WorldWideScience

Sample records for halide molecular liquids

  1. Interactions between halide anions and a molecular hydrophobic interface.

    Science.gov (United States)

    Rankin, Blake M; Hands, Michael D; Wilcox, David S; Fega, K Rebecca; Slipchenko, Lyudmila V; Ben-Amotz, Dor

    2013-01-01

    Interactions between halide ions (fluoride and iodide) and t-butyl alcohol (TBA) dissolved in water are probed using a recently developed hydration-shell spectroscopic technique and theoretical cluster and liquid calculations. High ignal-to-noise Raman spectroscopic measurements are combined with multivariate curve resolution (Raman-MCR) to reveal that while there is little interaction between aqueous fluoride ions and TBA, iodide ions break down the tetrahedral hydration-shell structure of TBA and produce a red-shift in its CH stretch frequency, in good agreement with the theoretical effective fragment potential (EFP) molecular dynamics simulations and hybrid quantum/EFP frequency calculations. The results imply that there is a significantly larger probability of finding iodide than fluoride in the first hydration shell of TBA, although the local iodide concentration is apparently not as high as in the surrounding bulk aqueous NaI solution.

  2. A quantum mechanical study of alkylimidazolium halide ionic liquids

    Science.gov (United States)

    Li, Wei; Qi, Chuansong; Rong, Hua; Wu, Xinmin; Gong, Liangfa

    2012-07-01

    Thirty imidazolium (IM) halide compounds were studied using quantum chemical calculations. Geometry optimization and interaction energy calculations were performed using the B3LYP/6-311++G(d,p) method for ions composed of one alkylimidazolium cation and two or three halogen anions. The obtained structures were consistent with experimental results. In addition, a linear correlation between melting points and interaction energies was obtained for the compounds studied, and this relationship was consistent with that obtained for amino acid cation based ionic liquids. Our Letter demonstrates the potential for quantum mechanical calculations to predict the melting points of ionic liquids.

  3. Physics of solid and liquid alkali halide surfaces near the melting point

    Science.gov (United States)

    Zykova-Timan, T.; Ceresoli, D.; Tartaglino, U.; Tosatti, E.

    2005-10-01

    This paper presents a broad theoretical and simulation study of the high-temperature behavior of crystalline alkali halide surfaces typified by NaCl(100), of the liquid NaCl surface near freezing, and of the very unusual partial wetting of the solid surface by the melt. Simulations are conducted using two-body rigid-ion Born-Mayer-Huggins-Fumi-Tosi (BMHFT) potentials, with full treatment of long-range Coulomb forces. After a preliminary check of the description of bulk NaCl provided by these potentials, which seems generally good even at the melting point, we carry out a new investigation of solid and liquid surfaces. Solid NaCl(100) is found in this model to be very anharmonic and yet exceptionally stable when hot. It is predicted by a thermodynamic integration calculation of the surface free energy that NaCl(100) should be a well-ordered, nonmelting surface, metastable even well above the melting point. By contrast, the simulated liquid NaCl surface is found to exhibit large thermal fluctuations and no layering order. In spite of that, it is shown to possess a relatively large surface free energy. The latter is traced to a surface entropy deficit, reflecting some kind of surface short-range order. We show that the surface short-range order is most likely caused by the continuous transition of the bulk ionic melt into the vapor, made of NaCl molecules and dimers rather than of single ions. Finally, the solid-liquid interface free energy is derived through Young's equation from direct simulation of partial wetting of NaCl(100) by a liquid droplet. The resulting interface free energy is large, in line with the conspicuous solid-liquid 27% density difference. A partial wetting angle near 50° close to the experimental value of 48° is obtained in the process. It is concluded that three elements, namely, the exceptional anharmonic stability of the solid (100) surface, the molecular short-range order at the liquid surface, and the costly solid-liquid interface, all

  4. Regioselective chlorination and bromination of unprotected anilines under mild conditions using copper halides in ionic liquids

    Directory of Open Access Journals (Sweden)

    Han Wang

    2012-05-01

    Full Text Available By using ionic liquids as solvents, the chlorination or bromination of unprotected anilines at the para-position can be achieved in high yields with copper halides under mild conditions, without the need for potentially hazardous operations such as supplementing oxygen or gaseous HCl.

  5. Ionic and Molecular Liquids

    DEFF Research Database (Denmark)

    Chaban, Vitaly V.; Prezhdo, Oleg

    2013-01-01

    Because of their outstanding versatility, room-temperature ionic liquids (RTILs) are utilized in an ever increasing number of novel and fascinating applications, making them the Holy Grail of modern materials science. In this Perspective, we address the fundamental research and prospective...... applications of RTILs in combination with molecular liquids, concentrating on three significant areas: (1) the use of molecular liquids to decrease the viscosity of RTILs; (2) the role of RTIL micelle formation in water and organic solvents; and (3) the ability of RTILs to adsorb pollutant gases. Current...

  6. Solubility of alkali metal halides in the ionic liquid [C4C1im][OTf].

    Science.gov (United States)

    Kuzmina, O; Bordes, E; Schmauck, J; Hunt, P A; Hallett, J P; Welton, T

    2016-06-28

    The solubilities of the metal halides LiF, LiCl, LiBr, LiI, NaF, NaCl, NaBr, NaI, KF, KCl, KBr, KI, RbCl, CsCl, CsI, were measured at temperatures ranging from 298.15 to 378.15 K in the ionic liquid 1-butyl-3-methylimidazolium trifluoromethanesulfonate ([C4C1im][OTf]). Li(+), Na(+) and K(+) salts with anions matching the ionic liquid have also been investigated to determine how well these cations dissolve in [C4C1im][OTf]. This study compares the influence of metal cation and halide anion on the solubility of salts within this ionic liquid. The highest solubility found was for iodide salts, and the lowest solubility for the three fluoride salts. There is no outstanding difference in the solubility of salts with matching anions in comparison to halide salts. The experimental data were correlated employing several phase equilibria models, including ideal mixtures, van't Hoff, the λh (Buchowski) equation, the modified Apelblat equation, and the non-random two-liquid model (NRTL). It was found that the van't Hoff model gave the best correlation results. On the basis of the experimental data the thermodynamic dissolution parameters (ΔH, ΔS, and ΔG) were determined for the studied systems together with computed gas phase metathesis parameters. Dissolution depends on the energy difference between enthalpies of fusion and dissolution of the solute salt. This demonstrates that overcoming the lattice energy of the solid matrix is the key to the solubility of inorganic salts in ionic liquids.

  7. Vibrational energy relaxation of liquid aryl-halides X-C6H5 (X = F, Cl, Br, I).

    Science.gov (United States)

    Pein, Brandt C; Seong, Nak-Hyun; Dlott, Dana D

    2010-10-07

    Anti-Stokes Raman spectroscopy was used to probe vibrational energy dynamics in liquid ambient-temperature aryl-halides, X-Ph (X = F, Cl, Br, I; -Ph = C(6)H(5)), following IR excitation of a 3068 cm(-1) CH-stretching transition. Five ring vibrations and two substituent-dependent vibrations were monitored in each aryl-halide. Overall, the vibrational relaxation (VR) lifetimes in aryl-halides were shorter than those in normal benzene (H-Ph). The aryl-halide CH-stretch lifetimes increased in the order F, Cl, Br, I, ranging from 2.5 to 3.4 ps, compared with 6.2 ps in H-Ph. The aryl-halide energy transfer processes were similar overall with four exceptions. Three of the four exceptions could be explained as a result of faster VR of midrange vibrations (1000-1600 cm(-1)) in the heavier aryl-halides. The fourth appeared to result from a coincidental resonance in chlorobenzene that does not occur in the other aryl-halides. Among the aryl-halides, the decay of CH-stretching excitations (∼3070 cm(-1)) was slower in the heavier species, but the decay of midrange vibrations was faster in the heavier species. This seeming contradiction could be explained if VR depended primarily on the density of states (DOS) of the lower tiers of vibrational excitations. The DOS for the first few (1-4) tiers is similar for all aryl-halides in the CH-stretch region, but DOS increases with increasing halide mass in the midrange region.

  8. Molecular Modeling and Monte Carlo Simulation of Concentrated Aqueous Alkali Halide Solutions at 25 C.

    Science.gov (United States)

    Llano-Restrepo, Mario Andres

    A study of concentrated aqueous alkali halide solutions is made at the molecular level, through modeling and computer simulation of their structural and thermodynamic properties. It is found that the HNC approximation is the best integral equation theory to predict such properties within the framework of the primitive model (PM). The intrinsic limitations of the PM in describing ionic association and hydration effects are addressed and discussed in order to emphasize the need for explicitly including the water molecules in the treatment of aqueous electrolyte solutions by means of a civilized model (CM). As a step toward developing a CM as simple as possible, it is shown that a modified version of the SPC model of liquid water in which the Lennard-Jones interaction between intermolecular oxygen sites is replaced by a hard core interaction, is still successful enough to predict the degree of hydrogen bonding of real water. A simple civilized model (SCM) (in which the ions are treated as hard spheres interacting through Coulombic potentials and the water molecules are simulated using the simplified SPC model) is introduced in order to study the changes in the structural features of various aqueous alkali halide solutions upon varying both the concentration and the size of the ions. Both cations and anions are found to be solvated by the water molecules at expense of a breakdown in the hydrogen-bonded water network. Hydration numbers are reported for the first time for NaBr and KBr, and the first simulation -based estimates for LiBr, NaI and KI are also obtained. In several cases, values of the hydration numbers based on the SCM are found to be in excellent agreement with available experimental results obtained from x-ray diffraction measurements. Finally, it is shown that a neoprimitive model (NPM) can be developed by incorporating some of the structural features seen in the SCM into the short-range part of the PM interionic potential via a shielded square well whose

  9. Solvation structures and dynamics of alkaline earth metal halides in supercritical water: A molecular dynamics study

    Science.gov (United States)

    Keshri, Sonanki; Mandal, Ratnamala; Tembe, B. L.

    2016-09-01

    Constrained molecular dynamics simulations of alkaline earth metal halides have been carried out to investigate their structural and dynamical properties in supercritical water. Potentials of mean force (PMFs) for all the alkaline earth metal halides in supercritical water have been computed. Contact ion pairs (CIPs) are found to be more stable than all other configurations of the ion pairs except for MgI2 where solvent shared ion pair (SShIP) is more stable than the CIP. There is hardly any difference in the PMFs between the M2+ (M = Mg, Ca, Sr, Ba) and the X- (X = F, Cl, Br, I) ions whether the second X- ion is present in the first coordination shell of the M2+ ion or not. The solvent molecules in the solvation shells diffuse at a much slower rate compared to the bulk. Orientational distribution functions of solvent molecules are sharper for smaller ions.

  10. Crystal and electronic structures of substituted halide perovskites based on density functional calculation and molecular dynamics

    Science.gov (United States)

    Takaba, Hiromitsu; Kimura, Shou; Alam, Md. Khorshed

    2017-03-01

    Durability of organo-lead halide perovskite are important issue for its practical application in a solar cells. In this study, using density functional theory (DFT) and molecular dynamics, we theoretically investigated a crystal structure, electronic structure, and ionic diffusivity of the partially substituted cubic MA0.5X0.5PbI3 (MA = CH3NH3+, X = NH4+ or (NH2)2CH+ or Cs+). Our calculation results indicate that a partial substitution of MA induces a lattice distortion, resulting in preventing MA or X from the diffusion between A sites in the perovskite. DFT calculations show that electronic structures of the investigated partially substituted perovskites were similar with that of MAPbI3, while their bandgaps slightly decrease compared to that of MAPbI3. Our results mean that partial substitution in halide perovskite is effective technique to suppress diffusion of intrinsic ions and tune the band gap.

  11. High-Purity Hybrid Organolead Halide Perovskite Nanoparticles Obtained by Pulsed-Laser Irradiation in Liquid

    KAUST Repository

    Amendola, Vincenzo

    2016-11-17

    Nanoparticles of hybrid organic-inorganic perovskites have attracted a great deal of attention due to their variety of optoelectronic properties, their low cost, and their easier integration into devices with complex geometry, compared with microcrystalline, thin-film, or bulk metal halides. Here we present a novel one-step synthesis of organolead bromide perovskite nanocrystals based on pulsed-laser irradiation in a liquid environment (PLIL). Starting from a bulk CHNHPbBr crystal, our PLIL procedure does not involve the use of high-boiling-point polar solvents or templating agents, and runs at room temperature. The resulting nanoparticles are characterized by high crystallinity and are completely free of any microscopic product or organic coating layer. We also demonstrate the straightforward inclusion of laser-generated perovskite nanocrystals in a polymeric matrix to form a nanocomposite with single- and two-photon luminescence properties.

  12. Passivation Using Molecular Halides Increases Quantum Dot Solar Cell Performance

    KAUST Repository

    Lan, Xinzheng

    2015-11-18

    © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim. Here we report a solution-based passivation scheme is developed featuring the use of molecular iodine and PbS colloidal quantum dots (CQDs). The improved passivation translates into a longer carrier diffusion length in the solid film. This allows thicker solar-cell devices to be built while preserving efficient charge collection, leading to a certified power conversion efficiency of 9.9%, which is a new record in CQD solar cells.

  13. Passivation Using Molecular Halides Increases Quantum Dot Solar Cell Performance.

    Science.gov (United States)

    Lan, Xinzheng; Voznyy, Oleksandr; Kiani, Amirreza; García de Arquer, F Pelayo; Abbas, Abdullah Saud; Kim, Gi-Hwan; Liu, Mengxia; Yang, Zhenyu; Walters, Grant; Xu, Jixian; Yuan, Mingjian; Ning, Zhijun; Fan, Fengjia; Kanjanaboos, Pongsakorn; Kramer, Illan; Zhitomirsky, David; Lee, Philip; Perelgut, Alexander; Hoogland, Sjoerd; Sargent, Edward H

    2016-01-13

    A solution-based passivation scheme is developed featuring the use of molecular iodine and PbS colloidal quantum dots (CQDs). The improved passivation translates into a longer carrier diffusion length in the solid film. This allows thicker solar-cell devices to be built while preserving efficient charge collection, leading to a certified power conversion efficiency of 9.9%, which is a new record in CQD solar cells. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  14. A lead-halide perovskite molecular ferroelectric semiconductor.

    Science.gov (United States)

    Liao, Wei-Qiang; Zhang, Yi; Hu, Chun-Li; Mao, Jiang-Gao; Ye, Heng-Yun; Li, Peng-Fei; Huang, Songping D; Xiong, Ren-Gen

    2015-05-29

    Inorganic semiconductor ferroelectrics such as BiFeO3 have shown great potential in photovoltaic and other applications. Currently, semiconducting properties and the corresponding application in optoelectronic devices of hybrid organo-plumbate or stannate are a hot topic of academic research; more and more of such hybrids have been synthesized. Structurally, these hybrids are suitable for exploration of ferroelectricity. Therefore, the design of molecular ferroelectric semiconductors based on these hybrids provides a possibility to obtain new or high-performance semiconductor ferroelectrics. Here we investigated Pb-layered perovskites, and found the layer perovskite (benzylammonium)2PbCl4 is ferroelectric with semiconducting behaviours. It has a larger ferroelectric spontaneous polarization Ps=13 μC cm(-2) and a higher Curie temperature Tc=438 K with a band gap of 3.65 eV. This finding throws light on the new properties of the hybrid organo-plumbate or stannate compounds and provides a new way to develop new semiconductor ferroelectrics.

  15. Molecular Relaxation in Liquids

    CERN Document Server

    Bagchi, Biman

    2012-01-01

    This book brings together many different relaxation phenomena in liquids under a common umbrella and provides a unified view of apparently diverse phenomena. It aligns recent experimental results obtained with modern techniques with recent theoretical developments. Such close interaction between experiment and theory in this area goes back to the works of Einstein, Smoluchowski, Kramers' and de Gennes. Development of ultrafast laser spectroscopy recently allowed study of various relaxation processes directly in the time domain, with time scales going down to picosecond (ps) and femtosecond (fs

  16. Conformation analysis of isomers of imidoyl halides

    Energy Technology Data Exchange (ETDEWEB)

    Gershikov, A.G.; Vul' fov, A.L.; Savelova, V.A.; Drizhd, L.P.

    1985-09-01

    The possible mechanisms of the intramolecular syn-anti isomerization of imidoyl halides have been analyzed with the aid of nonempirical quantum-chemical calculations. In the liquid phase isomerization can occur after a preliminary step of ionization with the formation of nitrilium cations. The conformational features have been studied by the methods of molecular mechanics, the differences between the energies of the syn and anti isomers of a number of imidoyl halides and closely related azomethines have been calculated, and the relative equilibrium concentrations of the isomeric forms at 298/sup 0/K have been evaluated.

  17. Molecular catalytic coal liquid conversion

    Energy Technology Data Exchange (ETDEWEB)

    Stock, L.M.; Yang, Shiyong [Univ. of Chicago, IL (United States)

    1995-12-31

    This research, which is relevant to the development of new catalytic systems for the improvement of the quality of coal liquids by the addition of dihydrogen, is divided into two tasks. Task 1 centers on the activation of dihydrogen by molecular basic reagents such as hydroxide ion to convert it into a reactive adduct (OH{center_dot}H{sub 2}){sup {minus}} that can reduce organic molecules. Such species should be robust withstanding severe conditions and chemical poisons. Task 2 is focused on an entirely different approach that exploits molecular catalysts, derived from organometallic compounds that are capable of reducing monocyclic aromatic compounds under very mild conditions. Accomplishments and conclusions are discussed.

  18. A Simple Halide-to-Anion Exchange Method for Heteroaromatic Salts and Ionic Liquids

    Directory of Open Access Journals (Sweden)

    Neus Mesquida

    2012-04-01

    Full Text Available A broad and simple method permitted halide ions in quaternary heteroaromatic and ammonium salts to be exchanged for a variety of anions using an anion exchange resin (A− form in non-aqueous media. The anion loading of the AER (OH− form was examined using two different anion sources, acids or ammonium salts, and changing the polarity of the solvents. The AER (A− form method in organic solvents was then applied to several quaternary heteroaromatic salts and ILs, and the anion exchange proceeded in excellent to quantitative yields, concomitantly removing halide impurities. Relying on the hydrophobicity of the targeted ion pair for the counteranion swap, organic solvents with variable polarity were used, such as CH3OH, CH3CN and the dipolar nonhydroxylic solvent mixture CH3CN:CH2Cl2 (3:7 and the anion exchange was equally successful with both lipophilic cations and anions.

  19. C(aryl-O Bond Formation from Aryl Methanesulfonates via Consecutive Deprotection and SNAr Reactions with Aryl Halides in an Ionic Liquid

    Directory of Open Access Journals (Sweden)

    Yang Chen

    2007-04-01

    Full Text Available An efficient K3PO4-mediated synthesis of unsymmetrical diaryl ethers using the ionic liquid [Bmim]BF4 (1-butyl-3-methylimidazolium tetrafluoroborate as solvent has been developed. The procedure involves consecutive deprotection of aryl methane-sulfonates and a nucleophilic aromatic substitution (SNAr with activated aryl halides.

  20. Silver halide fiber-based evanescent-wave liquid droplet sensing with room temperature mid-infrared quantum cascade lasers

    Science.gov (United States)

    Chen, J. Z.; Liu, Z.; Gmachl, C. F.; Sivco, D. L.

    2005-08-01

    Quantum cascade lasers and unclad silver halide fibers were used to assemble mid-infrared fiber-optics evanescent-wave sensors suitable to measure the chemical composition of liquid droplets. The laser wavelengths were chosen to be in the regions which offer the largest absorption contrast between constituents inside the mixture droplets. A pseudo-Beer-Lambert law fits well with the experimental data. Using a 300μm diameter fiber with a 25 mm immersion length, the signal to noise ratios correspond to 1 vol.% for α-tocophenol in squalane and 2 vol.% for acetone in aqueous solution for laser wavenumbers of 1208 cm-1 and 1363 cm-1, respectively.

  1. Microwave-Assisted Preparation of CdS Nanoparticles in a Halide-Free Ionic Liquid and Their Photocatalytic Activities

    Institute of Scientific and Technical Information of China (English)

    M. ESMAILI, A; HABIBI-YANGJEH

    2011-01-01

    A microwave-assisted (4-6 min) method was used for the preparation ofCdS nanoparticles in 1-ethyl-3-methylimidazolium ethyl sulfate, a halide-free room-temperature ionic liquid (RTIL). The samples were characterized by powder X-ray diffraction, energy dispersive X-ray spectroscopy, and scanning electron microscopy. Diffuse reflectance spectra showed a 1.33 eV blue shift relative to bulk CdS. The photocatalytic activities of the nanoparticles for photodegradation of methylene blue (MB) using UV and visible light were measured. The photodegradation of MB decreased with calcination temperature. First order rate constants for the reaction under visible and UV irradiations over the nanoparticles prepared in the RTIL rich media were 5.4 and 2.5 higher, respectively, than the sample prepared in water.

  2. Combinatorial screening of halide perovskite thin films and solar cells by mask-defined IR laser molecular beam epitaxy.

    Science.gov (United States)

    Kawashima, Kazuhiro; Okamoto, Yuji; Annayev, Orazmuhammet; Toyokura, Nobuo; Takahashi, Ryota; Lippmaa, Mikk; Itaka, Kenji; Suzuki, Yoshikazu; Matsuki, Nobuyuki; Koinuma, Hideomi

    2017-01-01

    As an extension of combinatorial molecular layer epitaxy via ablation of perovskite oxides by a pulsed excimer laser, we have developed a laser molecular beam epitaxy (MBE) system for parallel integration of nano-scaled thin films of organic-inorganic hybrid materials. A pulsed infrared (IR) semiconductor laser was adopted for thermal evaporation of organic halide (A-site: CH3NH3I) and inorganic halide (B-site: PbI2) powder targets to deposit repeated A/B bilayer films where the thickness of each layer was controlled on molecular layer scale by programming the evaporation IR laser pulse number, length, or power. The layer thickness was monitored with an in situ quartz crystal microbalance and calibrated against ex situ stylus profilometer measurements. A computer-controlled movable mask system enabled the deposition of combinatorial thin film libraries, where each library contains a vertically homogeneous film with spatially programmable A- and B-layer thicknesses. On the composition gradient film, a hole transport Spiro-OMeTAD layer was spin-coated and dried followed by the vacuum evaporation of Ag electrodes to form the solar cell. The preliminary cell performance was evaluated by measuring I-V characteristics at seven different positions on the 12.5 mm × 12.5 mm combinatorial library sample with seven 2 mm × 4 mm slits under a solar simulator irradiation. The combinatorial solar cell library clearly demonstrated that the energy conversion efficiency sharply changes from nearly zero to 10.2% as a function of the illumination area in the library. The exploration of deposition parameters for obtaining optimum performance could thus be greatly accelerated. Since the thickness ratio of PbI2 and CH3NH3I can be freely chosen along the shadow mask movement, these experiments show the potential of this system for high-throughput screening of optimum chemical composition in the binary film library and application to halide perovskite solar cell.

  3. Deep Extractive Desulfurization of Gasoline with Ionic Liquids Based on Metal Halide

    Institute of Scientific and Technical Information of China (English)

    Wang Haojie; He Jianxun; Yang Cairong; Zhang Hang

    2014-01-01

    Ionic liquid [Et3NH]Cl-FeCl3/CuCl was synthesized by mixing [Et3NH]Cl, anhydrous FeCl3 and anhydrous CuCl, and the desulfurization activity of this ionic liquid was tested. It exhibited remarkable ability in effective desulfurization of model gasoline (thiophene in n-octane) and lfuid catalytic cracking (FCC) gasoline, and the sulfur removal of thiophene in model oil (V(IL):V(oil)=0.08) could reach 93.9%in 50 min at 50℃. Low-sulfur (﹤10μg/g) FCC gasoline could be obtained after three extraction runs at an ionic liquid/oil volume ratio of 0.1, with the yield of FCC gasoline reaching 94.3%. The ionic liquid could be recycled 5 times with merely a slight decrease in activity.

  4. Magadiite Templated High Surface Area Graphene-Type Carbons from Metal-Halide based Ionic Liquids

    Energy Technology Data Exchange (ETDEWEB)

    Fulvio, Pasquale F [ORNL; Hillesheim, Patrick C [ORNL; Bauer, John C [ORNL; Mahurin, Shannon Mark [ORNL; Dai, Sheng [ORNL; Arend, Nikolas [ORNL

    2013-01-01

    Freestanding silicon films with a thickness ranging from 1 nm to several micrometers were prepared by Cat-CVD onto ionic liquid ([BMIM][BF4]) surfaces for the first time. The films, obtained without a solid substrate, can be facilely characterized by TEM and AFM to study the film formation and growth process.

  5. Amination Reactions of Aryl Halides with Nitrogen-Containing Reagents Catalyzed by Cul in Ionic Liquid

    Institute of Scientific and Technical Information of China (English)

    YAN,Jin-Can; ZHOU,Li; WANG,Lei

    2008-01-01

    CuI-catalyzed coupling reactions of aryl iodides and electron-deficient aryl bromides with nitrogen-containing reagents, such as imidazole, benzimidazole, aliphatic primary and secondary amines, aniline, primary and secondary amides, in ionic liquid were developed. The reaction conditions involved the use of[Bmim][BF4] as the solvent,potassium phosphate as the base, and CuI as the catalyst. The CuI and[Bmim][BF4] could be recovered and recycled for five consecutive trials without significant loss of their activity.

  6. Molecular Dynamics Simulations of Simple Liquids

    Science.gov (United States)

    Speer, Owner F.; Wengerter, Brian C.; Taylor, Ramona S.

    2004-01-01

    An experiment, in which students were given the opportunity to perform molecular dynamics simulations on a series of molecular liquids using the Amber suite of programs, is presented. They were introduced to both physical theories underlying classical mechanics simulations and to the atom-atom pair distribution function.

  7. Molecular Dynamics Simulations of Simple Liquids

    Science.gov (United States)

    Speer, Owner F.; Wengerter, Brian C.; Taylor, Ramona S.

    2004-01-01

    An experiment, in which students were given the opportunity to perform molecular dynamics simulations on a series of molecular liquids using the Amber suite of programs, is presented. They were introduced to both physical theories underlying classical mechanics simulations and to the atom-atom pair distribution function.

  8. Silver halide fiber-based evanescent-wave liquid droplet sensing with thermoelectrically cooled room temperature mid-infrared quantum cascade lasers

    Science.gov (United States)

    Chen, Jian Z.; Liu, Zhijun; Gmachl, Claire F.; Sivco, Deborah L.

    2005-11-01

    Quantum cascade lasers coupled directly to unclad silver halide fibers were used to assemble mid-infrared fiber-optics evanescent-wave sensors suitable to measure the chemical composition of simple liquid droplets. Quantum cascade lasers can be designed to emit across a wide range of mid-infrared wavelengths by tailoring the quantum-well structure, and the wavelength can be fine tuned by a thermoelectric cooler. Here, laser wavelengths were chosen which offer the largest absorption contrast between two constituents of a droplet. The laser was coupled to an unclad silver halide fiber, which penetrates through the droplet resting on a hydrophobic surface. For the same liquid composition and droplet size, the transmitted intensity is weaker for a droplet on a 1H,1H,2H,2H-perfluoro-octyltrichlorosilane coated glass slide than for one on a hexadecanethiol (HDT) coated Au-covered glass slide because of the high reflectivity of the HDT/Au surface at mid-infrared wavelengths. The absorption coefficients of water, glycerol, α-tocophenol acetate, and squalane were measured by varying the immersion length of the fiber; i.e. the droplet size. A pseudo-Beer-Lambert law fits well with the experimental data. We tested both aqueous liquid mixtures (acetone/water and ethanol/water) and oil-base solutions (n-dodecane/squalane and α-tocophenol acetate/squalane); α-tocophenol acetate and squalane are common ingredients of cosmetics, either as active ingredients or for chemical stabilization. Using a 300μm diameter silver halide fiber with a 25mm immersion length, the detection limits are 1 vol.% for α-tocophenol in squalane and 2 vol.% for acetone in water for laser wavenumbers of 1208 cm -1 and 1363 cm -1, respectively. This work was previously been reported in J. Z. Chen et al. Optics Express 13, 5953 (2005).

  9. Comparison between alkalimetal and group 11 transition metal halide and hydride tetramers: molecular structure and bonding.

    Science.gov (United States)

    El-Hamdi, Majid; Solà, Miquel; Frenking, Gernot; Poater, Jordi

    2013-08-22

    A comparison between alkalimetal (M = Li, Na, K, and Rb) and group 11 transition metal (M = Cu, Ag, and Au) (MX)4 tetramers with X = H, F, Cl, Br, and I has been carried out by means of the Amsterdam Density Functional software using density functional theory at the BP86/QZ4P level of theory and including relativistic effects through the ZORA approximation. We have obtained that, in the case of alkalimetals, the cubic isomer of Td geometry is more stable than the ring structure with D4h symmetry, whereas in the case of group 11 transition metal tetramers, the isomer with D4h symmetry (or D2d symmetry) is more stable than the Td form. To better understand the results obtained we have made energy decomposition analyses of the tetramerization energies. The results show that in alkalimetal halide and hydride tetramers, the cubic geometry is the most stable because the larger Pauli repulsion energies are compensated by the attractive electrostatic and orbital interaction terms. In the case of group 11 transition metal tetramers, the D4h/D2d geometry is more stable than the Td one due to the reduction of electrostatic stabilization and the dominant effect of the Pauli repulsion.

  10. The reversibility and first-order nature of liquid-liquid transition in a molecular liquid

    Science.gov (United States)

    Kobayashi, Mika; Tanaka, Hajime

    2016-11-01

    Liquid-liquid transition is an intriguing phenomenon in which a liquid transforms into another liquid via the first-order transition. For molecular liquids, however, it always takes place in a supercooled liquid state metastable against crystallization, which has led to a number of serious debates concerning its origin: liquid-liquid transition versus unusual nano-crystal formation. Thus, there have so far been no single example free from such debates, to the best of our knowledge. Here we show experimental evidence that the transition is truly liquid-liquid transition and not nano-crystallization for a molecular liquid, triphenyl phosphite. We kinetically isolate the reverse liquid-liquid transition from glass transition and crystallization with a high heating rate of flash differential scanning calorimetry, and prove the reversibility and first-order nature of liquid-liquid transition. Our finding not only deepens our physical understanding of liquid-liquid transition but may also initiate a phase of its research from both fundamental and applications viewpoints.

  11. Thermodynamics of small alkali metal halide cluster ions: comparison of classical molecular simulations with experiment and quantum chemistry.

    Science.gov (United States)

    Vlcek, Lukas; Uhlik, Filip; Moucka, Filip; Nezbeda, Ivo; Chialvo, Ariel A

    2015-01-22

    We evaluate the ability of selected classical molecular models to describe the thermodynamic and structural aspects of gas-phase hydration of alkali metal halide ions and the formation of small water clusters. To understand the effect of many-body interactions (polarization) and charge penetration effects on the accuracy of a force field, we perform Monte Carlo simulations with three rigid water models using different functional forms to account for these effects: (i) point charge nonpolarizable SPC/E, (ii) Drude point charge polarizable SWM4-DP, and (iii) Drude Gaussian charge polarizable BK3. Model predictions are compared with experimental Gibbs free energies and enthalpies of ion hydration, and with microscopic structural properties obtained from quantum DFT calculations. We find that all three models provide comparable predictions for pure water clusters and cation hydration but differ significantly in their description of anion hydration. None of the investigated classical force fields can consistently and quantitatively reproduce the experimental gas-phase hydration thermodynamics. The outcome of this study highlights the relation between the functional form that describes the effective intermolecular interactions and the accuracy of the resulting ion hydration properties.

  12. Molecular-dynamic study of liquid ethylenediamine

    Science.gov (United States)

    Balabaev, N. K.; Kraevskii, S. V.; Rodnikova, M. N.; Solonina, I. A.

    2016-10-01

    Models of liquid ethylenediamine (ED) are built using the molecular dynamics approach at temperatures of 293-363 K and a size of 1000 molecules in a basic cell as a cuboid. The structural and dynamic characteristics of liquid ED versus temperature are derived. The gauche conformation of the ED molecule that is characteristic of the gas phase is shown to transition easily into the trans conformation of the molecules in the liquid. NH···N hydrogen bonds are analyzed in liquid ED. The number of H-bonds per ED molecule is found to vary from 5.02 at 293 K to 3.86 at 363 K. The lifetimes in the range of the temperatures and dissociation activation energy for several H-bonds in liquid ED are found to range from 0.574 to 4.524 ps at 293 K; the activation energies are 8.8 kJ/mol for 50% of the H-bonds and 16.3 kJ/mol for 6.25% of them. A weaker and more mobile spatial grid of H-bonds in liquid ED is observed, compared to data calculated earlier for monoethanolamine.

  13. Interaction of the model alkyltrimethylammonium ions with alkali halide salts: an explicit water molecular dynamics study

    Directory of Open Access Journals (Sweden)

    M. Druchok

    2013-01-01

    Full Text Available We present an explicit water molecular dynamics simulation of dilute solutions of model alkyltrimethylammonium surfactant ions (number of methylene groups in the tail is 3, 5, 8, 10, and 12 in mixture with NaF, NaCl, NaBr, and NaI salts, respectively. The SPC/E model is used to describe water molecules. Results of the simulation at 298 K are presented in form of the radial distribution functions between nitrogen and carbon atoms of CH2 groups on the alkyltrimethylammonium ion, and the counterion species in the solution. The running coordination numbers between carbon atoms of surfactants and counterions are also calculated. We show that I- counterion exhibits the highest, and F- the lowest affinity to "bind" to the model surfactants. The results are discussed in view of the available experimental and simulation data for this and similar solutions.

  14. SN2 and SN2' reaction dynamics of cyclopropenyl chloride with halide ion : A direct ab initio molecular dynamics (MD) study

    OpenAIRE

    Tachikawa, Hiroto

    2005-01-01

    Direct ab initio molecular dynamics (MD) calculations have been carried out for the reaction of cyclopropenyl chloride with halide ion (F–) (F– + (CH)3Cl → F(CH)3 + Cl–) in gas phase. Both SN2 and SN2′ channels were found as product channels. These channels are strongly dependent on the collision angle of F– to the target (CH)3Cl molecule. The collision at one of the carbon atoms of the C=C double bond leads to the SN2′ reaction channel; whereas the collision at the methylene carbon atom lead...

  15. Temperature-dependent solubilities and mean ionic activity coefficients of alkali halides in water from molecular dynamics simulations

    Science.gov (United States)

    Mester, Zoltan; Panagiotopoulos, Athanassios Z.

    2015-07-01

    The mean ionic activity coefficients of aqueous KCl, NaF, NaI, and NaCl solutions of varying concentrations have been obtained from molecular dynamics simulations following a recently developed methodology based on gradual insertions of salt molecules [Z. Mester and A. Z. Panagiotopoulos, J. Chem. Phys. 142, 044507 (2015)]. The non-polarizable ion models of Weerasinghe and Smith [J. Chem. Phys. 119, 11342 (2003)], Gee et al. [J. Chem. Theory Comput. 7, 1369 (2011)], Reiser et al. [J. Chem. Phys. 140, 044504 (2014)], and Joung and Cheatham [J. Phys. Chem. B 112, 9020 (2008)] were used along with the extended simple point charge (SPC/E) water model [Berendsen et al., J. Phys. Chem. 91, 6269 (1987)] in the simulations. In addition to the chemical potentials in solution used to obtain the activity coefficients, we also calculated the chemical potentials of salt crystals and used them to obtain the solubility of these alkali halide models in SPC/E water. The models of Weerasinghe and Smith [J. Chem. Phys. 119, 11342 (2003)] and Gee et al. [J. Chem. Theory Comput. 7, 1369 (2011)] provide excellent predictions of the mean ionic activity coefficients at 298.15 K and 1 bar, but significantly underpredict or overpredict the solubilities. The other two models generally predicted the mean ionic activity coefficients only qualitatively. With the exception of NaF for which the solubility is significantly overpredicted, the model of Joung and Cheatham predicts salt solubilities that are approximately 40%-60% of the experimental values. The models of Reiser et al. [J. Chem. Phys. 140, 044504 (2014)] make good predictions for the NaCl and NaI solubilities, but significantly underpredict the solubilities for KCl and NaF. We also tested the transferability of the models to temperatures much higher than were used to parametrize them by performing simulations for NaCl at 373.15 K and 1 bar, and at 473.15 K and 15.5 bar. All models overpredict the drop in the values of mean ionic

  16. Solvation of uranium hexachloro complexes in room-temperature ionic liquids. A molecular dynamics investigation in two liquids.

    Science.gov (United States)

    Schurhammer, Rachel; Wipff, Georges

    2007-05-10

    We report a molecular dynamics study of the solvation of UCl(6)(-), UCl(6)(2-), and UCl(6)(3-) complexes in the [BMI][Tf(2)N] and [MeBu(3)N][Tf(2)N] ionic liquid cations based on the same anion (bis(trifluoromethylsulfonyl)imide (Tf(2)N-)) and the butyl-3-methyl-imidazolium+ (BMI+) or methyl-tri-n-butyl-ammonium (MeBu(3)N+) cation, respectively. The comparison of two electrostatic models of the complexes (ionic model with -1 charged halides versus quantum mechanically derived charges) yields similar solvation features of a given solute. In the two liquids, the first solvation shell of the complexes is positively charged and evolves from purely cationic in the case of UCl(6)(3-) to a mixture of cations and anions in the case of UCl(6)(-). UCl(6)(3-) is exclusively "coordinated" to BMI+ or MeBu(3)N+ solvent cations that mainly interact via their CH aromatic protons or their N-Me group, respectively. Around the less charged UCl(6)(-) complex, the cations interact via the less polar moieties (butyl chains of BMI+ or MeBu(3)N+) and the anions display nonspecific interactions. In no case does the uranium atom further coordinate solvent ions. According to an energy components analysis, UCl(6)(3-) interacts more attractively with the [BMI][Tf(2)N] liquid than with [MeBu(3)N][Tf(2)N], while UCl(6)(-) does not show any preference, suggesting a significant solvation effect of the redox properties of uranium, also supported by free energy perturbation simulations. The effect of ionic liquid (IL) humidity is investigated by simulating the three complexes in 1:8 water/IL mixtures. In contrast to the case of "naked" ions (e.g., lanthanide(3+), UO2(2+), alkali, or halides), water has little influence on the solvation of the UCl(6)(n-) complexes in the two simulated ILs, as indicated by structural and energy analysis. This is in full agreement with the experimental observations (Nikitenko, S. I.; et al. Inorg. Chem. 2005, 44, 9497).

  17. Molecular dynamics studies of aromatic hydrocarbon liquids

    Energy Technology Data Exchange (ETDEWEB)

    McLaughlin, E.; Gupta, S.

    1990-01-01

    This project mainly involves a molecular dynamics and Monte Carlo study of the effect of molecular shape on thermophysical properties of bulk fluids with an emphasis on the aromatic hydrocarbon liquids. In this regard we have studied the modeling, simulation methodologies, and predictive and correlating methods for thermodynamic properties of fluids of nonspherical molecules. In connection with modeling we have studied the use of anisotropic site-site potentials, through a modification of the Gay-Berne Gaussian overlap potential, to successfully model the aromatic rings after adding the necessary electrostatic moments. We have also shown these interaction sites should be located at the geometric centers of the chemical groups. In connection with predictive methods, we have shown two perturbation type theories to work well for fluids modeled using one-center anisotropic potentials and the possibility exists for extending these to anisotropic site-site models. In connection with correlation methods, we have studied, through simulations, the effect of molecular shape on the attraction term in the generalized van der Waals equation of state for fluids of nonspherical molecules and proposed a possible form which is to be studied further. We have successfully studied the vector and parallel processing aspects of molecular simulations for fluids of nonspherical molecules.

  18. Spin-orbit coupling, spin-lattice relaxation and spin-memory studies of F center/molecular ion pairs in alkali halides

    Energy Technology Data Exchange (ETDEWEB)

    Baldacchini, G.; Botti, S.; Grassano, U.M.; Luty, F.

    1992-12-31

    The spin-orbit parameter, spin-lattice relaxation time, and spin-mixing parameter of F/sub H/(OH/sup -/) and F/sub H/(CN/sup -/) centers in several alkali halides were studied with magnetic circular dichroism at about 2 K. A close comparison of the experimental results before and after optically induced association of the F center with the molecular ion was made. In crystals of NaCl structure, the negative spin-orbit parameter changes little between F and F/sub H/ centers in the same host. For CsCl and CsBr two values of spin-orbit parameter were derived for F/sub H/(CN/sup -/) centers with axes parallel or perpendicular to the magnetic field. In all studied systems, the spin-lattice relaxation time was already shorter before aggregation as compared with F centers in pure crystals, and became further shortened by the F/sub H/ center formation. The spin-mixing parameter decreased slightly for F/sub H/(OH/sup -/) as compared with F centers, while it increased drastically for F/sub H/(CN/sup -/) defects and reaches its maximum possible value, 0.5 in cesium halides. First attempts to interpret these magneto-optical results are presented in this paper.

  19. Molecular dynamics simulations of the dynamic and energetic properties of alkali and halide ions using water-model-specific ion parameters.

    Science.gov (United States)

    Joung, In Suk; Cheatham, Thomas E

    2009-10-01

    The dynamic and energetic properties of the alkali and halide ions were calculated using molecular dynamics (MD) and free energy simulations with various different water and ion force fields including our recently developed water-model-specific ion parameters. The properties calculated were activity coefficients, diffusion coefficients, residence times of atomic pairs, association constants, and solubility. Through calculation of these properties, we can assess the validity and range of applicability of the simple pair potential models and better understand their limitations. Due to extreme computational demands, the activity coefficients were only calculated for a subset of the models. The results qualitatively agree with experiment. Calculated diffusion coefficients and residence times between cation-anion, water-cation, and water-anion showed differences depending on the choice of water and ion force field used. The calculated solubilities of the alkali-halide salts were generally lower than the true solubility of the salts. However, for both the TIP4P(EW) and SPC/E water-model-specific ion parameters, solubility was reasonably well-reproduced. Finally, the correlations among the various properties led to the following conclusions: (1) The reliability of the ion force fields is significantly affected by the specific choice of water model. (2) Ion-ion interactions are very important to accurately simulate the properties, especially solubility. (3) The SPC/E and TIP4P(EW) water-model-specific ion force fields are preferred for simulation in high salt environments compared to the other ion force fields.

