF) methodology emphasizes, in addition to accurate structure and energy performance, comparable prediction of vibrational properties in order to improve reproduction of interaction forces. It is now applied to the determination of a molecular mechanics (MM) force field for the water monomer and dimer as an initial step in developing a more physically based treatment of the hydrogen bonding that not only underlies condensed-phase water but also must be important in molecular-level protein-water interactions. Essential electrical components of the SDFF for monomer water are found to be the following: an off-plane charge distribution, this distribution consisting of four off-atom charge sites in traditional lone pair (LP) but also in inverted lone pair (ILP) positions; allowance for a diffuse size to these off-atom sites; and the incorporation of charge fluxes (i.e., the change in charge with change in internal coordinate). Parametrization of such an LP/ILP model together with the SDFF analytically transformed valence force field results in essentially exact agreement with ab initio (in this case MP2/6-31++G(d,p)) structure, electrical, and vibrational properties. Although we demonstrate that the properties of this monomer electrical model together with its van der Waals and polarization interactions are transferable to the dimer, this is not sufficient in reproducing comparable dimer properties, most notably the huge increase in infrared intensity of a donor OH stretch mode. This deficiency, which can be eliminated by a large dipole-derivative-determined change in the effective charge flux of the donor hydrogen-bonded OH bond, is not accounted for by the charge flux change in this bond due to the induction effects of the acceptor electric field alone, and can only be fully removed by an added bond flux associated with the extent of overlap of the wave functions of the two molecules. We show that

  10. Sexuality of dissocial persons

    OpenAIRE

    Marta Janus; Agata Szulc

    2016-01-01

    Introduction. The development of personality disorders as well as sexual disorders is defined by the common time spectrum as well as deficits and changes in such areas as biological, environmental and mental area. Dissocial (antisocial) personality disorder is characterised by a pervasive pattern of disregard for, or violation of, the rights of others. The indices of the discussed disorder can be found in specific patterns of social inadequacy occurring during childhood and puberty. At the sa...

  11. Exploring the Nature of Silicon-Noble Gas Bonds in H3SiNgNSi and HSiNgNSi Compounds (Ng = Xe, Rn

    Directory of Open Access Journals (Sweden)

    Sudip Pan

    2015-03-01

    Full Text Available Ab initio and density functional theory-based computations are performed to investigate the structure and stability of H3SiNgNSi and HSiNgNSi compounds (Ng = Xe, Rn. They are thermochemically unstable with respect to the dissociation channel producing Ng and H3SiNSi or HSiNSi. However, they are kinetically stable with respect to this dissociation channel having activation free energy barriers of 19.3 and 23.3 kcal/mol for H3SiXeNSi and H3SiRnNSi, respectively, and 9.2 and 12.8 kcal/mol for HSiXeNSi and HSiRnNSi, respectively. The rest of the possible dissociation channels are endergonic in nature at room temperature for Rn analogues. However, one three-body dissociation channel for H3SiXeNSi and one two-body and one three-body dissociation channels for HSiXeNSi are slightly exergonic in nature at room temperature. They become endergonic at slightly lower temperature. The nature of bonding between Ng and Si/N is analyzed by natural bond order, electron density and energy decomposition analyses. Natural population analysis indicates that they could be best represented as (H3SiNg+(NSi− and (HSiNg+(NSi−. Energy decomposition analysis further reveals that the contribution from the orbital term (ΔEorb is dominant (ca. 67%–75% towards the total attraction energy associated with the Si-Ng bond, whereas the electrostatic term (ΔEelstat contributes the maximum (ca. 66%–68% for the same in the Ng–N bond, implying the covalent nature of the former bond and the ionic nature of the latter.

  12. Dissociative electron attachment to gas-phase 5-bromouracil

    Science.gov (United States)

    Abdoul-Carime, H.; Huels, M. A.; Brüning, F.; Illenberger, E.; Sanche, L.

    2000-08-01

    We report measurements of dissociative electron attachment (DEA) to gaseous 5-bromouracil (BrU) for incident electron energies between 0 and 16 eV. Low energy electron impact on BrU leads not only to the formation of a long lived parent anion BrU-, but also various anion fragments resulting from endo- and exo-cyclic bond ruptures, such as Br-, uracil-yl anions, i.e., (U-yl)-, OCN-, and a 68 amu anion tentatively attributed to H2C3NO-. The incident electron energy dependent signatures of either the Br- and (U-yl)- yields (at 0, 1.4, and 6 eV), or the OCN- and H2C3NO- yields (at 1.6 and 5.0 eV) suggests competing DEA channels for anion fragment formation. The production cross sections, at 0 eV incident electron energy, for BrU-, Br-, and (U-yl)- are estimated to be about 6×10-15, 6×10-14, and 1.0×10-15 cm2, respectively.

  13. Combined Infrared Multiphoton Dissociation with Ultraviolet Photodissociation for Ubiquitin Characterization

    Science.gov (United States)

    Halim, Mohammad A.; Girod, Marion; MacAleese, Luke; Lemoine, Jérôme; Antoine, Rodolphe; Dugourd, Philippe

    2016-06-01

    Herein we report the successful implementation of the consecutive and simultaneous photodissociation with high (213 nm) and low (10.6 μm) energy photons (HiLoPD, high-low photodissociation) on ubiquitin in a quadrupole-Orbitrap mass spectrometer. Absorption of high-energy UV photon is dispersed over the whole protein and stimulates extensive C-Cα backbone fragmentation, whereas low-energy IR photon gradually increases the internal energy and thus preferentially dissociates the most labile amide (C-N) bonds. We noticed that simultaneous irradiation of UV and IR lasers on intact ubiquitin in a single MS/MS experiment provides a rich and well-balanced fragmentation array of a/x, b/y, and z ions. Moreover, secondary fragmentation from a/x and z ions leads to the formation of satellite side-chain ions (d, v, and w) and can help to distinguish isomeric residues in a protein. Implementation of high-low photodissociation in a high-resolution mass spectrometer may offer considerable benefits to promote a comprehensive portrait of protein characterization.

  14. Structure and bonding of [(SIPr)AgX] (X = Cl, Br, I and OTf).

    Science.gov (United States)

    Wong, Valerie H L; White, Andrew J P; Hor, T S Andy; Hii, King Kuok Mimi

    2015-12-28

    A series of iso-structural complexes [(SIPr)AgX] (X = Cl, Br, I, OTf; SIPr = 1,3-bis(2,6-diisopropylphenyl)imidazolidene) were synthesised, including the first example of a N-heterocyclic carbene silver(I) complex containing an O-bound triflate. Bond Energy Dissociation and Natural Orbitals for Chemical Valence bond analyses (BEDA & ETS-NOCV) revealing a significant NHC → M σ-back-donation, which influences the stability and sigma-donicity of these complexes. PMID:26489888

  15. Bond Orientational Order, Molecular Motion and Free Energy of High Density DNA Mesophases

    OpenAIRE

    Podgornik, R.; Strey, H. H.; Gawrisch, K.; Rau, D C; Rupprecht, A; Parsegian, V. A.

    1995-01-01

    By equilibrating condensed DNA arrays against reservoirs of known osmotic stress and examining them with several structural probes, it has been possible to achieve a detailed thermodynamic and structural characterization of the change between two distinct regions on the liquid-crystalline phase diagram: (i) a higher density hexagonally packed region with long-range bond orientational order in the plane perpendicular to the average molecular direction and (ii) a lower density cholesteric regio...

  16. A molecular-beam study of the dissociative chemisorption of O2 on Ir(110)-(1×2)

    OpenAIRE

    Mullins, C B; Wang, Y.; Weinberg, W. H.

    1989-01-01

    The zero-coverage probability of dissociative chemisorption of O2 on Ir(110)-(1×2) has been measured using molecular-beam techniques for a wide range of incident kinetic energies, incident angles, and surface temperatures. The data indicate that a trapping-mediated mechanism is responsible for dissociative chemisorption at low energies, whereas at high energies a direct mechanism accounts for dissociative adsorption. Total energy scaling approximately describes the dissociative dynamics on th...

  17. Energy transport mechanism in the form of proton soliton in a one-dimensional hydrogen-bonded polypeptide chain.

    Science.gov (United States)

    Kavitha, L; Priya, R; Ayyappan, N; Gopi, D; Jayanthi, S

    2016-01-01

    The dynamics of protons in a one-dimensional hydrogen-bonded (HB) polypeptide chain (PC) is investigated theoretically. A new Hamiltonian is formulated with the inclusion of higher-order molecular interactions between peptide groups (PGs). The wave function of the excitation state of a single particle is replaced by a new wave function of a two-quanta quasi-coherent state. The dynamics is governed by a higher-order nonlinear Schrödinger equation and the energy transport is performed by the proton soliton. A nonlinear multiple-scale perturbation analysis has been performed and the evolution of soliton parameters such as velocity and amplitude is explored numerically. The proton soliton is thermally stable and very robust against these perturbations. The energy transport by the proton soliton is more appropriate to understand the mechanism of energy transfer in biological processes such as muscle contraction, DNA replication, and neuro-electric pulse transfer on biomembranes. PMID:26198375

  18. CO dissociation on Ni: The effect of steps and of nickel carbonyl

    DEFF Research Database (Denmark)

    Engbæk, Jakob; Lytken, Ole; Nielsen, Jane Hvolbæk;

    2008-01-01

    The dissociation of CO was investigated on a stepped Ni(141313) crystal. The experiments show that the monoatomic steps completely dominate the dissociation of CO on the nickel surface. The activation energy for dissociation of CO along the steps is measured at 500 K to be 150 kJ/mol in the press...

  19. Theory of dissociative tunneling ionization

    CERN Document Server

    Svensmark, Jens; Madsen, Lars Bojer

    2016-01-01

    We present a theoretical study of the dissociative tunneling ionization process. Analytic expressions for the nuclear kinetic energy distribution of the ionization rates are derived. A particularly simple expression for the spectrum is found by using the Born-Oppenheimer (BO) approximation in conjunction with the reflection principle. These spectra are compared to exact non-BO ab initio spectra obtained through model calculations with a quantum mechanical treatment of both the electronic and nuclear degrees freedom. In the regime where the BO approximation is applicable imaging of the BO nuclear wave function is demonstrated to be possible through reverse use of the reflection principle, when accounting appropriately for the electronic ionization rate. A qualitative difference between the exact and BO wave functions in the asymptotic region of large electronic distances is shown. Additionally the behavior of the wave function across the turning line is seen to be reminiscent of light refraction. For weak fiel...

  20. Ionisation and dissociation of water induced by swift multicharged ions; Etude de l'ionisation et de la dissociation d'H{sub 2}O induites par collision avec des ions multicharges rapides

    Energy Technology Data Exchange (ETDEWEB)

    Legendre, S

    2006-02-15

    Ionization and dissociation of water molecules and water clusters induced by 11.7 MeV/A Ni{sup 25+} ions were carried out by imaging techniques. Branching ratios, ionisation cross sections and Kinetic Energy Released distributions have been measured together with fragmentation dynamics studies. Multiple ionization represents approximately 30% of the ionizing events. Double ionization produces in significant way atomic oxygen, considered as a possible precursor of the large production of HO{sub 2} radical in liquid water radiolysis by ions of high Linear Energy Transfer. We evidence a strong selectivity of bond breakage in the case of ion-induced HOD fragmentation. Once the molecule doubly ionized, the breakage of the O-H bond is found 6.5 times more probable than that of the O-D bond. A semi-classical calculation simulating the fragmentation dynamics on the potential energy surface of the ground-state of di-cation H{sub 2}O{sup 2+} makes possible to as well reproduce the preferential nature of the breakage of the O-H bond as the position and the shift of the kinetic energy distributions. First results concerning interaction with water clusters are also reported. Measurements in coincidence are carried out giving access to correlation, with the distributions in energy and angle of the emitted fragments. Mass spectrum points fast intra-cluster proton transfer, leading to the emission of protonated clusters. (author)

  1. A first principle study for the adsorption and absorption of carbon atom and the CO dissociation on Ir(100) surface

    Energy Technology Data Exchange (ETDEWEB)

    Erikat, I. A., E-mail: ihsanas@yahoo.com [Department of Physics, Jerash University, Jerash-26150 (Jordan); Hamad, B. A. [Department of Physics, The University of Jordan, Amman-11942 (Jordan)

    2013-11-07

    We employ density functional theory to examine the adsorption and absorption of carbon atom as well as the dissociation of carbon monoxide on Ir(100) surface. We find that carbon atoms bind strongly with Ir(100) surface and prefer the high coordination hollow site for all coverages. In the case of 0.75 ML coverage of carbon, we obtain a bridging metal structure due to the balance between Ir–C and Ir–Ir interactions. In the subsurface region, the carbon atom prefers the octahedral site of Ir(100) surface. We find large diffusion barrier for carbon atom into Ir(100) surface (2.70 eV) due to the strong bonding between carbon atom and Ir(100) surface, whereas we find a very small segregation barrier (0.22 eV) from subsurface to the surface. The minimum energy path and energy barrier for the dissociation of CO on Ir(100) surface are obtained by using climbing image nudge elastic band. The energy barrier of CO dissociation on Ir(100) surface is found to be 3.01 eV, which is appreciably larger than the association energy (1.61 eV) of this molecule.

  2. A first principle study for the adsorption and absorption of carbon atom and the CO dissociation on Ir(100) surface

    International Nuclear Information System (INIS)

    We employ density functional theory to examine the adsorption and absorption of carbon atom as well as the dissociation of carbon monoxide on Ir(100) surface. We find that carbon atoms bind strongly with Ir(100) surface and prefer the high coordination hollow site for all coverages. In the case of 0.75 ML coverage of carbon, we obtain a bridging metal structure due to the balance between Ir–C and Ir–Ir interactions. In the subsurface region, the carbon atom prefers the octahedral site of Ir(100) surface. We find large diffusion barrier for carbon atom into Ir(100) surface (2.70 eV) due to the strong bonding between carbon atom and Ir(100) surface, whereas we find a very small segregation barrier (0.22 eV) from subsurface to the surface. The minimum energy path and energy barrier for the dissociation of CO on Ir(100) surface are obtained by using climbing image nudge elastic band. The energy barrier of CO dissociation on Ir(100) surface is found to be 3.01 eV, which is appreciably larger than the association energy (1.61 eV) of this molecule

  3. A first principle study for the adsorption and absorption of carbon atom and the CO dissociation on Ir(100) surface

    Science.gov (United States)

    Erikat, I. A.; Hamad, B. A.

    2013-11-01

    We employ density functional theory to examine the adsorption and absorption of carbon atom as well as the dissociation of carbon monoxide on Ir(100) surface. We find that carbon atoms bind strongly with Ir(100) surface and prefer the high coordination hollow site for all coverages. In the case of 0.75 ML coverage of carbon, we obtain a bridging metal structure due to the balance between Ir-C and Ir-Ir interactions. In the subsurface region, the carbon atom prefers the octahedral site of Ir(100) surface. We find large diffusion barrier for carbon atom into Ir(100) surface (2.70 eV) due to the strong bonding between carbon atom and Ir(100) surface, whereas we find a very small segregation barrier (0.22 eV) from subsurface to the surface. The minimum energy path and energy barrier for the dissociation of CO on Ir(100) surface are obtained by using climbing image nudge elastic band. The energy barrier of CO dissociation on Ir(100) surface is found to be 3.01 eV, which is appreciably larger than the association energy (1.61 eV) of this molecule.

  4. The Reaction of Dissociative Recombination in a Strong Light Field

    International Nuclear Information System (INIS)

    The DR theory of slow electrons with molecular ions in strong monochromatic light field is developed. The potential energy curves of the oxygen molecule O2** dissociative states are calculated. Classification of all possible transitions and reaction mechanisms are presented.

  5. Performance of a Nonempirical Density Functional on Molecules and Hydrogen-Bonded Complexes

    CERN Document Server

    Mo, Yuxiang; Car, Roberto; Staroverov, Viktor N; Scuseria, Gustavo E; Tao, Jianmin

    2016-01-01

    Recently, Tao and Mo (TM) derived a new meta-generalized gradient approximation based on a model exchange hole. In this work, the performance of this functional is assessed on standard test sets, using the 6-311++G(3df,3pd) basis set. These test sets include 223 G3/99 enthalpies of formation, 58 electron affinities, 8 proton affinities, 96 bond lengths, 82 harmonic vibrational frequencies, and 10 hydrogen-bonded molecular complexes. Our calculations show that the TM functional can achieve remarkable accuracy for most molecular properties, improving upon non-empirical density functionals considered here. In particular, it delivers the best accuracy for proton affinities, harmonic vibrational frequencies, and hydrogen-bonded dissociation energies and bond lengths, compared to other semilocal density-functional approximations considered in this work.

  6. Inverse Ubbelohde effect in the short hydrogen bond of photosystem II: Relation between H/D isotope effect and symmetry in potential energy profile.