  20. Determination of Halide Impurities in Ionic Liquids by Ion Chromatography with Direct Conductivity Detection%离子液体中卤素离子杂质的离子色谱-直接电导检测法分析

    Institute of Scientific and Technical Information of China (English)

    周爽; 高微; 于泓

    2009-01-01

    A method was developed for the determination of halide impurities including fluoride, chloride and bromide, in ionic liquids by ion chromatography coupled with direct conductivity detec-tion. The separation of analytes was performed on a Shim-pack IC-A3 anion-exchange column using potassium biphthalate as eluent. Influences of type, concentration and flow rate of eluent, and col-umn temperature on separation efficiency of halide ions were investigated. The optimized chromato-graphic conditions for determination of halide ions were using 1. 25 mmol/L potassium biphthalate as eluent with a flow rate of 1. 5 mL/min at 45 ℃. Under the optimal conditions, a good baseline separation of halide ions was achieved. Nitrate, tetrafluoroborate and sulfate did not interfere with the determination of halide ions. The detection limits ( S/N = 3 ) of halide ions by the method were in the range of 0. 02 - 0. 11 mg/L. The linear ranges of calibration curves between chromatographic peak area and concentration of analytes for fluoride, chloride and bromide were 0. 1 - 50, 0. 1 - 50 and 0. 5 - 100 mg/L, respectively. The relative standard deviations(RSDs) of chromatographic peak ar-eas for halide ions were less than 0. 7% (n = 5). The method was successfully applied to determine halide impurities in alkyl-imidazolium terafluoroborate ionic liquids. The spiked recoveries of halide ions ranged from 98% to 102% . The good linearity, repeatability and low detection limits of the method made it meet the requirements of quantitative analysis of halide impurities in ionic liquids.%研究了离子色谱-直接电导检测法分离测定离子液体中的卤素离子(F~-、Cl~-、Br~-)杂质.采用Shim-pack IC-A3阴离子交换色谱柱,考察了淋洗液种类及浓度、流速和色谱柱温度对分离测定的影响.最佳色谱条件为:以1.25 mmol/L邻苯二甲酸氢钾为淋洗液,流速1.5 mL/min,色谱柱温45 ℃.在此条件下可以基线分离卤素离子,且NO_3~-、BF_4~-

  1. Molecular kinetics of solid and liquid CHCl$_3$

    CERN Document Server

    Caballero, Nirvana B; Carignano, Marcelo A; Serra, Pablo

    2013-01-01

    We present a detailed analysis of the molecular kinetics of CHCl$_3$ in a range of temperatures covering the solid and liquid phases. Using nuclear quadrupolar resonance we determine the relaxation times for the molecular rotations in solid at pre-melting conditions. Molecular dynamics simulations are used to characterize the rotational dynamics in the solid and liquid phases and to study the local structure of the liquid in terms of the molecular relative orientations. We find that in the pre-melting regime the molecules rotate about the C-H bond, but the rotations are isotropic in the liquid, even at supercooled conditions.

  2. Convenient One-Pot Synthesis of 2,4,5-Triaryl-1H-imidazoles from Arylaldehydes, Benzyl Alcohols, or Benzyl Halides with HMDS in the Presence of Molecular Iodine

    Energy Technology Data Exchange (ETDEWEB)

    Veisi, Hojat; Heshmati, Leila [Payame Noor University, Tehran (Iran, Islamic Republic of); Khazaei, Ardashir [Bu-Ali Sina University, Hamedan (Iran, Islamic Republic of); Hemmati, Saba [Islamic Azad University, Kermanshah (Iran, Islamic Republic of)

    2012-04-15

    A one-pot efficient procedure for the synthesis of 2,4,5-triaryl-1H-imidazole derivatives in good to excellent yields by reaction between hexamethyldisilazane and arylaldehydes, benzyl alcohols, benzyl halides in the presence of molecular iodine has been developed. The remarkable advantages of this method are the simple workup procedure, high yields of products, and the availability of reagents

  3. Application of Magnetic Dicationic Ionic Liquid Phase Transfer Catalyst in Nuclophilic Substitution Reactions of Benzyl Halids in Water

    OpenAIRE

    Manouchehr Aghajeri; Ali Reza Kiasat; Bijan Mombeni Goodajdar

    2016-01-01

    magnetic dicationic ionic liquid (MDIL) was successfully prepared and evaluated as phase-transfer catalyst for nucleophilic substitution reactions. The reactions was occurred in water and furnished the corresponding benzyl derivatives in high yields. No evidence for the formation of by-product for example benzyl alcohol of the reaction was observed and the products were obtained in pure form without further purification.

  4. Application of Magnetic Dicationic Ionic Liquid Phase Transfer Catalyst in Nuclophilic Substitution Reactions of Benzyl Halids in Water

    Directory of Open Access Journals (Sweden)

    Manouchehr Aghajeri

    2016-06-01

    Full Text Available magnetic dicationic ionic liquid (MDIL was successfully prepared and evaluated as phase-transfer catalyst for nucleophilic substitution reactions. The reactions was occurred in water and furnished the corresponding benzyl derivatives in high yields. No evidence for the formation of by-product for example benzyl alcohol of the reaction was observed and the products were obtained in pure form without further purification.

  5. Elastic properties of surfactant monolayers at liquid-liquid interfaces: A molecular dynamics study

    DEFF Research Database (Denmark)

    Laradji, Mohamed; Mouritsen, Ole G.

    2000-01-01

    Using a simple molecular model based on the Lennard-Jones potential, we systematically study the elastic properties of liquid-liquid interfaces containing surfactant molecules by means of extensive and large-scale molecular dynamics simulations. The main elastic constants of the interface, corres...

  6. Molecular Beam Studies of Volatile Liquids and Fuel Surrogates Using Liquid Microjets

    Science.gov (United States)

    2014-12-18

    Molecular Beam Studies of Volatile Liquids and Fuel Surrogates Using Liquid Microjets Gilbert Nathanson, Department of Chemistry University of...alter the dynamics of evaporation from the commercial jet fuel Jet A. These results are outlined below. Exploring Fuels in Vacuum using Liquid ...hydrocarbon liquids inside a vacuum chamber. These jets, narrower than a human hair, are typically 10 – 40 µm in diameter. Their small surface area and

  7. Interfacial Properties of an Ionic Liquid by Molecular Dynamics

    NARCIS (Netherlands)

    Heggen, B.; Zhao, W.; Leroy, F.; Dammers, A.T.; Müller-Plathe, F.

    2010-01-01

    We studied the influence of a liquid-vapor interface on dynamic properties like reorientation and diffusion as well as the surface tension of the ionic liquid 1-butyl-3-methylimidazolium hexafluorophosphate ([bmim][PF6]) by molecular dynamics simulations. In the interfacial region, reorientation of

  8. Interfacial Properties of an Ionic Liquid by Molecular Dynamics

    NARCIS (Netherlands)

    Heggen, B.; Zhao, W.; Leroy, F.; Dammers, A.T.; Müller-Plathe, F.

    2010-01-01

    We studied the influence of a liquid-vapor interface on dynamic properties like reorientation and diffusion as well as the surface tension of the ionic liquid 1-butyl-3-methylimidazolium hexafluorophosphate ([bmim][PF6]) by molecular dynamics simulations. In the interfacial region, reorientation of

  9. Diffusion in Liquids: Equilibrium Molecular Simulations and Predictive Engineering Models

    NARCIS (Netherlands)

    Liu, X.

    2013-01-01

    The aim of this thesis is to study multicomponent diffusion in liquids using Molecular Dynamics (MD) simulations. Diffusion plays an important role in mass transport processes. In binary systems, mass transfer processes have been studied extensively using both experiments and molecular simulations.

  10. Halogen versus halide electronic structure

    Institute of Scientific and Technical Information of China (English)

    Willem-Jan; van; Zeist; F.Matthias; Bickelhaupt

    2010-01-01

    Halide anions X-are known to show a decreasing proton affinity(PA),as X descends in the periodic table along series F,Cl,Br and I.But it is also well-known that,along this series,the halogen atom X becomes less electronegative(or more electropositive).This corresponds to an increasing energy of the valence np atomic orbital(AO) which,somewhat contradictorily,suggests that the electron donor capability and thus the PA of the halides should increase along the series F,Cl,Br,I.To reconcile these contradictory observations,we have carried out a detailed theoretical analysis of the electronic structure and bonding capability of the halide anions X-as well as the halogen radicals X-,using the molecular orbital(MO) models contained in Kohn-Sham density functional theory(DFT,at SAOP/TZ2P as well as OLYP/TZ2P levels) and ab initio theory(at the HF/TZ2P level).We also resolve an apparent intrinsic contradiction in Hartree-Fock theory between orbital-energy and PA trends.The results of our analyses are of direct relevance for understanding elementary organic reactions such as nucleophilic substitution(SN2) and base-induced elimination(E2) reactions.

  11. Analysis of molecular structure, spectroscopic properties (FT-IR, micro-Raman and UV-vis) and quantum chemical calculations of free and ligand 2-thiopheneglyoxylic acid in metal halides (Cd, Co, Cu, Ni and Zn).

    Science.gov (United States)

    Gökce, Halil; Bahçeli, Semiha

    2013-12-01

    In this study, molecular geometries, experimental vibrational wavenumbers, electronic properties and quantum chemical calculations of 2-thiopheneglyoxylic acid molecule, (C6H4O3S), and its metal halides (Cd, Co, Cu, Ni and Zn) which are used as pharmacologic agents have been investigated experimentally by FT-IR, micro-Raman and UV-visible spectroscopies and elemental analysis. Meanwhile the vibrational calculations were verified by DFT/B3LYP method with 6-311++G(d,p) and LANL2DZ basis sets in the ground state, for free TPGA molecule and its metal halide complexes, respectively, for the first time. The calculated fundamental vibrational frequencies for the title compounds are in a good agreement with the experimental data.

  12. Metastable liquid-liquid transition in a molecular model of water

    Science.gov (United States)

    Palmer, Jeremy C.; Martelli, Fausto; Liu, Yang; Car, Roberto; Panagiotopoulos, Athanassios Z.; Debenedetti, Pablo G.

    2014-06-01

    Liquid water's isothermal compressibility and isobaric heat capacity, and the magnitude of its thermal expansion coefficient, increase sharply on cooling below the equilibrium freezing point. Many experimental, theoretical and computational studies have sought to understand the molecular origin and implications of this anomalous behaviour. Of the different theoretical scenarios put forward, one posits the existence of a first-order phase transition that involves two forms of liquid water and terminates at a critical point located at deeply supercooled conditions. Some experimental evidence is consistent with this hypothesis, but no definitive proof of a liquid-liquid transition in water has been obtained to date: rapid ice crystallization has so far prevented decisive measurements on deeply supercooled water, although this challenge has been overcome recently. Computer simulations are therefore crucial for exploring water's structure and behaviour in this regime, and have shown that some water models exhibit liquid-liquid transitions and others do not. However, recent work has argued that the liquid-liquid transition has been mistakenly interpreted, and is in fact a liquid-crystal transition in all atomistic models of water. Here we show, by studying the liquid-liquid transition in the ST2 model of water with the use of six advanced sampling methods to compute the free-energy surface, that two metastable liquid phases and a stable crystal phase exist at the same deeply supercooled thermodynamic condition, and that the transition between the two liquids satisfies the thermodynamic criteria of a first-order transition. We follow the rearrangement of water's coordination shell and topological ring structure along a thermodynamically reversible path from the low-density liquid to cubic ice. We also show that the system fluctuates freely between the two liquid phases rather than crystallizing. These findings provide unambiguous evidence for a liquid-liquid transition in

  13. Molecular thermodiffusion (thermophoresis) in liquid mixtures.

    Science.gov (United States)

    Semenov, Semen N; Schimpf, Martin E

    2005-10-01

    Thermodiffusion (thermophoresis) in liquid mixtures is theoretically examined using a hydrodynamic approach. Thermodiffusion is related to the local temperature-induced pressure gradient in the liquid layer surrounding the selected molecule and to the secondary macroscopic pressure gradient established in the system. The local pressure gradient is produced by excess pressure due to the asymmetry of interactions with surrounding molecules in a nonuniform temperature field. The secondary pressure gradient is considered an independent parameter related to the concentration gradient formed by volume forces, calculated from the generalized equations for mass transfer. Values of Soret coefficients for mixtures of toluene and -hexane are calculated using parameters in the literature. When the molecules are assumed to be similar in shape, the calculated Soret coefficients are lower than the empirical values found in the literature. However, by introducing an asymmetry parameter, which is calculated from independent measurements of component diffusion in the literature, very good agreement is obtained.

  14. Molecular Orbital Based Design Guidelines for Hypergolic Energetic Ionic Liquids

    Science.gov (United States)

    2015-01-01

    should be synthesized to further validate our probabilistic approach for identifying EIL hypergols. DMP is one anion that has a lower “energy gap”, but...orbitals (HOMO) of the anions for a series of ionic liquids and the lowest occupied molecular orbital (LUMO) of HNO3, and variation in the computed...relative heats of formation, DHf, of these anions to develop correlations to predict hypergol activity between an ionic liquid fuel and nitric acid as

  15. Hamiltonian adaptive resolution simulation for molecular liquids.

    Science.gov (United States)

    Potestio, Raffaello; Fritsch, Sebastian; Español, Pep; Delgado-Buscalioni, Rafael; Kremer, Kurt; Everaers, Ralf; Donadio, Davide

    2013-03-08

    Adaptive resolution schemes allow the simulation of a molecular fluid treating simultaneously different subregions of the system at different levels of resolution. In this work we present a new scheme formulated in terms of a global Hamiltonian. Within this approach equilibrium states corresponding to well-defined statistical ensembles can be generated making use of all standard molecular dynamics or Monte Carlo methods. Models at different resolutions can thus be coupled, and thermodynamic equilibrium can be modulated keeping each region at desired pressure or density without disrupting the Hamiltonian framework.

  16. Molecular structure of the coalescence of liquid interfaces

    Science.gov (United States)

    Koplik, Joel; Banavar, Jayanth R.

    1992-01-01

    When two bodies of liquid merge, their interfaces must also rupture and rearrange into one. Virtually no information is available concerning the small-scale dynamics of this process. Molecular dynamics simulations of coalescence in systems of about 10,000 Lennard-Jones particles have been performed, arranged so as to mimic laboratory experiments on dense liquids. The coalescence event begins when molecules near the boundary of one liquid body thermally fluctuate into the range of attraction of the other, forming a string of mutually attracting molecules. These molecules gradually thicken into a tendril, which continues to thicken as the bodies smoothly combine in a zipper-like merger.

  17. Diffusion in Liquids: Equilibrium Molecular Simulations and Predictive Engineering Models

    OpenAIRE

    Liu, X.

    2013-01-01

    The aim of this thesis is to study multicomponent diffusion in liquids using Molecular Dynamics (MD) simulations. Diffusion plays an important role in mass transport processes. In binary systems, mass transfer processes have been studied extensively using both experiments and molecular simulations. From a practical point of view, systems consisting more than two components are more interesting. However, experimental and simulation data on transport diffusion for such systems are scarce. There...

  18. Thermophoresis in liquids: a molecular dynamics simulation study.

    Science.gov (United States)

    Han, Minsub

    2005-04-01

    Thermophoresis in liquids is studied by molecular dynamics simulation (MD). A theory is developed that divides the problem in the way consistent with the characteristic scales. MD is then conducted to obtain the solution of each problem, which is to be all combined for macroscopic predictions. It is shown that when the temperature gradient is applied to the nonconducting liquid bath that contains neutral particles, there occurs a pressure gradient tangential to the particle surface at the particle-liquid interface. This may induce the flow in the interfacial region and eventually the particle to move. This applies to the material system that interacts through van der Waals forces and may be a general source of the thermophoresis phenomenon in liquids. The particle velocity is linearly proportional to the temperature gradient. And, in a large part of the given temperature range, the particle motion is in the direction toward the cold end and decreases with respect to the temperature. It is also shown that the particle velocity decreases or even reverses its sign in the lowest limit of the temperature range or with a particle of relatively weak molecular interactions with the liquid. The characteristics of the phenomenon are analyzed in molecular details.

  19. The Computer Simulation of Liquids by Molecular Dynamics.

    Science.gov (United States)

    Smith, W.

    1987-01-01

    Proposes a mathematical computer model for the behavior of liquids using the classical dynamic principles of Sir Isaac Newton and the molecular dynamics method invented by other scientists. Concludes that other applications will be successful using supercomputers to go beyond simple Newtonian physics. (CW)

  20. Polymer Alignment Behavior with Molecular Switching of Ferroelectric Liquid Crystal

    Science.gov (United States)

    Murashige, Takeshi; Fujikake, Hideo; Sato, Hiroto; Kikuchi, Hiroshi; Kurita, Taiichiro; Sato, Fumio

    2007-01-01

    This paper describes the molecular alignment behavior of polymer networks with switching of a ferroelectric liquid crystal (FLC) in a molecularly aligned FLC/polymer composite film. The polymer alignment in the composite film, which was slowly formed by photopolymerization-induced phase separation of a heated nematic-phase solution of FLC and monomers, was observed by polarization Raman spectral microscopy. Raman peak intensities originating from the polymers were changed with those from the FLC, when the applied voltage polarity was changed. The trace patterns of the Raman peak intensity with in-plane rotation of the composite film indicated that the formed flexible polymers can follow FLC molecular switching.

  1. Measuring the optical chirality of molecular aggregates at liquid-liquid interfaces.

    Science.gov (United States)

    Watarai, Hitoshi; Adachi, Kenta

    2009-10-01

    Some new experimental methods for measuring the optical chirality of molecular aggregates formed at liquid-liquid interfaces have been reviewed. Chirality measurements of interfacial aggregates are highly important not only in analytical spectroscopy but also in biochemistry and surface nanochemistry. Among these methods, a centrifugal liquid membrane method was shown to be a highly versatile method for measuring the optical chirality of the liquid-liquid interface when used in combination with a commercially available circular dichroism (CD) spectropolarimeter, provided that the interfacial aggregate exhibited a large molar absorptivity. Therefore, porphyrin and phthalocyanine were used as chromophoric probes of the chirality of itself or guest molecules at the interface. A microscopic CD method was also demonstrated for the measurement of a small region of a film or a sheet sample. In addition, second-harmonic generation and Raman scattering methods were reviewed as promising methods for detecting interfacial optical molecules and measuring bond distortions of chiral molecules, respectively.

  2. Cavities in molecular liquids and the theory of hydrophobic solubilities

    Science.gov (United States)

    Pohorille, A.; Pratt, L. R.; MacElroy, R. (Principal Investigator)

    1990-01-01

    Thermal configurational data on neat liquids are used to obtain the work of formation of hard spherical cavities of atomic size in six molecular solvents: n-hexane, n-dodecane, n-undecyl alcohol, chloroform, carbon tetrachloride, and water. These results are used to test a recent suggestion that the differences between nonaqueous solvents and liquid water in solvation of inert gases are not principally due to the hydrogen-bonded structure of liquid water but rather to the comparatively small size of the water molecule. The frequencies of occurrence of cavities in liquid water can be meaningfully distinguished from those in the organic solvents. Liquid water has a larger fractional free volume, but that free volume is distributed in smaller packets. With respect to cavity work, water is compared to a solvent of the same molecular density and composed of hard spheres of the same size as the water molecule. That comparison indicates that the hard-sphere liquid finds more ways to configure its free volume in order to accommodate an atomic solute of substantial size and thus, would be more favorable solvent for inert gases. The scaled particle model of inert gas solubility in liquid water predicts cavity works 20% below the numerical data for TIP4P water at 300 K and 1.0 g/cm3 for cavity radii near 2.0 angstroms. It is argued that the sign of this difference is just the sign that ought to be expected and that the magnitude of this difference measures structural differences between water and the directly comparable hard-sphere liquid. In conjunction with previous data, these results indicate that atomic sized cavities should be considered submacroscopic.

  3. Ab initio molecular dynamics study of liquid methanol

    CERN Document Server

    Handgraaf, J W; Meijer, E J; Handgraaf, Jan-Willem; Erp, Titus S. van; Meijer, Evert Jan

    2003-01-01

    We present a density-functional theory based molecular-dynamics study of the structural, dynamical, and electronic properties of liquid methanol under ambient conditions. The calculated radial distribution functions involving the oxygen and hydroxyl hydrogen show a pronounced hydrogen bonding and compare well with recent neutron diffraction data, except for an underestimate of the oxygen-oxygen correlation. We observe that, in line with infrared spectroscopic data, the hydroxyl stretching mode is significantly red-shifted in the liquid. A substantial enhancement of the dipole moment is accompanied by significant fluctuations due to thermal motion. Our results provide valuable data for improvement of empirical potentials.

  4. Molecular absorption cryogenic cooler for liquid hydrogen propulsion systems

    Science.gov (United States)

    Klein, G. A.; Jones, J. A.

    1982-01-01

    A light weight, long life molecular absorption cryogenic cooler (MACC) system is described which can use low temperature waste heat to provide cooling for liquid hydrogen propellant tanks for interplanetary spacecraft. Detailed tradeoff studies were made to evaluate the refrigeration system component interactions in order to minimize the mass of the spacecraft cooler system. Based on this analysis a refrigerator system mass of 31 kg is required to provide the .48 watts of cooling required by a 2.3 meter diameter liquid hydrogen tank.

  5. Phase equilibrium calculations of ternary liquid mixtures with binary interaction parameters and molecular size parameters determined from molecular dynamics.

    Science.gov (United States)

    Oh, Suk Yung; Bae, Young Chan

    2010-07-15

    The method presented in this paper was developed to predict liquid-liquid equilibria in ternary liquid mixtures by using a combination of a thermodynamic model and molecular dynamics simulations. In general, common classical thermodynamic models have many parameters which are determined by fitting a model with experimental data. This proposed method, however, provides a simple procedure for calculating liquid-liquid equilibria utilizing binary interaction parameters and molecular size parameters determined from molecular dynamics simulations. This method was applied to mixtures containing water, hydrocarbons, alcohols, chlorides, ketones, acids, and other organic liquids over various temperature ranges. The predicted results agree well with the experimental data without the use of adjustable parameters.

  6. Molecular ions of ionic liquids in the gas phase.

    Science.gov (United States)

    Gross, Jürgen H

    2008-09-01

    Ionic liquids form neutral ion pairs (CA) upon evaporation. The softness of the gas-phase ionization of field ionization has been used to generate "molecular ions," CA(+*), of ionic liquids, most probably by neutralization of the anion. In detail, 1-ethyl-3-methylimidazolium-thiocyanate, [C(6)H(11)N(2)](+) [SCN](-), 1-butyl-3-methylimidazolium-tricyanomethide, [C(8)H(15)N(2)](+) [C(4)N(3)](-), N-butyl-3-methylpyridinium-dicyanamide, [C(10)H(16)N](+) [C(2)N(3)](-), and 1-butyl-1-methylpyrrolidinium-bis[(trifluormethyl)sulfonyl]amide, [C(9)H(20)N](+) [C(2)F(6)NO(4)S(2)](-) were used. The assignment as CA(+*) ions, which has been confirmed by accurate mass measurements and misassignments due to thermal decomposition of the ionic liquids, has been ruled out by field desorption and electrospray ionization mass spectrometry of the residues.

  7. The Molecular Structure of the Liquid Ordered Phase

    Science.gov (United States)

    Lyman, Edward

    2014-03-01

    Molecular dynamics simulations reveal substructures within the liquid-ordered phase of lipid bilayers. These substructures, identified in a 10 μsec all-atom trajectory of liquid-ordered/liquid-disordered coexistence (Lo/Ld) , are composed of saturated hydrocarbon chains packed with local hexagonal order, and separated by interstitial regions enriched in cholesterol and unsaturated chains. Lipid hydrocarbon chain order parameters calculated from the Lo phase are in excellent agreement with 2H NMR measurements; the local hexagonal packing is also consistent with 1H-MAS NMR spectra of the Lo phase, NMR diffusion experiments, and small angle X-ray- and neutron scattering. The balance of cholesterol-rich to local hexagonal order is proposed to control the partitioning of membrane components into the Lo regions. The latter have been frequently associated with formation of so-called rafts, platforms in the plasma membranes of cells that facilitate interaction between components of signaling pathways.

  8. Recent advances in technetium halide chemistry.

    Science.gov (United States)

    Poineau, Frederic; Johnstone, Erik V; Czerwinski, Kenneth R; Sattelberger, Alfred P

    2014-02-18

    Transition metal binary halides are fundamental compounds, and the study of their structure, bonding, and other properties gives chemists a better understanding of physicochemical trends across the periodic table. One transition metal whose halide chemistry is underdeveloped is technetium, the lightest radioelement. For half a century, the halide chemistry of technetium has been defined by three compounds: TcF6, TcF5, and TcCl4. The absence of Tc binary bromides and iodides in the literature was surprising considering the existence of such compounds for all of the elements surrounding technetium. The common synthetic routes that scientists use to obtain binary halides of the neighboring elements, such as sealed tube reactions between elements and flowing gas reactions between a molecular complex and HX gas (X = Cl, Br, or I), had not been reported for technetium. In this Account, we discuss how we used these routes to revisit the halide chemistry of technetium. We report seven new phases: TcBr4, TcBr3, α/β-TcCl3, α/β-TcCl2, and TcI3. Technetium tetrachloride and tetrabromide are isostructural to PtX4 (X = Cl or Br) and consist of infinite chains of edge-sharing TcX6 octahedra. Trivalent technetium halides are isostructural to ruthenium and molybdenum (β-TcCl3, TcBr3, and TcI3) and to rhenium (α-TcCl3). Technetium tribromide and triiodide exhibit the TiI3 structure-type and consist of infinite chains of face-sharing TcX6 (X = Br or I) octahedra. Concerning the trichlorides, β-TcCl3 crystallizes with the AlCl3 structure-type and consists of infinite layers of edge-sharing TcCl6 octahedra, while α-TcCl3 consists of infinite layers of Tc3Cl9 units. Both phases of technetium dichloride exhibit new structure-types that consist of infinite chains of [Tc2Cl8] units. For the technetium binary halides, we studied the metal-metal interaction by theoretical methods and magnetic measurements. The change of the electronic configuration of the metal atom from d(3) (Tc

  9. Molecular dynamics simulation of liquid-vapor surface tension

    Institute of Scientific and Technical Information of China (English)

    王德; ZENG; Danling; 等

    2002-01-01

    A molecular dynamics simulation model is established based on the well-known Lennard-Jones 12-6 potential function to determine the surface tension of a Lennard-Jones liquid-vapor interface.The simulation is carried out with argon as the working fluid of a given molecular number at different temperature and different truncated radius.It is found that the surface tension of a Lennard-Jones fluid is likely to be bigger for a bigger truncated radius,and tends to be constant after the truncated radius increased to a certain value.It is also found that the surface tension becomes smaller as the temperature increases.

  10. Amorphization of Molecular Liquids of Pharmaceutical Drugs by Acoustic Levitation

    Directory of Open Access Journals (Sweden)

    C. J. Benmore

    2011-08-01

    Full Text Available It is demonstrated that acoustic levitation is able to produce amorphous forms from a variety of organic molecular compounds with different glass forming abilities. This can lead to enhanced solubility for pharmaceutical applications. High-energy x-ray experiments show that several viscous gels form from saturated pharmaceutical drug solutions after 10–20 min of levitation at room temperature, most of which can be frozen in solid form. Laser heating of ultrasonically levitated drugs can also result in the vitrification of molecular liquids, which is not attainable using conventional amorphization methods.

  11. Structure of a molecular liquid GeI4

    Science.gov (United States)

    Fuchizaki, Kazuhiro; Sakagami, Takahiro; Kohara, Shinji; Mizuno, Akitoshi; Asano, Yuta; Hamaya, Nozomu

    2016-11-01

    A molecular liquid GeI4 is a candidate that undergoes a pressure-induced liquid-to-liquid phase transition. This study establishes the reference structure of the low-pressure liquid phase. Synchrotron x-ray diffraction measurements were carried out at several temperatures between the melting and the boiling points under ambient pressure. The molecule has regular tetrahedral symmetry, and the intramolecular Ge-I length of 2.51 Å is almost temperature-independent within the measured range. A reverse Monte Carlo (RMC) analysis is employed to find that the distribution of molecular centers remains self-similar against heating, and thus justifying the length-scaling method adopted in determining the density. The RMC analysis also reveals that the vertex-to-face orientation of the nearest molecules are not straightly aligned, but are inclined at about 20 degrees, thereby making the closest intermolecular I-I distance definitely shorter than the intramolecular one. The prepeak observed at  ˜1 Å-1 in the structural factor slightly shifts and increases in height with increasing temperature. The origin of the prepeak is clearly identified to be traces of the 111 diffraction peak in the crystalline state. The prepeak, assuming the residual spatial correlation between germanium sites in the densest direction, thus shifts toward lower wavenumbers with thermal expansion. The aspect that a relative reduction in molecular size associated with the volume expansion is responsible for the increase in the prepeak’s height is confirmed by a simulation, in which the molecular size is changed.

  12. Molecular dynamics simulations of liquid crystals at interfaces

    CERN Document Server

    Shield, M

    2002-01-01

    Molecular dynamics simulations of an atomistic model of 4-n-octyl-4'-cyanobiphenyl (8CB) were performed for thin films of 8CB on solid substrates (a pseudopotential representation of the molecular topography of the (100) crystal surface of polyethylene (PE), a highly ordered atomistic model of a pseudo-crystalline PE surface and an atomistic model of a partially orientated film of PE), free standing thin films of 8CB and 8CB droplets in a hexagonal pit. The systems showed strong homeotropic anchoring at the free volume interface and planar anchoring at the solid interface whose strength was dependent upon the surface present. The free volume interface also demonstrated weak signs of smectic wetting of the bulk. Simulations of thin free standing films of liquid crystals showed the ordered nature of the liquid crystals at the two free volume interfaces can be adopted by the region of liquid crystal molecules between the homeotropic layer at each interface only if there is a certain number of liquid crystal mole...

  13. Molecular dynamics of the water liquid-vapor interface

    Science.gov (United States)

    Wilson, M. A.; Pohorille, A.; Pratt, L. R.; MacElroy, R. D. (Principal Investigator)

    1987-01-01

    The results of molecular dynamics calculations on the equilibrium interface between liquid water and its vapor at 325 K are presented. For the TIP4P model of water intermolecular pair potentials, the average surface dipole density points from the vapor to the liquid. The most common orientations of water molecules have the C2 nu molecular axis roughly parallel to the interface. The distributions are quite broad and therefore compatible with the intermolecular correlations characteristic of bulk liquid water. All near-neighbor pairs in the outermost interfacial layers are hydrogen bonded according to the common definition adopted here. The orientational preferences of water molecules near a free surface differ from those near rigidly planar walls which can be interpreted in terms of patterns found in hexagonal ice 1. The mean electric field in the interfacial region is parallel to the mean polarization which indicates that attention cannot be limited to dipolar charge distributions in macroscopic descriptions of the electrical properties of this interface. The value of the surface tension obtained is 132 +/- 46 dyn/cm, significantly different from the value for experimental water of 68 dyn/cm at 325 K.

  14. Molecular dynamics of the water liquid-vapor interface

    Science.gov (United States)

    Wilson, M. A.; Pohorille, A.; Pratt, L. R.; MacElroy, R. D. (Principal Investigator)

    1987-01-01

    The results of molecular dynamics calculations on the equilibrium interface between liquid water and its vapor at 325 K are presented. For the TIP4P model of water intermolecular pair potentials, the average surface dipole density points from the vapor to the liquid. The most common orientations of water molecules have the C2 nu molecular axis roughly parallel to the interface. The distributions are quite broad and therefore compatible with the intermolecular correlations characteristic of bulk liquid water. All near-neighbor pairs in the outermost interfacial layers are hydrogen bonded according to the common definition adopted here. The orientational preferences of water molecules near a free surface differ from those near rigidly planar walls which can be interpreted in terms of patterns found in hexagonal ice 1. The mean electric field in the interfacial region is parallel to the mean polarization which indicates that attention cannot be limited to dipolar charge distributions in macroscopic descriptions of the electrical properties of this interface. The value of the surface tension obtained is 132 +/- 46 dyn/cm, significantly different from the value for experimental water of 68 dyn/cm at 325 K.

  15. Heat capacities of ionic liquids and their heats of solution in molecular liquids

    Energy Technology Data Exchange (ETDEWEB)

    Waliszewski, D. [Department of Physical Chemistry, Univesity of Lodz, PL-90 236 Lodz (Poland); Stepniak, I. [Faculty of Chemical Technology, Poznan University of Technology, PL-60 965 Poznan (Poland); Piekarski, H. [Department of Physical Chemistry, Univesity of Lodz, PL-90 236 Lodz (Poland); Lewandowski, A. [Faculty of Chemical Technology, Poznan University of Technology, PL-60 965 Poznan (Poland)]. E-mail: andrzej.lewandowski@put.poznan.pl

    2005-08-01

    Heat capacities of ionic liquids (IL): 1-ethyl-3-methylimidazolium tetrafluoroborate (EMImBF{sub 4}), 1-ethyl-3-methyl imidazolium bis((trifluoromethyl)sulfonyl) imide (EMImN(CF{sub 3}SO{sub 2}){sub 2}), 1-bytyl-3-methylimidazolium tetrafluoroborate (BMImBF{sub 4}) and N,N-methyl, propyl pyrrolidinium bis((trifluoromethyl)sulfonyl) imide (MPPyN(CF{sub 3}SO{sub 2}){sub 2}) were measured from 283.15 to 358.15 K. Room temperature heat capacities have also been estimated by an additive group contribution method, based on the assumption that the heat capacity of a molecular compound equals the sum of individual atomic-group contributions. The C {sub p} {sup 293.15K} estimated values are about 12% higher than experimental values. The estimates suggest that heat capacities of ionic liquids do not differ considerably from those typical for molecular liquids (ML). The heats of solution, {delta}{sub sol} H, of ionic liquids EMImBF{sub 4}, BMImBF{sub 4} EMImN(CF{sub 3}SO{sub 2}){sub 2} and MPPyN(CF{sub 3}SO{sub 2}){sub 2} were measured in water, acetonitrile (AN) and methanol, as a function of ionic liquid concentration c {sub m}. The measured {delta}{sub sol} H values decrease with decreasing c {sub m}. Enthalpies of ionic liquid transfer, {delta}{sub t} H deg., from water to methanol and acetonitrile were calculated from measured solution enthalpies. Values of {delta}{sub t} H deg. for the transfer from water to methanol are positive and those for the transfer to acetonitrile are negative.

  16. Zwitterionic and mesoionic liquids:Molecular aggregation in 3-methylsydnone

    Institute of Scientific and Technical Information of China (English)

    CASSEL; Stéphanie; RICO-LATTES; Isabelle; LATTES; Armand

    2010-01-01

    Ionic liquids are green solvents with interesting properties:displaying low melting points and high boiling points.They offer a new approach applicable in many instances.Nevertheless,the presence of free ions can be a matter in some cases,e.g.for the study of nucleophilic reactions,in electrochemistry,and in each situation where there is a competition between counter ions,as in micellization of ionic surfactants.Neutral compounds having formal unit electrical charges of opposite sign,and the same physical properties than ionic liquids would be a nice alternative to these latter solvents.There are two classes of chemical compounds having these characteristics:zwitterionic liquids(with no uncharged canonical representation) and mesoionic liquids(in which the negative and the positive charges are delocalized).In that last class we have chosen to work with 3-methylsydnone in order to examine,in this aprotic solvent,if it was possible to observe aggregation of surfactants in the same manner as in water.With all kinds of surfactants studied(ionic,zwitterionic and mesoionic) we have been able to demonstrate the formation of direct micelles:hydrogen bonding is thus not mandatory for molecular aggregation.Comparison of the behavior in water and in formamide showed that solvophobic interactions were qualitatively comparable but with a lower intensity.

  17. Reverse osmosis molecular differentiation of organic liquids using carbon molecular sieve membranes

    Science.gov (United States)

    Koh, Dong-Yeun; McCool, Benjamin A.; Deckman, Harry W.; Lively, Ryan P.

    2016-08-01

    Liquid-phase separations of similarly sized organic molecules using membranes is a major challenge for energy-intensive industrial separation processes. We created free-standing carbon molecular sieve membranes that translate the advantages of reverse osmosis for aqueous separations to the separation of organic liquids. Polymer precursors were cross-linked with a one-pot technique that protected the porous morphology of the membranes from thermally induced structural rearrangement during carbonization. Permeation studies using benzene derivatives whose kinetic diameters differ by less than an angstrom show kinetically selective organic liquid reverse osmosis. Ratios of single-component fluxes for para- and ortho-xylene exceeding 25 were observed and para- and ortho- liquid mixtures were efficiently separated, with an equimolar feed enriched to 81 mole % para-xylene, without phase change and at ambient temperature.

  18. Collective and molecular relaxation in ferroelectric liquid crystals

    Science.gov (United States)

    Wrobel, S.; Marzec, M.; Godlewska, Malgorzata; Gestblom, B.; Hiller, Steffen; Haase, Wolfgang

    1995-08-01

    Ferroelectric liquid crystals are molecular ferroelectrics showing up in the tilted liquid crystalline systems (SmC*, SmI*, SmF*) composed of chiral molecules. In this work, we present the dielectric, electro-optic, and calorimetric studies of a single component system: 3-octyloxy-6[2-fluor-4-(2-fluoroctyloxy)phenyl]-pyridine showing interesting ferroelectric properties. The compound exhibits a first order N*- SmC* phase transition which leads to a qualitatively new behavior, for instance the relaxation frequency of the soft mode below TC seems to be temperature independent. The high frequency relaxation process, connected with the reorientation around the long axis, is practically undisturbed at the N*-SmC* transition. Yet, it was found that in the SmC* phase, the best fit was obatined with two Cole-Cole functions yielding two relaxation times to describe a biased reorientation of molecules in the SmC* phase.

  19. Molecular simulation studies of reversed-phase liquid chromatography.

    Science.gov (United States)

    Lindsey, Rebecca K; Rafferty, Jake L; Eggimann, Becky L; Siepmann, J Ilja; Schure, Mark R

    2013-04-26

    Over the past 20 years, molecular simulation methods have been applied to the modeling of reversed-phase liquid chromatography (RPLC). The purpose of these simulations was to provide a molecular-level understanding of: (i) the structure and dynamics of the bonded phase and its interface with the mobile phase, (ii) the interactions of analytes with the bonded phase, and (iii) the retention mechanism for different analytes. However, the investigation of chromatographic systems poses significant challenges for simulations with respect to the accuracy of the molecular mechanics force fields and the efficiency of the sampling algorithms. This review discusses a number of aspects concerning molecular simulation studies of RPLC systems including the historical development of the subject, the background needed to understand the two prevalent techniques, molecular dynamics (MD) and Monte Carlo (MC) methods, and the wealth of insight provided by these simulations. Examples from the literature employing MD approaches and from the authors' laboratory using MC methods are discussed. The former can provide information on chain dynamics and transport properties, whereas the latter techniques are uniquely suited for the investigation of phase and sorption equilibria that underly RPLC retention, and both can be used to elucidate the bonded-chain conformations and solvent distributions. Copyright © 2013 Elsevier B.V. All rights reserved.

  20. Novel Silver Cobaltacarborane Complexes with a Linearly Bridging Halide

    Energy Technology Data Exchange (ETDEWEB)

    Park, Hyun Seo; Bae, Hye Jin; Do, Youngkyu [KAIST, Daejeon (Korea, Republic of); Park, Youngwhan [LG Chem/Research Park, Daejeon (Korea, Republic of); Go, Min Jeong; Lee, Junseong [Chonnam National Univ., Gwangju (Korea, Republic of)

    2013-10-15

    The structural versatility of halides mainly originates from their coordinating abilities of adopting a bridging bond between two or more metal atoms, as well as a terminal bond. Moreover, a halide bridging bond angle is so flexible that thermodynamic stability can be endowed with proper geometry, which conceptually varies from acute to right, obtuse, and linear. In spite of innumerable reports on molecular metal halides, examples of the linearly bridging fashion are very scarce. The reason for the rarity of the linear M. X. M arrangement can be easily explained by the VSEPR (Valence Shell Electron Pair Repulsion) concept. The linear M. X. M formation has only been achieved by adopting a macrocyclic chelate ligand, which is structurally demanding, so that the VSEPR repulsions among lone-pair electrons on the halide atom could be overcome.

  1. Nonresonant Multiple-Pulse Control of Molecular Motions in Liquid

    Directory of Open Access Journals (Sweden)

    Nikiforov V.G.

    2015-01-01

    Full Text Available We propose the implementation of the multiple-pulse excitation for manipulation of the molecular contributions to the optically-heterodyne-detected optical-Kerr-effect. The key parameters controlling the specificity of the multiple-pulse excitation scenarios are the pulses durations, the delays between pulses, the relation between the pump pulses amplitudes and the pulses polarizations. We model the high-order optical responses and consider some principles of the scenarios construction. We show that it is possible to adjust the excitation scenario in such a way that the some responses can be removed from detected signal along with the enhancement of the interested response amplitude. The theoretical analysis and first experimental data reveal that the multiple-pulse excitation technique can be useful for the selective spectroscopy of the molecular vibrations and rotations in liquid.

  2. Thermodynamics and intrinsic structure of the Al-Pb liquid-liquid interface: a molecular dynamics simulation study.

    Science.gov (United States)

    Yang, Yang; Laird, Brian B

    2014-07-17

    We examine the thermodynamics and intrinsic structure of the Al-Pb liquid-liquid interface using molecular dynamics simulation and embedded atom method potentials. The instantaneous interfacial positions, from which the intrinsic structure and the capillary fluctuation spectrum are determined, are calculated using a grid-based method. The interfacial free energy extracted from the capillary fluctuation spectrum is shown to be in excellent agreement with that calculated mechanically by integrating the stress profile. The intrinsic liquid-liquid interfacial density profile shows structural oscillations in the liquid phases in the interfacial region that are shown to be quantitatively similar to the radial distribution functions of the bulk liquid, consistent with theoretical predictions from classical density functional theory and with earlier simulations on liquid-liquid and liquid-vapor interfaces. In addition, we show the mean interfacial density profile for this system is well described as a convolution of the intrinsic density profile and the probability distribution of interfacial position.

  3. Molecular conformation and structural correlations of liquid D-1-propanol through neutron diffraction

    Indian Academy of Sciences (India)

    A Sahoo; S Sarkar; P S R Krishna; V Bhagat; R N Joarder

    2008-07-01

    An analysis of neutron diffraction data of liquid deuterated 1-propanol at room temperature to extract its molecular conformation is presented. Being a big molecule with twelve atomic sites, the analysis is tricky and needs careful consideration. The resulting molecular parameters are compared with electron diffraction (gas phase), X-ray diffraction (liquid phase) and MD simulation results. Information about the hydrogen-bonded intermolecular structure in liquid is extracted and nature of the probable molecular association suggested.

  4. Halide laser glasses

    Energy Technology Data Exchange (ETDEWEB)

    Weber, M.J.

    1982-01-14

    Energy storage and energy extraction are of prime importance for efficient laser action and are affected by the line strengths and linewidths of optical transitions, excited-state lifetimes, nonradiative decay processes, spectroscopic inhomogeneities, nonlinear refractive index, and damage threshold. These properties are all host dependent. To illustrate this, the spectroscopic properties of Nd/sup 3 +/ have been measured in numerous oxide, oxyhalide, and halide glasses. A table summarizes the reported ranges of stimulated emission cross sections, peak wavelengths, linewidths, and radiative lifetimes associated with the /sup 4/F/sub 3/2/ ..-->.. /sup 4/I/sub 11/2/ lasing transition.

  5. Molecular dynamics simulations of glycerol glass-forming liquid

    Energy Technology Data Exchange (ETDEWEB)

    Blieck, J. [Laboratoire de Dynamique et Structure des Materiaux Moleculaires, CNRS UMR 8024, BAT P5-Cite Scientifique, Universite Lille I, 59655 Villeneuve d' Ascq Cedex (France); Affouard, F. [Laboratoire de Dynamique et Structure des Materiaux Moleculaires, CNRS UMR 8024, BAT P5-Cite Scientifique, Universite Lille I, 59655 Villeneuve d' Ascq Cedex (France)], E-mail: frederic.affouard@univ-lille1.fr; Bordat, P. [Laboratoire de Dynamique et Structure des Materiaux Moleculaires, CNRS UMR 8024, BAT P5-Cite Scientifique, Universite Lille I, 59655 Villeneuve d' Ascq Cedex (France); Lerbret, A. [Laboratoire de Dynamique et Structure des Materiaux Moleculaires, CNRS UMR 8024, BAT P5-Cite Scientifique, Universite Lille I, 59655 Villeneuve d' Ascq Cedex (France); Descamps, M. [Laboratoire de Dynamique et Structure des Materiaux Moleculaires, CNRS UMR 8024, BAT P5-Cite Scientifique, Universite Lille I, 59655 Villeneuve d' Ascq Cedex (France)

    2005-10-31

    Structural and dynamical properties of liquid glycerol have been investigated by Molecular Dynamics simulations. An improved model based on a slight reparametrisation of the all-atoms AMBER force field used in [R. Chelli, P. Procacci, G. Cardini, R.G.D. Valle, S. Califano, Phys. Chem. Chem. Phys. 1 (1999) 871] is presented. The structure remains satisfactory, qualitatively similar to that obtained from the original model. This new model is also found to reproduce significantly better the diffusion coefficient and the correlations times as they can be deduced from neutron spin echo (NSE) experiments. Structural heterogeneities revealed as a pre-peak of the static structure factor S(Q) close to Q {approx} 0.6 A{sup -1} are observed. Our results are also found compatible with predictions of the Mode Coupling Theory.

  6. Molecular structure and elastic properties of thermotropic liquid crystals: Integrated molecular dynamics—Statistical mechanical theory vs molecular field approach

    Science.gov (United States)

    Capar, M. Ilk; Nar, A.; Ferrarini, A.; Frezza, E.; Greco, C.; Zakharov, A. V.; Vakulenko, A. A.

    2013-03-01

    The connection between the molecular structure of liquid crystals and their elastic properties, which control the director deformations relevant for electro-optic applications, remains a challenging objective for theories and computations. Here, we compare two methods that have been proposed to this purpose, both characterized by a detailed molecular level description. One is an integrated molecular dynamics-statistical mechanical approach, where the bulk elastic constants of nematics are calculated from the direct correlation function (DCFs) and the single molecule orientational distribution function [D. A. McQuarrie, Statistical Mechanics (Harper & Row, New York, 1973)]. The latter is obtained from atomistic molecular dynamics trajectories, together with the radial distribution function, from which the DCF is then determined by solving the Ornstein-Zernike equation. The other approach is based on a molecular field theory, where the potential of mean torque experienced by a mesogen in the liquid crystal phase is parameterized according to its molecular surface. In this case, the calculation of elastic constants is combined with the Monte Carlo sampling of single molecule conformations. Using these different approaches, but the same description, at the level of molecular geometry and torsional potentials, we have investigated the elastic properties of the nematic phase of two typical mesogens, 4'-n-pentyloxy-4-cyanobiphenyl and 4'-n-heptyloxy-4-cyanobiphenyl. Both methods yield K3(bend) >K1 (splay) >K2 (twist), although there are some discrepancies in the average elastic constants and in their anisotropy. These are interpreted in terms of the different approximations and the different ways of accounting for the structural properties of molecules in the two approaches. In general, the results point to the role of the molecular shape, which is modulated by the conformational freedom and cannot be fully accounted for by a single descriptor such as the aspect ratio.

  7. Mixtures of protic ionic liquids and molecular cosolvents: a molecular dynamics simulation.

    Science.gov (United States)

    Docampo-Álvarez, Borja; Gómez-González, Víctor; Méndez-Morales, Trinidad; Carrete, Jesús; Rodríguez, Julio R; Cabeza, Óscar; Gallego, Luis J; Varela, Luis M

    2014-06-07

    In this work, the effect of molecular cosolvents (water, ethanol, and methanol) on the structure of mixtures of these compounds with a protic ionic liquid (ethylammonium nitrate) is analyzed by means of classical molecular dynamics simulations. Included are as-yet-unreported measurements of the densities of these mixtures, used to test our parameterized potential. The evolution of the structure of the mixtures throughout the concentration range is reported by means of the calculation of coordination numbers and the fraction of hydrogen bonds in the system, together with radial and spatial distribution functions for the various molecular species and molecular ions in the mixture. The overall picture indicates a homogeneous mixing process of added cosolvent molecules, which progressively accommodate themselves in the network of hydrogen bonds of the protic ionic liquid, contrarily to what has been reported for their aprotic counterparts. Moreover, no water clustering similar to that in aprotic mixtures is detected in protic aqueous mixtures, but a somehow abrupt replacing of [NO3](-) anions in the first hydration shell of the polar heads of the ionic liquid cations is registered around 60% water molar concentration. The spatial distribution functions of water and alcohols differ in the coordination type, since water coordinates with [NO3](-) in a bidentate fashion in the equatorial plane of the anion, while alcohols do it in a monodentate fashion, competing for the oxygen atoms of the anion. Finally, the collision times of the different cosolvent molecules are also reported by calculating their velocity autocorrelation functions, and a caging effect is observed for water molecules but not in alcohol mixtures.

  8. Petascale Molecular Dynamics Simulations of Polymers and Liquid Crystals

    Science.gov (United States)

    Nguyen, Trung Dac; Carrillo, Jan-Michael; Brown, W. Michael

    2014-03-01

    The availability of faster and larger supercomputers and more efficient parallel algorithms now enable us to perform unprecedented simulations approaching experimental scales. Here we present two examples of our latest large-scale molecular dynamics simulations using the Titan supercomputer in the Oak Ridge Leadership Computing Facility (OLCF). In the first study, we address the rupture origin of liquid crystal thin films wetting a solid substrate. Our simulations show the key signatures of spinodal instability in isotropic and nematic films on top of thermal nucleation. Importantly, we found evidence of a common rupture mechanism independent of initial thickness and LC orientational ordering. In the second study, we used coarse-grained molecular dynamics to simulate the thermal annealing of poly(3-hexylthiophene) (P3HT) and Phenyl-C61-butyric acid methyl ester (PCBM) blends in the presence of a silicon substrate found in organic solar cells. Our simulations show different phase segregated morphologies dependent on the P3HT chain length and PCBM volume fraction in the blend. Furthermore, the ternary blend of short and long P3HT chains with PCBM affects the vertical phase segregation of PCBM decreasing its concentration in the vicinity of the substrate. U.S. DOE Contract No. DE-AC05-00OR22725.

  9. Learning Science Through Guided Discovery: Liquid Water and Molecular Networks

    Science.gov (United States)

    Essmann, U.; Glotzer, S.; Gyure, M.; Ostrovsky, B.; Poole, P. H.; Sastry, S.; Schwarzer, S.; Selinger, R.; Shann, M. H.; Shore, L. S.; Stanley, H. E.; Taylor, E. F.; Trunfio, P.

    In every drop of water, down at the scale of atoms and molecules, there is a world that can fascinate anyone—ranging from a non-verbal young science student to an ardent science-phobe. The objective of Learning Science through Guided Discovery: Liquid Water and Molecular Networks is to use advanced technology to provide a window into this submicroscopic world, and thereby allow students to discover by themselves a new world. We have developed a coordinated two-fold approach in which a cycle of hands-on activities, games, and experimentation is followed by a cycle of advanced computer simulations employing the full power of computer animation to "ZOOM" into the depths of his or her newly-discovered world, an interactive experience surpassing that of an OMNIMAX theater. Pairing of laboratory experiments with corresponding simulations challenges students to understand multiple representations of concepts. Answers to student questions, resolution of student misconceptions, and eventual personalized student discoveries are all guided by a clear set of "cues" which we build into the computer display. We thereby provide students with the opportunity to work in a fashion analogous to that in which practicing scientists work—e.g., by using advanced technology to "build up" to general principles from specific experiences. Moreover, the ability to visualize "real-time" dynamic motions allows for student-controlled animated graphic simulations on the molecular scale and interactive guided lessons superior to those afforded by even the most artful of existing texts.

  10. STUDY ON THE CATIONIC POLYMERIZATION OF 1,3-PENTADIENE INITIATED BY AlCl3/ALKYL HALIDE SYSTEMS

    Institute of Scientific and Technical Information of China (English)

    PENG Yuxing; LIU Jialin; DAI Hansong; CUN Linfeng

    1996-01-01

    The cationic polymerizations of 1, 3-pentadiene were initiated by AlCl3 in n-hexane at 30℃ in the presence of alkyl halides, i.e., tert-butyl chloride, tert-butyl bromide and isobutyl chloride. The effects of these halides on the polymer yield, molecular weight,crosslinking reaction, cyclization and polymer microstructure, have been investigated. Two main side reactions, crosslinking and cyclization, were suppressed and reduced by the addition of the halides. The proportion of 1, 4 units of polymer chains was increased by the presence of the halides, which reduced the polymer yield and the molecular weight of polymers.

  11. First-principles molecular dynamics simulation of liquid Mg3Bi2

    NARCIS (Netherlands)

    deWijs, GA; Pastore, G; Selloni, A; vanderLugt, W

    1996-01-01

    The liquid Mg-Bi system exhibits strong compound formation at the 'octet' composition (Mg3Bi2) We present results of first-principles molecular dynamics simulations of this alloy system at different compositions: the pure Mg and Bi liquid components, the stoichiometric liquid, and a Mg-rich composit

  12. Halide Influence on Molecular and Supramolecular Arrangements of Iron Complexes with a 3,5-Bis(2-Pyridyl)-1,2,4,6-Thiatriazine Ligand.

    Science.gov (United States)

    Harriman, Katie L M; Kühne, Irina A; Leitch, Alicea A; Korobkov, Ilia; Clérac, Rodolphe; Murugesu, Muralee; Brusso, Jaclyn L

    2016-06-06

    A series of iron centered complexes, namely, [Fe(Py2TTA)Cl2] (1), [Fe(Py2TTA)Br2] (2), and [Fe(μ-F)(Py2TTAO)F]∞ (3), were isolated via complexation of 3,5-bis(2-pyridyl)-1,2,4,6-thiatriazine (Py2TTAH) with various ferric halides (e.g., FeF3, FeCl3, and FeBr3). Comparison of the optical and electrochemical spectroscopy, structural analysis, and magnetic studies reveal numerous similarities between the chlorido (1) and bromido (2) derivatives, which crystallize as discrete five-coordinate iron centered complexes with coordination geometries that are intermediate between trigonal bipyramidal and square base pyramid. Conversely, the fluorido derivative (3) results in a completely different structure due to oxidation of the ligand and the formation of a one-dimensional coordination polymer held together through a bridging fluoride ion. Consequently, the spectroscopic and magnetic behavior of 3 differs significantly compared with 1 and 2. Complexes 1 and 2 exhibit paramagnetic properties typical for a mononuclear S = 5/2 system with weak intermolecular antiferromagnetic interactions at low temperatures, whereas complex 3 demonstrates significant exchange couplings within the chain and weak antiferromagnetic interchain interactions, which stabilize a canted antiferromagnetic state below 4.2 K.

  13. Zero-dipole molecular organic cations in mixed organic-inorganic halide perovskites: possible chemical solution for the reported anomalous hysteresis in the current-voltage curve measurements.

    Science.gov (United States)

    Giorgi, Giacomo; Yamashita, Koichi

    2015-11-06

    Starting from a brief description of the main architectures characterizing the novel solar technology of perovskite-based solar cells, we focus our attention on the anomalous hysteresis experimentally found to affect the measurement of the current-voltage curve of such devices. This detrimental effect, associated with slow dynamic reorganization processes, depends on several parameters; among them, the scan rate of the measurements, the architecture of the cell, and the perovskite deposition rate are crucial. Even if a conclusive explanation of the origin of the hysteresis has not been provided so far, several experimental findings ascribe its origin to ionic migration at an applied bias and dielectric polarization that occurs in the perovskite layer. Consistently, a dipole-moment-reduced cation such as formamidinium ion is experimentally reported to quantitatively reduce the hysteresis from perovskite-based devices. By means of a density-functional theory-based set of calculations, we have predicted and characterized guanidinium ion (GA = (+)[C(NH2)3], a zero-dipole moment cation by symmetry)-based organic-inorganic halide perovskite's structural and electronic properties, speculating that such a cation and the alloys it may form with other organic cations can represent a possible chemical solution for the puzzling issue of the hysteresis.

  14. Syntheses of aporphine and homoaporphine alkaloids by intramolecular ortho-arylation of phenols with aryl halides via SRN1 reactions in liquid ammonia.

    Science.gov (United States)

    Barolo, Silvia M; Teng, Xin; Cuny, Gregory D; Rossi, Roberto A

    2006-10-27

    The photostimulated intramolecular ortho-arylation reactions of bromoarenes linked with pendant phenoxy containing N-substituted tetrahydroisoquinolines in liquid ammonia afforded aporphine (54-82% yield) alkaloid derivatives via SRN1 reactions. This strategy was extended for the first time to the synthesis of a homoaporphine derivative (40% yield). Tetrahydroisoquinoline precursors that contained electron-withdrawing groups on nitrogen (i.e., amides, sulfonamides, and carbamates) gave cyclized products, whereas precursors with basic nitrogens (i.e., NH or NMe) either failed to yield cyclized products or gave aporphines in only low yield.

  15. Bulk and interfacial molecular structure near liquid-liquid critical points

    Energy Technology Data Exchange (ETDEWEB)

    Manzanares-Papayanopoulos, Emilio

    2000-09-01

    Critical behaviour occurs when two coexisting phases merge identity without abrupt change in physical properties. The detail of this behaviour is nowadays considered universal, being dominated by the divergence of the correlation length {xi}. Following this universality, the detailed behaviour can be studied experimentally using any convenient system. For that reason, the study of fluids, and in particular fluid mixtures, offers a useful platform since critical behaviour in such systems can often be studied at convenient temperatures and pressures. Although criticality is a consequence of the divergence of {xi}, and so in a sense is a large-scale phenomenon, nevertheless it has an influence on events at molecular level. This aspect of criticality has received relatively little study compared to the enormous effort expended over the past thirty years in elucidating the macroscopic or phenomenological aspects of criticality. The signature of criticality at molecular level is the central theme running through this research.The aim of the work described in this thesis was to investigate the surface and transport properties of near-critical binary liquid mixtures. The surface properties mainly concerned the adsorption and wetting behaviour at the vapour-liquid and liquid-solid interfaces. The transport property studied was the shear viscosity at bulk or macroscopic level and the corresponding property at molecular or microscopic level, the micro viscosity. The work presented in this thesis comprises the experimental measurements and the theoretical interpretations drawn from the results. The experimental work was varied, using both classical and modern techniques. The theoretical interpretation was used as directed towards validating and comparing the results of the experimental programme with the predictions of the current classical critical-state theories. The systems investigated have been mostly alkane + perfluoroalkane mixtures or mixtures with very similar

  16. Molecular dynamics study of solid-liquid heat transfer and passive liquid flow

    Science.gov (United States)

    Yesudasan Daisy, Sumith

    High heat flux removal is a challenging problem in boilers, electronics cooling, concentrated photovoltaic and other power conversion devices. Heat transfer by phase change is one of the most efficient mechanisms for removing heat from a solid surface. Futuristic electronic devices are expected to generate more than 1000 W/cm2 of heat. Despite the advancements in microscale and nanoscale manufacturing, the maximum passive heat flux removal has been 300 W/cm2 in pool boiling. Such limitations can be overcome by developing nanoscale thin-film evaporation based devices, which however require a better understanding of surface interactions and liquid vapor phase change process. Evaporation based passive flow is an inspiration from the transpiration process that happens in trees. If we can mimic this process and develop heat removal devices, then we can develop efficient cooling devices. The existing passive flow based cooling devices still needs improvement to meet the future demands. To improve the efficiency and capacity of these devices, we need to explore and quantify the passive flow happening at nanoscales. Experimental techniques have not advanced enough to study these fundamental phenomena at the nanoscale, an alternative method is to perform theoretical study at nanoscales. Molecular dynamics (MD) simulation is a widely accepted powerful tool for studying a range of fundamental and engineering problems. MD simulations can be utilized to study the passive flow mechanism and heat transfer due to it. To study passive flow using MD, apart from the conventional methods available in MD, we need to have methods to simulate the heat transfer between solid and liquid, local pressure, surface tension, density, temperature calculation methods, realistic boundary conditions, etc. Heat transfer between solid and fluids has been a challenging area in MD simulations, and has only been minimally explored (especially for a practical fluid like water). Conventionally, an

  17. a Study of Molecular Order and Motion in Nematic Liquid Crystal Mixtures.

    Science.gov (United States)

    Goetz, Jon Michael

    Materials which flow like fluids, but possess anisotropic properties like molecular crystals, are called 'liquid crystals'. Studies of liquid crystals contribute to our understanding of how molecular orientation influences macroscopic properties. This thesis presents experimental and theoretical investigations of molecular order and dynamics in nematic liquid crystal systems. First, deuterium nuclear magnetic resonance is used to determine the degree of orientational order of both components of a liquid crystal mixture simultaneously. The temperature dependence of the four order parameters is interpreted using a newly developed mean field theory of nematic binary mixtures composed of biaxial molecules. Next, mean field theory is applied to predict the phase behavior of arbitrarily shaped nematogens. For single component liquid crystals, the four order parameters needed to quantify orientational order of biaxial molecules in a biaxial nematic phase are calculated as a function of temperature for both rod-like and plate-like liquid crystals. For binary mixtures, temperature-concentration phase diagrams for a variety of molecular shapes are calculated. These theoretical predictions suggest that binary mixtures of highly asymmetric molecules with opposite shape anisotrophies may display stable biaxial nematic phases. Last, deuterium nuclear magnetic spin relaxation rates are measured as a function of temperature to investigate the molecular motion of a liquid crystal and a liquid crystal binary mixture. These experimental results are interpreted using an anisotropic viscosity model of molecular reorientation. The temperature dependence of the correlation times for the molecular motions is examined and discussed. It is demonstrated that mixing probe molecules into a liquid crystal has a profound effect on the molecular motion of the liquid crystal.

  18. Molecular alignment enhancement phenomenon of polymer formed from a liquid crystal monomer in a liquid crystal solvent

    Science.gov (United States)

    Fujikake, Hideo; Murashige, Takeshi; Sato, Hiroto; Kawakita, Masahiro; Kikuchi, Hiroshi

    2003-03-01

    We report an abnormal alignment enhancement phenomenon of polymer molecules. The alignment order of a rigid-skeleton polymer made from a liquid crystalline monomer in a low-molecular-weight liquid crystal solvent was drastically enhanced with increasing temperature, even though the alignment order of the solution of the liquid crystal and monomer decreased. From polymer molecular alignment observations using polarizing Raman scattering microscopy, it was found that the polymer alignment order was three times greater than that of the original aligned monomer and polymer. This super alignment technique of polymer using a molecular-scaled self-assembly mechanism is applicable to the formation of electrically and/or optically functional nanopolymer wires.

  19. Molecular conformation and liquid structure of 2-propanol through neutron diffraction

    Indian Academy of Sciences (India)

    A Sahoo; S Sarkar; P S R Krishna; R N Joarder

    2010-05-01

    The neutron diffraction data analysis of deuterated liquid 2-propanol at room temperature to define its molecular conformation is presented. 2-Propanol being a large molecule with twelve atomic sites, the conformation analysis is tricky and an improved method of data analysis is given. The intermolecular structural correlations, i.e., hydrogen-bonded liquid structure, can be modelled accurately to extract the nature of the average hydrogen-bonded molecular association in liquid state at room temperature. Like other alcohols these are mostly hexamer ring chain (HRC) clusters. The cluster analysis of recent X-ray data available in the literature also support the same liquid structure.

  20. Properties of hot liquid cerium by LDA + U molecular dynamics.

    Science.gov (United States)

    Siberchicot, Bruno; Clérouin, Jean

    2012-11-14

    We present ab initio simulations of liquid cerium in the framework of the LDA + U formulation. The liquid density has been determined self-consistently by searching for the zero pressure equilibrium state at 1320 K with the same set of parameters (U and J) and occupation matrices as those optimized for the γ phase. We have computed static and transport properties. The liquid produced by the simulations appears more structured than the available measurements. This raises questions regarding the ability of the theory to describe such a complex liquid. Conductivity calculations and temperature dependences are nevertheless in reasonable agreement with data.

  1. Structural properties of liquid N-methylacetamide via ab initio, path integral, and classical molecular dynamics

    Science.gov (United States)

    Whitfield, T. W.; Crain, J.; Martyna, G. J.

    2006-03-01

    In order to better understand the physical interactions that stabilize protein secondary structure, the neat liquid state of a peptidic fragment, N-methylacetamide (NMA), was studied using computer simulation. Three different descriptions of the molecular liquid were examined: an empirical force field treatment with classical nuclei, an empirical force field treatment with quantum mechanical nuclei, and an ab initio density functional theory (DFT) treatment. The DFT electronic structure was evaluated using the BLYP approximate functional and a plane wave basis set. The different physical effects probed by the three models, such as quantum dispersion, many-body polarization, and nontrivial charge distributions on the liquid properties, were compared. Much of the structural ordering in the liquid is characterized by hydrogen bonded chains of NMA molecules. Modest structural differences are present among the three models of liquid NMA. The average molecular dipole in the liquid under the ab initio treatment, however, is enhanced by 60% over the gas phase value.

  2. Structure and properties of forsterite-MgSiO3 liquid interface: molecular dynamics study

    National Research Council Canada - National Science Library

    Noritake, Fumiya; Kawamura, Katsuyuki

    2014-01-01

    .... We performed molecular dynamics simulations in terms of structures and diffusivities in forsterite-MgSiO3 liquid interfaces to obtain the nanoscale dynamic properties and structure of the interface...

  3. Phase behaviour and dynamics in primitive models of molecular ionic liquids

    Directory of Open Access Journals (Sweden)

    G.C. Ganzenmüller

    2011-09-01

    Full Text Available The phase behaviour and dynamics of molecular ionic liquids are studied using primitive models and extensive computer simulations. The models account for size disparity between cation and anion, charge location on the cation, and cation-shape anisotropy, which are all prominent features of important materials such as room-temperature ionic liquids. The vapour-liquid phase diagrams are determined using high-precision Monte Carlo simulations, setting the scene for in-depth studies of ion dynamics in the liquid state. Molecular dynamics simulations are used to explore the structure, single-particle translational and rotational autocorrelation functions, cation orientational autocorrelations, self diffusion, viscosity, and frequency-dependent conductivity. The results reveal some of the molecular-scale mechanisms for charge transport, involving molecular translation, rotation, and association.

  4. Plasmonic Photopatterning of Complex Molecular Orientations in Liquid Crystals

    Science.gov (United States)

    Guo, Yubing; Jiang, Miao; Peng, Chenhui; Sun, Kai; Yaroshchuk, Oleg; Lavrentovich, Oleg; Wei, Qi-Huo

    Aligning liquid crystal (LC) molecules in spatially non-uniform patterns are highly demanded for applications such as programmable origami and liquid crystal enabled nonlinear electrokinetics. We developed a high resolution projection photoalignment technique for patterning arbitrary LC alignment fields. The photoalignment is based on carefully engineered metasurfaces, or dubbed as plasmonic metamasks (PMMs). When illuminated by light, the PMMs generate patterns of both light intensity and polarization. By projecting the light transmitted through the PMMs onto liquid crystal cells coated with photosensitive materials, alignment patterns predesigned in polarization patterns of the PMMs can be imposed in liquid crystals. This technique makes the liquid crystal alignment a repeatable and scalable process similar to conventional photolithography, promising various applications. National Science Foundation CMMI-1436565.

  5. The spectra of molecular light scattering in high-viscosity glycerol-like liquids

    OpenAIRE

    Lishchuk, Sergey; Malomuzh, N. P.

    1996-01-01

    The mechanisms of formation of fine structures in the spectra of the polarized and depolarized components of molecular light scattering in high-viscosity liquids are studied. The temperature dependences of spectral parameters are examined. The results are treated in terms of the concept of a microheterogeneous structure of supercooled high-viscosity liquids.

  6. Improving the Molecular Ion Signal Intensity for In Situ Liquid SIMS Analysis

    Science.gov (United States)

    Zhou, Yufan; Yao, Juan; Ding, Yuanzhao; Yu, Jiachao; Hua, Xin; Evans, James E.; Yu, Xiaofei; Lao, David B.; Heldebrant, David J.; Nune, Satish K.; Cao, Bin; Bowden, Mark E.; Yu, Xiao-Ying; Wang, Xue-Lin; Zhu, Zihua

    2016-12-01

    In situ liquid secondary ion mass spectrometry (SIMS) enabled by system for analysis at the liquid vacuum interface (SALVI) has proven to be a promising new tool to provide molecular information at solid-liquid and liquid-vacuum interfaces. However, the initial data showed that useful signals in positive ion spectra are too weak to be meaningful in most cases. In addition, it is difficult to obtain strong negative molecular ion signals when m/z>200. These two drawbacks have been the biggest obstacle towards practical use of this new analytical approach. In this study, we report that strong and reliable positive and negative molecular signals are achievable after optimizing the SIMS experimental conditions. Four model systems, including a 1,8-diazabicycloundec-7-ene (DBU)-base switchable ionic liquid, a live Shewanella oneidensis biofilm, a hydrated mammalian epithelia cell, and an electrolyte popularly used in Li ion batteries were studied. A signal enhancement of about two orders of magnitude was obtained in comparison with non-optimized conditions. Therefore, molecular ion signal intensity has become very acceptable for use of in situ liquid SIMS to study solid-liquid and liquid-vacuum interfaces.

  7. Determination of Physical Properties of Energetic Ionic Liquids Using Molecular Simulations

    Science.gov (United States)

    2006-12-31

    Mexicano del Petr6leo, Mexico City, Mexico, October 22, 2004; "Development of New Molecular Dynamics Sampling Methods for Phase Equilibria Calculations...Properties and Toxicology of Ionic Liquids", Ionic Liquids Workshop "Background, State-of-the- Art and Academic/Industrial Applications", University

  8. Improving the Molecular Ion Signal Intensity for In Situ Liquid SIMS Analysis

    Science.gov (United States)

    Zhou, Yufan; Yao, Juan; Ding, Yuanzhao; Yu, Jiachao; Hua, Xin; Evans, James E.; Yu, Xiaofei; Lao, David B.; Heldebrant, David J.; Nune, Satish K.; Cao, Bin; Bowden, Mark E.; Yu, Xiao-Ying; Wang, Xue-Lin; Zhu, Zihua

    2016-09-01

    In situ liquid secondary ion mass spectrometry (SIMS) enabled by system for analysis at the liquid vacuum interface (SALVI) has proven to be a promising new tool to provide molecular information at solid-liquid and liquid-vacuum interfaces. However, the initial data showed that useful signals in positive ion spectra are too weak to be meaningful in most cases. In addition, it is difficult to obtain strong negative molecular ion signals when m/z>200. These two drawbacks have been the biggest obstacle towards practical use of this new analytical approach. In this study, we report that strong and reliable positive and negative molecular signals are achievable after optimizing the SIMS experimental conditions. Four model systems, including a 1,8-diazabicycloundec-7-ene (DBU)-base switchable ionic liquid, a live Shewanella oneidensis biofilm, a hydrated mammalian epithelia cell, and an electrolyte popularly used in Li ion batteries were studied. A signal enhancement of about two orders of magnitude was obtained in comparison with non-optimized conditions. Therefore, molecular ion signal intensity has become very acceptable for use of in situ liquid SIMS to study solid-liquid and liquid-vacuum interfaces.

  9. Molecular dynamics study on condensation/evaporation coefficients of chain molecules at liquid-vapor interface.

    Science.gov (United States)

    Nagayama, Gyoko; Takematsu, Masaki; Mizuguchi, Hirotaka; Tsuruta, Takaharu

    2015-07-07

    The structure and thermodynamic properties of the liquid-vapor interface are of fundamental interest for numerous technological implications. For simple molecules, e.g., argon and water, the molecular condensation/evaporation behavior depends strongly on their translational motion and the system temperature. Existing molecular dynamics (MD) results are consistent with the theoretical predictions based on the assumption that the liquid and vapor states in the vicinity of the liquid-vapor interface are isotropic. Additionally, similar molecular condensation/evaporation characteristics have been found for long-chain molecules, e.g., dodecane. It is unclear, however, whether the isotropic assumption is valid and whether the molecular orientation or the chain length of the molecules affects the condensation/evaporation behavior at the liquid-vapor interface. In this study, MD simulations were performed to study the molecular condensation/evaporation behavior of the straight-chain alkanes, i.e., butane, octane, and dodecane, at the liquid-vapor interface, and the effects of the molecular orientation and chain length were investigated in equilibrium systems. The results showed that the condensation/evaporation behavior of chain molecules primarily depends on the molecular translational energy and the surface temperature and is independent of the molecular chain length. Furthermore, the orientation at the liquid-vapor interface was disordered when the surface temperature was sufficiently higher than the triple point and had no significant effect on the molecular condensation/evaporation behavior. The validity of the isotropic assumption was confirmed, and we conclude that the condensation/evaporation coefficients can be predicted by the liquid-to-vapor translational length ratio, even for chain molecules.

  10. Transient birefringence of liquids induced by terahertz electric-field torque on permanent molecular dipoles

    CERN Document Server

    Sajadi, Mohsen; Kampfrath, Tobias

    2016-01-01

    Microscopic understanding of low-frequency molecular motions in liquids has been a longstanding goal in soft-matter science. So far, such low-frequency motions have mostly been accessed indirectly by off-resonant optical pulses. A more direct approach would be to interrogate the dynamic structure of liquids with terahertz (THz) radiation. Here, we provide evidence that resonant excitation with intense THz pulses is capable of driving reorientational-librational modes of aprotic polar liquids through coupling to the permanent molecular dipole moments. We observe a hallmark of this enhanced coupling: a transient optical birefringence up to an order of magnitude higher than obtained with optical excitation. Our results open up the path to applications such as efficient molecular alignment and systematic study of the coupling of rotational motion to other collective motions in liquids.

  11. The Plastic and Liquid Phases of CCl$_3$Br Studied by Molecular Dynamics Simulations

    CERN Document Server

    Caballero, Nirvana; Carignano, Marcelo; Serra, Pablo

    2013-01-01

    We present a molecular dynamics study of the liquid and plastic crystalline phases of CCl$_3$Br. We investigated the short-range orientational order using a recently developed classification method and we found that both phases behave in a very similar way. The only differences occur at very short molecular separations, which are shown to be very rare. The rotational dynamics was explored using time correlation functions of the molecular bonds. We found that the relaxation dynamics corresponds to an isotropic diffusive mode for the liquid phase, but departs from this behavior as the temperature is decreased and the system transitions into the plastic phase.

  12. Weak links between fast mobility and local structure in molecular and atomic liquids

    CERN Document Server

    Bernini, S; Leporini, D

    2016-01-01

    We investigate by Molecular-Dynamics simulations the fast mobility - the rattling amplitude of the particles temporarily trapped by the cage of the neighbors - in mildly supercooled states of dense molecular (linear trimers) and atomic (binary mixtures) liquids. The mixture particles interact by the Lennard-Jones potential. The non-bonded particles of the molecular system are coupled by the more general Mie potential with variable We investigate by Molecular-Dynamics simulations the fast mobility - the rattling amplitude of the particles temporarily trapped by the cage of the neighbors - in mildly supercooled states of dense molecular (linear trimers) and atomic (binary mixtures) liquids. The mixture particles interact by the Lennard-Jones potential. The non-bonded particles of the molecular system are coupled by the more general Mie potential with variable repulsive and attractive exponents in a range which is characteristic of small $n$-alkanes and $n$-alcohols. Possible links between the fast mobility and ...

  13. Molecular Dynamics Simulations of Liquid Phosphorus at High Temperature and Pressure

    Institute of Scientific and Technical Information of China (English)

    WU Yan-Ning; ZHAO Gang; LIU Chang-Song; ZHU Zhen-Gang

    2008-01-01

    By performing ab initio molecular dynamics simulations, we have investigated the mierostructure, dynam-ical and electronic properties of liquid phosphorus (P) under high temperature and pressure. In our simulations, the calculated coordination number (CN) changes discontinuously with density, and seems to increase rapidly after liquid P is compressed to 2.5 g/cm3. Under compression, liquid P shows the first-order liquid-liquid phase transition from the molecular liquid composed of the tetrahedral P4 molecules to complex polymeric form with three-dimensional network structure, accompanied by the nonmetal to metal transition of the electronic structure. The order parameters Q6 and Q4 are sensitive to the microstructural change of liquid P. By calculating diffusion coefficients, we show the dynamical anomaly of liquid P by compression. At lower temperatures, a maximum exists at the diffusion coefficients as a function of density; at higher temperatures, the anomalous behavior is weakened. The excess entropy shows the same phenom-ena as the diffusion coefficients. By analysis of the angle distribution functions and angular limited triplet correlation functions, we can clearly find that the Peierls distortion in polymeric form of liquid P is reduced by further compression.

  14. Phase behaviour of macromolecular liquid crystalline materials. Computational studies at the molecular level

    CERN Document Server

    Stimson, L M

    2003-01-01

    Molecular simulations provide an increasingly useful insight into the static and dynamic characteristics of materials. In this thesis molecular simulations of macro-molecular liquid crystalline materials are reported. The first liquid crystalline material that has been investigated is a side chain liquid crystal polymer (SCLCP). In this study semi-atomistic molecular dynamics simulations have been conducted at a range of temperatures and an aligning potential has been applied to mimic the effect of a magnetic field. In cooling the SCLCP from an isotropic melt, microphase separation was observed yielding a domain structure. The application of a magnetic field to this structure aligns the domains producing a stable smectic mesophase. This is the first study in which mesophases have been observed using an off-lattice model of a SCLCP. The second material that has been investigated is a dendrimer with terminal mesogenic functionalization. Here, a multi-scale approach has been taken with Monte Carlo studies of a s...

  15. Anion pairs in room temperature ionic liquids predicted by molecular dynamics simulation, verified by spectroscopic characterization

    Energy Technology Data Exchange (ETDEWEB)

    Schwenzer, Birgit; Kerisit, Sebastien N.; Vijayakumar, M.

    2014-01-01

    Molecular-level spectroscopic analyses of an aprotic and a protic room-temperature ionic liquid, BMIM OTf and BMIM HSO4, respectively, have been carried out with the aim of verifying molecular dynamics simulations that predict anion pair formation in these fluid structures. Fourier-transform infrared spectroscopy, Raman spectroscopy and nuclear magnetic resonance spectroscopy of various nuclei support the theoretically-determined average molecular arrangements.

  16. Studies on Molecular Interaction in Ternary Liquid Mixtures

    Directory of Open Access Journals (Sweden)

    R. Uvarani

    2010-01-01

    Full Text Available Ultrasonic velocity, density and viscosity for the ternary liquid mixtures of cyclohexanone with 1-propanol and 1-butanol in carbon tetrachloride were measured at 303 K. The acoustical parameters and their excess values were calculated. The trends in the variation of these excess parameters were used to discuss the nature and strength of the interactions present between the component molecules.

  17. Improving the Molecular Ion Signal Intensity for In Situ Liquid SIMS Analysis

    Energy Technology Data Exchange (ETDEWEB)

    Zhou, Yufan; Yao, Juan; Ding, Yuanzhao; Yu, Jiachao; Hua, Xin; Evans, James E.; Yu, Xiaofei; Lao, David B.; Heldebrant, David J.; Nune, Satish K.; Cao, Bin; Bowden, Mark E.; Yu, Xiao-Ying; Wang, Xue-Lin; Zhu, Zihua

    2016-09-06

    In situ liquid secondary ion mass spectrometry (SIMS) enabled by system for analysis at the liquid vacuum interface (SALVI) has proven to be a promising new tool to provide molecular information at solid–liquid and liquid–vacuum interfaces. However, the initial data showed that useful signals in positive ion spectra are too weak to be meaningful in most cases. In addition, it is difficult to obtain strong negative molecular ion signals when m/z>200. These two drawbacks have been the biggest obstacle towards practical use of this new analytical approach. In this study, we report that strong and reliable positive and negative molecular signals are achievable after optimizing the SIMS experimental conditions. Four model systems, including a 1,8-diazabicycloundec-7-ene (DBU)-base switchable ionic liquid, a live Shewanella oneidensis biofilm, a hydrated mammalian epithelia cell, and an electrolyte popularly used in Li ion batteries were studied. A signal enhancement of about two orders of magnitude was obtained in comparison with non-optimized conditions. Therefore, molecular ion signal intensity has become very acceptable to use for in situ liquid SIMS to study solid–liquid and liquid–vacuum interfaces.

  18. Mass transport thermodynamics in nonisothermal molecular liquid mixtures

    Energy Technology Data Exchange (ETDEWEB)

    Semenov, Semen N [Institute for Biochemical Physics, Russian Academy of Sciences, Moscow (Russian Federation); Schimpf, M E [Department of Chemistry and Biochemistry, Boise State University, Boise, ID (United States)

    2009-10-31

    Mass transport in a nonisothermal binary molecular mixture is systematically discussed in terms of nonequilibrium thermodynamics, which for the first time allows a consistent and unambiguous description of the process. The thermodynamic and hydrodynamic approaches are compared, revealing that nonequilibrium thermodynamics and physicochemical hydrodynamics yield essentially the same results for molecular systems. The applicability limits for the proposed version of the thermodynamic approach are determined for large particles. (methodological notes)

  19. Liquid Be, Ca and Ba. An orbital-free ab-initio molecular dynamics study

    Energy Technology Data Exchange (ETDEWEB)

    Rio, B. G. del; González, L. E. [Departamento de Física Teórica, Atómica y Óptica, Universidad de Valladolid, 47011 Valladolid (Spain)

    2015-08-17

    Several static and dynamic properties of liquid beryllium (l-Be), liquid calcium (l-Ca) and liquid barium (l-Ba) near their triple point have been evaluated by the orbital-free ab initio molecular dynamics method (OF-AIMD), where the interaction between valence electrons and ions is described by means of local pseudopotentials. These local pseudopotentials used were constructed through a force-matching process with those obtained from a Kohn-Sham ab initio molecular dynamics study (KS-AIMD) of a reduced system with non-local pseudopotentials. The calculated static structures show good agreement with the available experimental data, including an asymmetric second peak in the structure factor which has been linked to the existence of a marked icosahedral short-range order in the liquid. As for the dynamic properties, we obtain collective density excitations whose associated dispersion relations exhibit a positive dispersion.

  20. Isobaric first-principles molecular dynamics of liquid water with nonlocal van der Waals interactions

    CERN Document Server

    Miceli, Giacomo; Pasquarello, Alfredo

    2016-01-01

    We investigate the structural properties of liquid water at near ambient conditions using first-principles molecular dynamics simulations based on a semilocal density functional augmented with nonlocal van der Waals interactions. The adopted scheme offers the advantage of simulating liquid water at essentially the same computational cost of standard semilocal functionals. Applied to the water dimer and to ice Ih, we find that the hydrogen-bond energy is only slightly enhanced compared to a standard semilocal functional. We simulate liquid water through molecular dynamics in the NpH statistical ensemble allowing for fluctuations of the system density. The structure of the liquid departs from that found with a semilocal functional leading to more compact structural arrangements. This indicates that the directionality of the hydrogen-bond interaction has a diminished role as compared to the overall attractions, as expected when dispersion interactions are accounted for. This is substantiated through a detailed a...

  1. Chemical Reactivity Perspective into the Group 2B Metals Halides.

    Science.gov (United States)

    Özen, Alimet Sema; Akdeniz, Zehra

    2016-06-30

    Chemical reactivity descriptors within the conceptual density functional theory can be used to understand the nature of the interactions between two monomers of the Group 2B metal halides. This information might be valuable in the development of adequate force law parameters for simulations in the liquid state. In this study, MX2 monomers and dimers, where M = Zn, Cd, Hg and X = F, Cl, Br, I, were investigated in terms of chemical reactivity descriptors. Relativistic effects were taken into account using the effective core potential (ECP) approach. Correlations were produced between global and local reactivity descriptors and dimerization energies. Results presented in this work represent the first systematic investigation of Group 2B metal halides in the literature from a combined point of view of both relativistic effects and chemical reactivity descriptors. Steric effects were found to be responsible for the deviation from the chemical reactivity principles. They were introduced into the chemical reactivity descriptors such as local softness.