    Science.gov (United States)

    Kanematsu, Yusuke; Tachikawa, Masanori; Takano, Yu

    2016-09-01

    The short hydrogen bond between tyrosine Yz and D1-His190 of photosystem II (PSII) was investigated using multicomponent quantum mechanics, where the quantum fluctuation of a hydrogen nucleus was incorporated into electronic structure calculation. Our computation demonstrated that the deuteration for hydrogen in the short hydrogen bond of PSII led to the reduction of the O…N distance. It indicated an inverse Ubbelohde effect typically recognized in strong and symmetric hydrogen-bonding clusters such as FHF(-) and H3O2-. We confirmed that the relation between the geometric isotope effect and the symmetry of the potential energy profile of FHF(-) was reasonably agreed with that of PSII. According to this agreement, the short hydrogen bond in PSII can be regarded as a short strong hydrogen bond. © 2016 Wiley Periodicals, Inc. PMID:27349328

  7. Multiphoton dissociative ionization of molecular deuterium

    International Nuclear Information System (INIS)

    The kinetic energy spectra of deuterium ions produced from D2 arising from collision-free subpicosecond irradiation at 248 nm with intensities spanning the 10/sup 13/--10/sup 16/-W/cm2 range have been measured by time-of-flight analysis. The behaviors of the kinetic energy distributions of the fragments and the relative abundances of atomic (D+) and molecular (D2+) ions reveal the presence of two mechanisms of multiphoton dissociative ionization. Calibration of the energy scale for D+ is facilitated by comparison with He/sup 2+/. For intensities in the 10/sup 13/--10/sup 15/-W/cm2 region, intermediate three-photon resonances and the optical Stark shift play important roles. At an intensity /similar to/0/sup 16/ W/cm2, a direct transition from the molecular ground state to the dissociative ionic level appears as a significant channel. No evidence of direct double ionization was observed

  8. IV. Dissociative recombination of electrons and molecular ions

    International Nuclear Information System (INIS)

    The present state of the theory of the dissociative recombination of electrons and molecular ions is reviewed and its shortcomings shown. The mechanisms of direct and indirect dissociative processes are described. Several approximative methods employing the analogy with the recombination of atomic ions and electrons are used for the determination of the dissociative recombination factor. Analyzing the derived formulae the temperature dependence of the dissociative recombination factor is determined and the results are compared with experimental data obtained by several authors. The energy levels of atoms created at the dissociative recombination of He2+, Ar2+, and O2+ ions are described. Methods of measuring the recombination factor are listed. The existing experimental data are summarized and the possible explanation of the observed variations is presented. An exhaustive list of references is given. (J.U.)

  9. Dissociative recombination of N2H+

    Science.gov (United States)

    dos Santos, S. Fonseca; Ngassam, V.; Orel, A. E.; Larson, Å.

    2016-08-01

    The direct and indirect mechanisms of dissociative recombination of N2H+ are theoretically studied. At low energies, the electron capture is found to be driven by recombination into bound Rydberg states, while at collision energies above 0.1 eV, the direct capture and dissociation along electronic resonant states becomes important. Electron-scattering calculations using the complex Kohn variational method are performed to obtain the scattering matrix as well as energy positions and autoionization widths of resonant states. Potential-energy surfaces of electronic bound states of N2H and N2H+ are computed using structure calculations with the multireference configuration interaction method. The cross section for the indirect mechanism is calculated using a vibrational frame transformation of the elements of the scattering matrix at energies just above the ionization threshold. Here vibrational excitations of the ionic core from v =0 to v =1 and v =2 for all three normal modes are considered and autoionization is neglected. The cross section for the direct dissociation along electronic resonant states is computed with wave-packet calculations using the multiconfiguration time-dependent Hartree method, where all three internal degrees of freedom are considered. The calculated cross sections are compared to measurements.

  10. 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.

  11. Dissociation of deep-core-excited CH{sub 3}Cl

    Energy Technology Data Exchange (ETDEWEB)

    Hansen, D.L.; Martin, R.; Vanderford, B. [Univ. of Nevada, Las Vegas, NV (United States)] [and others

    1997-04-01

    Using x-rays from B.L. 9.3.1, a space-focused time-of-flight (TOF) was used to study photofragmentation of CH{sub 3}Cl following excitation in the neighborhood of the Cl K-shell threshold ({approximately} 2.8 keV). Multi-ion coincidence measurements were used to search for selective dissociation of specific bonds in the molecule. Such selectivity has been observed for excitation near outer-core-level thresholds (e.g., Cl 2p), but this is the first study in deep core levels, where very-short core-hole lifetimes and Auger cascade effects may influence fragmentation. Both high-resolution time-of-flight spectroscopy and multi-coincidence photoelectron-photoion-photoion (PE-PIPICO), as well as photoelectron-photoion-photoion-photoion (PE3PICO) measurements were performed. Dramatic changes in the line shapes for different fragment ions are observed as a function of the excitation energy, and are attributed to selective dissociation of the CH{sub 3}Cl molecule along the C-Cl bond. In addition, pronounced angular distributions of the ejected ions are observed on resonance.

  12. Dissociative adsorption of molecular deuterium on polycrystalline diamond films activated by medium surface temperature

    International Nuclear Information System (INIS)

    In this work we report on an investigation of thermally induced dissociative adsorption of molecular deuterium onto hydrogenated and bare polycrystalline diamond film surfaces studied by high resolution electron energy loss spectroscopy (HR-EELS). Hydrogenated diamond films (grown from CH4 and H2 gases) were heated at various temperatures in molecular D2 ambient at 5 x 10-6 Torr and then studied by HR-EELS. This study clearly shows the formation of C-D bonding on hydrogenated polycrystalline diamond surface and gradual disappearance of C-H mode as a function of annealing temperature. The C-D bonding configurations and thermal stability of adsorbed deuterium resulting from dissociate adsorption were compared to those occurring on deuterated diamond films (grown from CD4 and D2 gases). We report and assign at least three contributions to C-D stretching HR-EELS mode associated to (111), (100) crystallographic orientations as well as grain boundary associated vibrations in accordance with similar vibrations of C-H stretching vibrations, reported previously. (copyright 2014 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)

  13. The three-electron bond =Si2:·Yb absorption center of pre-darkened ytterbium-doped silica

    DEFF Research Database (Denmark)

    Mattsson, Kent Erik

    2013-01-01

    The formation and bleaching of color centers during annealing of pre-darkened ytterbium-doped silica fibers is modeled by three-electron bond (TEB) = Sidissociation of chemical...... bonds is described in terms of a Markov statistical model with state change set by Bose-Einstein phonon statistics. The center hold one terminal and four active states with activation energies for transitions among these found to match bond energies of molecular oxygen in ionic character bonds of 1 and...... 1½ bond order. Experimentally observed in- and decrease in absorption during ramp and isothermal annealing of pre-darkened ytterbium co-doped silica fibers are hereby matched by a set of = Si

  14. Dependência das vias de dissociação unimolecular com a energia interna da molécula de éter dimetílico Internal energy dependence of the unimolecular dissociation channels of dimethyl ether

    Directory of Open Access Journals (Sweden)

    Rodrigo Peres

    2004-02-01

    Full Text Available Internal energy dependence of the competitive unimolecular dissociation channels of dimethyl ether were studied with the statistical RRKM formalism. The C-O and C-H fission reactions and the 1,2-H and 1,3-H shifts, and 1,1-H2 and 1,3-H2 molecular eliminations are discussed as a function of energy dependence of k a(E*, the microcanonical rate constant for production of transition states. C-O fission is the dominant process while reaction channels involving C-H fission, 1,1-H2 and 1,3-H2 elimination and production of MeOH should be competitive at energies around 400 kJ mol-1. The less favorable process is the channel of CH4 formation.

  15. Data on ionization, excitation, dissociation and dissociative ionization of targets by helium ion bombardments, (1)

    International Nuclear Information System (INIS)

    This report presents a compilation of the experimental data on cross sections for the ionization, excitation, dissociation and dissociative ionization processes of targets in helium ion impacts on atoms and molecules under a single collision condition. These measurements were carried out in the energy range from several keV to 3.5 MeV. A systematic survey has been made on the literatures from 1975 to the end of 1982. A list of references is also given, including relevant papers published before 1975. (author)

  16. Characterization of oligodeoxynucleotides by electron detachment dissociation fourier transform ion cyclotron resonance mass spectrometry.

    Science.gov (United States)

    Yang, Jiong; Mo, Jingjie; Adamson, Julie T; Håkansson, Kristina

    2005-03-15

    Electron detachment dissociation (EDD), recently introduced by Zubarev and co-workers for the dissociation of multiply charged biomolecular anions via a radical ion intermediate, has been shown to be analogous to electron capture dissociation (ECD) in several respects, including more random peptide fragmentation and retention of labile posttranslational modifications. We have previously demonstrated unique fragmentation behavior in ECD compared to vibrational excitation for oligodeoxynucleotide cations. However, that approach is limited by the poor sensitivity for oligonucleotide ionization in positive ion mode. Here, we show implementation of EDD on a commercial Fourier transform ion cyclotron resonance mass spectrometer utilizing two different configurations: a heated filament electron source and an indirectly heated hollow dispenser cathode electron source. The dispenser cathode configuration provides higher EDD efficiency and additional fragmentation channels for hexamer oligodeoxynucleotides. As in ECD, even-electron d/w ion series dominate the spectra, but we also detect numerous a/z (both even-electron and radical species), (a/z - B), c/x, (c/x - B), and (d/w - B) ions with minimal nucleobase loss from the precursor ions. In contrast to previous high-energy collision-activated dissociation (CAD) and ion trap CAD of radical oligonucleotide anions, we only observe minimum sugar cross-ring cleavage, possibly due to the short time scale of EDD, which limits secondary fragmentation. Thus, EDD provides fragmentation similar to ECD for oligodeoxynucleotides but at enhanced sensitivity. Finally, we show that noncovalent bonding in a DNA duplex can be preserved following EDD, illustrating another analogy with ECD. We believe the latter finding implies EDD has promise for characterization of nucleic acid structure and folding. PMID:15762599

  17. Probing Electron-Induced Bond Cleavage at the Single-Molecule Level Using DNA Origami Templates

    DEFF Research Database (Denmark)

    Keller, Adrian Clemens; Bald, Ilko; Rotaru, Alexandru;

    2012-01-01

    nucleobases. Here we present a strategy that allows for the first time to visualize the electron-induced dissociation of single chemical bonds within complex, but well-defined self-assembled DNA nanostructures. We employ atomic force microscopy to image and quantify LEE-induced bond dissociations within...... chromatin, now becomes feasible....

  18. Dissociation dynamics of fast neutral molecules scattered under glancing incidence conditions from crystal surfaces

    Science.gov (United States)

    Snowdon, K. J.; Harder, R.; Nesbitt, A.

    1996-08-01

    When fast ( vthermal ≪ v dissolution of the intra-molecular bond, the difference in the surface normal momentum transfer to the two unbound atoms considerably exceeds the difference in the surface parallel momentum transfer. We investigate these two possibilities within a classical simulation of energy transfer from the translational to internal degrees of freedom of the molecule via repeated transitions between different electronic states of the molecule-surface system. These simulations suggest that in general, the observed surface-normal aligned final orientation of dissociatively scattered molecules is caused by strong vibrational excitation in the entrance channel region of the adiabatic ground state potential energy surface describing the interaction of the neutral molecule with the surface.

  19. Proton angular distribution following multiphoton dissociative ionization of H2

    International Nuclear Information System (INIS)

    The angular distribution of protons ejected following resonant (2+1)-photon dissociative ionization of H2 by 193-nm radiation through the E,F state has been obtained. The analysis shows that the Π character of the degenerate continuum states is approximately eight times larger than the Σ character, which is consistent with previous single-photon measurements. The analysis presented here, together with a previous analysis of the proton energy distribution, reveals the ionization channel to be significantly stronger than both the dissociation and dissociative ionization channels

  20. A periodic Energy Decomposition Analysis (pEDA) method for the Investigation of Chemical Bonding in Extended Systems

    CERN Document Server

    Raupach, Marc

    2015-01-01

    The development and first applications of a new periodic energy decomposition analysis (pEDA) scheme for extended systems based on the Kohn-Sham approach to density functional theory are described. The pEDA decomposes the binding energy between two fragments (e.g. the adsorption energy of a molecule on a surface) into several well-defined terms: preparation, electrostatic and dispersion interaction, Pauli repulsion and orbital relaxation energies. The pEDA presented here for an AO-based implementation can handle restricted and unrestricted fragments for 0D to 3D systems considering periodic boundary conditions with and without the determination of fragment occupations. For the latter case, reciprocal space sampling is enabled. The new method gives comparable results to established schemes for molecular systems and shows good convergence with respect to the basis set (TZ2P), the integration accuracy and k-space sampling. Four typical bonding scenarios for surface adsorbate complexes were chosen to highlight th...

  1. Benchmarking ab initio binding energies of hydrogen-bonded molecular clusters based on FTIR spectroscopy

    DEFF Research Database (Denmark)

    Bork, Nicolai Christian; Du, Lin; Reiman, Heidi;

    2014-01-01

    Gibbs free binding energies in molecular complexes and clusters based on gas phase FTIR spectroscopy. The acetonitrile-HCl molecular complex is identified via its redshifted H-Cl stretching vibrational mode. We determine the Gibbs free binding energy, ΔG°295 K, to between 4.8 and 7.9 kJ mol(-1) and......Models of formation and growth of atmospheric aerosols are highly dependent on accurate cluster binding energies. These are most often calculated by ab initio electronic structure methods but remain associated with significant uncertainties. We present a computational benchmarking study of the...

  2. Unusual dissociative adsorption of H2 over stoichiometric MgO thin film supported on molybdenum

    Science.gov (United States)

    Song, Zhenjun; Xu, Hu

    2016-03-01

    The dissociation of a hydrogen molecule on perfect MgO(0 0 1) films deposited on Mo(0 0 1) surface is investigated systematically using periodic density-functional theory (DFT) method. The unusual adsorption behavior of heterolytic dissociative hydrogen molecule at neighboring surface oxygen and surface magnesium, is clarified here. To our knowledge, this heterolytic dissociative state has never been found before on bulk MgO(0 0 1) or metal supported perfect MgO(0 0 1) surfaces (without low coordination sites). The results confirm that, in all cases, the heterolytic dissociation is much more favorable that homolytic dissociation both energetically and kinetically. The energy differences between two dissociative states are very large, in the range of 1.1 eV-1.5 eV for Mo supported 1 ML-3 ML oxide films, which inhibits, to a great extent, the homolytic dissociation in the respect of reaction thermodynamics. The energy barriers of heterolytic dissociation are about 0.5 eV, much lower that the barrier of homolytic dissociation. The transformation reaction on thick films will be more endothermic. Passing through heterolytic dissociation state has significantly lowered the reaction heat and the energy barrier for obtaining homolytic dissociative structure, which makes the homolytic splitting of H2 easier on 2 ML oxide films. The results provide a useful strategy for enhancing the reactivity of the nonreducible metal oxide.

  3. Communication: Enhanced dissociative chemisorption of CO2 via vibrational excitation

    Science.gov (United States)

    Jiang, Bin; Guo, Hua

    2016-03-01

    A fully coupled global nine-dimensional potential energy surface for the dissociative chemisorption of CO2 on Ni(100) is constructed from ˜18 000 density functional points. It reveals a complex reaction pathway dominated by two near iso-energetic transition states. The dissociation probabilities obtained by quasi-classical trajectories on the potential energy surface reproduced experimental trends, and indicate that vibrational excitations of CO2 significantly promote the dissociation. Using the sudden vector projection model, the behavior of the reactivity is rationalized by couplings with the reaction coordinate at each transition state. These results offer plausible rationalization for the observed enhancement of CO2 dissociation in non-thermal plasmas by metal surfaces.

  4. Bonding in Mercury Molecules Described by the Normalized Elimination of the Small Component and Coupled Cluster Theory

    OpenAIRE

    Cremer, Dieter; Kraka, Elfi; Filatov, Michael

    2008-01-01

    Bond dissociation energies (BDEs) of neutral HgX and cationic HgX(+) molecules range from less than a kcal mol(-1) to as much as 60 kcal mol(-1). Using NESCICCCSD(T) [normalized elimination of the small component and coupled-cluster theory with all single and double excitations and a perturbative treatment of the triple excitations] in combination with triple-zeta basis sets, bonding in 28 mercury molecules HgX (X=H, Li, Na, K, Rb, CH(3), SiH(3), GeH(3), SnH(3), NH(2), PH(2), AsH(2), SbH(2), ...

  5. Simulation investigations in the binding energy and mechanical properties of HMX-based polymer-bonded explosives

    Institute of Scientific and Technical Information of China (English)

    XIAO Jijun; FANG Guoyong; JI Guangfu; XIAO Heming

    2005-01-01

    The molecular simulations of the well-known high explosive β-HMX (cyclotetramethylene tetranitramine) and its fluorine containing polymer-bonded explosives (PBXs) were carried out with the combination method of quantum mechanics, molecular mechanics and molecular dynamics. The atomic cluster model, containing the β-HMX molecule and the polymer molecule whose chain dimension was about the same as β-HMX's, was fully optimized by AM1 and PM3 semi-empirical molecular orbital and molecular mechanical methods using COMPASS and PCFF force field. Then the calculated binding energy is found to be linearly correlated to each other. Molecular dynamics simulations using COMPASS force field were performed for β-HMX crystal and the PBXs involving β-HMX and a series of fluorine containing polymers. Their elastic coefficients, moduli and Poisson's ratios were calculated. It is found that the mechanical properties of β-HMX can be effectively improved by blending with fluorine containing polymers in small amounts.

  6. Three-particle dissociation of D{sub 3} and H{sub 3} (2sa'{sub 1}): energies and momentum correlation maps for selected rovibrational levels

    Energy Technology Data Exchange (ETDEWEB)

    Lehner, M; Jungen, M [Institut fuer Physikalische Chemie, Universitaet Basel, Klingelbergstrasse 80, CH-4056 Basel (Switzerland)], E-mail: martin.jungen@unibas.ch

    2009-03-28

    The short-lived 3{sup 2}A'(2sa'{sub 1}) electronic state of the molecules D{sub 3} and H{sub 3} is studied. First we present variational results for the rovibrational energy levels up to about 10 000 cm{sup -1}, based on a recent potential energy surface and using a program adapted to the D{sub 3h} symmetry point group. Three-particle fragmentation caused by non-adiabatic coupling to the dissociative ground state has been investigated by calculating diabatization angle functions and applying the semiclassical trajectory surface-hopping technique. For comparison with experiments we have constructed state resolved theoretical momentum correlation maps (Dalitz plots) for a few low-lying rovibrational levels.