  2. Application of molecular simulations: Insight into liquid bridging and jetting phenomena

    Directory of Open Access Journals (Sweden)

    I. Nezbeda

    2015-03-01

    Full Text Available Molecular dynamics simulations have been performed on pure liquid water, aqueous solutions of sodium chloride, and polymer solutions exposed to a strong external electric field with the goal to gain molecular insight into the structural response to the field. Several simulation methodologies have been used to elucidate the molecular mechanisms of the processes leading to the formation of liquid bridges and jets (in the production of nanofibers. It is shown that in the established nanoscale structures, the molecules form a chain with their dipole moments oriented parallel to the applied field throughout the entire sample volume. The presence of ions may disturb this structure leading to its ultimate disintegration into droplets; the concentration dependence of the threshold field required to stabilize a liquid column has been determined. Conformational changes of the polymer in the jetting process have also been observed.

  3. Transient birefringence of liquids induced by terahertz electric-field torque on permanent molecular dipoles

    Science.gov (United States)

    Sajadi, Mohsen; Wolf, Martin; Kampfrath, Tobias

    2017-04-01

    Collective low-frequency molecular motions have large impact on chemical reactions and structural relaxation in liquids. So far, these modes have mostly been accessed indirectly by off-resonant optical pulses. Here, we provide evidence that intense terahertz (THz) pulses can resonantly excite reorientational-librational modes of aprotic and strongly polar liquids through coupling to the permanent molecular dipole moments. We observe a significantly enhanced response because the transient optical birefringence is up to an order of magnitude higher than obtained with optical excitation. Frequency-dependent measurements and a simple analytical model indicate that the enhancement arises from resonantly driven librations and their coupling to reorientational motion, assisted by the pump field and/or a cage translational mode. Our results open up the path to applications such as efficient molecular alignment, enhanced transient Kerr signals and systematic resonant nonlinear THz spectroscopy of the coupling between intermolecular modes in liquids.

  4. Hydrogen bonding and related properties in liquid water: a Car-Parrinello molecular dynamics simulation study

    OpenAIRE

    Guàrdia Manuel, Elvira; Skarmoutsos, Ioannis; Masia, Marco

    2015-01-01

    The local hydrogen-bonding structure and dynamics of liquid water have been investigated using the Car-Parrinello molecular dynamics simulation technique. The radial distribution functions and coordination numbers around water molecules have been found to be strongly dependent on the number of hydrogen bonds formed by each molecule, revealing also the existence of local structural heterogeneities in the structure of the liquid. The results obtained have also revealed the strong effect of the ...

  5. Main-Group Halide Semiconductors Derived from Perovskite: Distinguishing Chemical, Structural, and Electronic Aspects.

    Science.gov (United States)

    Fabini, Douglas H; Labram, John G; Lehner, Anna J; Bechtel, Jonathon S; Evans, Hayden A; Van der Ven, Anton; Wudl, Fred; Chabinyc, Michael L; Seshadri, Ram

    2017-01-03

    Main-group halide perovskites have generated much excitement of late because of their remarkable optoelectronic properties, ease of preparation, and abundant constituent elements, but these curious and promising materials differ in important respects from traditional semiconductors. The distinguishing chemical, structural, and electronic features of these materials present the key to understanding the origins of the optoelectronic performance of the well-studied hybrid organic-inorganic lead halides and provide a starting point for the design and preparation of new functional materials. Here we review and discuss these distinguishing features, among them a defect-tolerant electronic structure, proximal lattice instabilities, labile defect migration, and, in the case of hybrid perovskites, disordered molecular cations. Additionally, we discuss the preparation and characterization of some alternatives to the lead halide perovskites, including lead-free bismuth halides and hybrid materials with optically and electronically active organic constituents.

  6. Large scale molecular dynamics simulations of a liquid crystalline droplet with fast multipole implementations

    Energy Technology Data Exchange (ETDEWEB)

    Wang, Z.; Lupo, J.; Patnaik, S.S.; McKenney, A.; Pachter, R.

    1999-07-01

    The Fast Multipole Method (FMM) offers an efficient way (order O(N)) to handle long range electrostatic interactions, thus enabling more realistic molecular dynamics simulations of large molecular systems. The performance of the fast molecular dynamics (FMD) code, a parallel MD code being developed in the group, using the three-dimensional fast multipole method, shows a good speedup. The application to the full atomic-scale molecular dynamics simulation of a liquid crystalline droplet of 4-n-pentyl-4{prime}-cyanobiphenyl (5CB) molecules, of size 35,872 atoms, shows strong surface effects on various orientational order parameters.

  7. Ab-initio molecular dynamics study of lanthanides in liquid sodium

    Science.gov (United States)

    Li, Xiang; Samin, Adib; Zhang, Jinsuo; Unal, C.; Mariani, R. D.

    2017-02-01

    To mitigate the fuel cladding chemical interaction (FCCI) phenomena in liquid sodium cooled fast reactors, a fundamental understanding of the lanthanide (Ln) transport through liquid Nasbnd Cs filled pores in Usbnd Zr fuel is necessary. In this study, we investigate three abundant Ln fission products diffusion coefficients in liquid Na at multiple temperatures. By utilization of Ab-initio Molecular Dynamics, the Ln diffusivities are found to be in the magnitude order of liquid diffusion (10-5cm2 /s) and the temperature dependence of the diffusivity for different lanthanides in liquid sodium was explored. It is also observed that dilute concentration of Pr and Nd led to a significant change in Na diffusivity. The structural and electronic properties of Nasbnd Ln metallic systems have been investigated. The total coordination number shows dependence on both the temperature and the composition.

  8. Wetting of Liquid Iron in Carbon Nanotubes and on Graphene Sheets: A Molecular Dynamics Study

    Institute of Scientific and Technical Information of China (English)

    GAO Yu-Feng; YANG Yang; SUN De-Yan

    2011-01-01

    Using molecular dynamics simulations, we study the wetting of liquid iron in a carbon nanotube and on a graphene sheet. It is found that the contact angle of a droplet in a carbon nanotube increases linearly with the increase of wall curvature but is independent of the length of the filled liquid. The contact angle for a droplet on a graphene sheet decreases with the increasing droplet size. The line tension of a droplet on a graphene sheet is also obtained.Detailed studies show that liquid iron near the carbon walls exhibits the ordering tendencies in both the normal and tangential directions.

  9. Mechanical model study of relationship of molecular configuration and multiphase in liquid crystal materials

    Institute of Scientific and Technical Information of China (English)

    Ma Heng; Sun Rui-Zhi; Li Zhen-Xin

    2006-01-01

    A mechanical model of liquid crystals (LCs) is applied to study the polymorphism of homologous series of terphenyl compounds. With a semi-experimental molecular orbit method, we calculate the moment of inertia which represents the rotation state to describe the phase transition temperature obtained from experimental data. We propose a novel explanation of the phase sequence or polymorphism of LC materials using the two key parameters, the moment of inertia and critical rotational velocity. The effect of molecular polarity on the appearance of liquid crystalline is also discussed.

  10. Correlation between Fragility and the Arrhenius Crossover Phenomenon in Metallic, Molecular, and Network Liquids.

    Science.gov (United States)

    Jaiswal, Abhishek; Egami, Takeshi; Kelton, K F; Schweizer, Kenneth S; Zhang, Yang

    2016-11-11

    We report the observation of a distinct correlation between the kinetic fragility index m and the reduced Arrhenius crossover temperature θ_{A}=T_{A}/T_{g} in various glass-forming liquids, identifying three distinguishable groups. In particular, for 11 glass-forming metallic liquids, we universally observe a crossover in the mean diffusion coefficient from high-temperature Arrhenius to low-temperature super-Arrhenius behavior at approximately θ_{A}≈2 which is in the stable liquid phases. In contrast, for fragile molecular liquids, this crossover occurs at much lower θ_{A}≈1.4 and usually in their supercooled states. The θ_{A} values for strong network liquids spans a wide range higher than 2. Intriguingly, the high-temperature activation barrier E_{∞} is universally found to be ∼11k_{B}T_{g} and uncorrelated with the fragility or the reduced crossover temperature θ_{A} for metallic and molecular liquids. These observations provide a way to estimate the low-temperature glassy characteristics (T_{g} and m) from the high-temperature liquid quantities (E_{∞} and θ_{A}).

  11. Little evidence for dynamic divergences in ultraviscous molecular liquids

    DEFF Research Database (Denmark)

    Hecksher, Tina; Nielsen, Albena; Olsen, Niels Boye

    2008-01-01

    The physics of the ultraviscous liquid phase preceding glass formation continues to pose major problems that remain unsolved. It is actively debated, for instance, whether the marked increase of the relaxation time reflects an underlying phase transition to a state of infinite relaxation time. To...... shows that there is no compelling evidence for the Vogel-Fulcher-Tammann (VFT) prediction that the relaxation time diverges at a finite temperature.We conclude that theories with a dynamic divergence of the VFT formlack a direct experimental basis....

  12. Bias-dependent molecular-level structure of electrical double layer in ionic liquid on graphite.

    Science.gov (United States)

    Black, Jennifer M; Walters, Deron; Labuda, Aleksander; Feng, Guang; Hillesheim, Patrick C; Dai, Sheng; Cummings, Peter T; Kalinin, Sergei V; Proksch, Roger; Balke, Nina

    2013-01-01

    Here we report the bias-evolution of the electrical double layer structure of an ionic liquid on highly ordered pyrolytic graphite measured by atomic force microscopy. We observe reconfiguration under applied bias and the orientational transitions in the Stern layer. The synergy between molecular dynamics simulation and experiment provides a comprehensive picture of structural phenomena and long and short-range interactions, which improves our understanding of the mechanism of charge storage on a molecular level.

  13. Molecular engineering of chiral colloidal liquid crystals using DNA origami

    Science.gov (United States)

    Siavashpouri, Mahsa; Wachauf, Christian H.; Zakhary, Mark J.; Praetorius, Florian; Dietz, Hendrik; Dogic, Zvonimir

    2017-08-01

    Establishing precise control over the shape and the interactions of the microscopic building blocks is essential for design of macroscopic soft materials with novel structural, optical and mechanical properties. Here, we demonstrate robust assembly of DNA origami filaments into cholesteric liquid crystals, one-dimensional supramolecular twisted ribbons and two-dimensional colloidal membranes. The exquisite control afforded by the DNA origami technology establishes a quantitative relationship between the microscopic filament structure and the macroscopic cholesteric pitch. Furthermore, it also enables robust assembly of one-dimensional twisted ribbons, which behave as effective supramolecular polymers whose structure and elastic properties can be precisely tuned by controlling the geometry of the elemental building blocks. Our results demonstrate the potential synergy between DNA origami technology and colloidal science, in which the former allows for rapid and robust synthesis of complex particles, and the latter can be used to assemble such particles into bulk materials.

  14. Effect of Molecular Weight on Liquid Crystal Photoalignment by Photosensitive Polyester Containing Thrifluoromethyl Moieties

    Institute of Scientific and Technical Information of China (English)

    FEI Chun-Hong; PENG Zeng-Hui; LV Feng-Zhen; ZHANG Ling-Li; YAO Li-Shuang; XUAN Li

    2006-01-01

    @@ We investigate the liquid-crystal (LC) alignment direction on photoalignment films formed from photosensitive polyester containing thrifluoromethyl moieties (PPDA ) with various molecular weights by crossed polarized optical microscopy. It is found that LC alignment behaviour changes with molecular weight of PPDA. The LC alignment on PPDA irradiated films with the highest molecular weight is homogeneous, while those with low and intermediate molecular weights are homeotropic. However, surface morphologies show weak dependence on molecular weight. The surfaces are smooth and there is no clear morphological anisotropy on these aligned films observed by an atomic force microscope. The surface energies of the irradiated films are also measured by using an indirect contact-angle method where both surface energy and its polar componentincrease with increasing molecular weight. Different polar surface energies can be considered as a main reason for different alignment characteristics.

  15. Video-microscopic observation of ionic liquid/alcohol interface and the corresponding molecular simulation study

    Science.gov (United States)

    Zhu, Peixi

    This research is aimed at studying the ionic liquid/n-pentanol interface via video-microscopy and molecular dynamic simulations. Understanding the interfacial phenomena and interfacial transport between ionic liquids and other liquids is of interest to the development and application of ionic liquids in a number of areas. One such area is the biphasic hydroformylation of alkenes to obtain alcohol and aldehyde, in which case ionic liquid is the reaction medium where a catalyst resides. The dissolution of an ionic liquid into an alcohol was studied by microscopically observing and measuring the shrinking of a micropipette-produced droplet in real time. Although microscopic investigation of droplet dissolution has been studied before, no attempt had been made to measure the diffusion coefficient D of the droplet species in the surrounding medium. A key finding of this work is that the Epstein-Plesset mathematical model, which describes the dissolution of a droplet/bubble in another fluid medium, can be used to measure D. Other experimental studies of the ionic liquid/alcohol system include electrical conductivity and UV-visible spectroscopy measurements of solutions of 1-hexyl-3-methylimidazolium tetrafluoroborate in n-pentanol. Those experiments were done in order to understand the molecular state of the particular ionic liquid in n-pentanol, as well as obtaining the dissociation constant K of such weak electrolyte solution. The experimental results provide an entry to the assessment of ionic liquid interaction with n-pentanol at molecular scale. Subsequently, molecular dynamics simulation was implemented for the investigation of such interaction. The computation started with simulation of the bulk phase of 1-butyl-3-methylimidazolium tetrafluoroborate, an affine ionic liquid on which molecular simulations had already been reported. A generalized probability based on Fuoss approximation for the closest ion to a distinguished countercharge ion was developed. In

  16. Determination of the structure of liquids containing free radical molecules: Inter-molecular correlations in liquid chlorine dioxide

    Science.gov (United States)

    Shimakura, H.; Ogata, N.; Kawakita, Y.; Ohara, K.; Takeda, S.

    2013-04-01

    X-ray diffraction spectra of liquid ClO2 at 204, 223, 248 and 273 K were measured at the BL04B2 beamline in the SPring-8 synchrotron radiation facility. The obtained structure factors are well reproduced by reverse Monte Carlo (RMC) structural modelling. With increasing temperature, the first peak located at around Q = 1.8 Å -1 slightly shifts to higher Q and the tail at the lower-Q side intensifies. In the pair distribution function, g(r), the intensity of the peak at around 3.2 Å that corresponds to the nearest-neighbour distance decreases with increasing temperature. The analysis of the RMC configurations shows that strong directional O-O interaction exists in liquid ClO2 and the instantaneous inter-molecular orientation depends on this interaction.

  17. Determination of low molecular weight thiols using monobromobimane fluorescent labeling and high-performance liquid chromatography

    Science.gov (United States)

    Fahey, Robert C.; Newton, Gerald L.

    1988-01-01

    Methods are described for the preparation and high-performance liquid chromatography (HPLC) analysis of monobromobimane derivatives of low molecular weight thiols in extracts of biological samples. Typical problems encountered in the development and application of these methods are discussed. Analysis of mung bean extract is used as an example.

  18. PREDICTION OF THE MIXING ENTHALPIES OF BINARY LIQUID ALLOYS BY MOLECULAR INTERACTION VOLUME MODEL

    Institute of Scientific and Technical Information of China (English)

    H.W.Yang; D.P.Tao; Z.H.Zhou

    2008-01-01

    The mixing enthalpies of 23 binary liquid alloys are calculated by molecular interaction volume model (MIVM), which is a two-parameter model with the partial molar infinite dilute mixing enthalpies. The predicted values are in agreement with the experimental data and then indicate that the model is reliable and convenient.

  19. Dielectric Constant and Structure of Liquid 18-Crown-6 Calculated from Molecular Dynamics Simulations

    NARCIS (Netherlands)

    Leuwerink, F.T.H.; Briels, W.J.

    1997-01-01

    The results are presented for molecular dynamics simulations of liquid 18-crown-6 using different potential models. The results offer the possibility of investigating the influence of the flexibility of the dihedral angles and the effects of the united atom approach. The radial distribution function

  20. Communication: High pressure specific heat spectroscopy reveals simple relaxation behavior of glass forming molecular liquid

    DEFF Research Database (Denmark)

    Roed, Lisa Anita; Niss, Kristine; Jakobsen, Bo

    2015-01-01

    The frequency dependent specific heat has been measured under pressure for the molecular glass forming liquid 5-polyphenyl-4-ether in the viscous regime close to the glass transition. The temperature and pressure dependences of the characteristic time scale associated with the specific heat...

  1. Preparation of Mesoporous Molecular Sieves Al-MSU-S Using Ionic Liquids as Template

    Institute of Scientific and Technical Information of China (English)

    YU Xin-Yu; LIU Cai-Hua; YANG Jian-Guo; WU Hai-Hong; WU Peng; HE Ming-Yuan

    2006-01-01

    Mesoporous molecular sieves Al-MSU-S has been prepared from the precursor of zeolite Y using ionic liquids l-hexadecane-3-methylimidazolium bromide (CMIMB) as a template in basic medium, which exhibited larger pore diameter, pore volume and surface area than that synthesized using cetyl trimethyl ammonium bromide (CTAB)template.

  2. Photoinduced Reorganization of Motor-Doped Chiral Liquid Crystals : Bridging Molecular Isomerization and Texture Rotation

    NARCIS (Netherlands)

    Bosco, Alessandro; Jongejan, Mahthild G. M.; Eelkema, Rienk; Katsonis, Nathalie; Lacaze, Ernmanuelle; Ferrarini, Alberta; Feringa, Ben L.; Lacaze, Emmanuelle

    2008-01-01

    We recently reported that the photoisomerization of molecular motors used as chiral dopants in a cholesteric liquid crystal film induces a rotational reorganization which can be observed by optical microscopy and produces the motion of microscopic objects placed on top of the film (Feringa, B. L.;

  3. Generation of thermodynamic data for organic liquid mixtures from molecular simulations

    DEFF Research Database (Denmark)

    Christensen, Steen; Peters, Günther H.j.; Hansen, Flemming Yssing

    2007-01-01

    Fluctuation solution theory (FST) is employed to analyze results of molecular dynamics (MD) simulations of liquid mixtures. The objective is to generate parameters for macroscopic thermodynamic property models. Two benchmark systems, benzene-methyl acetate at 303.15 K and benzene-ethanol at 298...

  4. Molecular motions in thermotropic liquid crystals studied by NMR spin-lattice relaxation

    Energy Technology Data Exchange (ETDEWEB)

    Zamar, R.C.; Gonzalez, C.E.; Mensio, O. [Cordoba Univ. Nacional (Argentina). Facultad de Matematica, Astronomia y Fisica

    1998-12-01

    Nuclear magnetic resonance relaxation experiments with field cycling techniques proved to be a valuable tool for studying molecular motions in liquid crystals, allowing a very broad Larmor frequency variation, sufficient to separate the cooperative motions from the liquid like molecular diffusion. In new experiments combining NMR field cycling with the Jeener-Broekaert order-transfer pulse sequence, it is possible to measure the dipolar order relaxation time (T{sub 1D}), in addition to the conventional Zeeman relaxation time (T{sub 1Z}) in a frequency range of several decades. When applying this technique to nematic thermotropic liquid crystals, T{sub 1D} showed to depend almost exclusively on the order fluctuation of the director mechanism in the whole frequency range. This unique characteristic of T{sub 1D} makes dipolar order relaxation experiments specially useful for studying the frequency and temperature dependence of the spectral properties of the collective motions. (author)

  5. Low-temperature metallic liquid hydrogen: an ab-initio path-integral molecular dynamics perspective

    Science.gov (United States)

    Chen, Ji; Li, Xin-Zheng; Zhang, Qianfan; Probert, Matthew; Pickard, Chris; Needs, Richard; Michaelides, Angelos; Wang, Enge

    2013-03-01

    Experiments and computer simulations have shown that the melting temperature of solid hydrogen drops with pressure above about 65 GPa, suggesting that a low temperature liquid state might exist. It has also been suggested that this liquid state might be non-molecular and metallic, although evidence for such behaviour is lacking. Using a combination of ab initio path-integral molecular dynamics and the two-phase methods, we have simulated the melting of solid hydrogen under finite temperatures. We found an atomic solid phase from 500 to 800 GPa which melts at < 200 K. Beyond this and up to pressures of 1,200 GPa a metallic atomic liquid is stable at temperatures as low as 50 K. The quantum motion of the protons is critical to the low melting temperature in this system as ab initio simulations with classical nuclei lead to a considerably higher melting temperature of ~300 K across the entire pressure range considered.

  6. Do all the protic ionic liquids exist as molecular aggregates in the gas phase?

    Science.gov (United States)

    Zhu, Xiao; Wang, Yong; Li, Haoran

    2011-10-21

    According to an EI-MS study of 1,1,3,3-tetramethylguanidium-based protic ionic liquids (PILs), it has been concluded that not all PILs exist as molecular aggregates in the gas phase. The detection of both ions of m/z 115.0 and m/z 116.0 for the 1,1,3,3-tetramethylguanidinium trifluoromethylsulfonate (TMGS) protic ionic liquid indicates that both the molecular and ionic aggregates co-exist in the gas phase, which is to say that the TMGS may also evaporate via the ionic aggregates just like aprotic ionic liquids. Furthermore, investigation on triethylamine-based and 1-methylimidazole-based PILs confirmed that the gas phase structure of PILs depends on both the acidity and basicity of the corresponding acid and base.

  7. Molecular catalytic hydrogenation of aromatic hydrocarbons and hydrotreating of coal liquids.

    Energy Technology Data Exchange (ETDEWEB)

    Yang, Shiyong; Stock, L.M.

    1996-05-01

    This report presents the results of research on the development of new catalytic pathways for the hydrogenation of multiring aromatic hydrocarbons and the hydrotreating of coal liquids at The University of Chicago under DOE Contract No. DE-AC22-91PC91056. The work, which is described in three parts, is primarily concerned with the research on the development of new catalytic systems for the hydrogenation of aromatic hydrocarbons and for the improvement of the quality of coal liquids by the addition of dihydrogen. Part A discusses the activation of dihydrogen by very basic molecular reagents to form adducts that can facilitate the reduction of multiring aromatic hydrocarbons. Part B examines the hydrotreating of coal liquids catalyzed by the same base-activated dihydrogen complexes. Part C concerns studies of molecular organometallic catalysts for the hydrogenation of monocyclic aromatic hydrocarbons under mild conditions.

  8. The liquid surface of chiral ionic liquids as seen from molecular dynamics simulations combined with intrinsic analysis

    Energy Technology Data Exchange (ETDEWEB)

    Lísal, Martin, E-mail: lisal@icpf.cas.cz [E. Hála Laboratory of Thermodynamics, Institute of Chemical Process Fundamentals of the ASCR, v. v. i., 165 02 Prague 6-Suchdol, Czech Republic and Department of Physics, Faculty of Science, J. E. Purkinje University, 400 96 Ústí n. Lab. (Czech Republic)

    2013-12-07

    We present molecular-level insight into the liquid/gas interface of two chiral room-temperature ionic liquids (RTILs) derived from 1-n-butyl-3-methylimidazolium bromide ([bmim][Br]); namely, (R)-1-butyl-3-(3-hydroxy-2-methylpropyl)imidazolium bromide (hydroxypropyl) and 1-butyl-3-[(1R)-nopyl]imidazolium bromide (nopyl). We use our currently developed force field which was validated against the experimental bulk density, heat of vaporization, and surface tension of [bmim][Br]. The force field for the RTILs adopts the Chemistry at Harvard Molecular Mechanics (CHARMM) parameters for the intramolecular and repulsion-dispersion interactions along with the reduced partial atomic charges based on ab initio calculations. The net charges of the ions are around ±0.8e, which mimic the anion to cation charge transfer and many-body effects. Molecular dynamics simulations in the slab geometry combined with the intrinsic interface analysis are employed to provide a detailed description of the RTIL/gas interface in terms of the structural and dynamic properties of the interfacial, sub-interfacial, and central layers at a temperature of 300 K. The focus is on the comparison of the liquid/gas interface for the chiral RTILs with the interface for parent [bmim][Br]. The structure of the interface is elucidated by evaluating the surface roughness, intrinsic atomic density profiles, and orientation ordering of the cations. The dynamics of the ions at the interfacial region is characterized by computing the survival probability, and normal and lateral self-diffusion coefficients in the layers.

  9. The liquid surface of chiral ionic liquids as seen from molecular dynamics simulations combined with intrinsic analysis

    Science.gov (United States)

    Lísal, Martin

    2013-12-01

    We present molecular-level insight into the liquid/gas interface of two chiral room-temperature ionic liquids (RTILs) derived from 1-n-butyl-3-methylimidazolium bromide ([bmim][Br]); namely, (R)-1-butyl-3-(3-hydroxy-2-methylpropyl)imidazolium bromide (hydroxypropyl) and 1-butyl-3-[(1R)-nopyl]imidazolium bromide (nopyl). We use our currently developed force field which was validated against the experimental bulk density, heat of vaporization, and surface tension of [bmim][Br]. The force field for the RTILs adopts the Chemistry at Harvard Molecular Mechanics (CHARMM) parameters for the intramolecular and repulsion-dispersion interactions along with the reduced partial atomic charges based on ab initio calculations. The net charges of the ions are around ±0.8e, which mimic the anion to cation charge transfer and many-body effects. Molecular dynamics simulations in the slab geometry combined with the intrinsic interface analysis are employed to provide a detailed description of the RTIL/gas interface in terms of the structural and dynamic properties of the interfacial, sub-interfacial, and central layers at a temperature of 300 K. The focus is on the comparison of the liquid/gas interface for the chiral RTILs with the interface for parent [bmim][Br]. The structure of the interface is elucidated by evaluating the surface roughness, intrinsic atomic density profiles, and orientation ordering of the cations. The dynamics of the ions at the interfacial region is characterized by computing the survival probability, and normal and lateral self-diffusion coefficients in the layers.

  10. Cohesive Energy-Lattice Constant and Bulk Modulus-Lattice Constant Relationships: Alkali Halides, Ag Halides, Tl Halides

    Science.gov (United States)

    Schlosser, Herbert

    1992-01-01

    In this note we present two expressions relating the cohesive energy, E(sub coh), and the zero pressure isothermal bulk modulus, B(sub 0), of the alkali halides. Ag halides and TI halides, with the nearest neighbor distances, d(sub nn). First, we show that the product E(sub coh)d(sub 0) within families of halide crystals with common crystal structure is to a good approximation constant, with maximum rms deviation of plus or minus 2%. Secondly, we demonstrate that within families of halide crystals with a common cation and common crystal structure the product B(sub 0)d(sup 3.5)(sub nn) is a good approximation constant, with maximum rms deviation of plus or minus 1.36%.

  11. Molecular interactions and thermal instability of coal derived liquids

    Energy Technology Data Exchange (ETDEWEB)

    Galya, L.G.

    1983-01-01

    The purpose of the first part of this research was to investigate interactions between the acid/neutral and base fractions of coal derived asphaltenes. These interactions are thought to cause high viscosities in coal derived liquids which are obtained from catalytic processes. The asphaltenes were obtained from Synthoil and separated into acid/neutral and base fractions. The interactions of model compounds, o-phenylphenol and quinoline, and the acid/neutral and base fractions with these model compounds were studied by proton nuclear magnetic resonance spectroscopy and solution colorimetry. The results indicate that interactions between the acid/neutral and base fractions of the asphaltenes are partially responsible for high viscosities in these synthetic fuels. The purpose of the second part of this research was to investigate the causes and mechanism of formation of deposits from SRC II naphtha in heat exchangers. Formation of these deposits causes plugging and results in pilot plant shutdowns. A deposit obtained from a hydrogenation reactor was examined, and the deposit precursors were concentrated through distillation and ion exchange chromatography. The results indicate that phenols and alkylated nitrogenous bases are responsible for deposit formation. Phenols react through coupling reactions to give arylethers and water. Alkylated nitrogenous bases react by pyrolysis to produce free radicals which crosslink to produce carbonaceous deposits. These reactons have been followed using thermogravimetric analysis, Fourier transform infrared spectroscopy and gas chromatography in the temperature range of 250-400/sup 0/C.

  12. Study of atomic structure of liquid Hg-In alloys using ab-initio molecular dynamics

    Energy Technology Data Exchange (ETDEWEB)

    Sharma, Nalini; Ahluwalia, P. K. [Department of Physics, Himachal Pradesh University, Shimla(HP)-171005 (India); Thakur, Anil [Department of Physics, Govt. P. G. College Solan (HP)-173212 (India)

    2015-05-15

    Ab-initio molecular dynamics simulations are performed to study the structural properties of liquid Hg-In alloys. The interatomic interactions are described by ab-initio pseudopotentials given by Troullier and Martins. Five liquid Hg-In mixtures (Hg{sub 10}In{sub 90}, Hg{sub 30}In{sub 70}, Hg{sub 50}In{sub 50}, Hg{sub 70}In{sub 30} and Hg{sub 90}In{sub 10}) at 299K are considered. The radial distribution function g(r) and structure factor S(q) of considered alloys are compared with respective experimental results for liquid Hg (l-Hg) and (l-In). The radial distribution function g(r) shows the presence of short range order in the systems considered. Smooth curves of Bhatia-Thornton partial structure factors factor shows the presence of liquid state in the considered alloys.

  13. Atomistic molecular point of view for liquid lead and lithium in Nuclear Fusion technology

    Energy Technology Data Exchange (ETDEWEB)

    Fraile, A. [Instituto de Fusión Nuclear, ETSI Industriales, Universidad Politécnica de Madrid, José Gutierrez Abascal, 2, 28006 Madrid (Spain); Cuesta-López, S., E-mail: scuesta@ubu.es [Universidad de Burgos, Parque Científico I-D-I, Plaza Misael Bañuelos s/n, 09001 Burgos (Spain); Iglesias, R. [Universidad de Oviedo, Departamento de Física, Calvo Sotelo s/n, 33007 Oviedo (Spain); Caro, A. [Los Alamos National Laboratory, Los Alamos, NM 87545 (United States); Perlado, J.M. [Instituto de Fusión Nuclear, ETSI Industriales, Universidad Politécnica de Madrid, José Gutierrez Abascal, 2, 28006 Madrid (Spain)

    2013-09-15

    Understanding the behavior and properties of liquid metals is a crucial milestone in different current Nuclear Technology developments. Extracting both structural and dynamical properties of liquid metals via Molecular Dynamics simulations, represents a strong pillar for multiscale modeling efforts aiming to understand the suitability of these compounds. Here we present first results on the validation of two semi-empirical potentials for Li and Pb in liquid phase. Our results establish a solid base as a previous, but crucial step, to implement a LiPb cross potential. Structural and thermodynamical analyses confirm that the analyzed potentials for Li and Pb are sufficiently accurate to simulate both elements in the liquid phase, and in conditions of interest for Nuclear Technology.

  14. Ordering layers of [bmim][PF6] ionic liquid on graphite surfaces: molecular dynamics simulation.

    Science.gov (United States)

    Maolin, Sha; Fuchun, Zhang; Guozhong, Wu; Haiping, Fang; Chunlei, Wang; Shimou, Chen; Yi, Zhang; Jun, Hu

    2008-04-01

    Microscopic structures of room temperature ionic liquid (IL) [bmim][PF6] on hydrophobic graphite surfaces have been studied in detail by molecular dynamics simulation. It is clearly shown that both the mass and electron densities of the surface adsorbed ionic liquid are oscillatory, and the first peak adjacent to the graphite surface is considerably higher than others, corresponding to a solidlike IL bottom layer of 6 angstroms thick. Three IL layers are indicated between the graphite surface and the inner bulk IL liquid. The individually simulated properties of single-, double-, and triple-IL layers on the graphite surface are very similar to those of the layers between the graphite surface and the bulk liquid, indicating an insignificant effect of vapor-IL interface on the ordered IL layers. The simulation also indicates that the imidazolium ring and butyl tail of the cation (bmim+) of the IL bottom layer lie flat on the graphite surface.

  15. Local order evolution of liquid Cu during glass transition under different pressures: A molecular dynamics study

    Energy Technology Data Exchange (ETDEWEB)

    Li, Y.D., E-mail: ydli@ustc.edu [School of Physics and Material Science, Anhui University, Hefei 230039 (China); Lu, Q.L. [School of Physics and Material Science, Anhui University, Hefei 230039 (China); Wang, C.C., E-mail: ccwang@ahu.edu.cn [School of Physics and Material Science, Anhui University, Hefei 230039 (China); Huang, S.G. [School of Physics and Material Science, Anhui University, Hefei 230039 (China); Liu, C.S. [Key Laboratory of Materials Physics, Institute of Solid State Physics, Chinese Academy of Sciences, P. O. Box 1129, Hefei 230031 (China)

    2013-01-01

    Based on the second-moment approximation of tight-binding scheme, constant-pressure molecular dynamics simulations are performed for liquid Cu during the glass transition under different pressures. By means of pair analysis technique and bond orientational order analysis we find that the dominant bond pairs are those related to fcc and hcp crystalline order not those representing icosahedral short-range order (ISRO) when the systems enter into glass transition region. Although these two kinds of bond pairs compete with each other, the system tends towards a mixture of crystalline bond pairs during glass formation. The effect on various bond pairs brought about by higher pressure is much less for liquids than for glasses. The experimental observation of a shoulder on the second peak of the structure factor for supercooled liquids might not merely attribute to ISRO, since supercooled liquid Cu exhibits such a shoulder, but does not display an enhanced icosahedral symmetry.

  16. Synchronized molecular-dynamics simulation for the thermal lubrication of a polymeric liquid between parallel plates

    CERN Document Server

    Yasuda, Shugo

    2015-01-01

    The Synchronized Molecular-Dynamics simulation which was recently proposed by authors [Phys. Rev. X {\\bf 4}, 041011 (2014)] is applied to the analysis of polymer lubrication between parallel plates. The rheological properties, conformational change of polymer chains, and temperature rise due to the viscous heating are investigated with changing the values of thermal conductivity of the polymeric liquid. It is found that at a small applied shear stress on the plate, the temperature of polymeric liquid only slightly increases in inverse proportion to the thermal conductivity and the apparent viscosity of polymeric liquid is not much affected by changing the thermal conductivity. However, at a large shear stress, the transitional behaviors of the polymeric liquid occur due to the interplay of the shear deformation and viscous heating by changing the thermal conductivity. This transition is characterized by the Nahme-Griffith number $Na$ which is defined as the ratio of the viscous heating to the thermal conducti...

  17. Computational screening of mixed metal halide ammines

    DEFF Research Database (Denmark)

    Jensen, Peter Bjerre; Lysgaard, Steen; Quaade, Ulrich

    Metal halide ammines, e.g. Mg(NH3)6Cl2 and Sr(NH3)8Cl2, can reversibly store ammonia, with high volumetric hydrogen storage capacities. The storage in the halide ammines is very safe, and the salts are therefore highly relevant as a carbon-free energy carrier in future transportation infrastructure...

  18. Molecular shear heating and vortex dynamics in thermostatted two-dimensional Yukawa liquids

    CERN Document Server

    Gupta, Akanksha; Joy, Ashwin

    2016-01-01

    It is well known that two-dimensional macroscale shear flows are susceptible to instabilities leading to macroscale vortical structures. The linear and nonlinear fate of such a macroscale flow in a strongly coupled medium is a fundamental problem. A popular example of a strongly coupled medium is a dusty plasma, often modelled as a Yukawa liquid. Recently, laboratory experiments and MD studies of shear flows in strongly coupled Yukawa liquids, indicated occurrence of strong molecular shear heating, which is found to reduce the coupling strength exponentially leading to destruction of macroscale vorticity. To understand the vortex dynamics of strongly coupled molecular fluids undergoing macroscale shear flows and molecular shear heating, MD simulation has been performed, which allows the macroscopic vortex dynamics to evolve while at the same time, "removes" the microscopically generated heat without using the velocity degrees of freedom. We demonstrate that by using a configurational thermostat in a novel way...

  19. Heat Transfer Characteristics in an Asymmetrical Solid-Liquid System by Molecular Dynamics Simulations

    Science.gov (United States)

    Feng, Yuan; Liang, Xingang

    2015-07-01

    Solid-liquid systems widely exist in micro- and nanodevices, and it is necessary to study the heat transfer mechanism through solid-liquid interfaces. An asymmetrical sandwich structure of a solid-liquid system consisting of liquid argon and artificial solid walls that have the same FCC structure with argon but a different atomic masses is composed. Heat transfer characteristics are investigated by the molecular dynamics method. The interaction strength between a liquid and solid plays an essential role in heat transport at solid-liquid interfaces, and the thermal resistance length is inversely proportional to it. The mass arrangement of artificial solid walls also has a significant effect on heat transport as well. A maximum heat flux comes up due to the mismatch in phonon spectra with the increasing atomic mass of one solid wall. The asymmetrical liquid density profiles are obtained with various mass differences between solid walls. Especially, a thermal rectification effect is observed and the magnitude is inextricably bound up with asymmetry.

  20. Structure and diffusion of nanoparticle monolayers floating at liquid/vapor interfaces: a molecular dynamics study.

    Science.gov (United States)

    Cheng, Shengfeng; Grest, Gary S

    2012-06-07

    Large-scale molecular dynamics simulations are used to simulate a layer of nanoparticles floating on the surface of a liquid. Both a low viscosity liquid, represented by Lennard-Jones monomers, and a high viscosity liquid, represented by linear homopolymers, are studied. The organization and diffusion of the nanoparticles are analyzed as the nanoparticle density and the contact angle between the nanoparticles and liquid are varied. When the interaction between the nanoparticles and liquid is reduced the contact angle increases and the nanoparticles ride higher on the liquid surface, which enables them to diffuse faster. In this case the short-range order is also reduced as seen in the pair correlation function. For the polymeric liquids, the out-of-layer fluctuation is suppressed and the short-range order is slightly enhanced. However, the diffusion becomes much slower and the mean square displacement even shows sub-linear time dependence at large times. The relation between diffusion coefficient and viscosity is found to deviate from that in bulk diffusion. Results are compared to simulations of the identical nanoparticles in 2-dimensions.

  1. Topological defects in liquid crystals as templates for molecular self-assembly

    Science.gov (United States)

    Wang, Xiaoguang; Miller, Daniel S.; Bukusoglu, Emre; de Pablo, Juan J.; Abbott, Nicholas L.

    2016-01-01

    Topological defects in liquid crystals (LCs) have been widely used to organize colloidal dispersions and template polymerization, leading to a range of assemblies, elastomers and gels. However, little is understood about molecular-level assembly processes within defects. Here, we report that nanoscopic environments defined by LC topological defects can selectively trigger processes of molecular self-assembly. By using fluorescence microscopy, cryogenic transmission electron microscopy and super-resolution optical microscopy, we observed signatures of molecular self-assembly of amphiphilic molecules in topological defects, including cooperativity, reversibility and controlled growth. We also show that nanoscopic o-rings synthesized from Saturn-ring disclinations and other molecular assemblies templated by defects can be preserved by using photocrosslinkable amphiphiles. Our results reveal that, in analogy to other classes of macromolecular templates such as polymer-surfactant complexes, topological defects in LCs are a versatile class of three-dimensional, dynamic and reconfigurable templates that can direct processes of molecular self-assembly.

  2. Effects of molecular structure on microscopic heat transport in chain polymer liquids

    Energy Technology Data Exchange (ETDEWEB)

    Matsubara, Hiroki, E-mail: matsubara@microheat.ifs.tohoku.ac.jp; Kikugawa, Gota; Ohara, Taku [Institute of Fluid Science, Tohoku University, 2-1-1 Katahira, Aoba-ku, Sendai 980-8577 (Japan); Bessho, Takeshi; Yamashita, Seiji [Higashifuji Technical Center, Toyota Motor Corporation, 1200 Mishuku, Susono, Shizuoka 410-1193 (Japan)

    2015-04-28

    In this paper, we discuss the molecular mechanism of the heat conduction in a liquid, based on nonequilibrium molecular dynamics simulations of a systematic series of linear- and branched alkane liquids, as a continuation of our previous study on linear alkane [T. Ohara et al., J. Chem. Phys. 135, 034507 (2011)]. The thermal conductivities for these alkanes in a saturated liquid state at the same reduced temperature (0.7T{sub c}) obtained from the simulations are compared in relation to the structural difference of the liquids. In order to connect the thermal energy transport characteristics with molecular structures, we introduce the new concept of the interatomic path of heat transfer (atomistic heat path, AHP), which is defined for each type of inter- and intramolecular interaction. It is found that the efficiency of intermolecular AHP is sensitive to the structure of the first neighbor shell, whereas that of intramolecular AHP is similar for different alkane species. The dependence of thermal conductivity on different lengths of the main and side chain can be understood from the natures of these inter- and intramolecular AHPs.

  3. Transport properties of liquid para-hydrogen: The path integral centroid molecular dynamics approach

    Science.gov (United States)

    Yonetani, Yoshiteru; Kinugawa, Kenichi

    2003-11-01

    Several fundamental transport properties of a quantum liquid para-hydrogen (p-H2) at 17 K have been numerically evaluated by means of the quantum dynamics simulation called the path integral centroid molecular dynamics (CMD). For comparison, classical molecular dynamics (MD) simulations have also been performed under the same condition. In accordance with the previous path integral simulations, the calculated static properties of the liquid agree well with the experimental results. For the diffusion coefficient, thermal conductivity, and shear viscosity, the CMD predicts the values closer to the experimental ones though the classical MD results are far from the reality. The agreement of the CMD result with the experimental one is especially good for the shear viscosity with the difference less than 5%. The calculated diffusion coefficient and the thermal conductivity agree with the experimental values at least in the same order. We predict that the ratio of bulk viscosity to shear viscosity for liquid p-H2 is much larger than classical van der Waals simple liquids such as rare gas liquids.

  4. F center-molecular ion couples in alkali halides: Magneto-optics study (part two). Spin lattice relaxation time and electron spin memory; Studi di magnetoottica sulla coppia centro F-ione molecolare negli alogenuri alcalini: Parte 2. Misura del tempo di rilassamento spin-reticolo e della memoria di spin dell`elettrone nel ciclo ottico

    Energy Technology Data Exchange (ETDEWEB)

    Baldacchini, G.; Botti, S.; Grassano, U.M.; Luty, F.