  7. The infrared multiphoton dissociation of three nitrolkanes

    Science.gov (United States)

    Wodtke, A. M.; Hintsa, E. J.; Lee, Y. T.

    1986-01-01

    Infrared multiphoton dissociation in a molecular beam has been studied in order to elucidate the collision free, 'thermal' chemistry and dynamics of nitromethane, nitroethane and 2-nitropropane. The isomerization of CH3NO2 to CH3ONO was observed by detecting the CH3O and NO products from the dissociation of the very internally hot, isomerized nitromethane. A novel application of RRKM theory was used to estimate the barrier height to isomerization at 55.5 kcal/mol. The barrier height determination method was tested and found to give excellent results by applying it to the determintaion of the barrier height to HONO elimination from nitroethane, a value which is well known from activation energy measurements. The method was then applied to the case of HONO elimination from 2-nitropropane and it appears that there is good to believe that the barrier height is 3-5 kcal/mol lower in 2-nitropropane than in nitroethane. The success of this method for determining barrier heights shows how a microscopic molecular beam experiment, using infrared multiphoton dissociation where the concept of temperature has no place, can be quantitatively related to pyrolysis experiments which are conducted under collisional, thermal conditions and measure phenomenological quantities such as activation energies.

  8. Coulomb dissociation in nonrelativistic and relativistic collisions

    International Nuclear Information System (INIS)

    Electromagnetic excitations in the Coulomb field of nuclei have been studied using quantum as well as semiclassical methods. Even at relatively modest incident energies, the Coulomb dissociation cross sections of projectiles with relatively low particle thresholds could be of sizeable order of magnitude. Such a study complements our knowledge about radiative capture processes, which are of interest for nuclear astrophysics. Quite a few questions remain to be answered, like the importance of nuclear interactions for small angle scattering, interference of different multipolarities for triple differentiial cross sections and distortion effects on the three-body final states. In the case of dissociation at relativistic energies it is shown that only for the total cross section both semiclassical and quantim-mechanical methods yield the same results. As an example the Primakoff effect is considered, where in an M1 excitation of ≅ 80 MeV a Λ hyperion is converted into a Σo hyperion by means of the virtual photon field of heavy target nuclei. Virtual photon spectra for all multipolarities can be calculated. This provides a sound basis for the analysis of electromagnetic dissociation experiments at relativistic heavy ion accelerators, like the BEVALAC. 10 figs., 25 refs

  9. Study of SI engine fueled with methanol vapor and dissociation gas based on exhaust heat dissociating methanol

    International Nuclear Information System (INIS)

    Highlights: • The full load power decreases successively from gasoline engine, methanol vapor engine to dissociated methanol engine. • Both power and thermal efficiency of dissociated methanol engine can be improved by boosting pressure. • The conversion efficiency of recovered exhaust gas energy is largely influenced by the BMEP. • At the same BMEP, dissociated methanol engine has higher thermal efficiency than methanol vapor engine and gasoline engine. - Abstract: To improve the fuel efficiency of internal combustion (IC) engine and also achieve the goal of direct usage of methanol fuel on IC engine, an approach of exhaust heat dissociating methanol was investigated, which is a kind of method for IC engine exhaust heat recovery (EHR). A bottom cycle system is coupled with the IC engine exhaust system, which uses the exhaust heat to evaporate and dissociate methanol in its catalytic cracker. The methanol dissociation gas (including methanol vapor) is used as the fuel for IC engine. This approach was applied to both naturally aspirated (NA) engine and turbocharged engine, and the engine performance parameters were predicted by the software GT-power under various kinds of operating conditions. The improvement to IC engine performance and the conversion efficiency of recovered exhaust gas energy can be evaluated by comparing the performances of IC engine fueled with various kinds of fuels (or their compositions). Results show that, from gasoline engine, methanol vapor engine to dissociated methanol engine, the full load power decreases successively in the entire speed area due to the declining of volumetric efficiency, while it is contrary in the thermal efficiency at the same brake mean effective pressure (BMEP) level because of the improving of fuel heating value. With the increase of BMEP, the conversion efficiency of recovered exhaust gas energy is promoted. All those results indicate that the approach of exhaust heat dissociating methanol has large

  10. Dipolar dissociation dynamics in electron collisions with oxygen molecules

    CERN Document Server

    Nag, Pamir

    2016-01-01

    The dipolar dissociation of molecular oxygen due to 21-35 eV energy electron collision has been studied using the time sliced velocity map imaging technique. A rough estimation about the threshold of the process and the kinetic energy and angular distribution of the fragment negative ions are measured. The dipolar dissociation found to be occur due to pre-dissociation of a Rydberg state via ion-pair state for lower incident electron energies as well from also direct excitation to the ion-pair states for relatively higher primary beam energy. The location and symmetry of the excited states were determined from the kinetic energy and angular distribution data respectively.

  11. Copper wire bonding

    CERN Document Server

    Chauhan, Preeti S; Zhong, ZhaoWei; Pecht, Michael G

    2014-01-01

    This critical volume provides an in-depth presentation of copper wire bonding technologies, processes and equipment, along with the economic benefits and risks.  Due to the increasing cost of materials used to make electronic components, the electronics industry has been rapidly moving from high cost gold to significantly lower cost copper as a wire bonding material.  However, copper wire bonding has several process and reliability concerns due to its material properties.  Copper Wire Bonding book lays out the challenges involved in replacing gold with copper as a wire bond material, and includes the bonding process changes—bond force, electric flame off, current and ultrasonic energy optimization, and bonding tools and equipment changes for first and second bond formation.  In addition, the bond–pad metallurgies and the use of bare and palladium-coated copper wires on aluminum are presented, and gold, nickel and palladium surface finishes are discussed.  The book also discusses best practices and re...

  12. Bond selective chemistry beyond the adiabatic approximation

    Energy Technology Data Exchange (ETDEWEB)

    Butler, L.J. [Univ. of Chicago, IL (United States)

    1993-12-01

    One of the most important challenges in chemistry is to develop predictive ability for the branching between energetically allowed chemical reaction pathways. Such predictive capability, coupled with a fundamental understanding of the important molecular interactions, is essential to the development and utilization of new fuels and the design of efficient combustion processes. Existing transition state and exact quantum theories successfully predict the branching between available product channels for systems in which each reaction coordinate can be adequately described by different paths along a single adiabatic potential energy surface. In particular, unimolecular dissociation following thermal, infrared multiphoton, or overtone excitation in the ground state yields a branching between energetically allowed product channels which can be successfully predicted by the application of statistical theories, i.e. the weakest bond breaks. (The predictions are particularly good for competing reactions in which when there is no saddle point along the reaction coordinates, as in simple bond fission reactions.) The predicted lack of bond selectivity results from the assumption of rapid internal vibrational energy redistribution and the implicit use of a single adiabatic Born-Oppenheimer potential energy surface for the reaction. However, the adiabatic approximation is not valid for the reaction of a wide variety of energetic materials and organic fuels; coupling between the electronic states of the reacting species play a a key role in determining the selectivity of the chemical reactions induced. The work described below investigated the central role played by coupling between electronic states in polyatomic molecules in determining the selective branching between energetically allowed fragmentation pathways in two key systems.

  13. CO dissociation on magnetic Fen clusters

    KAUST Repository

    Jedidi, Abdesslem

    2014-01-01

    This work theoretically investigates the CO dissociation on Fen nanoparticles, for n in the range of 1-65, focusing on size dependence in the context of the initial step of the Fischer-Tropsch reaction. CO adsorbs molecularly through its C-end on a triangular facet of the nanoparticle. Dissociation becomes easier when the cluster size increases. Then, the C atom is bonded to a square facet that is generated as a result of the adsorption if it does not yet exist in the bare cluster, while the O atom is adsorbed on a triangular facet. In the most stable situation, the two adsorbed atoms remain close together, both having in common one shared first-neighbor iron atom. There is a partial spin quenching of the neighboring Fe atoms, which become more positively charged than the other Fe atoms. The shared surface iron atom resembles a metal-cation from a complex. Despite the small size of the iron cluster considered, fluctuations due to specific configurations do not influence properties for n > 25 and global trends seem significant.

  14. Perturbing peptide cation-radical electronic states by thioxoamide groups: formation, dissociations, and energetics of thioxopeptide cation-radicals.

    Science.gov (United States)

    Zimnicka, Magdalena; Chung, Thomas W; Moss, Christopher L; Tureček, František

    2013-02-14

    Thioxodipeptides Gly-thio-Lys (GtK), Ala-thio-Lys (AtK), and Ala-thio-Arg (AtR) in which the amide group has been modified to a thioxoamide were made into dications by electrospray ionization and converted to cation-radicals, (GtK + 2H)(+•), (AtK + 2H)(+•), and (AtR + 2H)(+•), by electron transfer dissociation (ETD) tandem mass spectrometry using fluoranthene anion-radical as an electron donor. The common and dominant dissociation of these cation-radicals was the loss of a hydrogen atom. The dissociation products were characterized by collision-induced dissociation (CID) multistage tandem mass spectrometry up to CID-MS(5). The ground electronic states of several (GtK + 2H)(+•), (AtK + 2H)(+•), and (AtR + 2H)(+•) conformers were explored by extensive ab initio and density functional theory calculations of the potential energy surface. In silico electron transfer to the precursor dications, (GtK + 2H)(2+), (AtK + 2H)(2+), and (AtR + 2H)(2+), formed zwitterionic intermediates containing thioenol anion-radical and ammonium cation groups that were local energy minima on the potential energy surface of the ground electronic state. The zwitterions underwent facile isomerization by N-terminal ammonium proton migration to the thioenol anion-radical group forming aminothioketyl intermediates. Combined potential energy mapping and RRKM calculations of dissociation rate constants identified N-C(α) bond cleavages as the most favorable dissociation pathways, in a stark contrast to the experimental results. This discrepancy is interpreted as being due to the population upon electron transfer of low-lying excited electronic states that promote loss of hydrogen atoms. For (GtK + 2H)(+•), these excited states were characterized by time-dependent density functional theory as A-C states that had large components of Rydberg-like 3s molecular orbitals at the N-terminal and lysine ammonium groups that are conducive to hydrogen atom loss. PMID:22765351

  15. Isotope effects in the dissociation of partially deuterated dimethyl ether, CH3OCD+3 ions

    Science.gov (United States)

    Dutuit, Odile; Baer, Tomas; Metayer, C.; Lemaire, J.

    1991-11-01

    The dissociation of partially deuterated dimethyl ether ions(CH3OCD+3) is studied from the ionization potential of 10.03-16eV photon energy. Ions are produced by photoionization with synchrotron radiation and selected in internal energy by threshold photoelectron--photoion coincidence. Up to 13eV the major fragments correspond to an H or D atom loss by a simple bond cleavage. However, the shift in the H and D loss onsets indicates that there is a small reverse activation energy as a result of the zero point energies in the C---X deformation modes. A new value for [Delta]H°fo(CH3OCH+2) of 161.1 kcalmol-1 is derived. The CH2OH+ and CD2OD+ products appear at 11.75 eV, 0.95 eV above their thermochemical onset, and remain minor fragments in the whole energy range studied. No scrambling of the H and D atoms is observed. Modeling of the breakdown graph by RRKM theory indicates that the CX2OX+ (X = H or D) fragments are produced via a 1.35 eV barrier. We observe an isotope effect in both these dissociation channels which is well explained by zero point energy, and density of states differences in the framework of the RRKM calculations. The analysis shows that in the energy range investigated, tunneling is not an important process in the CH2OH+ formation. At 15 and 16 eV photon energies, the main fragments are XCO+ and CX+3 (X = H or D). Non-statistical scrambling of the hydrogen atoms in CX+3 is observed.

  16. Formation and Dissociation of Phosphorylated Peptide Radical Cations

    Science.gov (United States)

    Kong, Ricky P. W.; Quan, Quan; Hao, Qiang; Lai, Cheuk-Kuen; Siu, Chi-Kit; Chu, Ivan K.

    2012-12-01

    In this study, we generated phosphoserine- and phosphothreonine-containing peptide radical cations through low-energy collision-induced dissociation (CID) of the ternary metal-ligand phosphorylated peptide complexes [CuII(terpy) p M]·2+ and [CoIII(salen) p M]·+ [ p M: phosphorylated angiotensin III derivative; terpy: 2,2':6',2''-terpyridine; salen: N, N '-ethylenebis(salicylideneiminato)]. Subsequent CID of the phosphorylated peptide radical cations ( p M·+) revealed fascinating gas-phase radical chemistry, yielding (1) charge-directed b- and y-type product ions, (2) radical-driven product ions through cleavages of peptide backbones and side chains, and (3) different degrees of formation of [M - H3PO4]·+ species through phosphate ester bond cleavage. The CID spectra of the p M·+ species and their non-phosphorylated analogues featured fragment ions of similar sequence, suggesting that the phosphoryl group did not play a significant role in the fragmentation of the peptide backbone or side chain. The extent of neutral H3PO4 loss was influenced by the peptide sequence and the initial sites of the charge and radical. A preliminary density functional theory study, at the B3LYP 6-311++G(d,p) level of theory, of the neutral loss of H3PO4 from a prototypical model— N-acetylphosphorylserine methylamide—revealed several factors governing the elimination of neutral phosphoryl groups through charge- and radical-induced mechanisms.

  17. Modeling Proton Dissociation and Transfer Using Dissipative Particle Dynamics Simulation.

    Science.gov (United States)

    Lee, Ming-Tsung; Vishnyakov, Aleksey; Neimark, Alexander V

    2015-09-01

    We suggest a coarse-grained model for dissipative particle dynamics (DPD) simulations of solutions with dissociated protons. The model uses standard short-range soft repulsion and smeared charge electrostatic potentials between the beads, representing solution components. The proton is introduced as a separate charged bead that forms dissociable bonds with proton receptor base beads, such as water or deprotonated acid anions. The proton-base bonds are described by Morse potentials. When the proton establishes the Morse bonds with two bases, they form an intermediate complex, and the proton is able to "hop" between the bases artificially mimicking the Grotthuss diffusion mechanism. By adjusting the Morse potential parameters, one can regulate the potential barrier associated with intermediate complex formation and breakup and control the hopping frequency. This makes the proposed model applicable to simulations of proton mobility and reaction equilibria between protonated and deprotonated acid forms in aqueous solutions. The proposed model provides quantitative agreement with experiments for the proton self-diffusion coefficient and hopping frequency, as well as for the degree of dissociation of benzenesulfonic acid. PMID:26575931

  18. Thermal Dissociation and Roaming Isomerization of Nitromethane: Experiment and Theory.

    Science.gov (United States)

    Annesley, Christopher J; Randazzo, John B; Klippenstein, Stephen J; Harding, Lawrence B; Jasper, Ahren W; Georgievskii, Yuri; Ruscic, Branko; Tranter, Robert S

    2015-07-16

    The thermal decomposition of nitromethane provides a classic example of the competition between roaming mediated isomerization and simple bond fission. A recent theoretical analysis suggests that as the pressure is increased from 2 to 200 Torr the product distribution undergoes a sharp transition from roaming dominated to bond-fission dominated. Laser schlieren densitometry is used to explore the variation in the effect of roaming on the density gradients for CH3NO2 decomposition in a shock tube for pressures of 30, 60, and 120 Torr at temperatures ranging from 1200 to 1860 K. A complementary theoretical analysis provides a novel exploration of the effects of roaming on the thermal decomposition kinetics. The analysis focuses on the roaming dynamics in a reduced dimensional space consisting of the rigid-body motions of the CH3 and NO2 radicals. A high-level reduced-dimensionality potential energy surface is developed from fits to large-scale multireference ab initio calculations. Rigid body trajectory simulations coupled with master equation kinetics calculations provide high-level a priori predictions for the thermal branching between roaming and dissociation. A statistical model provides a qualitative/semiquantitative interpretation of the results. Modeling efforts explore the relation between the predicted roaming branching and the observed gradients. Overall, the experiments are found to be fairly consistent with the theoretically proposed branching ratio, but they are also consistent with a no-roaming scenario and the underlying reasons are discussed. The theoretical predictions are also compared with prior theoretical predictions, with a related statistical model, and with the extant experimental data for the decomposition of CH3NO2, and for the reaction of CH3 with NO2. PMID:25886024

  19. VB studies on bonding features of HNCHCN

    Institute of Scientific and Technical Information of China (English)

    LIAO; Xinli(

    2003-01-01

    [1]Skurski, P., Gutowski, M., Simons, J., Ab initio electronic structure of HCN- and HNC-dipole-bound anions and a description of electron loss upon tautomerization, J. Chem. Phys., 2001, 114(17): 7443-7449.[2]Jursic, B. S., Complete basis set ab initio study of potential energy surfaces of the dissociation recombination reaction HCNH++e(-), J. Mol. Struct., 1999, 487(3): 211-220.[3]Abashkin, Y., Russo, N., Toscano, M., Transition states and energy barriers from density functional studies: representative isomerization reactions, Int. J. Quantum Chem., 1994, 52: 695-704.[4]Bentley, J. A., Bowman, J. M., Gazdy, B. et al., A global ab initio potential for HCN/HNC exact vibrational energies and comparision to experiment, Chem. Phys. Lett., 1992, 198(6): 563-569.[5]Bentley, J. A., Huang, C. M., Wyatt, R. E., Highly vibrationally excited HCN/HNC: eigenvalues, wave functions, and stimulated emission pumping spectra, J. Chem. Phys., 1992, 98(7): 5207-5221.[6]Peric, M., Mladrenovic, M., Peyerimhoff, S. D. et al., Ab initio study of the isomerization HNC-HCN, 1. Ab initio calculation of the HNV reversible HCN potential surface and the corresponding energy-levels, Chem. Phys., 1983, 82: 317-336.[7]Zhang, Q. E., Li, X. Z., Bonded tableau method for many-electron systems, J. Mol. Struct. (Theochem.), 1989, 198: 413-425.[8]Li, X. Z., Zhang, Q. E., Bonded tableau unitary group approach to the many-electron correlation problem, Int. J. Quantum Chem., 1989, 36: 599-632.[9]Li, J. B., Wu, W., New algorithm for nonorthogonal ab initio valence-bond calculations, Theor. Chim. Acta, 1994, 89: 105-121.[10]Wu, W., Mo, Y. R., Zhang, Q. E., On the resonance theory, J. Mol. Struct., 1993, 283: 227-236.[11]Mo, Y. R., Wu, W., Zhang, Q. E., Valence bond description for the ground state and several low-lying excited states of LiH, J. Mol. Struct., 1993, 283: 237-249.[12]Pauling, L., The Nature of Chemical Bond, 3rd ed., Ithaca, New York: Cornell

  20. Theory of dissociative tunneling ionization

    Science.gov (United States)

    Svensmark, Jens; Tolstikhin, Oleg I.; Madsen, Lars Bojer

    2016-05-01

    We present a theoretical study of the dissociative tunneling ionization process. Analytic expressions for the nuclear kinetic energy distribution of the ionization rates are derived. A particularly simple expression for the spectrum is found by using the Born-Oppenheimer (BO) approximation in conjunction with the reflection principle. These spectra are compared to exact non-BO ab initio spectra obtained through model calculations with a quantum mechanical treatment of both the electronic and nuclear degrees of freedom. In the regime where the BO approximation is applicable, imaging of the BO nuclear wave function is demonstrated to be possible through reverse use of the reflection principle, when accounting appropriately for the electronic ionization rate. A qualitative difference between the exact and BO wave functions in the asymptotic region of large electronic distances is shown. Additionally, the behavior of the wave function across the turning line is seen to be reminiscent of light refraction. For weak fields, where the BO approximation does not apply, the weak-field asymptotic theory describes the spectrum accurately.

  1. Surface structure, bonding, and dynamics: The universality of zincblende (110) potential energy surfaces

    International Nuclear Information System (INIS)

    Using a tight-binding, total energy (TBTE) model we examine the hypothesis that the potential energy surfaces (PES) describing the (110) cleavage faces of the tetrahedrally coordinated, zincblende-structure compound semiconductors exhibit a common ''universal'' form if expressed in terms of suitably scaled parameters. TBTE calculations on both III-V and II-VI compounds reveal a linear scaling with bulk lattice constant of the geometric parameters of the reconstructed surfaces. This scaling is analogous to that found using low-energy, electron-diffraction surface-structure determination. The surface atomic force constants (found from a TBTE calculation) also scale monotonically with the lattice constant. Using TBTE models proposed previously for GaP, GaAs, GaSb, InP, and ZnSe, we find that the force constants scale as the inverse square of the bulk lattice constant. These results suggest that if distances are measured in units of the bulk lattice constant, the PES may be a universal function for the cleavage surface of zincblende-structure compound semiconductors, on average, with small fluctuations from this average occurring in individual materials. 22 refs., 5 figs., 1 tab

  2. Dissociative Tendencies and Traffic Incidents

    Directory of Open Access Journals (Sweden)

    Valle, Virginia

    2012-01-01

    Full Text Available This paper analyses the relationship between dissociative experiences and road traffic incidents (crashes and traffic tickets in drivers (n=295 from Mar del Plata (Argentina city. A self-report questionnaire was applied to assess traffic crash involvement and sociodemographic variables. Dissociative tendencies were assessed by a modified version of the DES scale. To examine differences in DES scores tests of the difference of means were applied. Drivers who reported to be previously involved in traffic incidents obtained higher puntuations in the dissociative experiences scale than drivers who did not report such events. This result is observed for the total scale and for the three sub-scales (absorption, amnesia and depersonalization. However, differences appeared mainly for minor damage collisions. Further studies are needed to evaluate the role of dissociative tendencies as a risk factor in road traffic safety.

  3. Neural complexity, dissociation, and schizophrenia

    Czech Academy of Sciences Publication Activity Database

    Bob, P.; Šusta, M.; Chládek, Jan; Glaslová, K.; Fedor-Ferybergh, P.

    2007-01-01

    Roč. 13, č. 10 (2007), HY1-5. ISSN 1234-1010 Institutional research plan: CEZ:AV0Z20650511 Keywords : neural complexity * dissociation * schizophrenia Subject RIV: FH - Neurology Impact factor: 1.607, year: 2007

  4. Dissociation pressure of polonium dioxide

    International Nuclear Information System (INIS)

    Information on determining the temperature dependence of the vapour pressure during polonium-210 dissociation is given. To determine the vapour pressure of polonium during PoO2 dissociation, the method based on remote measuring the amount of the vapour of the radioactive element by its own radiation in a known volume with dynamic equilibrium inside an ampoule evacuated to 10-2 Torr has been used. The vapour pressure of P0 in vacuum within the temperature range from 530 to 595 deg C obeys the equation lg Psub(mm)=19.4440+-0.7140-(16920+-50O)/T. The polonium evaporation heat during PoO2 dissociation is 77.4+-2.3 kcal/mol. Enthalpy of PoO2 dissociation is 154.8 kcal/mol

  5. On the optimization of the DF-SAPT-DFT interaction energies of hydrogen-bonded systems

    Czech Academy of Sciences Publication Activity Database

    Czernek, Jiří

    Budapest: World Scientific and Engineering Academy and Society, 2009 - (Rudas, I.; Demiralp, M.; Mastorakis, N.), s. 237-241. (Mathematics and Computers in Science and Engineering). ISBN 978-960-474-113-7. [WSEAS International Symposium on Simulation, Modelling and Optimization /9./. Budapest (HU), 03.09.2009-05.09.2009] R&D Projects: GA AV ČR IAA400500602; GA MŠk 2B08021 Institutional research plan: CEZ:AV0Z40500505 Keywords : optimization * ab initio * DFT * interaction energy Subject RIV: CD - Macromolecular Chemistry http://www.wseas.us/books/2009/budapest/SMO.pdf

  6. Silver-catalyzed silicon-hydrogen bond functionalization by carbene insertion.

    Science.gov (United States)

    Iglesias, M José; Nicasio, M Carmen; Caballero, Ana; Pérez, Pedro J

    2013-01-28

    The catalytic functionalization of silicon-hydrogen bonds by means of the insertion of carbene units :CHCO(2)Et from ethyl diazoacetate (EDA) has been achieved using a silver-based catalyst, constituting the first example of this metal to promote this transformation. Competition experiments have revealed that the relative reactivity of substituted silanes depends on the bond dissociation energy of the Si-H bond (tertiary > secondary > primary for ethyl substituted). In the presence of bulky substituents such order reverts to secondary > primary ≈ tertiary (for phenyl substituted). Screening with other diazo compounds has shown that N(2)C(Ph)CO(2)Et displays similar reactivity to that of EDA, whereas other N(2)C(R)CO(2)Et (R = Me, CO(2)Et) gave lower conversions. PMID:23114570

  7. Compositions and chemical bonding in ceramics by quantitative electron energy-loss spectrometry

    Energy Technology Data Exchange (ETDEWEB)

    Bentley, J.; Horton, L.L. [Oak Ridge National Lab., TN (United States); McHargue, C.J. [Tennessee Univ., Knoxville, TN (United States); McKernan, S.; Carter, C.B. [Minnesota Univ., Minneapolis, MN (United States). Dept. of Chemical Engineering; Revcolevschi, A. [Univ. de Paris-Sud, Lab. de Chemie des Solides (France); Tanaka, S.; Davis, R.F. [North Carolina State Univ., Raleigh, NC (United States). Dept. of Materials Science and Engineering

    1993-12-31

    Quantitative electron energy-loss spectrometry was applied to a range of ceramic materials at a spatial resolution of <5 nm. Analysis of Fe L{sub 23} white lines indicated a low-spin state with a charge transfer of {approximately}1.5 electrons/atom onto the Fe atoms implanted into (amorphized) silicon carbide. Gradients of 2 to 5% in the Co:O stoichiometry were measured across 100-nm-thick Co{sub 3}O{sub 4} layers in an oxidized directionally solidified CoO-ZrO{sub 2} eutectic, with the highest O levels near the ZrO{sub 2}. The energy-loss near-edge structures were dramatically different for the two cobalt oxides; those for CO{sub 3}O{sub 4} have been incorrectly ascribed to CoO in the published literature. Kinetically stabilized solid solubility occurred in an AlN-SiC film grown by low-temperature molecular beam epitaxy (MBE) on {alpha}(6H)-SiC, and no detectable interdiffusion occurred in couples of MBE-grown AlN on SiC following annealing at up to 1750C. In diffusion couples of polycrystalline AlN on SiC, interfacial 8H sialon (aluminum oxy-nitride) and pockets of Si{sub 3}N{sub 4}-rich {beta}{prime} sialon in the SiC were detected.

  8. Water's Hydrogen Bond Strength

    CERN Document Server

    Chaplin, Martin

    2007-01-01

    Water is necessary both for the evolution of life and its continuance. It possesses particular properties that cannot be found in other materials and that are required for life-giving processes. These properties are brought about by the hydrogen bonded environment particularly evident in liquid water. Each liquid water molecule is involved in about four hydrogen bonds with strengths considerably less than covalent bonds but considerably greater than the natural thermal energy. These hydrogen bonds are roughly tetrahedrally arranged such that when strongly formed the local clustering expands, decreasing the density. Such low density structuring naturally occurs at low and supercooled temperatures and gives rise to many physical and chemical properties that evidence the particular uniqueness of liquid water. If aqueous hydrogen bonds were actually somewhat stronger then water would behave similar to a glass, whereas if they were weaker then water would be a gas and only exist as a liquid at sub-zero temperature...

  9. Dissociative and non-dissociative photoionization of molecular fluorine from inner and valence shells

    Energy Technology Data Exchange (ETDEWEB)

    Ayuso, D.; Palacios, A. [Departamento de Química, Módulo 13, Universidad Autónoma de Madrid, Cantoblanco, 28049 Madrid (Spain); Decleva, P. [Dipartimento di Scienze Chimiche e Farmaceutiche, Università di Trieste, 34127 Trieste (Italy); CNR-IOM, Trieste (Italy); Martín, F., E-mail: fernando.martin@uam.es [Departamento de Química, Módulo 13, Universidad Autónoma de Madrid, Cantoblanco, 28049 Madrid (Spain); Instituto Madrileño de Estudios Avanzados en Nanociencia, Cantoblanco, 28049 Madrid (Spain)

    2014-08-15

    Highlights: • We theoretically analyze the angle-integrated photoionization cross sections of the fluorine molecule, which have been computed up to hundreds of eV using a DFT-like methodology that takes into account the nuclear degrees of freedom. • We have considered electron ejection from all the molecular orbitals and found that the corresponding cross sections show an oscillatory behavior as a function of the photoelectron momentum, which is the result of the double-slit type interferences. • We further compute dissociative and non-dissociative ionization channels. • Dissociative ionization is negligible in other diatomic molecules such N{sub 2} or CO, whereas is visible for F{sub 2} when the electron is ejected from the 1u or the 3σ{sub g} molecular orbitals. - Abstract: We present a theoretical study of F{sub 2} photoionization in the range 0–40 a.u. of photoelectron energy, where the undulatory behavior of the corresponding angle-integrated cross sections due to electron emission from equivalent centers is apparent. These double-slit type interferences are observed in both inner- and valence-shell ionization. We analyze confinement effects that appear at given energies when the electron is ejected parallel to the molecular axis. Since we account for the nuclear degrees of freedom, we evaluate and discuss the vibrationally resolved cross sections, including both dissociative and non-dissociative ionization channels. We also analyze the ratios between the latter cross sections and the relationship between the observed oscillations and the structure of the molecule.

  10. Dissociative recombination of small molecular ions

    International Nuclear Information System (INIS)

    In this thesis an analysis is given of merged electron-ion beam experiment and work on dissociative recombination of molecular ions and electrons is described. Chapter II covers a brief introduction of the theory of dissociative recombination. In chapter III, a description is given of the merged electron-ion beam experiment and a method is described which allows the determination of the mean angle between the electron and ion trajectories in a merged electron-ion beam experiment. In chapter IV a paper on the three dominant atmospheric diatomic ions NO+, O2+ and N2+ is presented and in chapter V the dissociative recombination for N2H+ and N2D+ is discussed. In chapter VI two papers on the polyatomic ions of the carbon-containing molecular ions are presented, and in chapter VII a letter with some results of the work presented in more detail in the chapters IV, V and VI is presented. The magnitude and the energy dependence of the cross-section measured by the merged beam technique and by other techniques is compared and discussed. (Auth.)

  11. Optimization of two tailored rectangular femtosecond laser pulses in methane dissociation

    Science.gov (United States)

    Sadighi-Bonabi, R.; Dehghani, Z.; Irani, E.

    2010-05-01

    Based on the quantum mechanics principles and classically calculated dressed potential surfaces by using field assisted dissociation model the dissociation probability for CH4+ molecule exposed with a 100 femtosecond 8 Jcm-2 Ti:sapphire laser pulses is calculated. Using the gradient optimization method two tailored rectangular laser pulses for controlling the dissociation of C-H bond of CH4+ molecule along laser pulse direction is found. In the proposed optimization method, the complicacy of solving Schrodinger wave equation is reduced by using classical method and in contrast to the usual controlling and pulse shaping methods of chemical reactions, the experimental data is not needed and this reduces the controlling costs.

  12. Dissociative experiences and dissociative minds: Exploring a nomological network of dissociative functioning.

    Science.gov (United States)

    Schimmenti, Adriano

    2016-01-01

    In this study, the psychometric properties of the Dissociative Experiences Scale-II (DES-II) were tested in a sample of Italian adults, and a nomological network of dissociative functioning based on current psychodynamic research was examined. A total of 794 participants (55% females) ranging in age from 18 to 64 completed the DES-II and other measures of theory of mind, alexithymia, attachment style, and empathy. The Italian translation of the DES-II showed high internal consistency, adequate item-to-scale homogeneity, and good split-half reliability. A single-factor solution including the 8 items of pathological dissociation (DES-T) adequately fit the data. Participants who reported higher levels of dissociative experiences showed significantly lower scores on theory of mind and empathy than other participants. They also showed significantly higher scores on alexithymia, preoccupied attachment, and fearful attachment. Results of the study support the view that people who suffer from severe dissociative experiences may also have difficulties mentalizing and regulating affects and that they may feel uncomfortable in close relationships because they have a negative view of the self. This can inform clinical work with dissociative individuals, who could benefit from therapies that consider their potential problems with mentalization, empathy, affect regulation, and attachment. PMID:26507547

  13. Quantum chemical study of mechanisms of dissociation and isomerization reactions in some molecules and radicals of astrophysical significance: Cyanides and related molecules

    Indian Academy of Sciences (India)

    V P Gupta; Archina Sharma

    2006-09-01

    A theoretical study of the mechanism of photodecomposition in carbonyl cyanide, diethynyl ketone, acetyl cyanide and formyl cyanide has been conducted using density functional and MP2 theories. A complete analysis of the electronic spectra of these molecules in terms of nature, energy and intensity of electronic transitions has been provided by time-dependent density functional theory. Mixing coefficients and main configurations of the electronic states have been used to identify the states leading to the photodecomposition process. While the Rydberg state 1(n,3s) is involved in the dissociation of formyl cyanide and acetyl cyanide, the $^{*}_{CC} / ^{*}_{CN}$ states are involved in the case of carbonyl cyanide and diethynyl ketone. In all cases, however, stepwise decomposition process is preferred over the concerted reaction process. Based on potential energy curves for bond dissociation and the transition state and IRC studies, it is found that besides the direct dissociation of carbonyl cyanide, a photoisomerization process through a non-planar transition state may also occur resulting in the formation of a stable and planar isomer CNC(O)CN. A complete vibrational analysis of the higher energy isomer has been conducted and several new fundamental bands are predicted. Some of the earlier experimental results on the photodecomposition mechanism and energies of photofragments in carbonyl cyanide and acetyl cyanide have also been rationalized.

  14. Dissociation reactive thermal conductivity in a two-temperature plasma

    Energy Technology Data Exchange (ETDEWEB)

    Nemchinsky, Valerian [ESAB Welding and Cutting Products, Florence, SC 29501 (United States); Francis Marion University, Florence, SC 29501 (United States)

    2005-10-21

    Dissociation reactive thermal conductivity (DRTC) is the transfer of dissociation energy in plasma with temperature and, therefore, composition gradient. In the existing theories, calculation of the DRTC coefficient consists of the calculation of diffusion coefficients and plasma composition. The heat flux is then calculated by assigning to every molecule the dissociation energy and by the multiplication of the molecule flux density by this energy. This approach, correct for the LTE plasma, is not adequate for the non-equilibrium two-temperature plasma: it does not allow one to separate the total DRTC coefficient into two components responsible for the heat transfer by electrons and heavy particles (atoms, molecules, ions). Only at LTE, during atom reassociation, do the electrons recuperate the energy they spent during the molecule dissociation. Therefore, in order to separate these two components of DRTC, the kinetics of the dissociation-reassociation processes should be considered. This is done in this paper for nitrogen plasma at atmospheric pressure. F{sub e}, the electron fraction of the total DRTC coefficient, was calculated for T{sub e} (electron temperature) in the range 0.4-1.0 eV and T{sub h} (heavy particles temperature) from 0.2 eV to T{sub e}. It is shown that F{sub e} depends mostly on the electron temperature and increases with increasing electron temperature.