    1991-10-01

    The spin-lattice relaxation time in the ground state, T/sub 1/, and the spin-mixing parameter during the optical cycle, epsilon, were measured in FH(OH) and FH(CN) centers in various alkali halides (KCl, KBr, KI, CsCl, and CsBr). For a close comparison, all experiments were performed before and after the optical association of the F center and molecular ion. T/sub 1/ becomes shorter before and still more after aggregation with respect to the values measured in the pure crystal, especially at very low magnetic fields. Epsilon decreases a little in crystals doped with OH-, while it increases a lot in crystals doped with CN-. Part of these results can be interpreted within the actual knowledge of the F-center physics. Part have been used to shed some light on the various unknown aspects of the energy transfer between the excited F-center and the molecular ion.

  5. Is liquid-based cytology the magic bullet for performing molecular techniques?

    Science.gov (United States)

    Abedi-Ardekani, Behnoush; Vielh, Philippe

    2014-01-01

    The role of pathology has evolved from the first microscopic definitions of diseases by Virchow to the new concept of molecular cytopathology. The management of diseases is now a multidisciplinary approach with the translation of morphological, imagery and molecular findings to therapeutic protocols. Obtaining the most reliable diagnostic material is the essential part of the medical management of patients. Here, we try to gain a concise insight into the available data regarding the role of cytology in the application of molecular techniques, focusing on cancer cytopathology. Obtaining cytological material is now feasible by different methods, and in some cases it is the only possible approach to a lesion which is not easily accessible for tissue sampling. The methods of obtaining cytological material have evolved in recent years in parallel with rapid advances in high-throughput molecular techniques, opening new windows for the diagnosis and management of diseases. Different kinds of cytological material are reliable for the application of molecular techniques. Cytological material obtained in a liquid base has advantages such as the better preservation of cytomorphological features and the use of the remaining liquid for nucleic acid extraction even after long storage and the application of molecular methods.

  6. Connection between slow and fast dynamics of molecular liquids around the glass transition

    DEFF Research Database (Denmark)

    Niss, Kristine; Dalle-Ferrier, Cecile; Frick, Bernhard

    2010-01-01

    The mean-square displacement (MSD) was measured by neutron scattering at various temperatures and pressures for a number of molecular glass-forming liquids. The MSD is invariant along the glass-transition line at the pressure studied, thus establishing an “intrinsic” Lindemann criterion for any...... given liquid. A one-to-one connection between the MSD’s temperature dependence and the liquid’s fragility is found when the MSD is evaluated on a time scale of ∼4 ns, but does not hold when the MSD is evaluated at shorter times. The findings are discussed in terms of the elastic model and the role...

  7. Transport properties of room temperature ionic liquids from classical molecular dynamics

    CERN Document Server

    Andreussi, Oliviero

    2012-01-01

    Room Temperature Ionic Liquids (RTILs) have attracted much of the attention of the scientific community in the past decade due the their novel and highly customizable properties. Nonetheless their high viscosities pose serious limitations to the use of RTILs in practical applications. To elucidate some of the physical aspects behind transport properties of RTILs, extensive classical molecular dynamics (MD) calculations are reported. Bulk viscosities and ionic conductivities of butyl-methyl-imidazole based RTILs are presented over a wide range of temperatures. The dependence of the properties of the liquids on simulation parameters, e.g. system size effects and choice of the interaction potential, is analyzed.

  8. A molecular dynamics study of ferroelectric nanoparticles immersed in a nematic liquid crystal.

    Science.gov (United States)

    Pereira, M S S; Canabarro, A A; de Oliveira, I N; Lyra, M L; Mirantsev, L V

    2010-01-01

    A large number of interesting phenomena related to the insertion of colloidal particles in liquid crystals (LC) have recently been reported. Here, we investigate effects caused by the addition of spherically shaped ferroelectric nanoparticles to a nematic liquid crystal. Using molecular dynamics (MD) simulations, the density of LC molecules, the orientational order parameter, and the polar and azimuthal angle profiles are calculated as functions of the distance to the center of the immersed nanoparticle for different temperatures of the system. We observe that the assembly of ferroelectric nanoparticles enhances the nematic order in the LC medium changing many properties of its host above the nematic-isotropic transition temperature T (*) (NI) .

  9. Statistical mechanics of glass formation in molecular liquids with OTP as an example.

    Science.gov (United States)

    Boué, Laurent; Hentschel, H G E; Ilyin, Valery; Procaccia, Itamar

    2011-12-08

    We extend our statistical mechanical theory of the glass transition from examples consisting of point particles to molecular liquids with internal degrees of freedom. As before, the fundamental assertion is that supercooled liquids are ergodic, although becoming very viscous at lower temperatures, and are therefore describable in principle by statistical mechanics. The theory is based on analyzing the local neighborhoods of each molecule, and a statistical mechanical weight is assigned to every possible local organization. This results in an approximate theory that is in very good agreement with simulations regarding both thermodynamical and dynamical properties.

  10. Evolution of atomic structure in Al75Cu25 liquid from experimental and ab initio molecular dynamics simulation studies.

    Science.gov (United States)

    Xiong, L H; Yoo, H; Lou, H B; Wang, X D; Cao, Q P; Zhang, D X; Jiang, J Z; Xie, H L; Xiao, T Q; Jeon, S; Lee, G W

    2015-01-28

    X-ray diffraction and electrostatic levitation measurements, together with the ab initio molecular dynamics simulation of liquid Al(75)Cu(25) alloy have been performed from 800 to 1600 K. Experimental and ab initio molecular dynamics simulation results match well with each other. No abnormal changes were experimentally detected in the specific heat capacity over total hemispheric emissivity and density curves in the studied temperature range for a bulk liquid Al(75)Cu(25) alloy measured by the electrostatic levitation technique. The structure factors gained by the ab initio molecular dynamics simulation precisely coincide with the experimental data. The atomic structure analyzed by the Honeycutt-Andersen index and Voronoi tessellation methods shows that icosahedral-like atomic clusters prevail in the liquid Al(75)Cu(25) alloy and the atomic clusters evolve continuously. All results obtained here suggest that no liquid-liquid transition appears in the bulk liquid Al(75)Cu(25) alloy in the studied temperature range.

  11. Bilayer molecular assembly at a solid/liquid interface as triggered by a mild electric field.

    Science.gov (United States)

    Zheng, Qing-Na; Liu, Xuan-He; Liu, Xing-Rui; Chen, Ting; Yan, Hui-Juan; Zhong, Yu-Wu; Wang, Dong; Wan, Li-Jun

    2014-12-01

    The construction of a spatially defined assembly of molecular building blocks, especially in the vertical direction, presents a great challenge for surface molecular engineering. Herein, we demonstrate that an electric field applied between an STM tip and a substrate triggered the formation of a bilayer structure at the solid-liquid interface. In contrast to the typical high electric-field strength (10(9)  V m(-1) ) used to induce structural transitions in supramolecular assemblies, a mild electric field (10(5)  V m(-1) ) triggered the formation of a bilayer structure of a polar molecule on top of a nanoporous network of trimesic acid on graphite. The bilayer structure was transformed into a monolayer kagome structure by changing the polarity of the electric field. This tailored formation and large-scale phase transformation of a molecular assembly in the perpendicular dimension by a mild electric field opens perspectives for the manipulation of surface molecular nanoarchitectures.

  12. Direct induction of molecular alignment in liquid crystal polymer network film by photopolymerization

    Science.gov (United States)

    Hisano, K.; Aizawa, M.; Ishizu, M.; Kurata, Y.; Shishido, A.

    2016-09-01

    Liquid crystal (LC) is the promising material for the fabrication of high-performance soft, flexible devices. The fascinating and useful properties arise from their cooperative effect that inherently allows the macroscopic integration and control of molecular alignment through various external stimuli. To date, light-matter interaction is the most attractive stimuli and researchers developed photoalignment through photochemical or photophysical reactions triggered by linearly polarized light. Here we show the new choice based on molecular diffusion by photopolymerization. We found that photopolymerization of a LC monomer and a crosslinker through a photomask enables to direct molecular alignment in the resultant LC polymer network film. The key generating the molecular alignment is molecular diffusion due to the difference of chemical potentials between irradiated and unirradiated regions. This concept is applicable to various shapes of photomask and two-dimensional molecular alignments can be fabricated depending on the spatial design of photomask. By virtue of the inherent versatility of molecular diffusion in materials, the process would shed light on the fabrication of various high-performance flexible materials with molecular alignment having controlled patterns.

  13. Solubility and permeability of steroids in water in the presence of potassium halides.

    Science.gov (United States)

    Messner, M; Loftsson, T

    2010-02-01

    Water forms a network of hydrogen bonded water molecules that gives liquid water unique physicochemical properties. Ions that affect the network structure, e.g. potassium halides, are known to either increase or decrease aqueous solubilities of drugs. Most biological membranes consist of hydrophilic exterior and a lipophilic interior. Mathematically they can be treated as two-layer membranes, i.e. a hydrophilic water layer that is referred to as unstirred water layer (UWL) and a lipophilic membrane. The purpose of this study was to investigate if and then how ions affect drug permeation through the UWL. The effects of potassium halides on the solubility and permeability of dexamethasone and hydrocortisone was investigated. The potassium halides had either increasing or decreasing effect on their aqueous solubility but did not have any effect on their permeability through UWL.

  14. Molecular electrocatalysis for oxygen reduction by cobalt porphyrins adsorbed at liquid/liquid interfaces.

    Science.gov (United States)

    Su, Bin; Hatay, Imren; Trojánek, Antonín; Samec, Zdenek; Khoury, Tony; Gros, Claude P; Barbe, Jean-Michel; Daina, Antoine; Carrupt, Pierre-Alain; Girault, Hubert H

    2010-03-03

    Molecular electrocatalysis for oxygen reduction at a polarized water/1,2-dichloroethane (DCE) interface was studied, involving aqueous protons, ferrocene (Fc) in DCE and amphiphilic cobalt porphyrin catalysts adsorbed at the interface. The catalyst, (2,8,13,17-tetraethyl-3,7,12,18-tetramethyl-5-p-amino-phenylporphyrin) cobalt(II) (CoAP), functions like conventional cobalt porphyrins, activating O(2) via coordination by the formation of a superoxide structure. Furthermore, due to the hydrophilic nature of the aminophenyl group, CoAP has a strong affinity for the water/DCE interface as evidenced by lipophilicity mapping calculations and surface tension measurements, facilitating the protonation of the CoAP-O(2) complex and its reduction by ferrocene. The reaction is electrocatalytic as its rate depends on the applied Galvani potential difference between the two phases.

  15. The Molecular Structure of the Liquid Ordered Phase of Lipid Bilayers

    Science.gov (United States)

    Sodt, Alexander J.; Sandar, Michael Logan; Gawrisch, Klaus; Pastor, Richard W.; Lyman, Edward

    2014-01-01

    Molecular dynamics simulations reveal substructures within the liquid-ordered phase of lipid bilayers. These substructures, identified in a 10 μsec all-atom trajectory of liquid-ordered/liquid-disordered coexistence (Lo/Ld), are composed of saturated hydrocarbon chains packed with local hexagonal order, and separated by interstitial regions enriched in cholesterol and unsaturated chains. Lipid hydrocarbon chain order parameters calculated from the Lo phase are in excellent agreement with 2H NMR measurements; the local hexagonal packing is also consistent with 1H-MAS NMR spectra of the Lo phase, NMR diffusion experiments, and small angle X-ray- and neutron scattering. The balance of cholesterol-rich to local hexagonal order is proposed to control the partitioning of membrane components into the Lo regions. The latter have been frequently associated with formation of so-called rafts, platforms in the plasma membranes of cells that facilitate interaction between components of signaling pathways. PMID:24345334

  16. Molecular Dynamics Investigation of Efficient SO₂ Absorption by Anion-Functionalized Ionic Liquids

    Indian Academy of Sciences (India)

    ANIRBAN MONDAL; SUNDARAM BALASUBRAMANIAN

    2017-07-01

    Ionic liquids are appropriate candidates for the absorption of acid gases such as SO₂. Six anion functionalized ionic liquids with different basicities have been studied for SO₂ absorption capacity by employing quantum chemical calculations and molecular dynamics (MD) simulations. Gas phase quantum calculations unveil that the high uptake of SO₂ in these ionic liquids originates from the basicity of the anions and the consequent enhanced anion-SO₂ interactions. MD simulations of SO₂–IL mixtures reveal the crucial role of both cations and anions in SO₂ dissolution. Multiple-site interactions of SO₂ with the anions have been identified. The calculated solvation free energy substantiates these observations. The order of computed Henry’s law constant values with change in the anion is in fair agreement with experimentally determined SO₂ solubility order.

  17. A molecular dynamics study of structure and dynamics in high-density liquids

    Science.gov (United States)

    Variyar, Jayasankar E.; Noro, Massimo; Kivelson, Daniel

    By means of molecular dynamics simulations we have investigated increasing configurational ordering and decreasing particle mobility with increasing density ρ of a three-dimensional equilibrated liquid composed of soft discs. The equal-time correlation function h(n)3 (0) which includes two-, three- and four-body correlations is introduced as a measure of structural order; this function is related to the dipole-induced-dipole equal-time correlation function and its sensitivity to structural order in the liquid is associated with the cancellation effect, i.e. the cancellation of the positive contributions of the two- and four- body correlations by the negative contribution of the three-body correlations. The analogous time-dependent correlation function h(4)3 (t) is also studied. The possible implications of these results to the study of supercooled liquids and glasses is discussed.

  18. Ab Initio Molecular Dynamics Simulations on Structural Properties of Liquid In20Sn80

    Institute of Scientific and Technical Information of China (English)

    ZHAO Gang; LIU Chang-Song; ZHU Zhen-Gang

    2005-01-01

    @@ Ab initio molecular dynamics simulations on liquid In20Sn80 alloy are carried out at six different temperatures from 798 K to 1193 K. The temperature dependences of binding energy, volume, pair-correlation function and structurefactor are studied. The first-peak position of our calculated pair correlation function is in agreement with the experimental data. A shoulder is reproduced in the high wave number side of the first peak in our calculated structure factor, implying the existence of the residual directional bonds of Sn atoms in liquid In20Sn80 alloy. The first-peak height of our calculated structure factor and the coordination number of Sn atom decrease more sharply in the low-temperature region from 798K to 986K than that in the high-temperature region from 986K to 1193K, suggesting that a discontinuous structural change may occur at around 986K in liquid In20Sn80 alloy.

  19. Effect of Molecular Interactions between the Solid Wall and Liquid on the Flow Properties in Microtubes

    Institute of Scientific and Technical Information of China (English)

    BAO Fu-Bing; LIN Jian-Zhong

    2009-01-01

    The flow properties in microtubes, such as velocity profiles and pressure distributions, are different from those in macrotubes. We attribute this phenomenon to the molecular interactions between the solid wall and inner liquid. The apparent viscosity, which takes into consideration the molecular interactions, is introduced in the present study and the Navier-Stokes equations are solved. Water is adopted in the calculation. For the hydrophilic material wall, the water is more like to adhere to the wall. The velocity near the wall is smaller than that of conventional theory, while the centerline velocity and pressure gradients are much larger. Such a phenomenon becomes much more obvious with the decrease in tube diameter.

  20. Interaction of monovalent ions with the water liquid-vapor interface - A molecular dynamics study

    Science.gov (United States)

    Wilson, Michael A.; Pohorille, Andrew

    1991-01-01

    Results of molecular dynamics calculations are presented for a series of ions at infinite dilution near the water liquid-vapor interface. The free energies of ion transfer from the bulk to the interface are discussed, as are the accompanying changes of water structure at the surface and ion mobilities as a function of their proximity to the interface. It is shown that simple dielectric models do not provide an accurate description of ions at the water surface. The results of the study should be useful in the development of better models incorporating the shape and molecular structure of the interface.

  1. Polarization Raman Microscopic Study of Molecular Alignment Behavior in Liquid Crystal/Polymer Composite Films

    Science.gov (United States)

    Murashige, Takeshi; Fujikake, Hideo; Sato, Hiroto; Kikuchi, Hiroshi; Kurita, Taiichiro; Sato, Fumio

    2005-12-01

    We clarified that the molecular alignment of aggregated polymers is partially synchronized with liquid crystal (LC) director reorientation in an LC/polymer composite film. The molecular alignment behavior in composite films with LC- and polymer-rich regions formed by photopolymerization-induced phase separation was investigated using polarization Raman spectral microscopy. Raman scattering intensity induced by aligned side chains of polymers in the LC-rich region changed with LC director reorientation when voltage was applied to the composite film. It was confirmed for the first time that polymers capable of movement are formed in the LC-rich region.

  2. Study of Molecular Interactions in Binary Liquid Mixtures by Acoustical Method at 303K

    Directory of Open Access Journals (Sweden)

    P. Paul Divakar

    2012-01-01

    Full Text Available Ultrasonic velocity and density measurements were made in two binary liquid mixtures Isopropyl acetate (IPA and Isobutyl acetate (IBA with cyclohexanone (CY as a common component at 303K, at fixed frequency of 2MHz using single crystal variable path interferometer and specific gravity bottle respectively. The experimental data have been used to calculate the acoustic impedance, adiabatic compressibility, inter molecular free length and molar volume. The excess thermodynamic parameters have been evaluated and discussed in the light of molecular interactions.

  3. Relationship between Multi-Phase Formation and Molecular Structure for Liquid Crystal System

    Institute of Scientific and Technical Information of China (English)

    LI Zhenxin; MA Heng; LI Shipu

    2005-01-01

    A mechanical model of liquid crystals ( LCs ) was used to explain the phase formation and thermal properties. The LC phases in the model are micro-machine systems consisting of an ensemble of molecular rotors, and some dynamic parameters in a semi-experiment molecular orbit method. A novel explanation on the multi-phase formation of LC system is obtained. It is found that the value of the critical rotational velocity is a key parameter for the characterization of each homologous series. The dipole moment of the molecules was also discussed.

  4. Interaction of monovalent ions with the water liquid-vapor interface - A molecular dynamics study

    Science.gov (United States)

    Wilson, Michael A.; Pohorille, Andrew

    1991-01-01

    Results of molecular dynamics calculations are presented for a series of ions at infinite dilution near the water liquid-vapor interface. The free energies of ion transfer from the bulk to the interface are discussed, as are the accompanying changes of water structure at the surface and ion mobilities as a function of their proximity to the interface. It is shown that simple dielectric models do not provide an accurate description of ions at the water surface. The results of the study should be useful in the development of better models incorporating the shape and molecular structure of the interface.

  5. Comparison of two turbulent models in simulating evaporating liquid film in a wiped molecular distillator

    Institute of Scientific and Technical Information of China (English)

    XIANG Aishuang; XU Songlin

    2005-01-01

    Velocity field of evaporating liquid film in a wiped molecular distillator was simulated with a computational fluid dynamics (CFD) software, and two turbulent models treating near-wall flow were compared. Differences between wiped and other molecular distillations were introduced to explain why turbulent model should be used in this simulation. Three assumptions were made in order to simplify simulating processes. In rotating coordinate system, fixed other settings, the above two turbulent models were used, and the volume of fluid (VOF) multiphase model was also applied to tracking the liquid-gas surface. Both of the simulating results are basically identical with real situation and were compared in several aspects. It was concluded that both of the turbulent models are suitable in this simulation.

  6. Fast Quantum Molecular Dynamics Simulations of Simple Organic Liquids under Shock Compression

    Science.gov (United States)

    Cawkwell, Marc; Niklasson, Anders; Manner, Virginia; McGrane, Shawn; Dattelbaum, Dana

    2013-06-01

    The responses of liquid formic acid, acrylonitrile, and nitromethane to shock compression have been studied using quantum-based molecular dynamics simulations with the self-consistent tight-binding code LATTE. Microcanonical Born-Oppenheimer trajectories with precise energy conservation were computed without relying on an iterative self-consistent field optimization of the electronic degrees of freedom at each time step via the Fast Quantum Mechanical Molecular Dynamics formalism. The input shock pressures required to initiate chemistry in our simulations agree very well with recent laser- and flyer-plate-driven shock compression experiments. On-the-fly analysis of the electronic structure of the liquids over hundreds of picoseconds after dynamic compression revealed that their reactivity is strongly correlated with the temperature and pressure dependence of their HOMO-LUMO gap.

  7. Molecular Density Functional Theory for water with liquid-gas coexistence and correct pressure

    CERN Document Server

    Jeanmairet, Guillaume; Sergiievskyi, Volodymyr; Borgis, Daniel

    2015-01-01

    The solvation of hydrophobic solutes in water is special because liquid and gas are almost at coexistence. In the common hypernetted chain approximation to integral equations, or equivalently in the homogenous reference fluid of molecular density functional theory, coexistence is not taken into account. Hydration structures and energies of nanometer-scale hydrophobic solutes are thus incorrect. In this article, we propose a bridge functional that corrects this thermodynamic inconsistency by introducing a metastable gas phase for the homogeneous solvent. We show how this can be done by a third order expansion of the functional around the bulk liquid density that imposes the right pressure and the correct second order derivatives. Although this theory is not limited to water, we apply it to study hydrophobic solvation in water at room temperature and pressure and compare the results to all-atom simulations. With this correction, molecular density functional theory gives, at a modest computational cost, quantita...

  8. Influence of Halide Solutions on Collagen Networks: Measurements of Physical Properties by Atomic Force Microscopy

    Science.gov (United States)

    Kempe, André; Lackner, Maximilian

    2016-01-01

    The influence of aqueous halide solutions on collagen coatings was tested. The effects on resistance against indentation/penetration on adhesion forces were measured by atomic force microscopy (AFM) and the change of Young's modulus of the coating was derived. Comparative measurements over time were conducted with halide solutions of various concentrations. Physical properties of the mesh-like coating generally showed large variability. Starting with a compact set of physical properties, data disperse after minutes. A trend of increase in elasticity and permeability was found for all halide solutions. These changes were largest in NaI, displaying a logical trend with ion size. However a correlation with concentration was not measured. Adhesion properties were found to be independent of mechanical properties. The paper also presents practical experience for AFM measurements of soft tissue under liquids, particularly related to data evaluation. The weakening in physical strength found after exposure to halide solutions may be interpreted as widening of the network structure or change in the chemical properties in part of the collagen fibres (swelling). In order to design customized surface coatings at optimized conditions also for medical applications, halide solutions might be used as agents with little impact on the safety of patients.

  9. Liquid Methanol from DFT and DFT/MM Molecular Dynamics Simulations.

    Science.gov (United States)

    Sieffert, Nicolas; Bühl, Michael; Gaigeot, Marie-Pierre; Morrison, Carole A

    2013-01-08

    We present a comparative study of computational protocols for the description of liquid methanol from ab initio molecular dynamics simulations, in view of further applications directed at the modeling of chemical reactivity of organic and organometallic molecules in (explicit) methanol solution. We tested density functional theory molecular dynamics (DFT-MD) in its Car-Parrinello Molecular Dynamics (CPMD) and Quickstep/Born-Oppenheimer MD (CP2K) implementations, employing six popular density functionals with and without corrections for dispersion interactions (namely BLYP, BLYP-D2, BLYP-D3, BP86, BP86-D2, and B97-D2). Selected functionals were also tested within the two QM/MM frameworks implemented in CPMD and CP2K, considering one DFT molecule in a MM environment (described by the OPLS model of methanol). The accuracy of each of these methods at describing the bulk liquid phase under ambient conditions was evaluated by analyzing their ability to reproduce (i) the average structure of the liquid, (ii) the mean squared displacement of methanol molecules, (iii) the average molecular dipole moments, and (iv) the gas-to-liquid red-shift observed in their infrared spectra. We show that it is difficult to find a DFT functional that describes these four properties equally well within full DFT-MD simulations, despite a good overall performance of B97-D2. On the other hand, DFT/MM-MD provides a satisfactory description of the solvent-solute polarization effects with all functionals and thus represents a good alternative for the modeling of methanol solutions in the context of chemical reactivity in an explicit environment.

  10. Scaling Model of Low-Temperature Transport Properties for Molecular and Ionic Liquids

    Directory of Open Access Journals (Sweden)

    Vitaly B. Rogankov

    2015-01-01

    Full Text Available The universal scaling concept is applied to the low-temperature range of any liquid states and substances located between the melting (Tm and normal boiling (Tb points far away from the critical region. The physical reason to develop such approach is the revealed collapse of all low-temperature isotherms onto the single universal one argued by the model of fluctuational thermodynamics (FT proposed recently by author. The pressure reduced by the molecular parameters of the effective short-range Lennard-Jones (LJ potential depends here only on the reduced density. To demonstrate the extraordinary predictive abilities of the developed low-temperature scaling model it has been applied to the prediction of equilibrium and transport (kinetic and dynamic viscosity, self-diffusion, and thermal conductivity properties not only for molecular liquids but also for molten organic salts termed ionic liquids (ILs. The best argument in favor of the proposed methodology is the appropriate consistency with the scarce experiments prediction of transport coefficients for ILs on the base of universal scaling function constructed for the simplest LJ-like liquid argon. The only input data of any substance for prediction are the linear approximations of T-dependent density and isobaric heat capacity taken from the standard measurements at atmospheric pressure.

  11. Fully atomistic molecular-mechanical model of liquid alkane oils: Computational validation.

    Science.gov (United States)

    Zahariev, Tsvetan K; Slavchov, Radomir I; Tadjer, Alia V; Ivanova, Anela N

    2014-04-15

    Fully atomistic molecular dynamics simulations were performed on liquid n-pentane, n-hexane, and n-heptane to derive an atomistic model for middle-chain-length alkanes. All simulations were based on existing molecular-mechanical parameters for alkanes. The computational protocol was optimized, for example, in terms of thermo- and barostat, to reproduce properly the properties of the liquids. The model was validated by comparison of thermal, structural, and dynamic properties of the normal alkane liquids to experimental data. Two different combinations of temperature and pressure coupling algorithms were tested. A simple differential approach was applied to evaluate fluctuation-related properties with sufficient accuracy. Analysis of the data reveals a satisfactory representation of the hydrophobic systems behavior. Thermodynamic parameters are close to the experimental values and exhibit correct temperature dependence. The observed intramolecular geometry corresponds to extended conformations domination, whereas the intermolecular structure demonstrates all characteristics of liquid systems. Cavity size distribution function was calculated from coordinates analysis and was applied to study the solubility of gases in hexane and heptane oils. This study provides a platform for further in-depth research on hydrophobic solutions and multicomponent systems.

  12. Evaporation characteristics of thin film liquid argon in nano-scale confinement: A molecular dynamics study

    Science.gov (United States)

    Hasan, Mohammad Nasim; Shavik, Sheikh Mohammad; Rabbi, Kazi Fazle; Haque, Mominul

    2016-07-01

    Molecular dynamics simulation has been carried out to explore the evaporation characteristics of thin liquid argon film in nano-scale confinement. The present study has been conducted to realize the nano-scale physics of simultaneous evaporation and condensation inside a confined space for a three phase system with particular emphasis on the effect of surface wetting conditions. The simulation domain consisted of two parallel platinum plates; one at the top and another at the bottom. The fluid comprised of liquid argon film at the bottom plate and vapor argon in between liquid argon and upper plate of the domain. Considering hydrophilic and hydrophobic nature of top and bottom surfaces, two different cases have been investigated: (i) Case A: Both top and bottom surfaces are hydrophilic, (ii) Case B: both top and bottom surfaces are hydrophobic. For all cases, equilibrium molecular dynamics (EMD) was performed to reach equilibrium state at 90 K. Then the lower wall was set to four different temperatures such as 110 K, 120 K, 130 K and 140 K to perform non-equilibrium molecular dynamics (NEMD). The variation of temperature and density as well as the variation of system pressure with respect to time were closely monitored for each case. The heat fluxes normal to top and bottom walls were estimated and discussed to illuminate the effectiveness of heat transfer in both hydrophilic and hydrophobic confinement at various boundary temperatures of the bottom plate.

  13. Fick diffusion coefficients of liquid mixtures directly obtained from equilibrium molecular dynamics.

    Science.gov (United States)

    Liu, Xin; Schnell, Sondre K; Simon, Jean-Marc; Bedeaux, Dick; Kjelstrup, Signe; Bardow, André; Vlugt, Thijs J H

    2011-11-10

    A methodology for computing Fick diffusivities directly from equilibrium molecular dynamics (MD) simulations is presented and validated for acetone-methanol and acetone-tetrachloromethane liquid mixtures. Fick diffusivities are obtained from Maxwell-Stefan (MS) diffusivities and the so-called thermodynamic factor. MS diffusivities describe the friction between different components, while the thermodynamic factor is the concentration derivative of the activity describing the deviation from ideal mixing behavior. It is important to note that all mutual diffusion experiments measure Fick diffusion coefficients, while molecular simulation provides MS diffusivities. The required thermodynamic factor to convert MS into Fick diffusivities and vice versa, however, is usually difficult to extract from both simulations and experiments leaving a gap between theory and application. Here, we employ our novel method to compute the thermodynamic factor from small-scale density fluctuations in equilibrium MD simulations [Chem. Phys. Lett.2011, 504, 199-201]. Previously, this method was developed and validated for molecules with single interaction sites only. In this work, we applied this method to acetone-methanol and acetone-tetrachloromethane liquid mixtures and show that the method also works well in these more complex systems. This provides the missing step to extract Fick diffusion coefficients directly from equilibrium MD simulations. The computed Fick diffusivities of acetone-methanol and acetone-tetrachloromethane mixtures are in excellent agreement with experimental values. The suggested framework thus provides an efficient route to model diffusion in liquids on the basis of a consistent molecular picture.

  14. Ab initio molecular dynamics study of the properties of cerium in liquid sodium at 1000 K temperature

    Energy Technology Data Exchange (ETDEWEB)

    Samin, Adib; Li, Xiang; Zhang, Jinsuo [Nuclear Engineering Program, Department of Mechanical and Aerospace Engineering, The Ohio State University, 201 W 19th Avenue, Columbus, Ohio 43210 (United States); Mariani, R. D. [Idaho National Laboratory, Materials and Fuels Complex, Idaho Falls, Idaho 83415 (United States); Unal, Cetin [Los Alamos National Laboratory, P.O. Box 1663, Los Alamos, New Mexico 87545 (United States)

    2015-12-21

    For liquid-sodium-cooled fast nuclear reactor systems, it is crucial to understand the behavior of lanthanides and other potential fission products in liquid sodium or other liquid metal solutions such as liquid cesium-sodium. In this study, we focus on lanthanide behavior in liquid sodium. Using ab initio molecular dynamics, we found that the solubility of cerium in liquid sodium at 1000 K was less than 0.78 at. %, and the diffusion coefficient of cerium in liquid sodium was calculated to be 5.57 × 10{sup −9} m{sup 2}/s. Furthermore, it was found that cerium in small amounts may significantly alter the heat capacity of the liquid sodium system. Our results are consistent with the experimental results for similar materials under similar conditions.

  15. Ab initio molecular dynamics study of the properties of cerium in liquid sodium at 1000 K temperature

    Science.gov (United States)

    Samin, Adib; Li, Xiang; Zhang, Jinsuo; Mariani, R. D.; Unal, Cetin

    2015-12-01

    For liquid-sodium-cooled fast nuclear reactor systems, it is crucial to understand the behavior of lanthanides and other potential fission products in liquid sodium or other liquid metal solutions such as liquid cesium-sodium. In this study, we focus on lanthanide behavior in liquid sodium. Using ab initio molecular dynamics, we found that the solubility of cerium in liquid sodium at 1000 K was less than 0.78 at. %, and the diffusion coefficient of cerium in liquid sodium was calculated to be 5.57 × 10-9 m2/s. Furthermore, it was found that cerium in small amounts may significantly alter the heat capacity of the liquid sodium system. Our results are consistent with the experimental results for similar materials under similar conditions.

  16. Molecular Dynamics Simulation for the Binary Mixtures of High Pressure Carbon Dioxide and Ionic Liquids

    Institute of Scientific and Technical Information of China (English)

    徐君臣; 王松; 喻文; 徐琴琴; 王伟彬; 银建中

    2014-01-01

    Molecular dynamics simulation with an all-atom force field has been carried out on the two binary sys-tems of [bmim][PF6]-CO2 and [bmim][NO3]-CO2 to study the transport properties, volume expansion and micro-structures. It was found that addition of CO2 in the liquid phase can greatly decrease the viscosity of ionic liquids (ILs) and increase their diffusion coefficient obviously. Furthermore, the volume expansion of ionic liquids was found to increase with the increase of the mole fraction of CO2 in the liquid phase but less than 35%for the two simulated systems, which had a significant difference with CO2 expanded organic solvents. The main reason was that there were some void spaces inter and intra the molecules of ionic liquids. Finally, site to site radial distribution functions and corresponding number integrals were investigated and it was found that the change of microstructures of ILs by addition CO2 had a great influence on the properties of ILs.

  17. Cooling rate dependence of solidification for liquid aluminium: a large-scale molecular dynamics simulation study.

    Science.gov (United States)

    Hou, Z Y; Dong, K J; Tian, Z A; Liu, R S; Wang, Z; Wang, J G

    2016-06-29

    The effect of the cooling rate on the solidification process of liquid aluminium is studied using a large-scale molecular dynamics method. It is found that there are various types of short-range order (SRO) structures in the liquid, among which the icosahedral (ICO)-like structures are dominant. These SRO structures are in dynamic fluctuation and transform each other. The effect of the cooling rate on the microstructure is very weak at high temperatures and in supercooled liquids, and it appears only below the liquid-solid transition temperature. Fast cooling rates favour the formation of amorphous structures with ICO-like features, while slow cooling rates favour the formation of FCC crystalline structures. Furthermore, FCC and HCP structures can coexist in crystalline structures. It is also found that nanocrystalline aluminium can be achieved at appropriate cooling rates, and its formation mechanism is thoroughly investigated by tracing the evolution of nanoclusters. The arrangement of FCC and HCP atoms in the nanograins displays various twinned structures as observed using visualization analysis, which is different from the layering or phase separation structures observed in the solidification of Lennard-Jones fluids and some metal liquids.

  18. Ion Transport and Structural Properties of Polymeric Electrolytes and Ionic Liquids from Molecular Dynamics Simulations

    Science.gov (United States)

    Borodin, Oleg

    2010-03-01

    Molecular dynamics simulations are well suited for exploring electrolyte structure and ion transport mechanisms on the nanometer length scale and the nanosecond time scales. In this presentation we will describe how MD simulations assist in answering fundamental questions about the lithium transport mechanisms in polymeric electrolytes and ionic liquids. In particular, in the first part of the presentation the extent of ion aggregation, the structure of ion aggregates and the lithium cation diffusion in binary polymeric electrolytes will be compared with that of single-ion conducting polymers. In the second part of the talk, the lithium transport in polymeric electrolytes will be compared with that of three ionic liquids ( [emim][FSI] doped with LiFSI , [pyr13][FSI] doped with LiFSI, [emim][BF4] doped with LiBF4). The relation between ionic liquid self-diffusion, conductivity and thermodynamic properties will be discussed in details. A number of correlations between heat of vaporization Hvap, cation-anion binding energy (E+/-), molar volume (Vm), self-diffusion coefficient (D) and ionic conductivity for 29 ionic liquids have been investigated using MD simulations. A significant correlation between D and Hvap has been found, while best correlation was found for -log((D Vm)) vs. Hvap+0.28E+/-. A combination of enthalpy of vaporization and a fraction of the cation-anion binding energy was suggested as a measure of the effective cohesive energy for ionic liquids.

  19. The [BMI][Tf2N] ionic liquid/water binary system: a molecular dynamics study of phase separation and of the liquid-liquid interface.

    Science.gov (United States)

    Sieffert, N; Wipff, G

    2006-07-01

    We report molecular dynamics (MD) simulations of the aqueous interface of the hydrophobic [BMI][Tf2N] ionic liquid (IL), composed of 1-butyl-3-methylimidazolium cations (BMI+) and bis(trifluoromethylsulfonyl)imide anions (Tf2N-). The questions of water/IL phase separation and properties of the neat interface are addressed, comparing different liquid models (TIP3P vs TIP5P water and +1.0/-1.0 vs +0.9/-0.9 charged IL ions), the Ewald vs the reaction field treatments of the long range electrostatics, and different starting conditions. With the different models, the "randomly" mixed liquids separate much more slowly (in 20 to 40 ns) than classical water-oil mixtures do (typically, in less than 1 ns), finally leading to distinct nanoscopic phases separated by an interface, as in simulations which started with a preformed interface, but the IL phase is more humid. The final state of water in the IL thus depends on the protocol and relates to IL heterogeneities and viscosity. Water mainly fluctuates in hydrophilic basins (rich in O(Tf2N) and aromatic CH(BMI) groups), separated by more hydrophobic domains (rich in CF3(Tf2N) and alkyl(BMI) groups), in the form of monomers and dimers in the weakly humid IL phase, and as higher aggregates when the IL phase is more humid. There is more water in the IL than IL in water, to different extents, depending on the model. The interface is sharper and narrower (approximately 10 A) than with the less hydrophobic [BMI][PF6] IL and is overall neutral, with isotropically oriented molecules, as in the bulk phases. The results allow us to better understand the analogies and differences of aqueous interfaces with hydrophobic (but hygroscopic) ILs, compared to classical organic liquids.

  20. Influence of the molecular-oriented structure of ionic liquids on the crystallinity of aluminum hydroxide prepared by a sol-gel process in ionic liquids.

    Science.gov (United States)

    Kinoshita, K; Yanagimoto, H; Suzuki, T; Minami, H

    2015-07-28

    The influence of the structure of ionic liquids on the crystallinity of aluminum hydroxide (Al(OH)3) prepared by a sol-gel process with aluminum isopropoxide (Al(OPr(i))3) in imidazolium-based ionic liquids was investigated. When Al(OH)3 was prepared in ionic liquids having long alkyl chains, such as 1-butyl-3-methylimidazolium salts and 1-methyl-3-octylimidazolium salts, highly crystalline products were obtained. In contrast, Al(OH)3 obtained using the 1-ethyl-3-methylimidazolium salt was an amorphous material, indicating that hydrophobic interaction of the alkyl tail of the imidazolium cation of the ionic liquid strongly affects the crystallinity of sol-gel products and the local structure of the ionic liquid. Moreover, the crystallinity of Al(OH)3 prepared in ionic liquids increased relative to the amount of additional water (ionic liquid/water = 1.28/2.0-3.5/0.2, w/w). In the case of addition of a small amount of water (ionic liquid/water = 3.5/0.2, w/w), the product was amorphous. These results implied that the presence of an ionic liquid and a sufficient amount of water was crucial for the successful synthesis of sol-gel products with high crystallinity. (1)H NMR analyses revealed a shift of the peak associated with the imidazolium cation upon addition of water, which suggested that the molecular orientation of the ionic liquid was similar to that of a micelle.

  1. Molecular microstructure in thermotropic liquid crystals studied by nuclear quadrupole resonance spectroscopy

    Energy Technology Data Exchange (ETDEWEB)

    Pusiol, Daniel J.; Anoardo, Estaban [Cordoba Univ. Nacional (Argentina). Facultad de Matematica, Astronomia y Fisica

    1998-12-01

    Nuclear Quadrupole Resonance studies in Nematic and Smectic C thermotropic liquid crystalline mesophases of p-heptyl azoxyanizole are reported. The local molecular microstructure is modeled from NQR spectra. In the Smectic C mesophase, the NQR data is explained by assuming two features: biaxiality in the electric field gradients at the sites occupied by {sup 14} N nuclei, and the elemental unit cell of the mesophase is composed by two Hp AB molecules. These bimolecular units coexist together with single ,molecules and the relative proportions change with temperature, the quantity of individual molecules being predominant as the temperature approaches the Nematic phase transition. At the lowest temperatures in the Nematic mesophase the NQR spectrum behaves similarly to the corresponding at low temperatures in the SmC mesophase; this means that we can propose again the existence of huge number of bio molecular and biaxial unit cells. At higher temperatures the transition to single molecular units is deduced from NQR spectra. That transition is characterized by the one describing the passage from a partially disordered molecular system - the system is conserving some local anisotropic properties of symmetry from the crystalline solid state - to a partially ordered system that resembles an oriented liquid. (author)

  2. Weak links between fast mobility and local structure in molecular and atomic liquids

    Energy Technology Data Exchange (ETDEWEB)

    Bernini, S. [Dipartimento di Fisica “Enrico Fermi,” Università di Pisa, Largo B. Pontecorvo 3, I-56127 Pisa (Italy); Puosi, F. [Laboratoire de Physique de l’École Normale Supérieure de Lyon, UMR CNRS 5672, 46 allée d’Italie, 69007 Lyon (France); Leporini, D., E-mail: dino.leporini@df.unipi.it [Dipartimento di Fisica “Enrico Fermi,” Università di Pisa, Largo B. Pontecorvo 3, I-56127 Pisa (Italy); IPCF-CNR, UOS Pisa, Pisa (Italy)

    2015-03-28

    We investigate by molecular-dynamics simulations, the fast mobility—the rattling amplitude of the particles temporarily trapped by the cage of the neighbors—in mildly supercooled states of dense molecular (linear trimers) and atomic (binary mixtures) liquids. The mixture particles interact by the Lennard-Jones potential. The non-bonded particles of the molecular system are coupled by the more general Mie potential with variable repulsive and attractive exponents in a range which is a characteristic of small n-alkanes and n-alcohols. Possible links between the fast mobility and the geometry of the cage (size and shape) are searched. The correlations on a per-particle basis are rather weak. Instead, if one groups either the particles in fast-mobility subsets or the cages in geometric subsets, the increase of the fast mobility with both the size and the asphericity of the cage is revealed. The observed correlations are weak and differ in states with equal relaxation time. Local forces between a tagged particle and the first-neighbour shell do not correlate with the fast mobility in the molecular liquid. It is concluded that the cage geometry alone is unable to provide a microscopic interpretation of the known, universal link between the fast mobility and the slow structural relaxation. We suggest that the particle fast dynamics is affected by regions beyond the first neighbours, thus supporting the presence of collective, extended fast modes.

  3. Molecular simulation of fluid mixtures in bulk and at solid-liquid interfaces

    Science.gov (United States)

    Kern, Jesse L.

    The properties of a diverse range of mixture systems at interfaces are investigated using a variety of computational techniques. Molecular simulation is used to examine the thermodynamic, structural, and transport properties of heterogeneous systems of theoretical and practical importance. The study of binary hard-sphere mixtures at a hard wall demonstrates the high accuracy of recently developed classical-density functionals. The study of aluminum--gallium solid--liquid heterogeneous interfaces predicts a significant amount of prefreezing of the liquid by adopting the structure of the solid surface. The study of ethylene-expanded methanol within model silica mesopores shows the effect of confinement and surface functionalzation on the mixture composition and transport inside of the pores. From our molecular-dynamics study of binary hard-sphere fluid mixtures at a hard wall, we obtained high-precision calculations of the wall-fluid interfacial free energies, gamma. We have considered mixtures of varying diameter ratio, alpha = 0.7,0.8,0.9; mole fraction, x 1 = 0.25,0.50,0.75; and packing fraction, eta compressive stress on the Ga atoms. Bulk methanol--ethylene mixtures under vapor-liquid equilibrium conditions have been characterized using Monte Carlo and molecular dynamics. The simulated vapor-liquid coexistence curves for the pure-component and binary mixtures agree well with experiment, as do the mixture volumetric expansion results. Using chemical potentials obtained from the bulk simulations, the filling of a number of model silica mesopores with ethylene and methanol is simulated. We report the compositions of the confined fluid mixtures over a range of pressures and for three degrees of nominal pore hydrophobicity.

  4. Designs of Plasmonic Metamasks for Photopatterning Molecular Orientations in Liquid Crystals

    Directory of Open Access Journals (Sweden)

    Yubing Guo

    2016-12-01

    Full Text Available Aligning liquid crystal (LC molecules into spatially non-uniform orientation patterns is central to the functionalities of many emerging LC devices. Recently, we developed a new projection photopatterning technique by using plasmonic metamasks (PMMs, and demonstrated high-resolution and high-throughput patterning of molecular orientations into arbitrary patterns. Here we present comparisons between two different types of metamask designs: one based on curvilinear nanoslits in metal films; the other based on rectangular nanoapertures in metal films. By using numerical simulations and experimental studies, we show that the PMMs based on curvilinear nanoslits exhibit advantages in their broadband and high optical transmission, while face challenges in mask designing for arbitrary molecular orientations. In contrast, the PMMs based on nanoapertures, though limited in optical transmission, present the great advantage of allowing for patterning arbitrary molecular orientation fields.

  5. Molecular threading: mechanical extraction, stretching and placement of DNA molecules from a liquid-air interface.

    Directory of Open Access Journals (Sweden)

    Andrew C Payne

    Full Text Available We present "molecular threading", a surface independent tip-based method for stretching and depositing single and double-stranded DNA molecules. DNA is stretched into air at a liquid-air interface, and can be subsequently deposited onto a dry substrate isolated from solution. The design of an apparatus used for molecular threading is presented, and fluorescence and electron microscopies are used to characterize the angular distribution, straightness, and reproducibility of stretched DNA deposited in arrays onto elastomeric surfaces and thin membranes. Molecular threading demonstrates high straightness and uniformity over length scales from nanometers to micrometers, and represents an alternative to existing DNA deposition and linearization methods. These results point towards scalable and high-throughput precision manipulation of single-molecule polymers.

  6. Epitaxial Halide Perovskite Lateral Double Heterostructure.

    Science.gov (United States)

    Wang, Yiping; Chen, Zhizhong; Deschler, Felix; Sun, Xin; Lu, Toh-Ming; Wertz, Esther A; Hu, Jia-Mian; Shi, Jian

    2017-03-28

    Epitaxial III-V semiconductor heterostructures are key components in modern microelectronics, electro-optics, and optoelectronics. With superior semiconducting properties, halide perovskite materials are rising as promising candidates for coherent heterostructure devices. In this report, spinodal decomposition is proposed and experimentally implemented to produce epitaxial double heterostructures in halide perovskite system. Pristine epitaxial mixed halide perovskites rods and films were synthesized via van der Waals epitaxy by chemical vapor deposition method. At room temperature, photon was applied as a knob to regulate the kinetics of spinodal decomposition and classic coarsening. By this approach, halide perovskite double heterostructures were created carrying epitaxial interfaces and outstanding optical properties. Reduced Fröhlich electron-phonon coupling was discovered in coherent halide double heterostructure, which is hypothetically attributed to the classic phonon confinement effect widely existing in III-V double heterostructures. As a proof-of-concept, our results suggest that halide perovskite-based epitaxial heterostructures may be promising for high-performance and low-cost optoelectronics, electro-optics, and microelectronics. Thus, ultimately, for practical device applications, it may be worthy to pursue these heterostructures via conventional vapor phase epitaxy approaches widely practised in III-V field.

  7. Quantum molecular dynamics simulations of transport properties in liquid and dense-plasma plutonium

    Science.gov (United States)

    Kress, J. D.; Cohen, James S.; Kilcrease, D. P.; Horner, D. A.; Collins, L. A.

    2011-02-01

    We have calculated the viscosity and self-diffusion coefficients of plutonium in the liquid phase using quantum molecular dynamics (QMD) and in the dense-plasma phase using orbital-free molecular dynamics (OFMD), as well as in the intermediate warm dense matter regime with both methods. Our liquid metal results for viscosity are about 40% lower than measured experimentally, whereas a previous calculation using an empirical interatomic potential (modified embedded-atom method) obtained results 3-4 times larger than the experiment. The QMD and OFMD results agree well at the intermediate temperatures. The calculations in the dense-plasma regime for temperatures from 50 to 5000 eV and densities about 1-5 times ambient are compared with the one-component plasma (OCP) model, using effective charges given by the average-atom code inferno. The inferno-OCP model results agree with the OFMD to within about a factor of 2, except for the viscosity at temperatures less than about 100 eV, where the disagreement is greater. A Stokes-Einstein relationship of the viscosities and diffusion coefficients is found to hold fairly well separately in both the liquid and dense-plasma regimes.

  8. Comparative study of local structure of two cyanobiphenyl liquid crystals by molecular dynamics method

    Energy Technology Data Exchange (ETDEWEB)

    Gerts, Egor D., E-mail: gerts-e-d@yandex.ru; Komolkin, Andrei V., E-mail: komolkin@nmr.phys.spbu.ru [Physical Faculty, Saint Petersburg State University, Saint Petersburg 198504 (Russian Federation); Burmistrov, Vladimir A. [Ivanovo State University of Chemical Technology, Ivanovo 153000 (Russian Federation); Alexandriysky, Victor V. [Ivanovo State University of Chemical Technology, Ivanovo 153000 (Russian Federation); Institute of Solution Chemistry, Russian Academy of Sciences, Ivanovo 153045 (Russian Federation); Dvinskikh, Sergey V. [Laboratory of Biomolecular NMR, Saint Petersburg State University, Saint Petersburg 199034 (Russian Federation); Department of Chemistry, KTH Royal Institute of Technology, Stockholm SE-100 44 (Sweden)

    2014-08-21

    Fully-atomistic molecular dynamics simulations were carried out on two similar cyanobiphenyl nematogens, HO-6OCB and 7OCB, in order to study effects of hydrogen bonds on local structure of liquid crystals. Comparable length of these two molecules provides more evident results on the effects of hydrogen bonding. The analysis of radial and cylindrical distribution functions clearly shows the differences in local structure of two mesogens. The simulations showed that anti-parallel alignment is preferable for the HO-6OCB. Hydrogen bonds between OH-groups are observed for 51% of HO-6OCB molecules, while hydrogen bonding between CN- and OH-groups occurs only for 16% of molecules. The lifetimes of H-bonds differ due to different mobility of molecular fragments (50 ps for N⋅⋅⋅H–O and 41 ps for O⋅⋅⋅H–O). Although the standard Optimized Potentials for Liquid Simulations - All-Atom force field cannot reproduce some experimental parameters quantitatively (order parameters are overestimated, diffusion coefficients are not reproduced well), the comparison of relative simulated results for the pair of mesogens is nevertheless consistent with the same relative experimental parameters. Thus, the comparative study of simulated and experimental results for the pair of similar liquid crystals still can be assumed plausible.

  9. Molecular theory of nematic liquid crystals viewed as effect of collective excitation in ferromagnetic systems

    Institute of Scientific and Technical Information of China (English)

    Liu Jian-Jun; Shen Man; Liu Xiao-Jing; Yang Guo-Chen

    2006-01-01

    We develop a microscopic theory of the nematic phase with consideration of the effect of the collective excitation on properties of nematic liquid crystals. The model is based on the Heisenberg's exchange model of the ferromagnetic materials. Since the orientation of the molecular long axis and the angular momentum of the molecule rotating around its long axis have the same direction, operators can be introduced to research the nematic liquid crystals. Using the lattice model and the Holstein-Primakoff transformation, the Hamiltonian of the system can be obtained, which has the same form as that of the ferromagnetic substance. The relation between the order parameter and reduced temperature can be gotten. It is in good agreement with the experimental results in the low temperature region, the accordance is better than that of the molecular field theory and the computer simulation. In high temperature region close to the transition point, by considering the effect of the higher-order terms in the Hamiltonian, theoretical prediction is in better agreement with the experiment. That indicates the many-body effect is important to nematic liquid crystals.

  10. Quantum molecular dynamics simulations of transport properties in liquid and dense-plasma plutonium.

    Science.gov (United States)

    Kress, J D; Cohen, James S; Kilcrease, D P; Horner, D A; Collins, L A

    2011-02-01

    We have calculated the viscosity and self-diffusion coefficients of plutonium in the liquid phase using quantum molecular dynamics (QMD) and in the dense-plasma phase using orbital-free molecular dynamics (OFMD), as well as in the intermediate warm dense matter regime with both methods. Our liquid metal results for viscosity are about 40% lower than measured experimentally, whereas a previous calculation using an empirical interatomic potential (modified embedded-atom method) obtained results 3-4 times larger than the experiment. The QMD and OFMD results agree well at the intermediate temperatures. The calculations in the dense-plasma regime for temperatures from 50 to 5000 eV and densities about 1-5 times ambient are compared with the one-component plasma (OCP) model, using effective charges given by the average-atom code INFERNO. The INFERNO-OCP model results agree with the OFMD to within about a factor of 2, except for the viscosity at temperatures less than about 100 eV, where the disagreement is greater. A Stokes-Einstein relationship of the viscosities and diffusion coefficients is found to hold fairly well separately in both the liquid and dense-plasma regimes.

  11. Liquid chromatographic separation in metal-organic framework MIL-101: a molecular simulation study.

    Science.gov (United States)

    Hu, Zhongqiao; Chen, Yifei; Jiang, Jianwen

    2013-02-05

    A molecular simulation study is reported to investigate liquid chromatographic separation in metal-organic framework MIL-101. Two mixtures are considered: three amino acids (Arg, Phe, and Trp) in aqueous solution and three xylene isomers (p-, m-, and o-xylene) dissolved in hexane. For the first mixture, the elution order is found to be Arg > Phe > Trp. The hydrophilic Arg has the strongest interaction with the polar mobile phase (water) and the weakest interaction with the stationary phase (MIL-101), and thus transports at the fastest velocity. Furthermore, Arg forms the largest number of hydrogen bonds with water and possesses the largest hydrophilic solvent-accessible surface area. For the second mixture, the elution order is p-xylene > m-xylene > o-xylene, consistent with available experimental observation. With the largest polarity as compared to p- and m-xylenes, o-xylene interacts the most strongly with the stationary phase and exhibits the slowest transport velocity. For both mixtures, the underlying separation mechanism is elucidated from detailed energetic and structural analysis. It is revealed that the separation can be attributed to the cooperative solute-solvent and solute-framework interactions. This simulation study, for the first time, provides molecular insight into liquid chromatographic separation in a MOF and suggests that MIL-101 might be an interesting material for the separation of industrially important liquid mixtures.

  12. Fast Quantum Molecular Dynamics Simulations of Shock-induced Chemistry in Organic Liquids

    Science.gov (United States)

    Cawkwell, Marc

    2014-03-01

    The responses of liquid formic acid and phenylacetylene to shock compression have been investigated via quantum-based molecular dynamics simulations with the self-consistent tight-binding code LATTE. Microcanonical Born-Oppenheimer trajectories with precise conservation of the total energy were computed without relying on an iterative self-consistent field optimization of the electronic degrees of freedom at each time step via the Fast Quantum Mechanical Molecular Dynamics formalism [A. M. N. Niklasson and M. J. Cawkwell, Phys. Rev. B, 86, 174308 (2012)]. The conservation of the total energy in our trajectories was pivotal for the capture of adiabatic shock heating as well as temperature changes arising from endo- or exothermic chemistry. Our self-consistent tight-binding parameterizations yielded very good predictions for the gas-phase geometries of formic acid and phenylacetylene molecules and the principal Hugoniots of the liquids. In accord with recent flyer-plate impact experiments, our simulations revealed i) that formic acid reacts at relatively low impact pressures but with no change in volume between products and reactants, and ii) a two-step polymerization process for phenylacetylene. Furthermore, the evolution of the HOMO-LUMO gap tracked on-the-fly during our simulations could be correlated with changes transient absorption measured during laser-driven shock compression experiments on these liquids.

  13. Molecular density functional theory for water with liquid-gas coexistence and correct pressure

    Energy Technology Data Exchange (ETDEWEB)

    Jeanmairet, Guillaume, E-mail: g.jeanmairet@fkf.mpg.de; Levesque, Maximilien, E-mail: maximilien.levesque@ens.fr [École Normale Supérieure - PSL Research University, Département de Chimie, Sorbonne Universités - UPMC Univ. Paris 06, CNRS UMR 8640 PASTEUR, 24 rue Lhomond, 75005 Paris (France); Sergiievskyi, Volodymyr [SIS2M, LIONS, CEA, Saclay (France); Borgis, Daniel [École Normale Supérieure - PSL Research University, Département de Chimie, Sorbonne Universités - UPMC Univ. Paris 06, CNRS UMR 8640 PASTEUR, 24 rue Lhomond, 75005 Paris (France); Maison de la Simulation, USR 3441, CEA - CNRS - INRIA - Univ. Paris-Sud - Univ. de Versailles, 91191 Gif-sur-Yvette Cedex (France)

    2015-04-21

    The solvation of hydrophobic solutes in water is special because liquid and gas are almost at coexistence. In the common hypernetted chain approximation to integral equations, or equivalently in the homogenous reference fluid of molecular density functional theory, coexistence is not taken into account. Hydration structures and energies of nanometer-scale hydrophobic solutes are thus incorrect. In this article, we propose a bridge functional that corrects this thermodynamic inconsistency by introducing a metastable gas phase for the homogeneous solvent. We show how this can be done by a third order expansion of the functional around the bulk liquid density that imposes the right pressure and the correct second order derivatives. Although this theory is not limited to water, we apply it to study hydrophobic solvation in water at room temperature and pressure and compare the results to all-atom simulations. The solvation free energy of small molecular solutes like n-alkanes and hard sphere solutes whose radii range from angstroms to nanometers is now in quantitative agreement with reference all atom simulations. The macroscopic liquid-gas surface tension predicted by the theory is comparable to experiments. This theory gives an alternative to the empirical hard sphere bridge correction used so far by several authors.

  14. Bubble nucleation in simple and molecular liquids via the largest spherical cavity method

    Energy Technology Data Exchange (ETDEWEB)

    Gonzalez, Miguel A., E-mail: m.gonzalez12@imperial.ac.uk [Departamento de Química Física, Facultad de Ciencias Químicas, Universidad Complutense de Madrid, 28040 Madrid (Spain); Department of Chemistry, Imperial College London, London SW7 2AZ (United Kingdom); Abascal, José L. F.; Valeriani, Chantal [Departamento de Química Física, Facultad de Ciencias Químicas, Universidad Complutense de Madrid, 28040 Madrid (Spain); Bresme, Fernando [Department of Chemistry, Imperial College London, London SW7 2AZ (United Kingdom); Department of Chemistry, Norwegian University of Science and Technology, Trondheim (Norway)

    2015-04-21

    In this work, we propose a methodology to compute bubble nucleation free energy barriers using trajectories generated via molecular dynamics simulations. We follow the bubble nucleation process by means of a local order parameter, defined by the volume of the largest spherical cavity (LSC) formed in the nucleating trajectories. This order parameter simplifies considerably the monitoring of the nucleation events, as compared with the previous approaches which require ad hoc criteria to classify the atoms and molecules as liquid or vapor. The combination of the LSC and the mean first passage time technique can then be used to obtain the free energy curves. Upon computation of the cavity distribution function the nucleation rate and free-energy barrier can then be computed. We test our method against recent computations of bubble nucleation in simple liquids and water at negative pressures. We obtain free-energy barriers in good agreement with the previous works. The LSC method provides a versatile and computationally efficient route to estimate the volume of critical bubbles the nucleation rate and to compute bubble nucleation free-energies in both simple and molecular liquids.

  15. Methods for producing single crystal mixed halide perovskites

    Energy Technology Data Exchange (ETDEWEB)

    Zhu, Kai; Zhao, Yixin

    2017-07-11

    An aspect of the present invention is a method that includes contacting a metal halide and a first alkylammonium halide in a solvent to form a solution and maintaining the solution at a first temperature, resulting in the formation of at least one alkylammonium halide perovskite crystal, where the metal halide includes a first halogen and a metal, the first alkylammonium halide includes the first halogen, the at least one alkylammonium halide perovskite crystal includes the metal and the first halogen, and the first temperature is above about 21.degree. C.

  16. Dielectric properties and molecular motions of liquid crystal molecules in 4-(2-methylbytylphenyl 4-(4-octylphenylbenzoate liquid crystal having blue phase (CE8

    Directory of Open Access Journals (Sweden)

    Otowski W.

    2015-06-01

    Full Text Available Blue phase liquid crystals exhibit unique properties which are used in the new type of display. A blue-phase liquid crystal display was first presented commercially by Samsung in 2007. The blue-phase-three-color pixel display eliminates the need for color filters. This type of display uses blue-phase multi-component liquid crystal. Considering the one-component systems, it turns out that they are stable only in a very narrow range of temperatures between the isotropic and the chiral nematic phase (about 1 K. In 2005, a wide temperature range BP multi-component system was reported by researchers from the University of Cambridge. There are still several unsolved problems left. One of them is chemical stability and reliability. Therefore, the knowledge of molecular dynamics of blue phase liquid crystal is a prerequisite for understanding of blue-phase multi-component system. Understanding the molecular dynamics of a single component liquid-crystalline blue phase system can facilitate the solution of these problems. We present the molecular dynamics investigation of 4-(2-methylbytylphenyl 4-(4-octylphenylbenzoate (CE8, which may be a good candidate to form materials suitable for blue-phase liquid crystal displays.

  17. Direct molecular dynamics simulation of liquid-solid phase equilibria for a three-component plasma.

    Science.gov (United States)

    Hughto, J; Horowitz, C J; Schneider, A S; Medin, Zach; Cumming, Andrew; Berry, D K

    2012-12-01

    The neutron-rich isotope ²²Ne may be a significant impurity in carbon and oxygen white dwarfs and could impact how the stars freeze. We perform molecular dynamics simulations to determine the influence of ²²Ne in carbon-oxygen-neon systems on liquid-solid phase equilibria. Both liquid and solid phases are present simultaneously in our simulation volumes. We identify liquid, solid, and interface regions in our simulations using a bond angle metric. In general we find good agreement for the composition of liquid and solid phases between our MD simulations and the semianalytic model of Medin and Cumming. The trace presence of a third component, neon, does not appear to strongly impact the chemical separation found previously for two-component carbon and oxygen systems. This suggests that small amounts of ²²Ne may not qualitatively change how the material in white dwarf stars freezes. However, we do find systematically lower melting temperatures (higher Γ) in our MD simulations compared to the semianalytic model. This difference seems to grow with impurity parameter Q_{imp} and suggests a problem with simple corrections to the linear mixing rule for the free energy of multicomponent solid mixtures that is used in the semianalytic model.

  18. Direct molecular dynamics simulation of liquid-solid phase equilibria for two-component plasmas.

    Science.gov (United States)

    Schneider, A S; Hughto, J; Horowitz, C J; Berry, D K

    2012-06-01

    We determine the liquid-solid phase diagram for carbon-oxygen and oxygen-selenium plasma mixtures using two-phase molecular dynamics simulations. We identify liquid, solid, and interface regions using a bond angle metric. To study finite-size effects, we perform 27,648- and 55,296-ion simulations. To help monitor nonequilibrium effects, we calculate diffusion constants D(i). For the carbon-oxygen system we find that D(O) for oxygen ions in the solid is much smaller than D(C) for carbon ions and that both diffusion constants are 80 or more times smaller than diffusion constants in the liquid phase. There is excellent agreement between our carbon-oxygen phase diagram and that predicted by Medin and Cumming. This suggests that errors from finite-size and nonequilibrium effects are small and that the carbon-oxygen phase diagram is now accurately known. The oxygen-selenium system is a simple two-component model for more complex rapid proton capture nucleosynthesis ash compositions for an accreting neutron star. Diffusion of oxygen, in a predominantly selenium crystal, is remarkably fast, comparable to diffusion in the liquid phase. We find a somewhat lower melting temperature for the oxygen-selenium system than that predicted by Medin and Cumming. This is probably because of electron screening effects.

  19. Molecular dynamics of phenol at the liquid-vapor interface of water

    Science.gov (United States)

    Pohorille, Andrew; Benjamin, Ilan

    1991-01-01

    Results of molecular dynamics calculations on phenol at the water liquid-vapor interface are presented. The density profile of the center of mass of phenol exhibits a maximum 1 A from the Gibbs surface toward the vapor phase, indicating that the molecule is surface-active. Changes in the profile caused by the interface extend 6 A from the Gibbs surface into the liquid, significantly more than change in the density profile of water. The most probable orientation of the solute at the surface is such that its symmetry axis is perpendicular to the interface with the OH substituent pointing toward the liquid. An additional simulation with benzene shows that this molecule at the surface most often adopts orientations parallel to the interface. Deeper in the liquid all the solutes are preferentially ordered perpendicular to the surface. In the interfacial region the orientational preferences of the solute are primarily determined by cavity formation needed to accommodate the hydrophobic portion of the dissolved molecule.

  20. Hydrogen Bonding and Related Properties in Liquid Water: A Car-Parrinello Molecular Dynamics Simulation Study.

    Science.gov (United States)

    Guardia, Elvira; Skarmoutsos, Ioannis; Masia, Marco

    2015-07-23

    The local hydrogen-bonding structure and dynamics of liquid water have been investigated using the Car-Parrinello molecular dynamics simulation technique. The radial distribution functions and coordination numbers around water molecules have been found to be strongly dependent on the number of hydrogen bonds formed by each molecule, revealing also the existence of local structural heterogeneities in the structure of the liquid. The results obtained have also revealed the strong effect of the local hydrogen-bonding network on the local tetrahedral structure and entropy. The investigation of the dynamics of the local hydrogen-bonding network in liquid water has shown that this network is very labile, and the hydrogen bonds break and reform very rapidly. Nevertheless, it has been found that the hydrogen-bonding states associated with the formation of four hydrogen bonds by a water molecule exhibit the largest survival probability and corresponding lifetime. The reorientational motions of water molecules have also been found to be strongly dependent on their initial hydrogen-bonding state. Finally, the dependence of the librational and vibrational modes of water molecules on the local hydrogen-bonding network has been carefully examined, revealing a significant effect upon the libration and bond-stretching peak frequencies. The calculated low frequency peaks come in agreement with previously reported interpretations of the experimental low-frequency Raman spectrum of liquid water.

  1. Thermodynamical and structural properties of imidazolium based ionic liquids from molecular simulation

    Science.gov (United States)

    Raabe, Gabriele; Köhler, Jürgen

    2008-04-01

    We have performed molecular dynamics simulations to determine the densities and heat of vaporization as well as structural information for the 1-alkyl-3-methyl-imidazolium based ionic liquids [amim][Cl] and [amim][BF4] in the temperature range from 298to363K. In this simulation study, we used an united atom model of Liu et al. [Phys. Chem. Chem. Phys. 8, 1096 (2006)] for the [emim+] and [bmim+] cations, which we have extended for simulation in [hmim]-ILs and combined with parameters of Canongia Lopes et al. [J. Phys. Chem. B 108, 2038 (2004)] for the [Cl-] anion. Our simulation results prove that both the original united atoms approach by Liu et al. and our extension yield reasonable predictions for the ionic liquid with a considerably reduced computational expense than that required for all atoms models. Radial distribution functions and spatial distribution functions where employed to analyze the local structure of this ionic liquid, and in which way it is influenced by the type of the anion, the size of the cation, and the temperature. Our simulations give evidence for the occurrence of tail aggregations in these ionic liquids with increasing length of the side chain and also increasing temperature.

  2. Molecular dynamics simulation analysis of ion irradiation effects on plasma-liquid interface

    Science.gov (United States)

    Minagawa, Yudai; Shirai, Naoki; Uchida, Satoshi; Tochikubo, Fumiyoshi

    2013-09-01

    Nonthermal atmospheric plasmas are used in a wide range of fields because the high-density plasma can be easily irradiated to various substances such as solid, liquid, biological object and so on. On the other hand, the mechanisms of physical and chemical phenomena at the plasma-liquid interface are not well understood yet. To investigate the effects of ion impact from plasma on water surface, we analyzed behavior of liquid water by classical molecular dynamics simulation. Simulation system consists of an irradiation particle in gas phase and 2000 water molecules in liquid phase. O+ ion with 10 eV or 100 eV was impinged on the water surface. Ion impact induced increasing water temperature and ejection of water molecules. The averaged number of evaporated water molecules by ion impact is 0.6 molecules at 10 eV and 7.0 molecules at 100 eV. The maximum ion penetration depth was 1.14 nm at 10 eV and 2.75 nm at 100 eV. Ion entering into water disturbs the stable hydrogen bonding configurations between water molecules and gives energy to water molecules. Some water molecules rotated and moved by ion interaction impact on other water molecules one after another. When the water molecule near the surface received strongly repulsive force, it released into gas phase. This work was supported financially in part by a Grant-in-Aid for Scientific Research on Innovation Areas (No21110007) from MEXT, Japan.

  3. Molecular dynamics of phenol at the liquid-vapor interface of water

    Science.gov (United States)

    Pohorille, Andrew; Benjamin, Ilan

    1991-01-01

    Results of molecular dynamics calculations on phenol at the water liquid-vapor interface are presented. The density profile of the center of mass of phenol exhibits a maximum 1 A from the Gibbs surface toward the vapor phase, indicating that the molecule is surface-active. Changes in the profile caused by the interface extend 6 A from the Gibbs surface into the liquid, significantly more than change in the density profile of water. The most probable orientation of the solute at the surface is such that its symmetry axis is perpendicular to the interface with the OH substituent pointing toward the liquid. An additional simulation with benzene shows that this molecule at the surface most often adopts orientations parallel to the interface. Deeper in the liquid all the solutes are preferentially ordered perpendicular to the surface. In the interfacial region the orientational preferences of the solute are primarily determined by cavity formation needed to accommodate the hydrophobic portion of the dissolved molecule.

  4. Evaluation of molecularly imprinted anion-functionalized poly(ionic liquid)s by multi-phase dispersive extraction of flavonoids from plant.

    Science.gov (United States)

    Bi, Wentao; Tian, Minglei; Row, Kyung Ho

    2013-01-15

    Molecularly imprinted anion-functionalized poly(ionic liquid)s (MAPILs) were prepared by radical polymerization for the multi-phase dispersive extraction (MPDE) of flavonoids from plants. Poly(ionic liquid)s were functionalized with different anions via anion metathesis to enhance their separation efficiency, called anion-functionalized poly(ionic liquid)s (APILs). A molecularly imprinting technique was introduced to produce specific recognition sites by forming complexes between the template molecules and anion-functionalized ionic liquid monomers to reduce the interactions with the interference substances and increase the selectivity. Multi-phase dispersive extraction (MPDE) was applied for separation instead of the traditional solid phase extraction method. The target compounds were first extracted by three-phase (sample-solvent-sorbent) dispersive extraction and cleaned up after removing the sample matrix. This method significantly decrease in the interference and analysis cost. A suitable sorbent for MPDE could be identified based on the adsorption behaviors of flavonoids on different MAPILs. The mean recovery yields of quercitrin, myricetin, and amentoflavone from Chamaecyparis obtusa under the optimized conditions were 88.07, 93.59, and 95.13%. This is a promising method for the extraction, separation and determination of flavonoids or other polyphenolic compounds from natural and other sources. Copyright © 2012 Elsevier B.V. All rights reserved.

  5. True molecular solutions of natural cellulose in the binary ionic liquid-containing solvent mixtures.

    Science.gov (United States)

    Rein, Dmitry M; Khalfin, Rafail; Szekely, Noemi; Cohen, Yachin

    2014-11-04

    Evidence is presented for the first time of true molecular dissolution of cellulose in binary mixtures of common polar organic solvents with ionic liquid. Cryogenic transmission electron microscopy, small-angle neutron-, X-ray- and static light scattering were used to investigate the structure of cellulose solutions in mixture of dimethyl formamide and 1-ethyl-3-methylimidazolium acetate. Structural information on the dissolved chains (average molecular weight ∼ 5 × 10(4)g/mol; gyration radius ∼ 36 nm, persistence length ∼ 4.5 nm), indicate the absence of significant aggregation of the dissolved chains and the calculated value of the second virial coefficient ∼ 2.45 × 10(-2)mol ml/g(2) indicates that this solvent system is a good solvent for cellulose. More facile dissolution of cellulose could be achieved in solvent mixtures that exhibit the highest electrical conductivity. Highly concentrated cellulose solution in pure ionic liquid (27 wt.%) prepared according to novel method, utilizing the rapid evaporation of a volatile co-solvent in binary solvent mixtures at superheated conditions, shows insignificant cellulose molecular aggregation.

  6. GPU-accelerated molecular dynamics simulation for study of liquid crystalline flows

    Science.gov (United States)

    Sunarso, Alfeus; Tsuji, Tomohiro; Chono, Shigeomi

    2010-08-01

    We have developed a GPU-based molecular dynamics simulation for the study of flows of fluids with anisotropic molecules such as liquid crystals. An application of the simulation to the study of macroscopic flow (backflow) generation by molecular reorientation in a nematic liquid crystal under the application of an electric field is presented. The computations of intermolecular force and torque are parallelized on the GPU using the cell-list method, and an efficient algorithm to update the cell lists was proposed. Some important issues in the implementation of computations that involve a large number of arithmetic operations and data on the GPU that has limited high-speed memory resources are addressed extensively. Despite the relatively low GPU occupancy in the calculation of intermolecular force and torque, the computation on a recent GPU is about 50 times faster than that on a single core of a recent CPU, thus simulations involving a large number of molecules using a personal computer are possible. The GPU-based simulation should allow an extensive investigation of the molecular-level mechanisms underlying various macroscopic flow phenomena in fluids with anisotropic molecules.

  7. Structure of Rare-earth/Alkali Halide Complexes

    Science.gov (United States)

    Akdeniz, Z.; Önem, Z. Çiçek; Tosia, M. P.

    2001-11-01

    Vapour complex formation of rare-earth halides with alkali halides strongly increases the volatility of these compounds. We evaluate the structure taken by such complexes having the chemical formulas MRX4, M2RX5 and M3RX6, where X = F or Cl and typically M = Li or Na and R = La. The roles played by the two types of metal atom is investigated in MRX4 complexes by also taking M = K, Rb or Cs and R = Gd or Lu. The main predictions that emerge from our calculations are as follows: (i) in MRX4 a fourfold coordination of the rare-earth atom is accompanied by twofold or threefold coordination of the alkali atom, the energy difference in favour of the twofold-coordination state being about 0.3 eV in the case of the LiF complexing agent but even changing sign as the ionic radius of either the alkali or the halogen is increased; (ii) in M2RX5 a fivefold coordination of the rare-earth atom is energetically more stable than a fourfold one, by again not more than about 0.3 eV; (iii) in M3RX6 the fivefold and sixfold coordinations of the rare-earth atom are energetically competitive; and (iv) in both M2RX5 and M3RX6 each coordination state can be realized in various forms that differ in detail but are close in energy. Bond fluctuations and disorder around the rare-earth atom can be expected to be a general feature at elevated temperatures, both in the vapour and in liquid rare-earth/alkali halide mixtures.

  8. On the vapor-liquid equilibrium of attractive chain fluids with variable degree of molecular flexibility.

    Science.gov (United States)

    van Westen, Thijs; Vlugt, Thijs J H; Gross, Joachim

    2015-06-14

    We study the isotropic (vapor and liquid) phase behavior of attractive chain fluids. Special emphasis is placed on the role of molecular flexibility, which is studied by means of a rod-coil model. Two new equations of state (EoSs) are developed for square-well- (SW) and Lennard-Jones (LJ) chain fluids. The EoSs are developed by applying the perturbation theory of Barker and Henderson (BH) to a reference fluid of hard chain molecules. The novelty of the approach is based on (1) the use of a recently developed hard-chain reference EoS that explicitly incorporates the effects of molecular flexibility, (2) the use of recent molecular simulation data for the radial distribution function of hard-chain fluids, and (3) a newly developed effective segment size, which effectively accounts for the soft repulsion between segments of LJ chains. It is shown that the effective segment size needs to be temperature-, density-, and chain-length dependent. To obtain a simplified analytical EoS, the perturbation terms are fitted by polynomials in density (SW and LJ), chain length (SW and LJ), and temperature (only for LJ). It is shown that the equations of state result in an accurate description of molecular simulation data for vapor-liquid equilibria (VLE) and isotherms of fully flexible SW- and LJ chain fluids and their mixtures. To evaluate the performance of the equations of state in describing the effects of molecular flexibility on VLE, we present new Monte Carlo simulation results for the VLE of rigid linear- and partially flexible SW- and LJ chain fluids. For SW chains, the developed EoS is in a good agreement with simulation results. For increased rigidity of the chains, both theory and simulations predict an increase of the VL density difference and a slight increase of the VL critical temperature. For LJ chains, the EoS proves incapable of reproducing part of these trends.

  9. Molecular Dynamics Simulation of the Clustering of Minor Lead Additives in Liquid Sodium

    Directory of Open Access Journals (Sweden)

    Alexander L. Shimkevich

    2011-01-01

    Full Text Available A strong influence of minor lead additives on the liquid sodium microstructure is revealed in the molecular dynamics (MD simulation of the Na0.98Pb0.02 alloy. The obtained results can be explained by the existence of lead-sodium clusters in liquid sodium built up by ionic bonds, Na+–Pb−, due to essential distinction of the alloy components in the electronegativity. On this reason, MD simulation of the Na0.98Pb0.02 alloy is carried out within the framework of a three-component bipolar model, Na + Na+ + Pb−, with Na↔Na+ recharging the nearest-neighbor particles of solvent in every 3 ps (an optimal period during the numerical run.

  10. Ab initio molecular dynamics simulation of liquid water by quantum Monte Carlo

    Energy Technology Data Exchange (ETDEWEB)

    Zen, Andrea, E-mail: a.zen@ucl.ac.uk [Dipartimento di Fisica, “La Sapienza” - Università di Roma, piazzale Aldo Moro 5, 00185 Rome (Italy); London Centre for Nanotechnology, University College London, London WC1E 6BT (United Kingdom); Luo, Ye, E-mail: xw111luoye@gmail.com; Mazzola, Guglielmo, E-mail: gmazzola@phys.ethz.ch; Sorella, Sandro, E-mail: sorella@sissa.it [SISSA–International School for Advanced Studies, Via Bonomea 26, 34136 Trieste (Italy); Democritos Simulation Center CNR–IOM Istituto Officina dei Materiali, 34151 Trieste (Italy); Guidoni, Leonardo, E-mail: leonardo.guidoni@univaq.it [Dipartimento di Fisica, “La Sapienza” - Università di Roma, piazzale Aldo Moro 5, 00185 Rome (Italy); Dipartimento di Scienze Fisiche e Chimiche, Università degli Studi dell’ Aquila, via Vetoio, 67100 L’ Aquila (Italy)

    2015-04-14

    Although liquid water is ubiquitous in chemical reactions at roots of life and climate on the earth, the prediction of its properties by high-level ab initio molecular dynamics simulations still represents a formidable task for quantum chemistry. In this article, we present a room temperature simulation of liquid water based on the potential energy surface obtained by a many-body wave function through quantum Monte Carlo (QMC) methods. The simulated properties are in good agreement with recent neutron scattering and X-ray experiments, particularly concerning the position of the oxygen-oxygen peak in the radial distribution function, at variance of previous density functional theory attempts. Given the excellent performances of QMC on large scale supercomputers, this work opens new perspectives for predictive and reliable ab initio simulations of complex chemical systems.

  11. Liquid but Durable: Molecular Dynamics Simulations Explain the Unique Properties of Archaeal-Like Membranes

    Science.gov (United States)

    Chugunov, Anton O.; Volynsky, Pavel E.; Krylov, Nikolay A.; Boldyrev, Ivan A.; Efremov, Roman G.

    2014-12-01

    Archaeal plasma membranes appear to be extremely durable and almost impermeable to water and ions, in contrast to the membranes of Bacteria and Eucaryota. Additionally, they remain liquid within a temperature range of 0-100°C. These are the properties that have most likely determined the evolutionary fate of Archaea, and it may be possible for bionanotechnology to adopt these from nature. In this work, we use molecular dynamics simulations to assess at the atomistic level the structure and dynamics of a series of model archaeal membranes with lipids that have tetraether chemical nature and ``branched'' hydrophobic tails. We conclude that the branched structure defines dense packing and low water permeability of archaeal-like membranes, while at the same time ensuring a liquid-crystalline state, which is vital for living cells. This makes tetraether lipid systems promising in bionanotechnology and material science, namely for design of new and unique membrane nanosystems.

  12. Ab-initio molecular dynamics simulation of liquid water by Quantum Monte Carlo

    CERN Document Server

    Zen, Andrea; Mazzola, Guglielmo; Guidoni, Leonardo; Sorella, Sandro

    2014-01-01

    Despite liquid water is ubiquitous in chemical reactions at roots of life and climate on earth, the prediction of its properties by high-level ab initio molecular dynamics simulations still represents a formidable task for quantum chemistry. In this article we present a room temperature simulation of liquid water based on the potential energy surface obtained by a many-body wave function through quantum Monte Carlo (QMC) methods. The simulated properties are in excellent agreement with recent neutron scattering and X-ray experiments, particularly concerning the position of the oxygen-oxygen peak in the radial distribution function, at variance of previous Density Functional Theory attempts. Given the excellent performances of QMC on large scale supercomputers, this work opens new perspectives for predictive and reliable ab-initio simulations of complex chemical systems.

  13. Direct evidence of the molecular interaction propagation in the phase transition of liquid crystals

    Science.gov (United States)

    Katayama, Kenji; Sato, Takahiro; Kuwahara, Shota

    2016-09-01

    The molecular interaction sometimes propagates in a collective manner, reaching for a long distance on the order of millimeters. Such interactions have been well known in the field of strongly-correlated electron systems in a beautiful crystal interleaved by donor and acceptor layers, induced by photo-stimulus. The other examples can be found in liquid crystals (LCs), which could be found in many places in nature such as bio-membrane. Different from crystals, LCs features "softness", which enables it to be a curved structure such as a cell. In LCs, even a small molecular change would trigger the overall structural change by the propagation of the molecular interaction. Here we will show, for the first time, how long and how fast the molecular interaction propagates in LCs. The patterned phase transition was induced in a LC, causing the phase transition propagation in a controlled way and the propagation was measured with an time-resolved optical technique, called the transient grating. A LC sample doped with azobenzene was put into a thermally controlled LC cell. A grating pattern of a pulse light with 355 nm was impinged to the LC cell, and the light was absorbed by the dyes, releasing heat or photomechanical motion. We could observe the fringe spacing dependence on the phase transition response, which indicates that phase transition was delayed as the fringe spacing due to the delay by the phase transition propagation. This is the first direct evidence of the molecular interaction propagation of the LC molecules.

  14. Aqueous interfaces with hydrophobic room-temperature ionic liquids: a molecular dynamics study.

    Science.gov (United States)

    Chaumont, A; Schurhammer, R; Wipff, G

    2005-10-13

    We report a molecular dynamics study of the interface between water and (macroscopically) water-immiscible room-temperature ionic liquids "ILs", composed of PF6(-) anions and butyl- versus octyl-substituted methylimidazolium+ cations (noted BMI+ and OMI+). Because the parameters used to simulate the pure ILs were found to exaggerate the water/IL mixing, they have been modified by scaling down the atomic charges, leading to better agreement with the experiment. The comparison of [OMI][PF6] versus [BMI][PF6] ILs demonstrates the importance of the N-alkyl substituent on the extent of solvent mixing and on the nature of the interface. With the most hydrophobic [OMI][PF6] liquid, the "bulk" IL phase is dryer than with the [BMI][PF6] liquid. At the interface, the OMI+ cations retain direct contacts with the bulk IL, whereas the more hydrophilic PF6(-) anions gradually dilute in the local water micro-environment and are thus isolated from the "bulk" IL. The interfacial OMI+ cations are ordered with their imidazolium moiety pointing toward the aqueous side and their octyl chains toward the IL side of the interface. With the [BMI][PF6] liquid, the system gradually evolves from an IL-rich to a water-rich medium, leading to an ill-defined interfacial domain with high intersolvent mixing. As a result, the BMI+ cations are isotropically oriented "at the interface". Because the imidazolium cations are more hydrophobic than the PF6(-) anions, the charge distribution at the interface is heterogeneous, leading to a positive electrostatic potential at the interface with the two studied ILs. Mixing-demixing simulations on [BMI][PF6]/water mixtures are also reported, comparing Ewald versus reaction field treatments of electrostatics. Phase separation is very slow (at least 30 ns), in marked contrast with mixtures involving classical organic liquids, which separate in less than 0.5 ns at the microscopic level. The results allow us to better understand the specificity of the aqueous

  15. Crystalline and liquid Si3 N4 characterization by first-principles molecular dynamics simulations

    Directory of Open Access Journals (Sweden)

    Castellani Niccoló

    2011-05-01

    Full Text Available Silicon nitride (Si3 N4 has a wide range of engineering applications where its mechanical and electronic properties can be effectively exploited. In particular, in the microelectronics field, the amorphous silicon nitride films are widely used as charge storage layer in metal-alumina-nitrideoxide nonvolatile memory devices. Atomic structure of amorphous silicon nitride is characterized by an high concentration of traps that control the electric behavior of the final device by the trappingde-trapping mechanism of the electrical charge occurring in its traps. In order to have a deep understanding of the material properties and, in particular, the nature of the electrical active traps a detailed numerical characterization of the crystalline and liquid phases is mandatory. For these reasons first-principles molecular dynamics simulations are extensively employed to simulate the crystalline Si3 N4 in its crystalline and liquid phases. Good agreement with experimental results is obtained in terms of density and formation entalpy. Detailed characterization of c-Si3 N4 electronic properties is performed in terms of band structure and band gap. Then constant temperature and constant volume first-principles molecular dynamics is used to disorder a stoichiometric sample of Si3 N4 . Extensive molecular dynamics simulations are performed to obtain a reliable liquid sample whose atomic structure does not depend on the starting atomic configuration. Detailed characterization of the atomic structure is achieved in terms of radial distribution functions and total structure factor.