  15. Chemical Bonding of AlH3 Hydride by Al-L2,3 Electron Energy-Loss Spectra and First-Principles Calculations

    OpenAIRE

    Kazutaka Ikeda; Shin-Ichi Orimo; Kazuyoshi Tatsumi; Shunsuke Muto

    2012-01-01

    In a previous study, we used transmission electron microscopy and electron energy-loss (EEL) spectroscopy to investigate dehydrogenation of AlH3 particles. In the present study, we systematically examine differences in the chemical bonding states of Al-containing compounds (including AlH3) by comparing their Al-L2,3 EEL spectra. The spectral chemical shift and the fine peak structure of the spectra were consistent with the degree of covalent bonding of Al. This finding will be useful for futu...

  16. Chemical Bonding of AlH3 Hydride by Al-L2,3 Electron Energy-Loss Spectra and First-Principles Calculations

    Directory of Open Access Journals (Sweden)

    Kazutaka Ikeda

    2012-03-01

    Full Text Available In a previous study, we used transmission electron microscopy and electron energy-loss (EEL spectroscopy to investigate dehydrogenation of AlH3 particles. In the present study, we systematically examine differences in the chemical bonding states of Al-containing compounds (including AlH3 by comparing their Al-L2,3 EEL spectra. The spectral chemical shift and the fine peak structure of the spectra were consistent with the degree of covalent bonding of Al. This finding will be useful for future nanoscale analysis of AlH3 dehydrogenation toward the cell.

  17. Collision-induced dissociation and dissociative capture of H2+ in Ar and Kr

    International Nuclear Information System (INIS)

    Measurements of the absolute total and differential cross sections for the production of protons and hydrogen atoms in the energy range of 1-5 keV for reactions of H2+ molecular ions in Ar and Kr targets are reported. The results show that the cross section for the dissociative capture (DC) proccess is about one order of magnitude higher than that for the collision-induced dissociation. The angular distribution of the fragments in both targets and for all acceleration energies shows a monotonic decrease in the differential cross section with increasing angle. A sharp increase in the angular distribution at scattering angles <1.6 deg. is observed for hydrogen atoms resulting from DC and in particular for the Kr target

  18. Interference Effects in Strong-Field Dissociative Ionization

    DEFF Research Database (Denmark)

    Yue, Lun; Madsen, Lars Bojer

    2015-01-01

    We theoretically study dissociative ionization of H$_2^+$ exposed to strong linearly polarized few-cycle visible, near-infrared and midinfrared laser pulses. We find rich energy-sharing structures in the combined electron and nuclear kinetic energy spectra with features that are a priori at odds...

  19. Dissociation path for H2 on Al(110)

    DEFF Research Database (Denmark)

    Hammer, Bjørk; Jacobsen, Karsten Wedel; Nørskov, Jens Kehlet

    1992-01-01

    The minimum energy path is calculated for an H2 molecule dissociating on an Al(110) surface within local density functional theory. The properties of the potential energy surface along the five H2 ionic coordinates perpendicular to the reaction path are also determined and shown to be essential f...

  20. Dissociative recombination of HeH[sup +]: A reexamination

    Energy Technology Data Exchange (ETDEWEB)

    Yousif, F.B.; Mitchell, J.B.A.; Rogelstad, M.; Le Paddelec, A.; Canosa, A.; Chibisov, M.I. (Department of Physics and Center for Chemical Physics, University of Western Ontario, London, Ontario, N6A3K7 (Canada))

    1994-06-01

    A high-energy-resolution study of the dissociative recombination of HeH[sup +] has been performed. A theoretical analysis has indicated that the recombination at low energy is due to the presence of a metastable triplet-state component of the ion beam.

  1. Dissociation of deuteron, 6He and 11Be from Coulomb dissociation reaction cross-section

    Indian Academy of Sciences (India)

    Ramendra Nath Majumdar

    2008-05-01

    The fragmentation of deuteron, 6He and 11Be have been studied during interaction with the 208Pb nucleus at various projectile energies. The Coulomb dissociation cross-sections and the momentum distribution of the break-up fragments have been analysed within the framework of the direct fragmentation model. The post-acceleration effect of deuteron during break-up and the halo structures of both the 6He and 11Be have been investigated.

  2. Energy and structure of bonds in the interaction of organic anions with layered double hydroxide nanosheets: A molecular dynamics study

    Science.gov (United States)

    Tsukanov, A. A.; Psakhie, S. G.

    2016-01-01

    The application of hybrid and hierarchical nanomaterials based on layered hydroxides and oxyhydroxides of metals is a swiftly progressing field in biomedicine. Layered double hydroxides (LDH) possess a large specific surface area, significant surface electric charge and biocompatibility. Their physical and structural properties enable them to adsorb various kinds of anionic species and to transport them into cells. However, possible side effects resulting from the interaction of LDH with anions of the intercellular and intracellular medium need to be considered, since such interaction can potentially disrupt ion transport, signaling processes, apoptosis, nutrition and proliferation of living cells. In the present paper molecular dynamics is used to determine the energies of interaction of organic anions (aspartic acid, glutamic acid and bicarbonate) with a fragment of layered double hydroxide Mg/Al-LDH. The average number of hydrogen bonds between the anions and the hydroxide surface and characteristic binding configurations are determined. Possible effects of LDH on the cell resulting from binding of protein fragments and replacement of native intracellular anions with delivered anions are considered.

  3. Bond energies of ThO+ and ThC+: A guided ion beam and quantum chemical investigation of the reactions of thorium cation with O2 and CO

    Science.gov (United States)

    Cox, Richard M.; Citir, Murat; Armentrout, P. B.; Battey, Samuel R.; Peterson, Kirk A.

    2016-05-01

    Kinetic energy dependent reactions of Th+ with O2 and CO are studied using a guided ion beam tandem mass spectrometer. The formation of ThO+ in the reaction of Th+ with O2 is observed to be exothermic and barrierless with a reaction efficiency at low energies of k/kLGS = 1.21 ± 0.24 similar to the efficiency observed in ion cyclotron resonance experiments. Formation of ThO+ and ThC+ in the reaction of Th+ with CO is endothermic in both cases. The kinetic energy dependent cross sections for formation of these product ions were evaluated to determine 0 K bond dissociation energies (BDEs) of D0(Th+-O) = 8.57 ± 0.14 eV and D0(Th+-C) = 4.82 ± 0.29 eV. The present value of D0 (Th+-O) is within experimental uncertainty of previously reported experimental values, whereas this is the first report of D0 (Th+-C). Both BDEs are observed to be larger than those of their transition metal congeners, TiL+, ZrL+, and HfL+ (L = O and C), believed to be a result of lanthanide contraction. Additionally, the reactions were explored by quantum chemical calculations, including a full Feller-Peterson-Dixon composite approach with correlation contributions up to coupled-cluster singles and doubles with iterative triples and quadruples (CCSDTQ) for ThC, ThC+, ThO, and ThO+, as well as more approximate CCSD with perturbative (triples) [CCSD(T)] calculations where a semi-empirical model was used to estimate spin-orbit energy contributions. Finally, the ThO+ BDE is compared to other actinide (An) oxide cation BDEs and a simple model utilizing An+ promotion energies to the reactive state is used to estimate AnO+ and AnC+ BDEs. For AnO+, this model yields predictions that are typically within experimental uncertainty and performs better than density functional theory calculations presented previously.

  4. Chemical activation of molecules by metals: Experimental studies of electron distributions and bonding

    International Nuclear Information System (INIS)

    This quarter has witnessed further progress both in our experimental methods of photoelectron spectroscopy and in our understanding the fundamental relationships between ionization energies and the chemistry of transition metal species. Progress continues on the new gas phase photoelectron spectrometer that combine improved capabilities for HeI/HeII UPS, XPS, and Auger investigations of organometallic molecules. Several measurements have been accomplished this year that were not possible previously. We have published the formal relationship between measured molecular ionization energies and thermodynamic bond dissociation energies, and applied the relationships to homonuclear and heteronuclear diatomic molecules, multiple bonds, and metal-ligand bonds. Studies of C-H bond activation have continued with examination of different degrees of Si-H bond addition to metals. the electronic effects of intermolecular interactions have been observed by comparing the ionizations of metal complexes in the gas phase with the ionizations of monolayer solid organometallic films prepared in ultra-high vacuum. The orientations of the molecules have been determined by scanning tunneling microscopy. Especially interesting has been the recent application of these techniques to the characterization of the soccer-ball shaped C60 molecule, buckminsterfullerene. Studies of the following complexes are described : Fe, Os, Nb, Mo, Rh, Re, Al, and Mn. 19 refs

  5. Bond-selective fragmentation of water molecules with intense, ultrafast, carrier envelope phase stabilized laser pulses

    CERN Document Server

    Mathur, D; Dharmadhikari, J A; Dharmadhikari, A K

    2013-01-01

    Carrier envelope phase (CEP) stabilized pulses of intense 800 nm light of 5 fs duration are used to probe the dissociation dynamics of dications of isotopically-substituted water, HOD. HOD$^{2+}$ dissociates into either H$^+$ + OD$^+$ or D$^+$ + OH$^+$. The branching ratio for these two channels is CEP-dependent; the OD$^+$/OH$^+$ ratio (relative to that measured with CEP-unstabilized pulses) varies from 150% to over 300% at different CEP values, opening prospects of isotope-dependent control over molecular bond breakage. The kinetic energy released as HOD$^{2+}$ Coulomb explodes is also CEP-dependent. Formidable theoretical challenges are identified for proper insights into the overall dynamics which involve non-adiabatic field ionization from HOD to HOD$^+$ and, thence, to HOD$^{2+}$ via electron rescattering.

  6. Carrier-envelope-phase-dependent dissociation of hydrogen

    International Nuclear Information System (INIS)

    We studied the dependence of dissociative ionization in H2 on carrier-envelope phase (CEP) of few-cycle (6 fs) near-infrared laser pulses. For low-energy channels, we present the first experimental observation of the CEP dependence of combined dissociation yield (with protons emitted in both directions), as well as the highest degree of asymmetry reported to date (40%). The observed modulations in both asymmetry and combined yield could be understood in terms of interference between different n-photon dissociation pathways—n and (n + 1) photon channels for asymmetry, n and (n + 2) photon channels for yield—as suggested by the general theory of CEP effects (Roudnev and Esry 2007 Phys. Rev. Lett. 99 220406). The yield modulation is found to be π-periodic in CEP, with its phase strongly dependent on fragment kinetic energy (and reversing its sign within the studied energy range), indicating that the dissociation yield does not simply follow the CEP dependence of maximum electric field, as a naïve intuition might suggest. We also find that a positively chirped pulse can lead to a higher dissociation probability than a transform-limited pulse. (paper)

  7. Electron-impact dissociation and ionization of NO+ ions

    Science.gov (United States)

    Belic, D. S.; Urbain, X.; Cherkani-Hassani, H.; Defrance, P.

    2016-07-01

    Absolute cross sections for electron-impact ionization and dissociation of NO+ ions are reported. Simple ionization to NO2+ ion and production of singly charged N+ and O+ and doubly charged N2+ and O2+ fragments have been investigated. The animated electron-ion crossed-beam method is applied in the energy range from the respective thresholds up to 2.5 keV. The maximum of the simple ionization cross section is found to be (3.49 ± 0.07) × 10‑17 cm2 at 135 eV. The total cross sections for N+ and O+ fragments at the maximum are found to be (13.9 ± 1.0) × 10‑17 cm2 and (14.0 ± 1.4) × 10‑17 cm2, respectively, both at an energy of 85 eV. By performing careful magnetic field scans of the detected signal, contributions of dissociative excitation and dissociative ionization to N+ and O+ production are determined separately. The cross sections for asymmetric dissociative ionization to N2+ and O2+ are found to be over one order of magnitude smaller. Distributions of the kinetic energy release to the fragments are determined for all dissociation processes.

  8. Analytic potentials and vibrational energies for Li$_{2}$ states dissociating to $\\mbox{Li}\\left(2S\\right)+\\mbox{Li}\\left(3P\\right)$. Part 1: The $^{2S+1}\\Pi_{u/g}$ states

    CERN Document Server

    Dattani, Nikesh S

    2015-01-01

    Analytic potentials are built for all four $^{2S+1}\\Pi_{u/g}$ states of Li$_{2}$ dissociating to Li$(2S)$ + Li$(3P)$: $3b(3^{3}\\Pi_{u})$, $3B(3^{1}\\Pi_{u})$, $3C(3^{1}\\Pi_{g}),$ and $3d(3^{3}\\Pi_{g})$. These potentials include the effect of spin-orbit coupling for large internuclear distances, and include state of the art long-range constants. This is the first successful demonstration of fully analytic diatomic potentials that capture features that are usually considered too difficult to capture without a point-wise potential, such as multiple minima, and shelves. Vibrational energies for each potential are presented for the isotopologues $^{6,6}$Li$_{2}$, $^{6,7}$Li$_{2}$, $^{7,7}$Li$_{2}$, and the elusive `halo nucleonic molecule' $^{11,11}$Li$_{2}$. These energies are claimed to be accurate enough for new high-precision experimental setups such as the one presented in {[}Sebastian \\emph{et al.} Phys. Rev. A, \\textbf{90}, 033417 (2014){]} to measure and assign energy levels of these electronic states, all ...

  9. An experimental investigation of the dissociative ionization process of argon cluster ions induced by electron impact

    International Nuclear Information System (INIS)

    Utilizing the Cold Target Recoil Ions Momentum Spectrometer (COLTRIMS), dissociative ionization of argon cluster was experimentally investigated by electron impact. The recoil ions produced both in the pure ionization process and the dissociative ionization channels are measured with collision energies from 100 and 1000 eV. The ratios of the dimer ions from pure ionization (Ar2P+) and the dimer ions from small cluster dissociation (Ar+2D) to the atomic argon ion (Ar+) in different stagnation pressures were obtained.

  10. Ab initio study of symmetrical tilt grain boundaries in bcc Fe: structural units, magnetic moments, interfacial bonding, local energy and local stress

    International Nuclear Information System (INIS)

    We present first-principle calculations on symmetric tilt grain boundaries (GBs) in bcc Fe. Using density functional theory (DFT), we studied the structural, electronic and magnetic properties of Σ3(111) and Σ11(332) GBs formed by rotation around the [110] axis. The optimized structures, GB energies and GB excess free volumes are consistent with previous DFT and classical simulation studies. The GB configurations can be interpreted by the structural unit model as given by Nakashima and Takeuchi (2000 ISIJ 86 357). Both the GBs are composed of similar structural units of three- and five-membered rings with different densities at the interface according to the rotation angle. The interface atoms with larger atomic volumes reveal higher magnetic moments than the bulk value, while the interface atoms with shorter bond lengths have reduced magnetic moments in each GB. The charge density and local density of states reveal that the interface bonds with short bond lengths have more covalent nature, where minority-spin electrons play a dominant role as the typical nature of ferromagnetic Fe. In order to understand the structural stability of these GBs, we calculated the local energy and local stress for each atomic region using the scheme of Shiihara et al (2010 Phys. Rev. B 81 075441). In each GB, the interface atoms with larger atomic volumes and enhanced magnetic moments reveal larger local energy increase and tensile stress. The interface atoms constituting more covalent-like bonds with reduced magnetic moments have lower local energy increase, contributing to the stabilization, while compressive stress is generated at these atoms. The relative stability between the two GBs can be understood by the local energies at the structural units. The local energy and local stress analysis is a powerful tool to investigate the structural properties of GBs based on the behavior of valence electrons. (paper)

  11. Influence of duration of phosphoric acid pre-etching on bond durability of universal adhesives and surface free-energy characteristics of enamel.

    Science.gov (United States)

    Tsujimoto, Akimasa; Barkmeier, Wayne W; Takamizawa, Toshiki; Watanabe, Hidehiko; Johnson, William W; Latta, Mark A; Miyazaki, Masashi

    2016-08-01

    The purpose of this study was to evaluate the influence of duration of phosphoric acid pre-etching on the bond durability of universal adhesives and the surface free-energy characteristics of enamel. Three universal adhesives and extracted human molars were used. Two no-pre-etching groups were prepared: ground enamel; and enamel after ultrasonic cleaning with distilled water for 30 s to remove the smear layer. Four pre-etching groups were prepared: enamel pre-etched with phosphoric acid for 3, 5, 10, and 15 s. Shear bond strength (SBS) values of universal adhesive after no thermal cycling and after 30,000 or 60,000 thermal cycles, and surface free-energy values of enamel surfaces, calculated from contact angle measurements, were determined. The specimens that had been pre-etched showed significantly higher SBS and surface free-energy values than the specimens that had not been pre-etched, regardless of the aging condition and adhesive type. The SBS and surface free-energy values did not increase for pre-etching times of longer than 3 s. There were no significant differences in SBS values and surface free-energy characteristics between the specimens with and without a smear layer. The results of this study suggest that phosphoric acid pre-etching of enamel improves the bond durability of universal adhesives and the surface free-energy characteristics of enamel, but these bonding properties do not increase for phosphoric acid pre-etching times of longer than 3 s. PMID:27315775

  12. Ab initio study of symmetrical tilt grain boundaries in bcc Fe: structural units, magnetic moments, interfacial bonding, local energy and local stress.

    Science.gov (United States)

    Bhattacharya, Somesh Kr; Tanaka, Shingo; Shiihara, Yoshinori; Kohyama, Masanori

    2013-04-01

    We present first-principle calculations on symmetric tilt grain boundaries (GBs) in bcc Fe. Using density functional theory (DFT), we studied the structural, electronic and magnetic properties of Σ3(111) and Σ11(332) GBs formed by rotation around the [110] axis. The optimized structures, GB energies and GB excess free volumes are consistent with previous DFT and classical simulation studies. The GB configurations can be interpreted by the structural unit model as given by Nakashima and Takeuchi (2000 ISIJ 86 357). Both the GBs are composed of similar structural units of three- and five-membered rings with different densities at the interface according to the rotation angle. The interface atoms with larger atomic volumes reveal higher magnetic moments than the bulk value, while the interface atoms with shorter bond lengths have reduced magnetic moments in each GB. The charge density and local density of states reveal that the interface bonds with short bond lengths have more covalent nature, where minority-spin electrons play a dominant role as the typical nature of ferromagnetic Fe. In order to understand the structural stability of these GBs, we calculated the local energy and local stress for each atomic region using the scheme of Shiihara et al (2010 Phys. Rev. B 81 075441). In each GB, the interface atoms with larger atomic volumes and enhanced magnetic moments reveal larger local energy increase and tensile stress. The interface atoms constituting more covalent-like bonds with reduced magnetic moments have lower local energy increase, contributing to the stabilization, while compressive stress is generated at these atoms. The relative stability between the two GBs can be understood by the local energies at the structural units. The local energy and local stress analysis is a powerful tool to investigate the structural properties of GBs based on the behavior of valence electrons. PMID:23478447

  13. Quantitative assessment of the multiplicity of carbon-halogen bonds: carbenium and halonium ions with F, Cl, Br, and I.

    Science.gov (United States)

    Kalescky, Robert; Zou, Wenli; Kraka, Elfi; Cremer, Dieter

    2014-03-13

    CX (X = F, Cl, Br, I) and CE bonding (E = O, S, Se, Te) was investigated for a test set of 168 molecules using the local CX and CE stretching force constants k(a) calculated at the M06-2X/cc-pVTZ level of theory. The stretching force constants were used to derive a relative bond strength order (RBSO) parameter n. As alternative bond strength descriptors, bond dissociation energies (BDE) were calculated at the G3 level or at the two-component NESC (normalized elimination of the small component)/CCSD(T) level of theory for molecules with X = Br, I or E = Se, Te. RBSO values reveal that both bond lengths and BDE values are less useful when a quantification of the bond strength is needed. CX double bonds can be realized for Br- or I-substituted carbenium ions where as suitable reference the double bond of the corresponding formaldehyde homologue is used. A triple bond cannot be realized in this way as the diatomic CX(+) ions with a limited π-donor capacity for X are just double-bonded. The stability of halonium ions increases with the atomic number of X, which is reflected by a strengthening of the fractional (electron-deficient) CX bonds. An additional stability increase of up to 25 kcal/mol (X = I) is obtained when the X(+) ion can form a bridged halonium ion with ethene such that a more efficient 2-electron-3-center bonding situation is created. PMID:24555526

  14. Photogenerated Exciton Dissociation in Highly Coupled Lead Salt Nanocrystal Assemblies

    KAUST Repository

    Choi, Joshua J.

    2010-05-12

    Internanocrystal coupling induced excitons dissociation in lead salt nanocrystal assemblies is investigated. By combining transient photoluminescence spectroscopy, grazing incidence small-angle X-ray scattering, and time-resolved electric force microscopy, we show that excitons can dissociate, without the aid of an external bias or chemical potential gradient, via tunneling through a potential barrier when the coupling energy is comparable to the exciton binding energy. Our results have important implications for the design of nanocrystal-based optoelectronic devices. © 2010 American Chemical Society.

  15. Dipolar dissociation dynamics in electron collisions with carbon monoxide

    CERN Document Server

    Chakraborty, Dipayan; Nandi, Dhananjay

    2016-01-01

    Dipolar dissociation processes in the electron collisions with carbon monoxide have been studied using time of flight (TOF) mass spectroscopy in combination with the highly differential velocity slice imaging (VSI) technique. Probing ion-pair states both positive and/or negative ions may be detected. The ion yield curve of negative ions provides the threshold energy for the ion-pair production. On the other hand, the kinetic energy distributions and angular distributions of the fragment anion provide detailed dynamics of the dipolar dissociation process. Two ion-pair states have been identified based on angular distribution measurements using VSI technique.

  16. Reaction heats and bond strengths based on a series of lectures given to postgraduate students at the University of Keele, 1960

    CERN Document Server

    Mortimer, C T

    1962-01-01

    Reaction Heats and Bond Strengths presents the variations in the heats of particular types of reaction. This book covers a variety of topics, including the hydrogenation and polymerization of olefinic compounds, the dissociation of organic and organo-metallic compounds, and the molecular-addition compounds. Organized into 10 chapters, this book begins with an overview of the concept of bond energy that can be very useful where a comparison is being made between two dissimilar molecules. This text then examines the strain in cyclopropane and cyclobutane, which is largely a result of angular str

  17. DISSOCIATIVE RECOMBINATION OF VIBRATIONALLY COLD CH+3 AND INTERSTELLAR IMPLICATIONS

    International Nuclear Information System (INIS)

    CH+3 is an important molecular ion in the astrochemistry of diffuse clouds, dense clouds, cometary comae, and planetary ionospheres. However, the rate of one of the major destruction mechanisms of CH+3, dissociative recombination (DR), has long been uncertain, hindering the use of CH+3 as an astrochemical probe. Here, we present the first absolute measurement of the DR of vibrationally cold CH+3, which has been made using the heavy storage ring CRYRING in Stockholm, Sweden. From our collision-energy-dependent cross sections, we infer a thermal rate constant of k(T) = 6.97(± 0.03) × 10–7(T/300)–0.61(±0.01) cm3 s–1 over the region 10 K ≤ T ≤ 1000 K. At low collision energies, we have measured the branching fractions of the DR products to be CH3 (0.00+0.01–0.00), CH2 + H (0.35+0.01–0.01), CH + 2H (0.20+0.02–0.02), CH + H2 (0.10+0.01–0.01), and C + H2 + H (0.35+0.01–0.02), indicating that two or more C-H bonds are broken in 65% of all collisions. We also present vibrational calculations which indicate that the CH+3 ions in the storage ring were relaxed to the vibrational ground state by spontaneous emission during the storage time. Finally, we discuss the implications of these new measurements for the observation of CH+3 in regions of the diffuse interstellar medium where CH+ is abundant.

  18. Thermodynamics of water dimer dissociation in the primary hydration shell of the iodide ion with temperature-dependent vibrational predissociation spectroscopy.

    Science.gov (United States)

    Wolke, Conrad T; Menges, Fabian S; Tötsch, Niklas; Gorlova, Olga; Fournier, Joseph A; Weddle, Gary H; Johnson, Mark A; Heine, Nadja; Esser, Tim K; Knorke, Harald; Asmis, Knut R; McCoy, Anne B; Arismendi-Arrieta, Daniel J; Prosmiti, Rita; Paesani, Francesco

    2015-03-12

    The strong temperature dependence of the I(-)·(H2O)2 vibrational predissociation spectrum is traced to the intracluster dissociation of the ion-bound water dimer into independent water monomers that remain tethered to the ion. The thermodynamics of this process is determined using van't Hoff analysis of key features that quantify the relative populations of H-bonded and independent water molecules. The dissociation enthalpy of the isolated water dimer is thus observed to be reduced by roughly a factor of three upon attachment to the ion. The cause of this reduction is explored with electronic structure calculations of the potential energy profile for dissociation of the dimer, which suggest that both reduction of the intrinsic binding energy and vibrational zero-point effects act to weaken the intermolecular interaction between the water molecules in the first hydration shell. Additional insights are obtained by analyzing how classical trajectories of the I(-)·(H2O)2 system sample the extended potential energy surface with increasing temperature. PMID:25647222

  19. Structure and dissociation dynamics of the Ne/sub 2/Cl/sub 2/ van der Waals complex

    Energy Technology Data Exchange (ETDEWEB)

    Hair, S.R.; Cline, J.I.; Bieler, C.R.; Janda, K.C.

    1989-03-15

    The structure and dynamics of Ne/sub 2/Cl/sub 2/ and Ne/sub 3/Cl/sub 2/ are studied by laser pump--probe spectroscopy. Analysis of a rotationally resolved Bleft-arrowX excitation band shows that Ne/sub 2/Cl/sub 2/ has a distorted tetrahedral structure with a Ne--Ne bond length of 3.23 A and Ne/sub 2/ center of mass to Cl/sub 2/ center of mass distance of 3.12 A. This structure is very close to that predicted by summing the atom--atom interactions. Excitation spectral shifts suggest a Ne/sub 3/Cl/sub 2/ structure with the neon atoms encircling the Cl/sub 2/ bond axis. The total van der Waals binding energy of Ne/sub 2/Cl/sub 2/ is found to be between 145.6 and 148.6 cm/sup -1/, which is 20 cm/sup -1/ greater than 2*D/sub 0/(Ne--Cl/sub 2/)+D/sub 0/(Ne/sub 2/). For Cl/sub 2/ stretching levels below upsilon' = 10, transfer of one Cl/sub 2/ vibrational quantum to the van der Waals vibrational modes is sufficient to dissociate both neon atoms from the complex. This indicates that the two neon atoms need not dissociate via independent, impulsive ''half-collisions'' which would require two Cl/sub 2/ vibrational quanta. Observation of a NeCl/sub 2/ dissociation fragment, however, indicates that such a sequential mechanism competes with the direct dissociation. Cl/sub 2/ fragment rotational state population distributions for different initial vibrational levels are characterized using a simple rotational surprisal analysis. Comparison of these surprisal plots to those of the NeCl/sub 2/ dissociation shows that as the size of the complex increases, so does the degree of statistical redistribution during the reaction.

  20. Dissociation of H2 on carbon doped aluminum cluster Al6C

    International Nuclear Information System (INIS)

    The dissociation of H2 molecule is the first step for chemical storage of hydrogen, and the energy barrier of the dissociation is the key factor to decide the kinetics of the regeneration of the storage material. As a light element, aluminum is an important candidate component for storage materials with high gravimetric density. This paper investigates the adsorption and dissociation of H2 on carbon doping aluminum cluster Al6C. The study shows that doping carbon into aluminum cluster can significantly change the electronic structure and increase the stability. Al6C has a few stable isomers with close energies and their structures are quite flexible. The molecular adsorption of H2 on Al6C is very weak, but the H2 molecule can be dissociated easily on this cluster. The stable product of the dissociated adsorption is searched and the different paths for the dissociation are investigated. During the dissociation of H2, the structure of the cluster adjusts accordingly, and strong orbital interaction between the hydrogen and the cluster occurs. The calculated energy barrier for the dissociation is only 0.30 eV, which means the dissociation can take place at moderate temperatures

  1. Bond Boom

    Institute of Scientific and Technical Information of China (English)

    2011-01-01

    The Ministry of Finance recently kick-started a pilot program allowing local governments of Shanghai and Shenzhen,and Zhejiang and Guangdong provinces to issue bonds for the first time.How will the new policy affect fiscal capacities of local governments and the broader economy? What else should the country do to build a healthy bond market? Economists and experts discussed these issues in an interview with the Shanghai Securities Journal.Edited excerpts follow.

  2. Bond Boom

    Institute of Scientific and Technical Information of China (English)

    2011-01-01

    The Ministry of Finance recently kick-started a pilot program allowing local governments of Shanghai and Shenzhen, and Zhejiang and Guangdong provinces to issue bonds for the first time. How will the new policy affect fiscal capacities of local governments and the broader economy? What else should the country do to build a healthy bond market? Economists and experts discussed these issues in an interview with the ShanghaiSecuritiesJournal. Edited excerpts follow:

  3. On the ClC halogen bond: a rotational study of CF3Cl-CO.

    Science.gov (United States)

    Caminati, Walther; Evangelisti, Luca; Feng, Gang; Giuliano, Barbara M; Gou, Qian; Melandri, Sonia; Grabow, Jens-Uwe

    2016-07-21

    The rotational spectra of two isotopologues (CF3(35)Cl-CO and CF3(37)Cl-CO) of the CF3Cl-CO adduct have been investigated and analyzed using supersonic-jet Fourier transform microwave spectroscopy, and found to have the features of a symmetric top. Rotational, centrifugal distortion, and nuclear quadrupole ((35)Cl and (37)Cl) coupling constants have been precisely obtained from high-resolution measurements. The two subunits of the complex are held together via a ClC halogen bond interaction. Information on the internal dynamics and the dissociation energy of the complex is provided. PMID:27049637

  4. Difference of Electron Capture and Transfer Dissociation Mass Spectrometry on Ni2+-, Cu2+-, and Zn2+-Polyhistidine Complexes in the Absence of Remote Protons

    Science.gov (United States)

    Asakawa, Daiki; De Pauw, Edwin

    2016-07-01

    Electron capture dissociation (ECD) and electron transfer dissociation (ETD) in metal-peptide complexes are dependent on the metal cation in the complex. The divalent transition metals Ni2+, Cu2+, and Zn2+ were used as charge carriers to produce metal-polyhistidine complexes in the absence of remote protons, since these metal cations strongly bind to neutral histidine residues in peptides. In the case of the ECD and ETD of Cu2+-polyhistidine complexes, the metal cation in the complex was reduced and the recombination energy was redistributed throughout the peptide to lead a zwitterionic peptide form having a protonated histidine residue and a deprotonated amide nitrogen. The zwitterion then underwent peptide bond cleavage, producing a and b fragment ions. In contrast, ECD and ETD induced different fragmentation processes in Zn2+-polyhistidine complexes. Although the N-Cα bond in the Zn2+-polyhistidine complex was cleaved by ETD, ECD of Zn2+-polyhistidine induced peptide bond cleavage accompanied with hydrogen atom release. The different fragmentation modes by ECD and ETD originated from the different electronic states of the charge-reduced complexes resulting from these processes. The details of the fragmentation processes were investigated by density functional theory.

  5. Adsorption and dissociation of H{sub 2}S on Mo(1 0 0) surface by first-principles study

    Energy Technology Data Exchange (ETDEWEB)

    Luo, Haijun; Cai, Jianqiu [Department of Physics, Zhejiang University, Hangzhou 310027, Zhejiang (China); College of Physics and Electronic Information Engineering, Wenzhou University, Wenzhou 325035, Zhejiang (China); Tao, Xiangming [Department of Physics, Zhejiang University, Hangzhou 310027, Zhejiang (China); Tan, Mingqiu, E-mail: mqtan@zju.edu.cn [Department of Physics, Zhejiang University, Hangzhou 310027, Zhejiang (China)

    2014-02-15

    Density-functional theory calculations had been used to investigate the adsorption and dissociation of H{sub 2}S on Mo(1 0 0) surface. Adsorption mechanisms of H{sub 2}S, HS, S and H on the Mo(1 0 0) surface were analyzed. H{sub 2}S was found to be adsorbed at bridge, hollow and top sites with adsorption energies of −1.25, −1.03 and −0.92 eV, respectively. HS was strongly chemically absorbed at hollow, bridge and top sites with adsorption energies of −4.51, −4.08 and −3.45 eV, respectively, and sulfur and hydrogen preferred to be absorbed at hollow and bridge sites, respectively. In addition, potential energy profiles of H{sub 2}S dissociation on Mo(1 0 0) had been constructed by a climbing image nudged elastic band method. Four possible dissociation pathways of the first H{sub 2}S dehydrogenation were examined with reaction barriers of 0.28, 0.37, 0.075, and 0.21 eV, respectively, while the energy barrier to break the S-H bond of HS with or without hydrogen co-adsorption was almost the same low. This work showed that the decomposition of H{sub 2}S on the molybdenum surface was kinetically and thermodynamically facile. Local densities of electronic states were further used to characterize the interaction between H{sub 2}S and substrate.

  6. Dissociative symptoms and dissociative disorders comorbidity in obsessive compulsive disorder: Symptom screening, diagnostic tools and reflections on treatment

    OpenAIRE

    Belli, Hasan

    2014-01-01

    Borderline personality disorder, conversion disorder and obsessive compulsive disorder frequently have dissociative symptoms. The literature has demonstrated that the level of dissociation might be correlated with the severity of obsessive compulsive disorder (OCD) and that those not responding to treatment had high dissociative symptoms. The structured clinical interview for DSM-IV dissociative disorders, dissociation questionnaire, somatoform dissociation questionnaire and dissociative expe...

  7. Hydrogen dissociation on metal surfaces

    NARCIS (Netherlands)

    Wijzenbroek, M.

    2016-01-01

    Dissociative chemisorption is an important reaction step in many catalytic reactions. An example of such a reaction is the Haber-Bosch process, which is used commercially to produce ammonia, an important starting material in the production of fertilisers. In theoretical descriptions of such chemical

  8. [Gender differences in dissociative disorders].