  16. The structure of PX{sub 3} (X = Cl, Br, I) molecular liquids from X-ray diffraction, molecular dynamics simulations, and reverse Monte Carlo modeling

    Energy Technology Data Exchange (ETDEWEB)

    Pothoczki, Szilvia, E-mail: pothoczki.szilvia@wigner.mta.hu; Temleitner, László; Pusztai, László [Institute for Solid State Physics and Optics, Wigner Research Centre for Physics, Hungarian Academy of Sciences, Konkoly-Thege M. út 29-33, 1121 Budapest (Hungary)

    2014-02-07

    Synchrotron X-ray diffraction measurements have been conducted on liquid phosphorus trichloride, tribromide, and triiodide. Molecular Dynamics simulations for these molecular liquids were performed with a dual purpose: (1) to establish whether existing intermolecular potential functions can provide a picture that is consistent with diffraction data and (2) to generate reliable starting configurations for subsequent Reverse Monte Carlo modelling. Structural models (i.e., sets of coordinates of thousands of atoms) that were fully consistent with experimental diffraction information, within errors, have been prepared by means of the Reverse Monte Carlo method. Comparison with reference systems, generated by hard sphere-like Monte Carlo simulations, was also carried out to demonstrate the extent to which simple space filling effects determine the structure of the liquids (and thus, also estimating the information content of measured data). Total scattering structure factors, partial radial distribution functions and orientational correlations as a function of distances between the molecular centres have been calculated from the models. In general, more or less antiparallel arrangements of the primary molecular axes that are found to be the most favourable orientation of two neighbouring molecules. In liquid PBr{sub 3} electrostatic interactions seem to play a more important role in determining intermolecular correlations than in the other two liquids; molecular arrangements in both PCl{sub 3} and PI{sub 3} are largely driven by steric effects.

  17. Heat conduction in chain polymer liquids: molecular dynamics study on the contributions of inter- and intramolecular energy transfer.

    Science.gov (United States)

    Ohara, Taku; Yuan, Tan Chia; Torii, Daichi; Kikugawa, Gota; Kosugi, Naohiro

    2011-07-21

    In this paper, the molecular mechanisms which determine the thermal conductivity of long chain polymer liquids are discussed, based on the results observed in molecular dynamics simulations. Linear n-alkanes, which are typical polymer molecules, were chosen as the target of our studies. Non-equilibrium molecular dynamics simulations of bulk liquid n-alkanes under a constant temperature gradient were performed. Saturated liquids of n-alkanes with six different chain lengths were examined at the same reduced temperature (0.7T(c)), and the contributions of inter- and intramolecular energy transfer to heat conduction flux, which were identified as components of heat flux by the authors' previous study [J. Chem. Phys. 128, 044504 (2008)], were observed. The present study compared n-alkane liquids with various molecular lengths at the same reduced temperature and corresponding saturated densities, and found that the contribution of intramolecular energy transfer to the total heat flux, relative to that of intermolecular energy transfer, increased with the molecular length. The study revealed that in long chain polymer liquids, thermal energy is mainly transferred in the space along the stiff intramolecular bonds. This finding implies a connection between anisotropic thermal conductivity and the orientation of molecules in various organized structures with long polymer molecules aligned in a certain direction, which includes confined polymer liquids and self-organized structures such as membranes of amphiphilic molecules in water.

  18. Transport coefficients of normal liquid helium-4 calculated by path integral centroid molecular dynamics simulation

    Science.gov (United States)

    Imaoka, Haruna; Kinugawa, Kenichi

    2017-03-01

    Thermal conductivity, shear viscosity, and bulk viscosity of normal liquid 4He at 1.7-4.0 K are calculated using path integral centroid molecular dynamics (CMD) simulations. The calculated thermal conductivity and shear viscosity above lambda transition temperature are on the same order of magnitude as experimental values, while the agreement of shear viscosity is better. Above 2.3 K the CMD well reproduces the temperature dependences of isochoric shear viscosity and of the time integral of the energy current and off-diagonal stress tensor correlation functions. The calculated bulk viscosity, not known in experiments, is several times larger than shear viscosity.

  19. Molecular dynamics of liquid SiO2 under high pressure

    Science.gov (United States)

    Rustad, James R.; Yuen, David A.; Spera, Frank J.

    1990-01-01

    The molecular dynamics of pure SiO2 liquids was investigated up to pressures of 20 GPa at 4000 K using 252, 498, 864, and 1371 particles. The results obtained suggest that the pressure-induced maxima in the self-diffusion coefficients of both oxygen and silicon are dependent on the system size. In the case of larger systems, the maximum decreases and shifts to lower pressures. Changes in the velocity autocorrelation function with increasing pressure are described. The populations of anomalously coordinated silicon and oxygen are then discussed as a function of pressure and system size.

  20. Measurement and Correlation of the Ionic Conductivity of Ionic Liquid-Molecular Solvent Solutions

    Institute of Scientific and Technical Information of China (English)

    LI,Wen-Jing; HAN,Bu-Xing; TAO,Ran-Ting; ZHANG,Zhao-Fu; ZHANG,Jian-Ling

    2007-01-01

    The ionic conductivity of the solutions formed from 1-n-butyl-3-methylimidazolium tetrafluoroborate ([Bmim][BF4]) or 1-n-butyl-3-methylimidazolium hexafluorophosphate ([Bmim][PF6]) and different molecular solvents (MSs) were measured at 298.15 K. The molar conductivity of the ionic liquids (ILs) increased dramatically with increasing concentration of the MSs. It was found that the molar conductivity of the IL in the solutions studied in this work could be well correlated by the molar conductivity of the neat ILs and the dielectric constant and molar volume of the MSs.

  1. Rotational viscosity of a liquid crystal mixture:a fully atomistic molecular dynamics study

    Institute of Scientific and Technical Information of China (English)

    Zhang Ran; Peng Zeng-Hui; Liu Yong-Gang; Zheng Zhi-Gang; Xuan Li

    2009-01-01

    Fully atomistic molecular dynamics(MD)simulations at 293, 303 and 313 K have been performed for the four. component liquid crystal mixture, E7, using the software package Material Studio. Order parameters and orientational time correlation functions(TCFs)were calculated from MD trajectories. The rotational viscosity coefficients(RVCs)of the mixture were ca]culated using the Nemtsov-Zakharov and Fialkowski methods based on statistical-mechanical approaches. Temperature dependences of RVC and density were discussed in detall. Reasonable agreement between the simulated and experimental values was found.

  2. Static and dynamic properties of curved vapour-liquid interfaces by massively parallel molecular dynamics simulation

    CERN Document Server

    Horsch, Martin T; Vrabec, Jadran; Glass, Colin W; Niethammer, Christoph; Bernreuther, Martin F; Müller, Erich A; Jackson, George

    2011-01-01

    Curved fluid interfaces are investigated on the nanometre length scale by molecular dynamics simulation. Thereby, droplets surrounded by a metastable vapour phase are stabilized in the canonical ensemble. Analogous simulations are conducted for cylindrical menisci separating vapour and liquid phases under confinement in planar nanopores. Regarding the emergence of nanodroplets during nucleation, a non-equilibrium phenomenon, both the non-steady dynamics of condensation processes and stationary quantities related to supersaturated vapours are considered. Results for the truncated and shifted Lennard-Jones fluid and for mixtures of quadrupolar fluids confirm the applicability of the capillarity approximation and the classical nucleation theory.

  3. Rupture mechanism of liquid crystal thin films realized by large-scale molecular simulations

    Science.gov (United States)

    Nguyen, Trung Dac; Carrillo, Jan-Michael Y.; Matheson, Michael A.; Brown, W. Michael

    2014-02-01

    The ability of liquid crystal (LC) molecules to respond to changes in their environment makes them an interesting candidate for thin film applications, particularly in bio-sensing, bio-mimicking devices, and optics. Yet the understanding of the (in)stability of this family of thin films has been limited by the inherent challenges encountered by experiment and continuum models. Using unprecedented large-scale molecular dynamics (MD) simulations, we address the rupture origin of LC thin films wetting a solid substrate at length scales similar to those in experiment. Our simulations show the key signatures of spinodal instability in isotropic and nematic films on top of thermal nucleation, and importantly, for the first time, evidence of a common rupture mechanism independent of initial thickness and LC orientational ordering. We further demonstrate that the primary driving force for rupture is closely related to the tendency of the LC mesogens to recover their local environment in the bulk state. Our study not only provides new insights into the rupture mechanism of liquid crystal films, but also sets the stage for future investigations of thin film systems using peta-scale molecular dynamics simulations.The ability of liquid crystal (LC) molecules to respond to changes in their environment makes them an interesting candidate for thin film applications, particularly in bio-sensing, bio-mimicking devices, and optics. Yet the understanding of the (in)stability of this family of thin films has been limited by the inherent challenges encountered by experiment and continuum models. Using unprecedented large-scale molecular dynamics (MD) simulations, we address the rupture origin of LC thin films wetting a solid substrate at length scales similar to those in experiment. Our simulations show the key signatures of spinodal instability in isotropic and nematic films on top of thermal nucleation, and importantly, for the first time, evidence of a common rupture mechanism

  4. Molecular dynamics of liquid SiO2 under high pressure

    Science.gov (United States)

    Rustad, James R.; Yuen, David A.; Spera, Frank J.

    1990-01-01

    The molecular dynamics of pure SiO2 liquids was investigated up to pressures of 20 GPa at 4000 K using 252, 498, 864, and 1371 particles. The results obtained suggest that the pressure-induced maxima in the self-diffusion coefficients of both oxygen and silicon are dependent on the system size. In the case of larger systems, the maximum decreases and shifts to lower pressures. Changes in the velocity autocorrelation function with increasing pressure are described. The populations of anomalously coordinated silicon and oxygen are then discussed as a function of pressure and system size.

  5. Liquid-Phase Exfoliation of Phosphorene: Design Rules from Molecular Dynamics Simulations.

    Science.gov (United States)

    Sresht, Vishnu; Pádua, Agílio A H; Blankschtein, Daniel

    2015-08-25

    The liquid-phase exfoliation of phosphorene, the two-dimensional derivative of black phosphorus, in the solvents dimethyl sulfoxide (DMSO), dimethylformamide (DMF), isopropyl alcohol, N-methyl-2-pyrrolidone, and N-cyclohexyl-2-pyrrolidone is investigated using three molecular-scale "computer experiments". We modeled solvent-phosphorene interactions using an atomistic force field, based on ab initio calculations and lattice dynamics, that accurately reproduces experimental mechanical properties. We probed solvent molecule ordering at phosphorene/solvent interfaces and discovered that planar molecules such as N-methyl-2-pyrrolidone preferentially orient parallel to the interface. We subsequently measured the energy required to peel a single phosphorene monolayer from a stack of black phosphorus and analyzed the role of "wedges" of solvent molecules intercalating between phosphorene sheets in initiating exfoliation. The exfoliation efficacy of a solvent is enhanced when either molecular planarity "sharpens" this molecular wedge or strong phosphorene-solvent adhesion stabilizes the newly exposed phosphorene surfaces. Finally, we examined the colloidal stability of exfoliated flakes by simulating their aggregation and showed that dispersion is favored when the cohesive energy between the molecules in the solvent monolayer confined between the phosphorene sheets is high (as with DMSO) and is hindered when the adhesion between these molecules and phosphorene is strong; the molecular planarity in solvents like DMF enhances the cohesive energy. Our results are consistent with, and provide a molecular context for, experimental exfoliation studies of phosphorene and other layered solids, and our molecular insights into the significant role of solvent molecular geometry and ordering should complement prevalent solubility-parameter-based approaches in establishing design rules for effective nanomaterial exfoliation media.

  6. Discotic columnar liquid crystal studied in the bulk and nanoconfined states by molecular dynamics simulation.

    Science.gov (United States)

    Busselez, Rémi; Cerclier, Carole V; Ndao, Makha; Ghoufi, Aziz; Lefort, Ronan; Morineau, Denis

    2014-10-07

    A prototypical Gay Berne discotic liquid crystal was studied by means of molecular dynamics simulations both in the bulk state and under confinement in a nanoporous channel. The phase behavior of the confined system strongly differs from its bulk counterpart: the bulk isotropic-to-columnar transition is replaced by a continuous ordering from a paranematic to a columnar phase. Moreover, a new transition is observed at a lower temperature in the confined state, which corresponds to a reorganization of the intercolumnar order. It reflects the competing effects of pore surface interaction and genuine hexagonal packing of the columns. The translational molecular dynamics in the different phases has been thoroughly studied and discussed in terms of collective relaxation modes, non-Gaussian behavior, and hopping processes.

  7. Comparison of path integral molecular dynamics methods for the infrared absorption spectrum of liquid water

    Science.gov (United States)

    Habershon, Scott; Fanourgakis, George S.; Manolopoulos, David E.

    2008-08-01

    The ring polymer molecular dynamics (RPMD) and partially adiabatic centroid molecular dynamics (PA-CMD) methods are compared and contrasted in an application to the infrared absorption spectrum of a recently parametrized flexible, polarizable, Thole-type potential energy model for liquid water. Both methods predict very similar spectra in the low-frequency librational and intramolecular bending region at wavenumbers below 2500 cm-1. However, the RPMD spectrum is contaminated in the high-frequency O-H stretching region by contributions from the internal vibrational modes of the ring polymer. This problem is avoided in the PA-CMD method, which adjusts the elements of the Parrinello-Rahman mass matrix so as to shift the frequencies of these vibrational modes beyond the spectral range of interest. PA-CMD does not require any more computational effort than RPMD and it is clearly the better of the two methods for simulating vibrational spectra.

  8. Molecular field theory for nematic liquid crystal film with finite layers

    Institute of Scientific and Technical Information of China (English)

    Zhang Zhi-Dong; Li Jing; Wei Huai-Peng

    2005-01-01

    The nematic liquid crystal film composed of n molecular layers is studied based upon a spatially anisotropic pair potential, which reproduces approximately the elastic free energy density. On condition that the system has perfect nematic order, as in the Lebwohl-Lasher model, the director in the film is isotropic. The effect of the temperature is investigated by means of molecular field theory. Some new results are obtained. Firstly, symmetry breaking takes place when taking account of the temperature, and the state with the director along the normal of the film has the lowest free energy. Secondly, the N-I phase transition temperature increases as an effect of finite sizes instead of decreasing as in the Lebwohl-Lasher model. Thirdly, the nematic order is induced in the layers near the surface in the isotropic phase.

  9. First-principles molecular dynamics simulations at solid-liquid interfaces with a continuum solvent

    CERN Document Server

    Sanchez, Veronica M; Scherlis, Damian A

    2009-01-01

    Continuum solvent models have become a standard technique in the context of electronic structure calculations, yet, no implementations have been reported capable to perform molecular dynamics at solid-liquid interfaces. We propose here such a continuum approach in a DFT framework, using plane-waves basis sets and periodic boundary conditions. Our work stems from a recent model designed for Car-Parrinello simulations of quantum solutes in a dielectric medium [J. Chem. Phys. 124, 74103 (2006)], for which the permittivity of the solvent is defined as a function of the electronic density of the solute. This strategy turns out to be inadequate for systems extended in two dimensions, by introducing new term in the Kohn-Sham potential which becomes unphysically large at the interfacial region, seriously affecting the convergence. If the dielectric medium is properly redefined as a function of the atomic coordinates, a good convergence is obtained and the constant of motion is conserved during the molecular dynamics ...

  10. Molecular dynamics simulation study on behaviors of liquid 1,2-dichioroethane under external electric fields

    Institute of Scientific and Technical Information of China (English)

    杜志强; 陈正隆

    2003-01-01

    Molecular dynamics simulation was carried out to study the behavior of liquid 1,2-dichloroethane molecules under external electric fields including direct current field, alternating current field and positive-half-period cosin field. The maximum applied field strength was 108 V/m , the maximum frequency of the alternating current field and that of the positive-half-period cosine field was 1012 Hz . The simulation revealed that the field type and field strength act on the population of the molecular configuration. In the strong direct current field, all trans forms converted completely into gauche forms. Order parameter and the correlation of the system torsion angle were also investigated. The results suggested that these two dynamical parameters depended also on the field type and the field strength. The maximum of order parameter was found to be at 0.6in the strong direct current field.

  11. Molecular dynamics simulation study on behaviors of liquid 1,2-dichloroethane under external electric fields

    Institute of Scientific and Technical Information of China (English)

    杜志强; 陈正隆

    2003-01-01

    Molecular dynamics simulation was carried out to study the behavior of liquid 1,2-dichloroethane molecules under external electric fields including direct current field, alternating current field and positive-half-period cosin field. The maximum applied field strength was 108 V/m , the maximum frequency of the alternating current field and that of the positive-half-period cosine field was 1012 Hz .The simulation revealed that the field type and field strength act on the population of the molecular configuration. In the strong direct current field, all trans forms converted completely into gauche forms. Order parameter and the correlation of the system torsion angle were also investigated. The results suggested that these two dynamical parameters depended also on the field type and the field strength. The maximum of order parameter was found to be at 0.6 in the strong direct current field.

  12. Nanoscopic spontaneous motion of liquid trains: non-equilibrium molecular dynamics simulation

    CERN Document Server

    Bahrami, Amir Houshang

    2009-01-01

    Macroscale experiments show that a train of two immiscible liquid drops, a bislug, can spontaneously move in a capillary tube because of surface tension asymmetries. We use molecular dynamics simulation of Lennard-Jones fluids to demonstrate this phenomenon for NVT ensembles in sub-micron tubes. We deliberately tune the strength of intermolecular forces and control the velocity of bislug in different wetting and viscosity conditions. We compute the velocity profile of particles across the tube, and explain the origin of deviations from the classical parabolae. We show that the self-generated molecular flow resembles the Poiseuille law when the ratio of the tube radius to its length is less than a critical value.

  13. Molecular thermodynamic modeling of ionic liquids using the perturbation-based linear Yukawa isotherm regularity

    Science.gov (United States)

    Sohrabi Mahboub, Mahdi; Farrokhpour, Hossein

    2016-06-01

    In this paper, we present the results of an extensive study on a novel approach to the molecular modeling of pure ionic liquids (ILs) that incorporates the perturbed thermodynamic linear Yukawa isotherm regularity (LYIR), which is derived based on an effective nearest neighboring pair attractive interaction of the Yukawa potential. The LYIR was used to model the densities of ILs up to high pressures (35 MPa) and in the temperature range 293.15 to 393.15 K. To use the LYIR for ILs, a simple molecular model was proposed to describe their molecular structure, in which they were considered as a liquid consisting of the ion pairs moving together in the fluid, and each ion pair was assumed to be a one-center spherical united atom. The ILs under consideration contained one of the IL cations [C2mim]+, [C4mim]+, [C7mim]+, [C8mim]+, [C3mpy]+, [C3mpip]+, [C3mpyr]+ or [C4mpyr]+, and one of the IL anions [BF4]-, [C(CN)3]-, [CF3SO4]- or [NTf2]-. The reliability and physical significance of the parameters as well as the proposed molecular model were tested by calculating the densities of pure imidazolium-, pyridinium-, piperidinium- and pyrrolidimium-based ILs. The results showed that the LYIR can be used to predict and reproduce the density of ILs in good agreement with the experimental data. In addition, the LYIR enabled us to determine the physical quantities, such as an effective Yukawa screening length, λ eff, the product of the effective energy well depth and the effective coordination number, (ɛ eff/k)z eff, the contribution of the non-reference thermal pressure and also the influence of the anionic and cationic structure on the λ eff parameter. The standard deviation of the IL densities predicted in this work is lower than those calculated by the one other important equation of state reported in the literature.

  14. Designing molecular complexes using free-energy derivatives from liquid-state integral equation theory

    Science.gov (United States)

    Mrugalla, Florian; Kast, Stefan M.

    2016-09-01

    Complex formation between molecules in solution is the key process by which molecular interactions are translated into functional systems. These processes are governed by the binding or free energy of association which depends on both direct molecular interactions and the solvation contribution. A design goal frequently addressed in pharmaceutical sciences is the optimization of chemical properties of the complex partners in the sense of minimizing their binding free energy with respect to a change in chemical structure. Here, we demonstrate that liquid-state theory in the form of the solute-solute equation of the reference interaction site model provides all necessary information for such a task with high efficiency. In particular, computing derivatives of the potential of mean force (PMF), which defines the free-energy surface of complex formation, with respect to potential parameters can be viewed as a means to define a direction in chemical space toward better binders. We illustrate the methodology in the benchmark case of alkali ion binding to the crown ether 18-crown-6 in aqueous solution. In order to examine the validity of the underlying solute-solute theory, we first compare PMFs computed by different approaches, including explicit free-energy molecular dynamics simulations as a reference. Predictions of an optimally binding ion radius based on free-energy derivatives are then shown to yield consistent results for different ion parameter sets and to compare well with earlier, orders-of-magnitude more costly explicit simulation results. This proof-of-principle study, therefore, demonstrates the potential of liquid-state theory for molecular design problems.

  15. Designing molecular complexes using free-energy derivatives from liquid-state integral equation theory.

    Science.gov (United States)

    Mrugalla, Florian; Kast, Stefan M

    2016-09-01

    Complex formation between molecules in solution is the key process by which molecular interactions are translated into functional systems. These processes are governed by the binding or free energy of association which depends on both direct molecular interactions and the solvation contribution. A design goal frequently addressed in pharmaceutical sciences is the optimization of chemical properties of the complex partners in the sense of minimizing their binding free energy with respect to a change in chemical structure. Here, we demonstrate that liquid-state theory in the form of the solute-solute equation of the reference interaction site model provides all necessary information for such a task with high efficiency. In particular, computing derivatives of the potential of mean force (PMF), which defines the free-energy surface of complex formation, with respect to potential parameters can be viewed as a means to define a direction in chemical space toward better binders. We illustrate the methodology in the benchmark case of alkali ion binding to the crown ether 18-crown-6 in aqueous solution. In order to examine the validity of the underlying solute-solute theory, we first compare PMFs computed by different approaches, including explicit free-energy molecular dynamics simulations as a reference. Predictions of an optimally binding ion radius based on free-energy derivatives are then shown to yield consistent results for different ion parameter sets and to compare well with earlier, orders-of-magnitude more costly explicit simulation results. This proof-of-principle study, therefore, demonstrates the potential of liquid-state theory for molecular design problems.

  16. A comparative study of ibuprofen and ketoprofen glass-forming liquids by molecular dynamics simulations

    Science.gov (United States)

    Ottou Abe, M. T.; Correia, N. T.; Ndjaka, J. M. B.; Affouard, F.

    2015-10-01

    In this paper, structural and dynamical properties of ibuprofen and ketoprofen glass-forming liquids have been investigated by means of molecular dynamics simulations. Molecular mobility of both materials is analyzed with respect to the different inter-molecular linear/cyclic hydrogen bonding associations. For ibuprofen, the dominant organization is found to be composed of small hydrogen bonding aggregates corresponding to cyclic dimers through the carboxyl group. For ketoprofen, the propensity of cyclic dimers is significantly reduced by the formation of hydrogen bonds with the ketone oxygen of the molecule altering the hydrogen bond (HB) associating structures that can be formed and thus molecular dynamics. The issue of the presence/absence of the peculiar low frequency Debye-type process in dielectric relaxation spectroscopy (DRS) data in these materials is addressed. Results obtained from simulations confirm that the Debye process originates from the internal cis-trans conversion of the —COOH carboxyl group. It is shown that the specific intermolecular HB structures associated to a given profen control the main dynamical features of this conversion, in particular its separation from the α-process, which make it detectable or not from DRS. For ibuprofen, the possible role of the —CCCO torsion motion, more "local" than the —COOH motion since it is less influenced by the intermolecular HBs, is suggested in the microscopic origin of the quite intense secondary γ-relaxation process detected from DRS.

  17. Glass-Forming Tendency of Molecular Liquids and the Strength of the Intermolecular Attractions

    Science.gov (United States)

    Koperwas, Kajetan; Adrjanowicz, Karolina; Wojnarowska, Zaneta; Jedrzejowska, Agnieszka; Knapik, Justyna; Paluch, Marian

    2016-11-01

    When we cool down a liquid below the melting temperature, it can either crystallize or become supercooled, and then form a disordered solid called glass. Understanding what makes a liquid to crystallize readily in one case and form a stable glass in another is a fundamental problem in science and technology. Here we show that the crystallization/glass-forming tendencies of the molecular liquids might be correlated with the strength of the intermolecular attractions, as determined from the combined experimental and computer simulation studies. We use van der Waals bonded propylene carbonate and its less polar structural analog 3-methyl-cyclopentanone to show that the enhancement of the dipole-dipole forces brings about the better glass-forming ability of the sample when cooling from the melt. Our finding was rationalized by the mismatch between the optimal temperature range for the nucleation and crystal growth, as obtained for a modeled Lennard-Jones system with explicitly enhanced or weakened attractive part of the intermolecular 6-12 potential.

  18. Ab initio molecular dynamics study of collective dynamics in liquid Tl: Thermo-viscoelastic analysis

    Science.gov (United States)

    Bryk, Taras; Demchuk, Taras

    2017-08-01

    We studied collective dynamics of pure liquid metal Tl using a combination of ab initio molecular dynamics (AIMD) simulations and a thermoviscoelastic model applied to calculations of dynamic eigenmodes and dispersion of collective excitations in particular. We found that for liquid Tl at ambient pressure the transverse current spectral functions obtained directly in ab initio simulations for wave numbers larger than first pseudo-Brillouin-zone boundary contain two low-and high-frequency peaks that is an evidence of emergence of the unusually high-frequency transverse modes as it was observed before in liquid Li at very high pressures. The thermo-viscoelastic dynamic model shows perfect reproduction of the simulation-derived longitudinal current autocorrelation functions, and the acoustic eigenmodes are in nice agreement with the peaks of the longitudinal current spectral functions up to the first pseudo-Brillouin-zone boundary. The deviation of the dynamic eigenmodes from peak positions at higher wave numbers gives evidence of L-T coupling effects.

  19. Liquid Crystal Phases of Molecular Bananas: Polarity and Chirality as Broken Symmetries

    Science.gov (United States)

    Clark, Noel

    2006-03-01

    The study of the interplay of chirality and polarity has been a particularly rich theme of soft matter science since Meyer's seminal discovery that tilted smectics of chiral molecules are macroscopically polar. This event, and the subsequent realization of polar domains and high-speed electro-optic switching in chiral smectics, engaged the liquid crystal community in a worldwide pursuit of novel smectics for applications, featured by the synthesis of more than 50,000 new liquid crystal compounds, and by a consequent broad diversification of the palette of liquid crystal phases and possibilities for supermolecular ordering. A current important activity in this scenario is the study of polar order in synthetically achiral molecules, for example, in molecular bananas, which, as their shape suggests, might be expected to organize in a polar way. Indeed they do, but beyond this, almost everything learned about them has been surprising, including their persistent tendency to exhibit chirality as a spontaneously broken symmetry. I will discuss some of these new phases and phenomena, including the discovery of fluid conglomerates (Pasteur's experiment in a fluid), triclinic fluid order, chiral twist grain boundary phases of achiral molecules, chirality flipping and field-induced deracemization, ferroelectric and antiferroelectric phases with supermolecular- scale polarization modulation, and chiral thermotropic sponge phases.

  20. Molecular dynamics of supercooled ionic liquids studied by light scattering and dielectric spectroscopy

    Science.gov (United States)

    Pabst, Florian; Gabriel, Jan; Weigl, Peter; Blochowicz, Thomas

    2017-09-01

    We investigate molecular dynamics of two supercooled room temperature ionic liquids (RTILs) above of their glass transition temperature by means of dynamic light scattering and broadband dielectric spectroscopy from nanoseconds up to ≈105s . We show that a direct comparison of the raw data of these two techniques allows us to identify the reorientation of ions in the dielectric data, giving experimental evidence to a very recently proposed model of Gainaru et al. [1], stating that the conductivity process in ionic liquids takes place through a reorientational step of ions escaping their cage formed by surrounding counterions. Within this approach we can also understand the apparent decoupling of time constants from dielectric spectroscopy and light scattering, often found in ionic liquids, in a very natural way. Furthermore, as a consequence of knowing the reorientational part of the dielectric spectrum, we are able to show that two more processes contribute to these spectra, which are due to electrode polarization effects. The relative position of all three contributions vary among the systems and may overshadow each other, thus complicating the data analysis and favor misinterpretations.

  1. [BMIM][PF(6)] promotes the synthesis of halohydrin esters from diols using potassium halides.

    Science.gov (United States)

    Oromí-Farrús, Mireia; Eras, Jordi; Villorbina, Gemma; Torres, Mercè; Llopis-Mestre, Veronica; Welton, Tom; Canela, Ramon

    2008-10-01

    Haloesterification of diverse diols with various carboxylic acids was achieved using potassium halides (KX) as the only halide source in ionic liquids. The best yield was obtained in [BMIM][PF(6)] when 1,2-octanediol, palmitic acid and KBr were used. This yield was 85% and the regioisomer with the bromine in primary position was present in a 75:25 ratio. The regioisomeric ratio could be improved using either KCl or some phenylcarboxylic acids. [BMIM][PF(6)] acts as both reaction media and catalyst of the reaction. To the best of our knowledge, this type of combined reaction using an ionic liquid is unprecedented. The other solvents tested did not lead either to the same yield or to the same regioisomeric ratio.

  2. Structural and thermotropic peculiarities of hydrogen-bonded liquid crystals confined in mesoporous molecular sieves

    Science.gov (United States)

    Gnatyuk, I.; Gavrilko, T.; Yaroshchuk, O.; Holovina, N.; Shcherban, N.; Baran, J.; Drozd, M.

    2016-12-01

    The phase behaviour and structural organization of hydrogen-bonded liquid crystals were investigated under confinement to mesoporous molecular sieves. As such liquid crystalline compounds, 4-hexylbenzoic and 4-butylcyclohexanecarboxylic acids with different head group structure and alkyl chain length where selected and filled in the AlMCM-41 sieves. With FTIR spectroscopy it was found that some part of incorporated acid molecules, presumably located in the inner space of the AlMCM-41 pores, is in undissociated form of open dimers or chain associates and thus shows spectroscopic features characteristic to the bulk-like species. The other FTIR spectra components indicate strong interaction of the incorporated monomeric molecules with the pore surface. Two specific mechanisms are shown to be involved in molecular interactions at the interface: (1) deprotonation of monomeric acid molecules on the pore surface with formation of COO- carboxylate ions and (2) bonding of these ions to the pore surface by a coordinated bond R-COO-…Al+ with Lewis acid sites. Differential scanning calorimetry revealed that these near-surface processes lead to complete suppression of mesomorphic properties of the studied acids under confinement to nanopores.

  3. Field-dependent molecular ionization and excitation energies: Implications for electrically insulating liquids

    Directory of Open Access Journals (Sweden)

    N. Davari

    2014-03-01

    Full Text Available The molecular ionization potential has a relatively strong electric-field dependence as compared to the excitation energies which has implications for electrical insulation since the excited states work as an energy sink emitting light in the UV/VIS region. At some threshold field, all the excited states of the molecule have vanished and the molecule is a two-state system with the ground state and the ionized state, which has been hypothesized as a possible origin of different streamer propagation modes. Constrained density-functional theory is used to calculate the field-dependent ionization potential of different types of molecules relevant for electrically insulating liquids. The low singlet-singlet excitation energies of each molecule have also been calculated using time-dependent density functional theory. It is shown that low-energy singlet-singlet excitation of the type n → π* (lone pair to unoccupied π* orbital has the ability to survive at higher fields. This type of excitation can for example be found in esters, diketones and many color dyes. For alkanes (as for example n-tridecane and cyclohexane on the other hand, all the excited states, in particular the σ → σ* excitations vanish in electric fields higher than 10 MV/cm. Further implications for the design of electrically insulating dielectric liquids based on the molecular ionization potential and excitation energies are discussed.

  4. Influence of solid-liquid interactions on dynamic wetting: a molecular dynamics study

    Science.gov (United States)

    Bertrand, Emilie; Blake, Terence D.; De Coninck, Joël

    2009-11-01

    Large-scale molecular dynamics (MD) simulations of liquid drops spreading on a solid substrate have been carried out for a very wide range of solid-liquid interactions and equilibrium contact angles. The results for these systems are shown to be consistent with the molecular-kinetic theory (MKT) of dynamic wetting, which emphasizes the role of contact-line friction as the principal channel of energy dissipation. Several predictions have been confirmed. These include a quantitative link between the dynamics of wetting and the work of adhesion and the existence of an optimum equilibrium contact angle that maximizes the speed of wetting. A feature of the new work is that key parameters (κ0 and λ), normally accessible only by fitting the MKT to dynamic contact angle data, are also obtained directly from the simulations, with good agreement between the two sources. This validates the MKT at some fundamental level. Further verification is provided by contact angle relaxation studies, which also lend support to the interfacial tension relaxation process invoked in Shikhmurzaev's hydrodynamic model of dynamic wetting.

  5. Vortical flows in strongly coupled Yukawa liquids under external forcing - A molecular dynamics approach

    Science.gov (United States)

    Ganesh, Rajaraman; Charan, Harish

    2016-07-01

    Understanding vortical flows under external forcing in two dimensional (2D) fluids is a fundamental paradigm for structure formation in driven, dissipative systems. Considering Yukawa liquid as a prototype for strongly correlated or strongly coupled plasmas characterized by coupling strength (Γ, the ratio of average potential to kinetic energy per particle) and screening parameter (κ, ratio of mean inter-particle distance to shielding length), we address two important problems: 1. Onset of Rayleigh Benard convection cell (RBCC) in 2D Yukawa liquids subject to gravity and external temperature gradient 2. Onset of von Karman vortices in 2D Yukawa liquid under external pressure head, using large scale, first principles molecular dynamics simulations. For typical values of (Γ,κ), existence of a critical external temperature difference is demonstrated, beyond which RBCC are seen to set in. Beyond this critical external temperature difference, the strength of the maximum convective flow velocity is shown to exhibit a new, hitherto unsuspected linear relationship with external temperature difference and with a slope independent of (Γ,κ). The time taken for the transients to settle down to a steady state RBCC τ_s, is found to be maximum close to the above said critical external temperature difference and is seen to reduce with increasing external temperature difference. For the range of values of (Γ, κ) considered here, τ_s ≃ 10 000-20 000;ω^{-1}_{pd}, where ω_{pd} is dust plasma frequency. As Γ is increased to very high values, due to strong coupling effects, RBC cells are seen to be in a transient state without attaining a steady state for as long as 100 000;ω^{-1}_{pd}, even for a very high external temperature difference. In the second part, we address the existence of universal relation between Strouhal (St) and Rayleigh (Ry) numbers for Yukawa liquid using first principles based classical molecular dynamics. The flow past an obstacle is seen to indeed

  6. A perspective of mesoscopic solar cells based on metal chalcogenide quantum dots and organometal-halide perovskites

    National Research Council Canada - National Science Library

    Jae Hui Rhee; Chih-chun Chung; Eric Wei-guang Diau

    2013-01-01

    ...; only devices made of Sb2 S3 and PbS QDs attained cell efficiencies approaching ∼7%. In contrast, nanocrystalline lead halide perovskites have emerged since 2009 as potential photosensitizers in liquid-type sensitized TiO2 solar cells...

  7. Atomic Resolution Imaging of Halide Perovskites.

    Science.gov (United States)

    Yu, Yi; Zhang, Dandan; Kisielowski, Christian; Dou, Letian; Kornienko, Nikolay; Bekenstein, Yehonadav; Wong, Andrew B; Alivisatos, A Paul; Yang, Peidong

    2016-12-14

    The radiation-sensitive nature of halide perovskites has hindered structural studies at the atomic scale. We overcome this obstacle by applying low dose-rate in-line holography, which combines aberration-corrected high-resolution transmission electron microscopy with exit-wave reconstruction. This technique successfully yields the genuine atomic structure of ultrathin two-dimensional CsPbBr3 halide perovskites, and a quantitative structure determination was achieved atom column by atom column using the phase information of the reconstructed exit-wave function without causing electron beam-induced sample alterations. An extraordinarily high image quality enables an unambiguous structural analysis of coexisting high-temperature and low-temperature phases of CsPbBr3 in single particles. On a broader level, our approach offers unprecedented opportunities to better understand halide perovskites at the atomic level as well as other radiation-sensitive materials.

  8. Harmonic dynamical behaviour of thallous halides

    Indian Academy of Sciences (India)

    Sarvesh K Tiwari; L J Shukla; K S Upadhyaya

    2010-05-01

    Harmonic dynamical behaviour of thallous halides (TlCl and TlBr) have been studied using the new van der Waals three-body force shell model (VTSM), which incorporates the effects of the van der Waals interaction along with long-range Coulomb interactions, three-body interactions and short-range second neighbour interactions in the framework of rigid shell model (RSM). Phonon dispersion curves (PDC), variations of Debye temperature with absolute temperature and phonon density of state (PDS) curves have been reported for thallous halides using VTSM. Comparison of experimental values with those of VTSM and TSM are also reported in the paper and a good agreement between experimental and VTSM values has been found, from which it may be inferred that the incorporation of van der Waals interactions is essential for the complete harmonic dynamical behaviour of thallous halides.

  9. Molecular dynamics study to identify the reactive sites of a liquid squalane surface.

    Science.gov (United States)

    Köhler, Sven P K; Reed, Stewart K; Westacott, Robin E; McKendrick, Kenneth G

    2006-06-22

    Molecular dynamics simulations of liquid squalane, C30H62, were performed, focusing in particular on the liquid-vacuum interface. These theoretical studies were aimed at identifying potentially reactive sites on the surface, knowledge of which is important for a number of inelastic and reactive scattering experiments. A united atom force field (Martin, M. G.; Siepmann, J. I. J. Phys. Chem. B 1999, 103, 4508-4517) was used, and the simulations were analyzed with respect to their interfacial properties. A modest but clearly identifiable preference for methyl groups to protrude into the vacuum has been found at lower temperatures. This effect decreases when going to higher temperatures. Additional simulations tracking the flight paths of projectiles directed at a number of randomly chosen surfaces extracted from the molecular dynamics simulations were performed. The geometrical parameters for these calculations were chosen to imitate a typical abstraction reaction, such as the reaction between ground-state oxygen atoms and hydrocarbons. Despite the preference for methyl groups to protrude further into the vacuum, Monte Carlo tracking simulations suggest, on geometric grounds, that primary and secondary hydrogen atoms are roughly equally likely to react with incoming gas-phase atoms. These geometric simulations also indicate that a substantial fraction of the scattered products is likely to undergo at least one secondary collision with hydrocarbon side chains. These results help to interpret the outcome of previous measurements of the internal and external energy distribution of the gas-phase OH products of the interfacial reaction between oxygen atoms and liquid squalane.

  10. Atomistic simulation of solid-liquid coexistence for molecular systems: application to triazole and benzene.

    Science.gov (United States)

    Eike, David M; Maginn, Edward J

    2006-04-28

    A method recently developed to rigorously determine solid-liquid equilibrium using a free-energy-based analysis has been extended to analyze multiatom molecular systems. This method is based on using a pseudosupercritical transformation path to reversibly transform between solid and liquid phases. Integration along this path yields the free energy difference at a single state point, which can then be used to determine the free energy difference as a function of temperature and therefore locate the coexistence temperature at a fixed pressure. The primary extension reported here is the introduction of an external potential field capable of inducing center of mass order along with secondary orientational order for molecules. The method is used to calculate the melting point of 1-H-1,2,4-triazole and benzene. Despite the fact that the triazole model gives accurate bulk densities for the liquid and crystal phases, it is found to do a poor job of reproducing the experimental crystal structure and heat of fusion. Consequently, it yields a melting point that is 100 K lower than the experimental value. On the other hand, the benzene model has been parametrized extensively to match a wide range of properties and yields a melting point that is only 20 K lower than the experimental value. Previous work in which a simple "direct heating" method was used actually found that the melting point of the benzene model was 50 K higher than the experimental value. This demonstrates the importance of using proper free energy methods to compute phase behavior. It also shows that the melting point is a very sensitive measure of force field quality that should be considered in parametrization efforts. The method described here provides a relatively simple approach for computing melting points of molecular systems.

  11. The interplay between dynamic heterogeneities and structure of bulk liquid water: A molecular dynamics simulation study.

    Science.gov (United States)

    Demontis, Pierfranco; Gulín-González, Jorge; Masia, Marco; Sant, Marco; Suffritti, Giuseppe B

    2015-06-28

    In order to study the interplay between dynamical heterogeneities and structural properties of bulk liquid water in the temperature range 130-350 K, thus including the supercooled regime, we use the explicit trend of the distribution functions of some molecular properties, namely, the rotational relaxation constants, the atomic mean-square displacements, the relaxation of the cross correlation functions between the linear and squared displacements of H and O atoms of each molecule, the tetrahedral order parameter q and, finally, the number of nearest neighbors (NNs) and of hydrogen bonds (HBs) per molecule. Two different potentials are considered: TIP4P-Ew and a model developed in this laboratory for the study of nanoconfined water. The results are similar for the dynamical properties, but are markedly different for the structural characteristics. In particular, for temperatures higher than that of the dynamic crossover between "fragile" (at higher temperatures) and "strong" (at lower temperatures) liquid behaviors detected around 207 K, the rotational relaxation of supercooled water appears to be remarkably homogeneous. However, the structural parameters (number of NNs and of HBs, as well as q) do not show homogeneous distributions, and these distributions are different for the two water models. Another dynamic crossover between "fragile" (at lower temperatures) and "strong" (at higher temperatures) liquid behaviors, corresponding to the one found experimentally at T(∗) ∼ 315 ± 5 K, was spotted at T(∗) ∼ 283 K and T(∗) ∼ 276 K for the TIP4P-Ew and the model developed in this laboratory, respectively. It was detected from the trend of Arrhenius plots of dynamic quantities and from the onset of a further heterogeneity in the rotational relaxation. To our best knowledge, it is the first time that this dynamical crossover is detected in computer simulations of bulk water. On the basis of the simulation results, the possible mechanisms of the two

  12. Liquid/liquid interface layering of 1-butanol and [bmim]PF6 ionic liquid: a nonlinear vibrational spectroscopy and molecular dynamics simulation study.