    Science.gov (United States)

    Spitzer, C; Freyberger, H J

    2008-01-01

    The relationship between mental illness, on the one hand, and sex and gender, on the other hand, has received interest since the beginning of medicine in antique times. A prototypical example of a seemingly woman-specific disease is hysteria. The term itself, which is derived from the Greek word for womb, denotes a psychosexual dimension comprising the current attitude towards sexuality and the dominating gender relationship. In addition, the colourful history of hysteria indicates that illness is not exclusively determined by biological factors, but also significantly by socio-cultural influences, for example in the treatment of hysterical women. Even nowadays, there is a wide-spread belief that dissociative symptoms and disorders, which have succeeded hysteria in current classification systems, are predominantly seen in women. However, empirical studies in the general population and in different clinical samples using sound instruments have indicated that dissociative symptoms do not differ between the genders. The seemingly dominance of dissociative disorders in women may also depend on the socio-cultural context, because men with dissociative disorders usually do not enter the general health system, but rather the legal system, i.e. they can be found in jail or forensic institutions. PMID:18185968

  9. The study of energy band structure and chemical bonding in yttrium carbide, yttrium and strontium dicarbides by the LMTO and Xα DV method

    International Nuclear Information System (INIS)

    The energy band structures of yttrium carbide, yttrium and strontium dicarbides are studied by the LMTO-method. The cohesive energies and the total and partial pressures are calculated. The local electronic structure of yttrium dicarbide is studied by the Xα discrete variational method; the cluster Y6C2 which includes the group C2-2 and all the nearest neighbours of this group is used in this study. The results of this calculations are used to analyse the chemical bonding and some properties of the compounds. It is shown that the main contribution to the chemical bonding between C2-2 group and yttrium atoms is provided by the orbital of the eg-local symmetry which belongs to the zone of metallic state. In the SrC2 this orbital is empty which explains the instablity of its crystal lattice. (author)

  10. Assessing the distinguishable cluster approximation based on the triple bond-breaking in the nitrogen molecule

    Science.gov (United States)

    Rishi, Varun; Perera, Ajith; Bartlett, Rodney J.

    2016-03-01

    Obtaining the correct potential energy curves for the dissociation of multiple bonds is a challenging problem for ab initio methods which are affected by the choice of a spin-restricted reference function. Coupled cluster (CC) methods such as CCSD (coupled cluster singles and doubles model) and CCSD(T) (CCSD + perturbative triples) correctly predict the geometry and properties at equilibrium but the process of bond dissociation, particularly when more than one bond is simultaneously broken, is much more complicated. New modifications of CC theory suggest that the deleterious role of the reference function can be diminished, provided a particular subset of terms is retained in the CC equations. The Distinguishable Cluster (DC) approach of Kats and Manby [J. Chem. Phys. 139, 021102 (2013)], seemingly overcomes the deficiencies for some bond-dissociation problems and might be of use in quasi-degenerate situations in general. DC along with other approximate coupled cluster methods such as ACCD (approximate coupled cluster doubles), ACP-D45, ACP-D14, 2CC, and pCCSD(α, β) (all defined in text) falls under a category of methods that are basically obtained by the deletion of some quadratic terms in the double excitation amplitude equation for CCD/CCSD (coupled cluster doubles model/coupled cluster singles and doubles model). Here these approximate methods, particularly those based on the DC approach, are studied in detail for the nitrogen molecule bond-breaking. The N2 problem is further addressed with conventional single reference methods but based on spatial symmetry-broken restricted Hartree-Fock (HF) solutions to assess the use of these references for correlated calculations in the situation where CC methods using fully symmetry adapted SCF solutions fail. The distinguishable cluster method is generalized: 1) to different orbitals for different spins (unrestricted HF based DCD and DCSD), 2) by adding triples correction perturbatively (DCSD(T)) and iteratively (DCSDT

  11. Dissociation of Methanol and Acetylene by slow Highly Charged Ion Collision

    International Nuclear Information System (INIS)

    We report here the results of dissociation of multiple charged methanol and acetylene molecules in collision with 1.2 MeV Ar8+ projectiles. We observed a wide range of dissociation products from the TOF spectrum starting from undissociated molecular ions, fragments losing an hydrogen atom due to breakage of C-H and/or O-H bonds, to complete rupture of C-C and C-O skeletons for the respective molecules. From the coincidence map of the fragments, we could separate out the different dissociation channels between carbon and oxygen ionic fragments as well as complete two-body dissociation events. The most striking feature in the breakup of CH3OH is the formation of H2+ and H3+ due to intramolecular rearrangement of the C-H bonds within the methyl group. In dissociative ionization studies of C2H2, we observed a diatom-like behaviour of the C-C charged complex as evidenced from the measured slopes of the coincidence islands for carbon atomic charged fragments and theoretical values determined from the charge and momentum distribution of the correlated particles. The shape and orientation of the islands give further information about the momentum balance in the fragmentation process in two-body dissociation

  12. Structure, bonding and energetics of N-heterocyclic carbene (NHC) stabilized low oxidation state group 2 (Be, Mg, Ca, Sr and Ba) metal complexes: A theoretical study

    Indian Academy of Sciences (India)

    Ashim Baishya; V Rao Mundlapati; Sharanappa Nembenna; Himansu S Biswal

    2014-11-01

    A series of N-heterocyclic carbene stabilized low oxidation state group 2 metal halide and hydrides with metal-metal bonds ([L(X) M-M(X) L]; L = NHC ((CHNH)2C:), M = Be, Mg, Ca, Sr and Ba, and X = Cl or H) has been studied by computational methods. The main objective of this study is to predict whether it is possible to stabilize neutral ligated low oxidation state alkaline-earth metal complexes with metal-metal bonds. The homolytic metal-metal Bond Dissociation Energy (BDE) calculation, Natural Bond Orbital (NBO) and Energy Decomposition Analyses (EDA) on density functional theory (DFT) optimized [L(X)M-M(X)L] complexes revealed that they are as stable as their -diketiminate, guanidinate and -diimine counterparts. The optimized structures of the complexes are in trans-linear geometries. The bond order analyses such as Wiberg Bond Indices (WBI) and Fuzzi Bond Order (FBO) confirm the existence of single bond between two metal atoms, and it is covalent in nature.

  13. Selective breaking of bonds in water with intense, 2-cycle, infrared laser pulses

    Energy Technology Data Exchange (ETDEWEB)

    Mathur, D., E-mail: atmol1@tifr.res.in; Dharmadhikari, A. K. [Tata Institute of Fundamental Research, 1 Homi Bhabha Road, Mumbai 400 005 (India); Dota, K. [Tata Institute of Fundamental Research, 1 Homi Bhabha Road, Mumbai 400 005 (India); Centre for Atomic and Molecular Physics, Manipal University, Manipal 576 104 (India); Dey, D.; Tiwari, A. K. [Indian Institute of Science Education and Research Kolkata, Mohanpur 741 246 (India); Dharmadhikari, J. A. [Centre for Atomic and Molecular Physics, Manipal University, Manipal 576 104 (India); De, S. [Saha Institute of Nuclear Physics, Bidhan Nagar, Kolkata 700 064 (India); Vasa, P. [Department of Physics, Indian Institute of Technology Bombay, Mumbai 400 076 (India)

    2015-12-28

    One of the holy grails of contemporary science has been to establish the possibility of preferentially breaking one of several bonds in a molecule. For instance, the two O–H bonds in water are equivalent: given sufficient energy, either one of them is equally likely to break. We report bond-selective molecular fragmentation upon application of intense, 2-cycle pulses of 800 nm laser light: we demonstrate up to three-fold enhancement for preferential bond breaking in isotopically substituted water (HOD). Our experimental observations are rationalized by means of ab initio computations of the potential energy surfaces of HOD, HOD{sup +}, and HOD{sup 2+} and explorations of the dissociation limits resulting from either O–H or O–D bond rupture. The observations we report present a formidable theoretical challenge that need to be taken up in order to gain insights into molecular dynamics, strong field physics, chemical physics, non-adiabatic processes, mass spectrometry, and time-dependent quantum chemistry.

  14. Selective breaking of bonds in water with intense, 2-cycle, infrared laser pulses

    International Nuclear Information System (INIS)

    One of the holy grails of contemporary science has been to establish the possibility of preferentially breaking one of several bonds in a molecule. For instance, the two O–H bonds in water are equivalent: given sufficient energy, either one of them is equally likely to break. We report bond-selective molecular fragmentation upon application of intense, 2-cycle pulses of 800 nm laser light: we demonstrate up to three-fold enhancement for preferential bond breaking in isotopically substituted water (HOD). Our experimental observations are rationalized by means of ab initio computations of the potential energy surfaces of HOD, HOD+, and HOD2+ and explorations of the dissociation limits resulting from either O–H or O–D bond rupture. The observations we report present a formidable theoretical challenge that need to be taken up in order to gain insights into molecular dynamics, strong field physics, chemical physics, non-adiabatic processes, mass spectrometry, and time-dependent quantum chemistry

  15. Dissociating Prediction Failure: Considerations from Music Perception

    DEFF Research Database (Denmark)

    Ross, Suzi; Hansen, Niels Christian

    2016-01-01

    Dissociating Prediction Failure: Considerations from Music Perception The Journal of Neuroscience, 16 March 2016, 36(11): 3103-3105;......Dissociating Prediction Failure: Considerations from Music Perception The Journal of Neuroscience, 16 March 2016, 36(11): 3103-3105;...

  16. Scaling of the critical free length for progressive unfolding of self-bonded graphene

    Energy Technology Data Exchange (ETDEWEB)

    Kwan, Kenny; Cranford, Steven W., E-mail: s.cranford@neu.edu [Laboratory of Nanotechnology in Civil Engineering (NICE), Department of Civil and Environmental Engineering, Northeastern University, 400 Snell Engineering, 360 Huntington Avenue, Boston, Massachusetts 02115 (United States)

    2014-05-19

    Like filled pasta, rolled or folded graphene can form a large nanocapsule surrounding a hollow interior. Use as a molecular carrier, however, requires understanding of the opening of such vessels. Here, we investigate a monolayer sheet of graphene as a theoretical trial platform for such a nanocapsule. The graphene is bonded to itself via aligned disulfide (S-S) bonds. Through theoretical analysis and atomistic modeling, we probe the critical nonbonded length (free length, L{sub crit}) that induces fracture-like progressive unfolding as a function of folding radius (R{sub i}). We show a clear linear scaling relationship between the length and radius, which can be used to determine the necessary bond density to predict mechanical opening/closing. However, stochastic dissipated energy limits any exact elastic formulation, and the required energy far exceeds the dissociation energy of the S-S bond. We account for the necessary dissipated kinetic energy through a simple scaling factor (Ω), which agrees well with computational results.

  17. Unusual dissociative adsorption of H2 over stoichiometric MgO thin film supported on molybdenum

    CERN Document Server

    Song, Zhenjun

    2015-01-01

    The dissociation of a hydrogen molecule on MgO(001) films deposited on Mo(001) surface is investigated systematically using periodic density-functional theory method. The unusual adsorption behavior of heterolytic dissociative hydrogen molecule at neighboring surface oxygen and surface magnesium, is clarified here. To my knowledge, this heterolytic dissociative state has never been found before on bulk MgO(001) or metal supported MgO(001) surfaces. The results confirm that, in all cases, the heterolytic dissociation is much more favorable that homolytic dissociation both energetically and kinetically. The energy difference between two dissociative states are very large, in the range of 1.1 eV ~ 1.5 eV for Mo supported 1 ML ~ 3 ML oxide films, which inhibits, to a great extent, the homolytic dissociation in the respect of reaction thermodynamics. The energy barrier of heterolytic dissociation are about 0.5 eV, much lower that the barrier of homolytic dissociation. The transformation reaction on thick films wil...

  18. Dissociation of N2, NO, and CO on transition metal surfaces

    DEFF Research Database (Denmark)

    Mavrikakis, Manos; Hansen, Lars Bruno; Mortensen, Jens Jørgen; Hammer, Bjørk; Nørskov, Jens Kehlet

    Using density functional theory we study the dissociation of N2, NO, and CO on transition metal surfaces. We discuss an efficient method to locate the minimum energy path and the transition state, and review recent calculations using this method to determine the transition state for dissociation of...

  19. Molecular Dissociation Induced by Electron Collisions

    Science.gov (United States)

    Wolf, Andreas

    2009-05-01

    Free electrons can efficiently break molecules or molecular ions in low-energy collisions by the processes of dissociative recombination or attachment. These processes make slow electrons efficient chemical agents in many environments. For dissociative recombination, in particular, studies of the underlying reaction paths and mechanisms have become possible on a uniquely elementary level in recent years both for theory and experiment. On the experimental side, collisions can be prepared at resolved collision energies down to the meV (10 Kelvin) level, increasingly gaining control also over the initial molecular quantum level, and individual events are detected and kinematically analyzed by fast-beam coincidence fragment imaging. Experiments are reported from the ion cooler ring TSR in Heidelberg. Stored beams of molecular ions cooled in their external and internal degrees of freedom are collinearly merged with intense and cold electron beams from cryogenic GaAs photocathodes, recently shown to yield fast cooling of the center-of-mass motion also for heavy and correspondingly slow molecular ion beams. To reconstruct the molecular fragmentation events multiparticle imaging can now be used systematically with collision energies set a wide range, especially aiming at specific electron capture resonances. Thus, for CF^+ it is found that the electronic state of the C fragment (^3P or ^1D) switches resonantly when the collision energy is changed by only a small fraction. As a new powerful tool, an energy-sensitive multi-strip surface-barrier detector (EMU) has been set up to measure with near-unity efficiency the masses of all fragments together with their hit positions in high-multiplicity events. Among many uses, this device allows internal molecular excitations to be derived for individual chemical channels in polyatomic fragmentation. New results will be presented in particular on the breakup of the hydronium ion (D3O^+).

  20. Ion Mobility Spectrometry Reveals Duplex DNA Dissociation Intermediates

    Science.gov (United States)

    Burmistrova, Anastasia; Gabelica, Valérie; Duwez, Anne-Sophie; De Pauw, Edwin

    2013-11-01

    Electrospray ionization (ESI) soft desolvation is widely used to investigate fragile species such as nucleic acids. Tandem mass spectrometry (MS/MS) gives access to the gas phase energetics of the intermolecular interactions in the absence of solvent, by following the dissociation of mass-selected ions. Ion mobility mass spectrometry (IMS) provides indications on the tridimensional oligonucleotide structure by attributing a collision cross section (CCS) to the studied ion. Electrosprayed duplexes longer than eight bases pairs retain their helical structure in a solvent-free environment. However, the question of conformational changes under activation in MS/MS studies remains open. The objective of this study is to probe binding energetics and characterize the unfolding steps occurring prior to oligonucleotide duplex dissociation. Comparing the evolution of CCS with collision energy and breakdown curves, we characterize dissociation pathways involved in CID-activated DNA duplex separation into single strands, and we demonstrate here the existence of stable dissociation intermediates. At fixed duplex length, dissociation pathways were found to depend on the percentage of GC base pairs and on their position in the duplex. Our results show that pure GC sequences undergo a gradual compaction until reaching the dissociation intermediate: A-helix. Mixed AT-GC sequences were found to present at least two conformers: a classic B-helix and an extended structure where the GC tract is a B-helix and the AT tract(s) fray. The dissociation in single strands takes place from both conformers when the AT base pairs are enclosed between two GC tracts or only from the extended conformer when the AT tract is situated at the end(s) of the sequence.

  1. Intense 2-cycle laser pulses induce time-dependent bond-hardening in a polyatomic molecule

    CERN Document Server

    Dota, K; Tiwari, A K; Dharmadhikari, J A; Dharmadhikari, A K; Mathur, D

    2012-01-01

    A time-dependent bond-hardening process is discovered in a polyatomic molecule (tetramethyl silane, TMS) using few-cycle pulses of intense 800 nm light. In conventional mass spectrometry, symmetrical molecules like TMS do not exhibit a prominent molecular ion (TMS$^+$) as unimolecular dissociation into [Si(CH$_3$)$_3]^+$ proceeds very fast. Under strong field and few-cycle conditions, this dissociation channel is defeated by time-dependent bond-hardening: a field-induced potential well is created in the TMS$^+$ potential energy curve that effectively traps a wavepacket. The time-dependence of this bond hardening process is verified using longer-duration ($\\geq$ 100 fs) pulses; the relatively "slower" fall-off of optical field in such pulses allows the initially trapped wavepacket to leak out, thereby rendering TMS$^+$ unstable once again. Our results are significant as they demonstrate (i) optical generation of polyatomic ions that are normally inaccessible and (ii) optical control of dynamics in strong field...

  2. Environmentally dependent bond-order potentials: New developments and applications

    Indian Academy of Sciences (India)

    D Nguyen-Manh; D G Pettifor; D J H Cockayne; M Mrovec; S Znam; V Vitek

    2003-01-01

    The bond-order potentials (BOPs) idea employs the orthogonal two-centre tight-binding (TB) representation for the bond energy and the Harris–Foulkes approximation for the repulsive pairwise contribution. In the last ten years, although many efforts have been focused on theoretical calculations of the bond order expression, the BOPs still suffers from the uncertainty of how best to choose the semi-empirical TB parameters that enter the scheme. In this paper, we review recent developments to obtain the reliable and transferable BOPs which help to extend the accuracy and applicability to technologically important multicomponent systems. Firstly, we have found that a simple pair potential is unsuitable for describing the environmental screening effects due to the and orbital overlap repulsion in transition metal alloys and therefore the inability to reproduce the negative Cauchy pressures exhibiting in strong covalent systems. By adding the environmental dependent repulsive term, the Cauchy pressure problem has been removed and we are now able to get the BOPs for studying dislocations, extended defects and mechanical properties of hightemperature intermetallic Ti–Al alloys. In particular, new results on the core structures and possible dissociation of different type of dislocations will be discussed. Secondly, we present the first derivation of explicit analytic expressions for environmental dependence of , and bond integrals by inverting the non-orthogonal matrix. We illustrate the power of this new formalism by showing that it not only captures the transferability of bond integrals between Mo, Si and MoSi2 but also predicts the large discontinuities between first and second nearest neighbours for $pp\\sigma, pp\\pi$ and $dd\\pi$ even though absence of any discontinuity for the $dd\\sigma$ bond integral. A new environmentally dependent BOPs has been developed for bcc-Mo indicating that the core structure of 1/2$\\langle$111$\\rangle$ screw dislocations is

  3. Correlations in the hadronic double diffractive dissociation

    International Nuclear Information System (INIS)

    A given reaction of double diffractive dissociation is studied based on the three-component Deck Model. The correlations among the diffractive slope, the effective mass of the dissociated particle sub-system and the dissociation angle in the Gottfried-Jackson are studied based in this model. 9 refs, 19 figs

  4. Insulation bonding test system

    Science.gov (United States)

    Beggs, J. M.; Johnston, G. D.; Coleman, A. D.; Portwood, J. N.; Saunders, J. M.; Redmon, J. W.; Porter, A. C. (Inventor)

    1984-01-01

    A method and a system for testing the bonding of foam insulation attached to metal is described. The system involves the use of an impacter which has a calibrated load cell mounted on a plunger and a hammer head mounted on the end of the plunger. When the impacter strikes the insulation at a point to be tested, the load cell measures the force of the impact and the precise time interval during which the hammer head is in contact with the insulation. This information is transmitted as an electrical signal to a load cell amplifier where the signal is conditioned and then transmitted to a fast Fourier transform (FFT) analyzer. The FFT analyzer produces energy spectral density curves which are displayed on a video screen. The termination frequency of the energy spectral density curve may be compared with a predetermined empirical scale to determine whether a igh quality bond, good bond, or debond is present at the point of impact.

  5. Dissociative chemisorption of N2 on Rhenium

    DEFF Research Database (Denmark)

    Billing, Gert D.; Guldberg, Annette; Henriksen, Niels Engholm;

    1990-01-01

    The dissociative chemisorption of nitrogen on the (0001) rhenium surface is studied at low impact energies, where tunnelling processes are important. A quantum-classical model is used in which two coordinates, the distance from the surface and the vibrational coordinate, are treated quantum...

  6. Multidimensional effects on dissociation of N-2 on Ru(0001)

    DEFF Research Database (Denmark)

    Diaz, C.; Vincent, J.K.; Krishnamohan, G.P.;

    2006-01-01

    The applicability of the Born-Oppenheimer approximation to molecule-metal surface reactions is presently a topic of intense debate. We have performed classical trajectory calculations on a prototype activated dissociation reaction, of N-2 on Ru(0001), using a potential energy surface based on den...

  7. Dissociative sticking of CH4 on Ru(0001)

    DEFF Research Database (Denmark)

    Nielsen, Jane Hvolbæk; Holmblad, Peter Mikal; Chorkendorff, Ib

    1999-01-01

    In this study the CH4 dissociation probability on Ru(0001) is found for various translational and vibrational energies. The absolute sticking values are determined from King and Wells experiments and carbon uptake curves. The carbon amount is determined from the recombination signal of carbon with...

  8. BEP-relations for N2 dissociation over stepped transition metal and alloy surfaces

    DEFF Research Database (Denmark)

    Fronczek-Munter, Ture Rønved; Bligaard, Thomas; Christensen, Claus H.;

    2008-01-01

    We present density functional theory (DFT) calculations for N(2) dissociation on stepped face-centred cubic (211) surface slabs. By using the same crystal structure, the same adsorption site for atomic nitrogen, and the same transition-state bond length of N(2) over a range of pure metal surfaces...

  9. Electron-driven excitations and dissociation of molecules

    Energy Technology Data Exchange (ETDEWEB)

    Miller, Greg [Univ. of California, Davis, CA (United States); Orel, Ann E. [Univ. of California, Davis, CA (United States)

    2015-02-13

    This program studied how energy is interchanged in electron and photon collisions with molecules leading to ex-citation and dissociation. Modern ab initio techniques, both for the photoionization and electron scattering, and the subsequent nuclear dynamics studies, are used to accurately treat these problems. This work addresses vibrational ex-citation and dissociative attachment following electron impact, and the dynamics following inner shell photoionzation. These problems are ones for which a full multi-dimensional treatment of the nuclear dynamics is essential and where non-adiabatic effects are expected to be important.

  10. A direct, local model of dissociative recombination of HF+

    International Nuclear Information System (INIS)

    The direct mechanism of dissociative recombination of HF+ have been studied by propagating wave packets on 30 resonant states. The relevant electronic states have been calculated ab initio with electron scattering calculations and multireference configuration interaction calculations. We obtain a qualitative good agreement with experiments for energies in the range from 0.04 eV to 10 eV. Some of the structures in the experimental cross section can be explained by the direct capture and dissociation along the resonant states. To fully describe the measured cross section, the electronic couplings between the neutral states cannot be neglected.

  11. Multiphoton ionization/dissociation of osmium tetroxide

    International Nuclear Information System (INIS)

    The mechanisms leading to laser multiphoton ionization and dissociation (MPI/MPD) of osmium tetroxide (OsO4) have been investigated from measurements of the kinetic energies of product ions (Os+, Os2+, OsO+, O2+, O+) and photoelectrons as a function of the laser wavelength. Neutral channels, intermediate to the dominant Os+ ionization channel, such as OsO4→OsO4-n+nO are examined using resonance-enhanced multiphoton ionization (REMPI) of the fast O atoms. Equipartition of the available photon energy among the fragments is observed. The wavelength dependence of the Os+ ion signal suggests that one or more of the steps leading to Os+ ions involve molecular ions and/or excited neutral atoms. The observed preponderance of very slow (2+ is shown to result primarily from REMPI of Os+

  12. Dissociation from beloved unhealthy brands decreases preference for and consumption of vegetables.

    Science.gov (United States)

    Trump, Rebecca K; Connell, Paul M; Finkelstein, Stacey R

    2015-09-01

    Many people form strong bonds with brands, including those for unhealthy foods. Thus, prompting people to dissociate from beloved but unhealthy food brands is an intuitively appealing means to shift consumption away from unhealthy options and toward healthy options. Contrary to this position, we demonstrate that dissociating from unhealthy but beloved brands diminishes people's interest in consuming vegetables because the dissociation depletes self-regulatory resources. Across three experimental studies, we manipulate dissociation from two beloved brands both implicitly (studies 1-2) and explicitly (study 3) and observe effects on both preference for vegetables (studies 2-3) and actual vegetable consumption (study 1). In study 1, participants consumed fewer vegetables following dissociation from (vs. association with) a beloved candy brand. Study 2 demonstrates that the effect of depletion on preference for vegetables is more pronounced for those who strongly identify with the brand, as these individuals are most depleted by the dissociation attempt. Finally, study 3 illustrates that the difficulty experienced when trying to dissociate from beloved brands drives the observed effects on vegetable preference and consumption for those who strongly (vs. weakly) identify with the brand. PMID:26009206

  13. The influence of large-amplitude librational motion on the hydrogen bond energy for alcohol–water complexes

    DEFF Research Database (Denmark)

    Andersen, Jonas; Heimdal, J.; Larsen, René Wugt

    2015-01-01

    The far-infrared absorption spectra have been recorded for hydrogen-bonded complexes of water with methanol and t-butanol embedded in cryogenic neon matrices at 2.8 K. The partial isotopic substitution of individual subunits enabled by a dual inlet deposition procedure provides for the first time...... unambiguous assignments of the intermolecular high-frequency out-of-plane and low-frequency in-plane donor OH librational modes for mixed alcohol–water complexes. The vibrational assignments confirm directly that water acts as the hydrogen bond donor in the most stable mixed complexes and the tertiary alcohol...

  14. Dissociation of NO2 in femtosecond intense fields

    Institute of Scientific and Technical Information of China (English)

    ZHU Jingyi; GUO Wei; WANG Yanqiu; WANG Li

    2006-01-01

    Experimental investigations on the dissociation and ionization processes of NO2 in intense fields at wavelengths of 810, 405 and 270 nm, are presented. The ratios of NO~/NO+ are found to be independent of the laser intensity at these three wavelengths, but show strong dependence on the wavelengths. Longer wavelength produces a larger parent-ion yield in comparison with 405 nm. Peak profiles of all the fragment ions clearly show little kinetic energy releasing during the dissociation. Fragment ions are suggested to be produced from dissociation of the field ionized parent ions. Our results indicate that laser pulse wavelengths are the most important parameters in ionization-fragmen- tation process of polyatomic molecules in intense field other than the laser intensity.

  15. Reaction paths of phosphine dissociation on silicon (001)

    International Nuclear Information System (INIS)

    Using density functional theory and guided by extensive scanning tunneling microscopy (STM) image data, we formulate a detailed mechanism for the dissociation of phosphine (PH3) molecules on the Si(001) surface at room temperature. We distinguish between a main sequence of dissociation that involves PH2+H, PH+2H, and P+3H as observable intermediates, and a secondary sequence that gives rise to PH+H, P+2H, and isolated phosphorus adatoms. The latter sequence arises because PH2 fragments are surprisingly mobile on Si(001) and can diffuse away from the third hydrogen atom that makes up the PH3 stoichiometry. Our calculated activation energies describe the competition between diffusion and dissociation pathways and hence provide a comprehensive model for the numerous adsorbate species observed in STM experiments

  16. Reaction paths of phosphine dissociation on silicon (001)

    Science.gov (United States)

    Warschkow, O.; Curson, N. J.; Schofield, S. R.; Marks, N. A.; Wilson, H. F.; Radny, M. W.; Smith, P. V.; Reusch, T. C. G.; McKenzie, D. R.; Simmons, M. Y.

    2016-01-01

    Using density functional theory and guided by extensive scanning tunneling microscopy (STM) image data, we formulate a detailed mechanism for the dissociation of phosphine (PH3) molecules on the Si(001) surface at room temperature. We distinguish between a main sequence of dissociation that involves PH2+H, PH+2H, and P+3H as observable intermediates, and a secondary sequence that gives rise to PH+H, P+2H, and isolated phosphorus adatoms. The latter sequence arises because PH2 fragments are surprisingly mobile on Si(001) and can diffuse away from the third hydrogen atom that makes up the PH3 stoichiometry. Our calculated activation energies describe the competition between diffusion and dissociation pathways and hence provide a comprehensive model for the numerous adsorbate species observed in STM experiments.

  17. Iron-boron pair dissociation in silicon under strong illumination

    Directory of Open Access Journals (Sweden)

    Xiaodong Zhu

    2013-08-01

    Full Text Available The dissociation of iron-boron pairs (FeB in Czochralski silicon under strong illumination was investigated. It is found that the dissociation process shows a double exponential dependence on time. The first fast process is suggested to be caused by a positive Fe in FeB capturing two electrons and diffusion triggered by the electron-phonon interactions, while the second slow one would involve the capturing of one electron followed by temperature dependent dissociation with an activation energy of (0.21 ± 0.03 eV. The results are important for understanding and controlling the behavior of FeB in concentrator solar cells.

  18. Reaction paths of phosphine dissociation on silicon (001)

    Energy Technology Data Exchange (ETDEWEB)

    Warschkow, O.; McKenzie, D. R. [Centre for Quantum Computation and Communication Technology, School of Physics, The University of Sydney, Sydney, NSW 2006 (Australia); Curson, N. J. [Centre for Quantum Computation and Communication Technology, School of Physics, The University of New South Wales, Sydney, NSW 2052 (Australia); London Centre for Nanotechnology and Department of Electronic and Electrical Engineering, University College London, 17-19 Gordon Street, London WC1H 0AH (United Kingdom); Schofield, S. R. [Centre for Quantum Computation and Communication Technology, School of Physics, The University of New South Wales, Sydney, NSW 2052 (Australia); London Centre for Nanotechnology and Department of Physics and Astronomy, University College, 17-19 Gordon Street, London WC1H 0AH (United Kingdom); Marks, N. A. [Centre for Quantum Computation and Communication Technology, School of Physics, The University of Sydney, Sydney, NSW 2006 (Australia); Discipline of Physics & Astronomy, Curtin University, GPO Box U1987, Perth, WA (Australia); Wilson, H. F. [Centre for Quantum Computation and Communication Technology, School of Physics, The University of Sydney, Sydney, NSW 2006 (Australia); CSIRO Virtual Nanoscience Laboratory, Parkville, VIC 3052 (Australia); School of Applied Sciences, RMIT University, Melbourne, VIC 3000 (Australia); Radny, M. W.; Smith, P. V. [School of Mathematical and Physical Sciences, The University of Newcastle, Callaghan, NSW 2308 (Australia); Reusch, T. C. G.; Simmons, M. Y. [Centre for Quantum Computation and Communication Technology, School of Physics, The University of New South Wales, Sydney, NSW 2052 (Australia)

    2016-01-07

    Using density functional theory and guided by extensive scanning tunneling microscopy (STM) image data, we formulate a detailed mechanism for the dissociation of phosphine (PH{sub 3}) molecules on the Si(001) surface at room temperature. We distinguish between a main sequence of dissociation that involves PH{sub 2}+H, PH+2H, and P+3H as observable intermediates, and a secondary sequence that gives rise to PH+H, P+2H, and isolated phosphorus adatoms. The latter sequence arises because PH{sub 2} fragments are surprisingly mobile on Si(001) and can diffuse away from the third hydrogen atom that makes up the PH{sub 3} stoichiometry. Our calculated activation energies describe the competition between diffusion and dissociation pathways and hence provide a comprehensive model for the numerous adsorbate species observed in STM experiments.

  19. [Prison psychosis and dissociative disorders].

    Science.gov (United States)

    al Chaabani, S; Bataille, M

    2002-12-01

    Through a few clinical case histories stemming from their daily activities at the psychiatric section of the Lantin Prison, the authors propose to revisit the classic concept of Prison psychosis. They broaden its limits to include other psychotic and dissociative phenomena common to the jail population. This requires a strict differential diagnosis, allowing to eliminate some similar pathologies; nevertheless, some difficulties and imperfections persist. The development of the psychosis, the input from the jail architecture and milieu, the predisposing as well as facilitating factors linked to the personality of the inmate, and triggering phenomena are discussed. Finally, the comorbidity between these psychotic/dissociative phenomena and the borderline & histrionic personality disorders is envisaged. PMID:12632838

  20. Coulomb dissociation of N,2120

    Science.gov (United States)

    Röder, Marko; Adachi, Tatsuya; Aksyutina, Yulia; Alcantara, Juan; Altstadt, Sebastian; Alvarez-Pol, Hector; Ashwood, Nicholas; Atar, Leyla; Aumann, Thomas; Avdeichikov, Vladimir; Barr, M.; Beceiro, Saul; Bemmerer, Daniel; Benlliure, Jose; Bertulani, Carlos; Boretzky, Konstanze; Borge, Maria J. G.; Burgunder, G.; Caamaño, Manuel; Caesar, Christoph; Casarejos, Enrique; Catford, Wilton; Cederkäll, Joakim; Chakraborty, S.; Chartier, Marielle; Chulkov, Leonid; Cortina-Gil, Dolores; Crespo, Raquel; Datta Pramanik, Ushasi; Diaz-Fernandez, Paloma; Dillmann, Iris; Elekes, Zoltan; Enders, Joachim; Ershova, Olga; Estrade, A.; Farinon, F.; Fraile, Luis M.; Freer, Martin; Freudenberger, M.; Fynbo, Hans; Galaviz, Daniel; Geissel, Hans; Gernhäuser, Roman; Göbel, Kathrin; Golubev, Pavel; Gonzalez Diaz, D.; Hagdahl, Julius; Heftrich, Tanja; Heil, Michael; Heine, Marcel; Heinz, Andreas; Henriques, Ana; Holl, Matthias; Ickert, G.; Ignatov, Alexander; Jakobsson, Bo; Johansson, Hâkan; Jonson, Björn; Kalantar-Nayestanaki, Nasser; Kanungo, Rituparna; Kelic-Heil, Aleksandra; Knöbel, Ronja; Kröll, Thorsten; Krücken, Reiner; Kurcewicz, J.; Kurz, Nikolaus; Labiche, Marc; Langer, Christoph; Le Bleis, Tudi; Lemmon, Roy; Lepyoshkina, Olga; Lindberg, Simon; Machado, Jorge; Marganiec, Justyna; Mostazo Caro, Magdalena; Movsesyan, Alina; Najafi, Mohammad Ali; Nilsson, Thomas; Nociforo, Chiara; Panin, Valerii; Paschalis, Stefanos; Perea, Angel; Petri, Marina; Pietri, S.; Plag, Ralf; Prochazka, A.; Rahaman, Md. Anisur; Rastrepina, Ganna; Reifarth, Rene; Ribeiro, Guillermo; Ricciardi, M. Valentina; Rigollet, Catherine; Riisager, Karsten; Rossi, Dominic; Sanchez del Rio Saez, Jose; Savran, Deniz; Scheit, Heiko; Simon, Haik; Sorlin, Olivier; Stoica, V.; Streicher, Branislav; Taylor, Jon; Tengblad, Olof; Terashima, Satoru; Thies, Ronja; Togano, Yasuhiro; Uberseder, Ethan; Van de Walle, J.; Velho, Paulo; Volkov, Vasily; Wagner, Andreas; Wamers, Felix; Weick, Helmut; Weigand, Mario; Wheldon, Carl; Wilson, G.; Wimmer, Christine; Winfield, J. S.; Woods, Philip; Yakorev, Dmitry; Zhukov, Mikhail; Zilges, Andreas; Zuber, Kai; R3B Collaboration

    2016-06-01

    Neutron-rich light nuclei and their reactions play an important role in the creation of chemical elements. Here, data from a Coulomb dissociation experiment on N,2120 are reported. Relativistic N,2120 ions impinged on a lead target and the Coulomb dissociation cross section was determined in a kinematically complete experiment. Using the detailed balance theorem, the 19N (n ,γ )20N and 20N (n ,γ ) 21N excitation functions and thermonuclear reaction rates have been determined. The 19 (n ,γ )20N rate is up to a factor of 5 higher at T <1 GK with respect to previous theoretical calculations, leading to a 10% decrease in the predicted fluorine abundance.