    Science.gov (United States)

    Iwahashi, Takashi; Ishiyama, Tatsuya; Sakai, Yasunari; Morita, Akihiro; Kim, Doseok; Ouchi, Yukio

    2015-10-14

    IR-visible sum-frequency generation (IV-SFG) vibrational spectroscopy and a molecular dynamics (MD) simulation were used to study the local layering order at the interface of 1-butanol-d9 and 1-butyl-3-methylimidazolium hexafluorophosphate ([bmim]PF6), a room-temperature ionic liquid (RTIL). The presence of a local non-polar layer at the interface of the two polar liquids was successfully demonstrated. In the SFG spectra of 1-butanol-d9, we observed significant reduction and enhancement in the strength of the CD3 symmetric stretching (r(+)) mode and the antisymmetric stretching (r(-)) mode peaks, respectively. The results can be well explained by the presence of an oppositely oriented quasi-bilayer structure of butanol molecules, where the bottom layer is strongly bound by hydrogen-bonding with the PF6(-) anion. MD simulations reveal that the hydrogen-bonding of butanol with the PF6(-) anion causes the preferential orientation of the butanols; the restriction on the rotational distribution of the terminal methyl group along their C3 axis enhances the r(-) mode. As for the [bmim](+) cations, the SFG spectra taken within the CH stretch region indicate that the butyl chain of [bmim](+) points away from the bulk RTIL phase to the butanol phase at the interface. Combining the SFG spectroscopy and MD simulation results, we propose an interfacial model structure of layering, in which the butyl chains of the butanol molecules form a non-polar interfacial layer with the butyl chains of the [bmim](+) cations at the interface.

  13. Triiodide and mixed tri-halide anions from negative ion electrospray ionization of alkali halide solutions

    Science.gov (United States)

    Shukla, Anil

    2017-10-01

    Electrospray ionization of alkali halide solutions in the negative ion mode results in the formation of cluster ions of the general formula, (MX)nX-. However, alkali iodides form triiodide anion, I3-, in high abundance in addition to cluster ions. Br3- ions are observed in low abundance. Also, mixed tri-halide anions, I2Y-, are observed in high abundance when a small amount (<1%) of KI is added to other alkali halide solutions. These results are explained by the uniquely different physical characteristics of lithium and the iodide ions compared with others in the series.

  14. Angle-resolved molecular beam scattering of NO at the gas-liquid interface

    Science.gov (United States)

    Zutz, Amelia; Nesbitt, David J.

    2017-08-01

    This study presents first results on angle-resolved, inelastic collision dynamics of thermal and hyperthermal molecular beams of NO at gas-liquid interfaces. Specifically, a collimated incident beam of supersonically cooled NO (2 Π 1/2, J = 0.5) is directed toward a series of low vapor pressure liquid surfaces ([bmim][Tf2N], squalane, and PFPE) at θinc = 45(1)°, with the scattered molecules detected with quantum state resolution over a series of final angles (θs = -60°, -30°, 0°, 30°, 45°, and 60°) via spatially filtered laser induced fluorescence. At low collision energies [Einc = 2.7(9) kcal/mol], the angle-resolved quantum state distributions reveal (i) cos(θs) probabilities for the scattered NO and (ii) electronic/rotational temperatures independent of final angle (θs), in support of a simple physical picture of angle independent sticking coefficients and all incident NO thermally accommodating on the surface. However, the observed electronic/rotational temperatures for NO scattering reveal cooling below the surface temperature (Telec dynamical branching between thermal desorption and impulsive scattering (IS) pathways that depend strongly on θs. Characterization of the data in terms of the final angle, rotational state, spin-orbit electronic state, collision energy, and liquid permit new correlations to be revealed and investigated in detail. For example, the IS rotational distributions reveal an enhanced propensity for higher J/spin-orbit excited states scattered into near specular angles and thus hotter rotational/electronic distributions measured in the forward scattering direction. Even more surprisingly, the average NO scattering angle (⟨θs⟩) exhibits a remarkably strong correlation with final angular momentum, N, which implies a linear scaling between net forward scattering propensity and torque delivered to the NO projectile by the gas-liquid interface.

  15. The molecular structure of the interface between water and a hydrophobic substrate is liquid-vapor like.

    Science.gov (United States)

    Willard, Adam P; Chandler, David

    2014-11-14

    With molecular simulation for water and a tunable hydrophobic substrate, we apply the instantaneous interface construction [A. P. Willard and D. Chandler, "Instantaneous liquid interfaces," J. Phys. Chem. B 114, 1954-1958 (2010)] to examine the similarity between a water-vapor interface and a water-hydrophobic surface interface. We show that attractive interactions between a hydrophobic surface and water affect capillary wave fluctuations of the instantaneous liquid interface, but these attractive interactions have essentially no effect on the intrinsic interface. The intrinsic interface refers to molecular structure in terms of distances from the instantaneous interface. Further, the intrinsic interface of liquid water and a hydrophobic substrate differs little from that of water and its vapor. The same is not true, we show, for an interface between water and a hydrophilic substrate. In that case, strong directional substrate-water interactions disrupt the liquid-vapor-like interfacial hydrogen bonding network.

  16. Sulfonium-based Ionic Liquids Incorporating the Allyl Functionality

    Directory of Open Access Journals (Sweden)

    Paul J. Dyson

    2007-04-01

    Full Text Available A series of sulfonium halides bearing allyl groups have been prepared andcharacterized. Anion metathesis with Li[Tf2N] and Ag[N(CN2] resulted in sulfonium-basedionic liquids which exhibit low viscosities at room temperature. The solid state structure ofone of the halide salts was determined by single crystal X-ray diffraction.

  17. IONIC LIQUID-CATALYZED ALKYLATION OF ISOBUTANE WITH 2-BUTENE

    Science.gov (United States)

    A detailed study of the alkylation of isobutane with 2-butene in ionic liquid media has been conducted using 1-alkyl-3-methylimidazolium halides?aluminum chloride encompassing various alkyl groups (butyl-, hexyl-, and octyl-) and halides (Cl, Br, and I) on its cations and anions,...

  18. Quasielastic neutron scattering study of silver selenium halides

    CERN Document Server

    Major, A G; Barnes, A C; Howells, W S

    2002-01-01

    Both silver chalcogenides (Ag sub 2 S, Ag sub 2 Se, and Ag sub 2 Te) and silver halides (AgCl, AgBr, and AgI) are known to be fast-ion solids in which the silver ions can diffuse quickly in a sublattice formed by the other ions. To clarify whether mixtures of these materials (such as Ag sub 3 SeI) possess comparable properties and whether a systematic dependence on the cation-to-anion ratio can be observed, some of these mixtures were studied by quasielastic neutron scattering both in the solid and the liquid phases. To identify the diffusion mechanisms and constants, a new data-analysis method based on a two-dimensional maximum-likelihood fit is proposed. This method has the potential to give more reliable information on the diffusion mechanism than the traditional Bayesian method. (orig.)

  19. Correlation of the vapor pressure isotope effect with molecular force fields in the liquid state

    Energy Technology Data Exchange (ETDEWEB)

    Pollin, J.S.; Ishida, T.

    1976-07-01

    The present work is concerned with the development and application of a new model for condensed phase interactions with which the vapor pressure isotope effect (vpie) may be related to molecular forces and structure. The model considers the condensed phase as being represented by a cluster of regularly arranged molecules consisting of a central molecule and a variable number of molecules in the first coordination shell. The methods of normal coordinate analysis are used to determine the modes of vibration of the condensed phase cluster from which, in turn, the isotopic reduced partition function can be calculated. Using the medium cluster model, the observed vpie for a series of methane isotopes has been successfully reproduced with better agreement with experiment than has been possible using the simple cell model. We conclude, however, that insofar as the medium cluster model provides a reasonable picture of the liquid state, the vpie is not sufficiently sensitive to molecular orientation to permit an experimental determination of intermolecular configuration in the condensed phase through measurement of isotopic pressure ratios. The virtual independence of vapor pressure isotope effects on molecular orientation at large cluster sizes is a demonstration of the general acceptability of the cell model assumptions for vpie calculations.

  20. Unstable shear flows in two dimensional strongly correlated liquids - a hydrodynamic and molecular dynamics study

    Science.gov (United States)

    Gupta, Akanksha; Ganesh, Rajaraman; Joy, Ashwin

    2016-11-01

    In Navier-Stokes fluids, shear flows are known to become unstable leading to instability and eventually to turbulence. A class of flow namely, Kolmogorov Flows (K-Flows) exhibit such transition at low Reynolds number. Using fluid and molecular dynamics, we address the physics of transition from laminar to turbulent regime in strongly correlated-liquids such as in multi-species plasmas and also in naturally occurring plasmas with K-Flows as initial condition. A 2D phenomenological generalized hydrodynamic model is invoked wherein the effect of strong correlations is incorporated via a viscoelastic memory. To study the stability of K-Flows or in general any shear flow, a generalized eigenvalue solver has been developed along with a spectral solver for the full nonlinear set of fluid equations. A study of the linear and nonlinear features of K-Flow in incompressible and compressible limit exhibits cyclicity and nonlinear pattern formation in vorticity. A first principles based molecular dynamics simulation of particles interacting via Yukawa potential is performed with features such as configurational and kinetic thermostats for K-Flows. This work reveals several interesting similarities and differences between hydrodynamics and molecular dynamics studies.

  1. Thermodynamic scaling of dynamic properties of liquid crystals: verifying the scaling parameters using a molecular model.

    Science.gov (United States)

    Satoh, Katsuhiko

    2013-08-28

    The thermodynamic scaling of molecular dynamic properties of rotation and thermodynamic parameters in a nematic phase was investigated by a molecular dynamic simulation using the Gay-Berne potential. A master curve for the relaxation time of flip-flop motion was obtained using thermodynamic scaling, and the dynamic property could be solely expressed as a function of TV(γτ) , where T and V are the temperature and volume, respectively. The scaling parameter γτ was in excellent agreement with the thermodynamic parameter Γ, which is the logarithm of the slope of a line plotted for the temperature and volume at constant P2. This line was fairly linear, and as good as the line for p-azoxyanisole or using the highly ordered small cluster model. The equivalence relation between Γ and γ(τ) was compared with results obtained from the highly ordered small cluster model. The possibility of adapting the molecular model for the thermodynamic scaling of other dynamic rotational properties was also explored. The rotational diffusion constant and rotational viscosity coefficients, which were calculated using established theoretical and experimental expressions, were rescaled onto master curves with the same scaling parameters. The simulation illustrates the universal nature of the equivalence relation for liquid crystals.

  2. Pseudo-molecular approach for the elastic constants of nematic liquid crystals interacting via anisotropic dispersion forces

    Energy Technology Data Exchange (ETDEWEB)

    Simonário, P.S., E-mail: simonario@gmail.com [Departamento de Física, Universidade Estadual de Maringá, Avenida Colombo, 5790, 87020-900 Maringá, Paraná (Brazil); Freire, F.C.M.; Evangelista, L.R. [Departamento de Física, Universidade Estadual de Maringá, Avenida Colombo, 5790, 87020-900 Maringá, Paraná (Brazil); Teixeira-Souza, R.T. [Universidade Tecnológica Federal do Paraná – Câmpus Apucarana, Rua Marcílio Dias, 635, 86812-460 Apucarana, Paraná (Brazil)

    2014-01-17

    The bulk and the surface-like elastic constants of a nematic liquid crystal are calculated for an ensemble of particles interacting via anisotropic dispersion forces using the pseudo-molecular method. The geometrical anisotropy of the molecules is also taken into account in the calculations by choosing a molecular volume of ellipsoidal shape. Analytical expressions for the elastic constants are obtained as a function of the eccentricity in the molecular volume shape. The method allows one to explore the dependence on the molecular orientation with respect to the intermolecular vector by analyzing the magnitude and the behaviour of macroscopic elastic parameters defining the nematic phase.

  3. Ab initio molecular dynamics simulations of the static, dynamic and electronic properties of liquid lead using real-space pseudopotentials

    Energy Technology Data Exchange (ETDEWEB)

    Alemany, Manuel M. G. [Universidad de Santiago de Compostela; Longo, Roberto [Universidad de Santiago de Compostela; Gallego, Luis [Universidad de Santiago de Compostela; Gonzales, D. J. [Universidad de Valladolid; Gonzales, L. E. [Universidad de Valladolid; Tiago, Murilo L [ORNL; Chelikowsky, James [University of Texas, Austin

    2007-01-01

    We performed a comprehensive study of the static, dynamic and electronic properties of liquid Pb at T = 650 kelvins, density 0.0309 angstroms^{-3} by means of 216-particle ab initio molecular dynamics simulations based on a real-space implementation of pseudopotentials constructed within density-functional theory. The predicted results and available experimental data are very in good agreement, which confirms the adequacy of this technique to achieve a reliable description of the behavior of liquid metals, including their dynamic properties. Although some of the computed properties of liquid Pb are similar to those of simple liquid metals, others differ markedly. Our results show that an appropriate description of liquid Pb requires the inclusion of relativistic effects in the determination of the pseudopotentials of Pb.

  4. Determination of liquid's molecular interference function based on X-ray diffraction and dual-energy CT in security screening.

    Science.gov (United States)

    Zhang, Li; YangDai, Tianyi

    2016-08-01

    A method for deriving the molecular interference function (MIF) of an unknown liquid for security screening is presented. Based on the effective atomic number reconstructed from dual-energy computed tomography (CT), equivalent molecular formula of the liquid is estimated. After a series of optimizations, the MIF and a new effective atomic number are finally obtained from the X-ray diffraction (XRD) profile. The proposed method generates more accurate results with less sensitivity to the noise and data deficiency of the XRD profile.

  5. A molecular dynamics simulation study of dynamic process and mesoscopic structure in liquid mixture systems

    Science.gov (United States)

    Yang, Peng

    The focus of this dissertation is the Molecular Dynamics (MD) simulation study of two different systems. In thefirst system, we study the dynamic process of graphene exfoliation, particularly graphene dispersion using ionic surfactants (Chapter 2). In the second system, we investigate the mesoscopic structure of binary solute/ionic liquid (IL) mixtures through the comparison between simulations and corresponding experiments (Chapter 3 and 4). In the graphene exfoliation study, we consider two separation mechanisms: changing the interlayer distance and sliding away the relative distance of two single-layer graphene sheets. By calculating the energy barrier as a function of separation (interlayer or sliding-away) distance and performing sodium dodecyl sulfate (SDS) structure analysis around graphene surface in SDS surfactant/water + bilayer graphene mixture systems, we find that the sliding-away mechanism is the dominant, feasible separation process. In this process, the SDS-graphene interaction gradually replaces the graphene-graphene Van der Waals (VdW) interaction, and decreases the energy barrier until almost zero at critical SDS concentration. In solute/IL study, we investigate nonpolar (CS2) and dipolar (CH 3CN) solute/IL mixture systems. MD simulation shows that at low concentrations, IL is nanosegregated into an ionic network and nonpolar domain. It is also found that CS2 molecules tend to be localized into the nonpolar domain, while CH3CN interacts with nonpolar domain as well as with the charged head groups in the ionic network because of its amphiphilicity. At high concentrations, CH3CN molecules eventually disrupt the nanostructural organization. This dissertation is organized in four chapters: (1) introduction to graphene, ionic liquids and the methodology of MD; (2) MD simulation of graphene exfoliation; (3) Nanostructural organization in acetonitrile/IL mixtures; (4) Nanostructural organization in carbon disulfide/IL mixtures; (5) Conclusions. Results

  6. Liquid crystals and their interactions with colloidal particles and phospholipid membranes: Molecular simulation studies

    Science.gov (United States)

    Kim, Evelina B.

    Experimentally, liquid crystals (LC) can be used as the basis for optical biomolecular sensors that rely on LC ordering. Recently, the use of LC as a reporting medium has been extended to investigations of molecular scale processes at lipid laden aqueous-LC interfaces and at biological cell membranes. In this thesis, we present two related studies where liquid crystals are modelled at different length scales. We examine (a) the behavior of nanoscopic colloidal particles in LC systems, using Monte Carlo (MC) molecular simulations and a mesoscopic dynamic field theory (DyFT); and (b) specific interactions of two types of mesogens with a model phospholipid bilayer, using atomistic molecular dynamics (MD) at the A-nm scale. In (a), we consider colloidal particles suspended in a LC, confined between two walls. We calculate the colloid-substrate and colloid-colloid potentials of mean force (PMF). For the MC simulations, we developed a new technique (ExEDOS or Expanded Ensemble Density Of States) that ensures good sampling of phase space without prior knowledge of the energy landscape of the system. Both results, simulation and DyFT, indicate a repulsive force acting between a colloid and a wall. In contrast, both techniques indicate an overall colloid-colloid attraction and predict a new topology of the disclination lines that arises when the particles approach each other. In (b), we find that mesogens (pentylcyanobiphenyl [5CB] or difluorophenyl-pentylbicyclohexyl [5CF]) preferentially partition from the aqueous phase into a dipalmitoylphosphatidylcholine (DPPC) bilayer. We find highly favorable free energy differences for partitioning (-18kBT for 5CB, -26k BT for 5CF). We also simulated fully hydrated bilayers with embedded 5CB or 5CF at concentrations used in recent experiments (6 mol% and 20 mol%). The presence of mesogens in the bilayer enhances the order of lipid acyl tails and changes the spatial and orientational arrangement of lipid headgroup atoms. A stronger

  7. Three-Dimensional Molecular Dynamics Simulation on Heat Propagation in Liquid Argon

    Institute of Scientific and Technical Information of China (English)

    郭英奎; 过增元; 梁新刚

    2001-01-01

    The propagation behaviour of an initial thermal perturbation in liquid argon is simulated by the molecular dynamics method. The 12-6 Lennard-Jones potential and mirror boundary conditions are employed in the 32768particle three-dimensional simulation. Macroscopic characteristics such as the kinetic temperature, pressure and momentum profiles are monitored during the simulation in order to examine the heat propagation behaviour under a timescale comparable with the relaxation time. The results show that the behaviour is still diffusionlike; no features predicted by the Cattaneo-Vernotte model have been found. The wave-like front of the local temperature may be caused by the adiabatic compression and expansion by the pressure wave generated by the thermal expansion.

  8. Cage rattling does not correlate with the local geometry in molecular liquids

    CERN Document Server

    Bernini, S; Leporini, D

    2016-01-01

    Molecular-dynamics simulations of a liquid of short linear molecules have been performed to investigate the correlation between the particle dynamics in the cage of the neighbors and the local geometry. The latter is characterized in terms of the size and the asphericity of the Voronoi polyhedra. The correlation is found to be poor. In particular, in spite of the different Voronoi volume around the end and the inner monomers of a molecule, all the monomers exhibit coinciding displacement distribution when they are caged (as well as at longer times during the structural relaxation). It is concluded that the fast dynamics during the cage trapping is a non-local collective process involving monomers beyond the nearest neighbours.

  9. Liquid alkanes with targeted molecular weights from biomass-derived carbohydrates.

    Science.gov (United States)

    West, Ryan M; Liu, Zhen Y; Peter, Maximilian; Dumesic, James A

    2008-01-01

    Liquid transportation fuels must burn cleanly and have high energy densities, criteria that are currently fulfilled by petroleum, a non-renewable resource, the combustion of which leads to increasing levels of atmospheric CO(2). An attractive approach for the production of transportation fuels from renewable biomass resources is to convert carbohydrates into alkanes with targeted molecular weights, such as C(8)-C(15) for jet-fuel applications. Targeted n-alkanes can be produced directly from fructose by an integrated process involving first the dehydration of this C(6) sugar to form 5-hydroxymethylfurfural, followed by controlled formation of C-C bonds with acetone to form C(9) and C(15) compounds, and completed by hydrogenation and hydrodeoxygenation reactions to form the corresponding n-alkanes. Analogous reactions are demonstrated starting with 5-methylfurfural or 2-furaldehyde, with the latter leading to C(8) and C(13) n-alkanes.

  10. Photomobile polymer materials with crosslinked liquid-crystalline structures: molecular design, fabrication, and functions.

    Science.gov (United States)

    Ube, Toru; Ikeda, Tomiki

    2014-09-22

    Crosslinked liquid-crystalline polymer materials that macroscopically deform when irradiated with light have been extensively studied in the past decade because of their potential in various applications, such as microactuators and microfluidic devices. The basic motions of these materials are contraction-expansion and bending-unbending, which are observed mainly in polysiloxanes and polyacrylates that contain photochromic moieties. Other sophisticated motions such as twisting, oscillation, rotation, and translational motion have also been achieved. In recent years, efforts have been made to improve the photoresponsive and mechanical properties of this novel class of materials through the modification of molecular structures, development of new fabrication methods, and construction of composite structures. Herein, we review structures, functions, and working mechanisms of photomobile materials and recent advances in this field.

  11. MOLECULAR FIELD THEORY FOR NEMATIC LIQUID CRYSTAL POLYMER COMPRISING FLEXIBLE SPACER

    Institute of Scientific and Technical Information of China (English)

    WANG Xiaogong; LIU Deshan; ZHOU Qixiang

    1993-01-01

    Based on the new model and concept of intramolecular orientational order parameter, a molecular field theory was built up for main chain liquid crystalline polymer (MC-LCPs) with flexible spacers. The theory takes account of orientational correlation among all mesogens in a polymer chain and the relationship between the intramolecular orientation and spatial orientation of the mesogens. The free energy, temperature and entropy of the nematic-isotropic transition were determined with the theory and compared with experiments in current work. It was found that many unique transition properties of the MC-LCPs comprising flexible spacer are correctly predicted by the theory and the agreement of the theory with the experiments is impressive.

  12. Thermophysical properties of liquid Ni around the melting temperature from molecular dynamics simulation

    Science.gov (United States)

    Rozas, R. E.; Demiraǧ, A. D.; Toledo, P. G.; Horbach, J.

    2016-08-01

    Thermophysical properties of liquid nickel (Ni) around the melting temperature are investigated by means of classical molecular dynamics (MD) simulation, using three different embedded atom method potentials to model the interactions between the Ni atoms. Melting temperature, enthalpy, static structure factor, self-diffusion coefficient, shear viscosity, and thermal diffusivity are compared to recent experimental results. Using ab initio MD simulation, we also determine the static structure factor and the mean-squared displacement at the experimental melting point. For most of the properties, excellent agreement is found between experiment and simulation, provided the comparison relative to the corresponding melting temperature. We discuss the validity of the Hansen-Verlet criterion for the static structure factor as well as the Stokes-Einstein relation between self-diffusion coefficient and shear viscosity. The thermal diffusivity is extracted from the autocorrelation function of a wavenumber-dependent temperature fluctuation variable.

  13. Hydrogen bond dynamics in liquid water: Ab initio molecular dynamics simulation

    Energy Technology Data Exchange (ETDEWEB)

    Kim, Cheolhee; Kim, Eunae [College of Pharmacy, Chosun University, Gwangju (Korea, Republic of); Yeom, Min Sun [Korea Institute of Science and Technology Information, Daejeon (Korea, Republic of)

    2016-01-15

    The effect of intermolecular interaction on the distribution of the harmonic vibrational frequencies of water molecules was investigated through ab initio molecular dynamics simulations based on the Born-Oppenheimer approach. For single water, the effect of the dynamics of the oxygen atom in single water and the simulation time step on the frequency distribution were examined. The distributions of the OH stretching and HOH bending vibrational frequencies of liquid water were compared to those of single water. The probability distributions of the change in OH bond length and the lifetime of the dangling OH bond were also obtained. The distribution of the frequencies was strongly affected by the long lifetime of the dangling OH bond, resulting in the formation of hydrogen bonds between water molecules.

  14. Molecular dynamics of liquid alkaline-earth metals near the melting point

    Indian Academy of Sciences (India)

    J K Baria; A R Jani

    2010-10-01

    Results of the studies of the properties like binding energy, the pair distribution function (), the structure factor (), specific heat at constant volume, velocity autocorrelation function (VACF), radial distribution function, self-diffusion coefficient and coordination number of alkaline-earth metals (Be, Mg, Ca, Sr and Ba) near melting point using molecular dynamics (MD) simulation technique using a pseudopotential proposed by us are presented in this article. Good agreement with the experiment is achieved for the binding energy, pair distribution function and structure factor, and these results compare favourably with the results obtained by other such calculations, showing the transferability of the pseudopotential used from solid to liquid environment in the case of alkaline-earth metals.

  15. Ionothermal synthesis process for aluminophosphate molecular sieves in the mixed water/ionic liquid system.

    Science.gov (United States)

    Zhao, Zhenchao; Zhang, Weiping; Xu, Renshun; Han, Xiuwen; Tian, Zhijian; Bao, Xinhe

    2012-01-21

    The synthesis process of aluminophosphate AlPO(4)-11 molecular sieve in the mixed water/1-butyl- 3-methylimidazolium bromide ([bmim]Br) ionic liquid was investigated by XRD, multinuclear solid-state NMR, scanning electron microscopy (SEM) and X-ray energy dispersive spectroscopy (EDS). It was observed that a tablet phase, named SIZ-2, was formed at the early stage of crystallization. During crystallization metastable SIZ-2 with an incompletely condensed framework phosphorus disappeared gradually, and the phosphorous species became fully condensed through hydroxyl reaction with tetrahedral aluminum to form thermodynamically stable AlPO(4)-11 in the final product. It was found that [bmim]Br, acting as the structure-directing agent, was occluded into the AlPO(4)-11 channel.

  16. Detailed molecular characterization of castor oil ethoxylates by liquid chromatography multistage mass spectrometry.

    Science.gov (United States)

    Nasioudis, Andreas; van Velde, Jan W; Heeren, Ron M A; van den Brink, Oscar F

    2011-10-07

    The molecular characterization of castor oil ethoxylates (CASEOs) was studied by reverse-phase liquid chromatography (RPLC) mass spectrometry (MS) and multistage mass spectrometry (MS(n)). The developed RPLC method allowed the separation of the various CASEO components, and especially, the baseline separation of multiple nominal isobars (same nominal mass) and isomers (same exact mass). MS and MS(n) were used for the determination and structure elucidation of various structures and for the discrimination of the isobars and isomers. Different ionization techniques and adduct ions were also tested for optimization of the MS detection and the MS(n) fragmentation. A unique fragmentation pathway of ricinoleic acid is proposed, which can be used as a marker of the polymerization process and the topology of ethoxylation in the CASEO. In addition, characteristic neutral losses of ricinoleic acid reveal its (terminal or internal) position in the molecule.

  17. Gauge-origin independent magnetizabilities from hybrid quantum mechanics/molecular mechanics models: Theory and applications to liquid water

    Science.gov (United States)

    Aidas, Kestutis; Kongsted, Jacob; Nielsen, Christian B.; Mikkelsen, Kurt V.; Christiansen, Ove; Ruud, Kenneth

    2007-07-01

    The theory of a hybrid quantum mechanics/molecular mechanics (QM/MM) approach for gauge-origin independent calculations of the molecular magnetizability using Hartree-Fock or Density Functional Theory is presented. The method is applied to liquid water using configurations generated from classical Molecular Dynamics simulation to calculate the statistical averaged magnetizability. Based on a comparison with experimental data, treating only one water molecule quantum mechanically appears to be insufficient, while a quantum mechanical treatment of also the first solvation shell leads to good agreement between theory and experiment. This indicates that the gas-to-liquid phase shift for the molecular magnetizability is to a large extent of non-electrostatic nature.

  18. Solvation of lithium salts in protic ionic liquids: a molecular dynamics study.

    Science.gov (United States)

    Méndez-Morales, Trinidad; Carrete, Jesús; Cabeza, Óscar; Russina, Olga; Triolo, Alessandro; Gallego, Luis J; Varela, Luis M

    2014-01-23

    The structure of solutions of lithium nitrate in a protic ionic liquid with a common anion, ethylammonium nitrate, at room temperature is investigated by means of molecular dynamics simulations. Several structural properties, such as density, radial distribution functions, hydrogen bonds, spatial distribution functions, and coordination numbers, are analyzed in order to get a picture of the solvation of lithium cations in this hydrogen-bonded, amphiphilically nanostructured environment. The results reveal that the ionic liquid mainly retains its structure upon salt addition, the interaction between the ammonium group of the cation and the nitrate anion being only slightly perturbed by the addition of the salt. Lithium cations are solvated by embedding them in the polar nanodomains of the solution formed by the anions, where they coordinate with the latter in a solid-like fashion reminiscent of a pseudolattice structure. Furthermore, it is shown that the average coordination number of [Li](+) with the anions is 4, nitrate coordinating [Li](+) in both monodentate and bidentate ways, and that in the second coordination layer both ethylammonium cations and other lithiums are also found. Additionally, the rattling motion of lithium ions inside the cages formed by their neighboring anions, indicative of the so-called caging effect, is confirmed by the analysis of the [Li](+) velocity autocorrelation functions. The overall picture indicates that the solvation of [Li](+) cations in this amphiphilically nanostructured environment takes place by means of a sort of inhomogeneous nanostructural solvation, which we could refer to as nanostructured solvation, and which could be a universal solvation mechanism in ionic liquids.

  19. Molecular characterization of gel and liquid-crystalline structures of fully hydrated POPC and POPE bilayers.

    Science.gov (United States)

    Leekumjorn, Sukit; Sum, Amadeu K

    2007-05-31

    Molecular dynamics simulations were used for a comprehensive study of the structural properties of monounsaturated POPC and POPE bilayers in the gel and liquid-crystalline state at a number of temperatures, ranging from 250 to 330 K. Though the chemical structures of POPC and POPE are largely similar (choline versus ethanolamine headgroup), their transformation processes from a gel to a liquid-crystalline state are contrasting. In the similarities, the lipid tails for both systems are tilted below the phase transition and become more random above the phase transition temperature. The average area per lipid and bilayer thickness were found less sensitive to phase transition changes as the unsaturated tails are able to buffer reordering of the bilayer structure, as observed from hysteresis loops in annealing simulations. For POPC, changes in the structural properties such as the lipid tail order parameter, hydrocarbon trans-gauche isomerization, lipid tail tilt-angle, and level of interdigitation identified a phase transition at about 270 K. For POPE, three temperature ranges were identified, in which the lower one (270-280 K) was associated with a pre-transition state and the higher (290-300 K) with the post-transition state. In the pre-transition state, there was a significant increase in the number of gauche arrangements formed along the lipid tails. Near the main transition (280-290 K), there was a lowering of the lipid order parameters and a disappearance of the tilted lipid arrangement. In the post-transition state, the carbon atoms along the lipid tails became less hindered as their density profiles showed uniform distributions. This study also demonstrates that atomistic simulations of current lipid force fields are capable of capturing the phase transition behavior of lipid bilayers, providing a rich set of molecular and structural information at and near the main transition state.

  20. Liquid- and Ice-Phase Kinetics of Singlet Molecular Oxygen with Organic Pollutants

    Science.gov (United States)

    Bower, J. P.; Anastasio, C.

    2012-12-01

    Singlet molecular oxygen (1O2*), a reactive state of dissolved oxygen, is formed from a sensitizer chromophore that absorbs light and transfers energy to ground-state O2. The chemistry of 1O2* has been studied predominantly in surface waters and aqueous atmospheric drops, where 1O2* can be an important sink for electron-rich pollutants. In our recent work we have shown that 1O2* concentrations can be enhanced by several orders of magnitude on ice compared to in identical, but unfrozen, aqueous solutions. The goal of this work is to assess the potential importance of 1O2* to the decay of organic pollutants on ice in order to better understand pollutant cycling in the cryosphere. Using 549 nm radiation we illuminated liquid and bulk ice samples containing a 1O2* sensitizer (Rose Bengal), salt (NaCl), and an organic pollutant at a controlled temperature. Organic species were chosen to represent several chemical classes, including furans (furfuryl alcohol), phenols (bisphenol A), and amino acids (tryptophan). During illumination the decay of the pollutant was measured to determine the rate constant for loss by reaction with 1O2*. In all cases we observe enhanced loss of pollutants on ice relative to liquid samples. We will discuss how the magnitude of the ice-phase enhancement depends on the different pollutant classes, their aqueous solubility, and freezing point depression.

  1. Identification of low molecular weight proteins isolated by 2-D liquid separations.

    Science.gov (United States)

    Zhu, Kan; Miller, Fred R; Barder, Timothy J; Lubman, David M

    2004-07-01

    Proteins with molecular mass (M(r)) <20 kDa are often poorly separated in 2-D sodium dodecyl sulfate polyacrylamide gel electrophoresis. In addition, low-M(r) proteins may not be readily identified using peptide mass fingerprinting (PMF) owing to the small number of peptides generated in tryptic digestion. In this work, we used a 2-D liquid separation method based on chromatofocusing and non-porous silica reversed-phase high-performance liquid chromatography to purify proteins for matrix-assisted laser desorption/ionization time-of-flight mass spectrometric (MALDI-TOFMS) analysis and protein identification. Several proteins were identified using the PMF method where the result was supported using an accurate M(r) value obtained from electrospray ionization TOFMS. However, many proteins were not identified owing to an insufficient number of peptides observed in the MALDI-TOF experiments. The small number of peptides detected in MALDI-TOFMS can result from internal fragmentation, the few arginines in its sequence and incomplete tryptic digestion. MALDI-QTOFMS/MS can be used to identify many of these proteins. The accurate experimental M(r) and pI confirm identification and aid in identifying post-translational modifications such as truncations and acetylations. In some cases, high-quality MS/MS data obtained from the MALDI-QTOF spectrometer overcome preferential cleavages and result in protein identification.

  2. Molecular dynamics studies on the adaptability of an ionic liquid in the extraction of solid nanoparticles.

    Science.gov (United States)

    Frost, Denzil S; Machas, Michael; Dai, Lenore L

    2012-10-02

    Recently, a number of publications have suggested that ionic liquids (ILs) can absorb solid particles. This development may have implications in fields like oil sand processing, oil spill beach cleanup, and water treatment. In this Article, we provide a computational investigation of this phenomenon via molecular dynamics simulations. Two particle surface chemistries were investigated: (1) hydrocarbon-saturated and (2) silanol-saturated, representing hydrophobic and hydrophilic particles, respectively. Employing 1-butyl-3-methylimidazolium hexafluorophosphate ([BMIM][PF(6)]) as a model IL, these nanoparticles were allowed to equilibrate at the IL/water and IL/hexane interfaces to observe the interfacial self-assembled structures. At the IL/water interface, the hydrocarbon-based nanoparticles were nearly completely absorbed by the IL, while the silica nanoparticles maintained equal volume in both phases. At the IL/hexane interface, the hydrocarbon nanoparticles maintained minimal interactions with the IL, whereas the silica nanoparticles were nearly completely absorbed by it. Studies of these two types of nanoparticles immersed in the bulk IL indicate that the surface chemistry has a great effect on the corresponding IL liquid structure. These effects include layering of the ions, hydrogen bonding, and irreversible absorption of some ions to the silica nanoparticle surface. We quantify these effects with respect to each nanoparticle. The results suggest that ILs likely exhibit this absorption capability because they can form solvation layers with reduced dynamics around the nanoparticles.

  3. Structure and dynamics of proton transfer in liquid imidazole. A molecular dynamics simulation.

    Science.gov (United States)

    Li, Ailin; Cao, Zhen; Li, Yao; Yan, Tianying; Shen, Panwen

    2012-10-25

    Proton transfer (PT) via the Grotthuss mechanism in liquid imidazole (im) at 393 K is studied with molecular dynamics simulation using a reactive multistate empirical valence bond (MS-EVB) model. It is found that the proton is tightly binded to an imidazole to form an imidazolium (imH(+)), which is solvated in a distorted Eigen-like complex (im-imH(+)-im), whereas the Zundel-like complex (im-H(+)-im) is rare. PT occurs via an Eigen-Zundel-Eigen scenario for switching the identity of imH(+) from an Eigen-like complex to another, intermediated by a Zundel-like complex. Structural and dynamical analyses demonstrate that PT in imidazole can be considered as a local event with very short spatial/temporal correlation, characterized by a few "rattling" or recurrent PT events. At long time scale, the trend of the PT correlation function may be recast with the diffusion model of reversible geminate recombination toward the power-law decay. The formation of the hydrogen bonds (HBs) for the imidazole molecules between the first and second solvation shell of imH(+) is crucial to pave the PT pathway. The above features may be understood by the flexibility of the HBs in liquid imidazole, as a stable HB network is essential for the Grotthuss mechanism.

  4. Hematite(001)-liquid water interface from hybrid density functional-based molecular dynamics

    Science.gov (United States)

    Falk von Rudorff, Guido; Jakobsen, Rasmus; Rosso, Kevin M.; Blumberger, Jochen

    2016-10-01

    The atom-scale characterisation of interfaces between transition metal oxides and liquid water is fundamental to our mechanistic understanding of diverse phenomena ranging from crystal growth to biogeochemical transformations to solar fuel production. Here we report on the results of large-scale hybrid density functional theory-based molecular dynamics simulations for the hematite(001)-liquid water interface. A specific focus is placed on understanding how different terminations of the same surface influence surface solvation. We find that the two dominant terminations for the hematite(001) surface exhibit strong differences both in terms of the active species formed on the surface and the strength of surface solvation. According to present simulations, we find that charged oxyanions (-O-) and doubly protonated oxygens (-OH2+ ) can be formed on the iron terminated layer via autoionization of neutral -OH groups. No such charged species are found for the oxygen terminated surface. In addition, the missing iron sublayer in the iron terminated surface strongly influences the solvation structure, which becomes less well ordered in the vicinity of the interface. These pronounced differences are likely to affect the reactivity of the two surface terminations, and in particular the energetics of excess charge carriers at the surface.

  5. Equilibrium fluctuations of liquid state static properties in a subvolume by molecular dynamics.

    Science.gov (United States)

    Heyes, D M; Dini, D; Smith, E R

    2016-09-14

    System property fluctuations increasingly dominate a physical process as the sampling volume decreases. The purpose of this work is to explore how the fluctuation statistics of various thermodynamic properties depend on the sampling volume, using molecular dynamics (MD) simulations. First an examination of various expressions for calculating the bulk pressure of a bulk liquid is made, which includes a decomposition of the virial expression into two terms, one of which is the Method of Planes (MOP) applied to the faces of the cubic simulation cell. Then an analysis is made of the fluctuations of local density, temperature, pressure, and shear stress as a function of sampling volume (SV). Cubic and spherical shaped SVs were used within a spatially homogeneous LJ liquid at a state point along the melting curve. It is shown that the MD-generated probability distribution functions (PDFs) of all of these properties are to a good approximation Gaussian even for SV containing only a few molecules (∼10), with the variances being inversely proportional to the SV volume, Ω. For small subvolumes the shear stress PDF fits better to a Gaussian than the pressure PDF. A new stochastic sampling technique to implement the volume averaging definition of the pressure tensor is presented, which is employed for cubic, spherical, thin cubic, and spherical shell SV. This method is more efficient for less symmetric SV shapes.

  6. Thermodynamic scaling of molecular dynamics in supercooled liquid state of pharmaceuticals: Itraconazole and ketoconazole.

    Science.gov (United States)

    Tarnacka, M; Madejczyk, O; Adrjanowicz, K; Pionteck, J; Kaminska, E; Kamiński, K; Paluch, M

    2015-06-14

    Pressure-Volume-Temperature (PVT) measurements and broadband dielectric spectroscopy were carried out to investigate molecular dynamics and to test the validity of thermodynamic scaling of two homologous compounds of pharmaceutical activity: itraconazole and ketoconazole in the wide range of thermodynamic conditions. The pressure coefficients of the glass transition temperature (dT(g)/dp) for itraconazole and ketoconazole were determined to be equal to 183 and 228 K/GPa, respectively. However, for itraconazole, the additional transition to the nematic phase was observed and characterized by the pressure coefficient dT(n)/dp = 258 K/GPa. From PVT and dielectric data, we obtained that the liquid-nematic phase transition is governed by the relaxation time since it occurred at constant τ(α) = 10(-5) s. Furthermore, we plotted the obtained relaxation times as a function of T(-1)v(-γ), which has revealed that the validity of thermodynamic scaling with the γ exponent equals to 3.69 ± 0.04 and 3.64 ± 0.03 for itraconazole and ketoconazole, respectively. Further analysis of the scaling parameter in itraconazole revealed that it unexpectedly decreases with increasing relaxation time, which resulted in dramatic change of the shape of the thermodynamic scaling master curve. While in the case of ketoconazole, it remained the same within entire range of data (within experimental uncertainty). We suppose that in case of itraconazole, this peculiar behavior is related to the liquid crystals' properties of itraconazole molecule.

  7. On the dissociative electron attachment as a potential source of molecular hydrogen in irradiated liquid water

    Energy Technology Data Exchange (ETDEWEB)

    Cobut, V.; Jay-Gerin, J.-P.; Frongillo, Y. [Sherbrooke Univ., PQ (Canada). Faculte de Medecine; Patau, J.P. [Toulouse-3 Univ., 31 (France)

    1996-02-01

    In the radiolysis of liquid water, different mechanisms for the formation of molecular hydrogen (H{sub 2}) are involved at different times after the initial energy disposition. It has been suggested that the contributions of the e{sub aq}{sup -} + e{sub aq}{sup -}, H + e{sub aq}{sup -} and H + H reactions between hydrated electrons (e{sub aq}{sup -}) and hydrogen atoms in the spurs are not sufficient to account for all of the observed H{sub 2} yield (0.45 molecules/100 eV) on the microsecond time scale. Addressing the question of the origin of an unscavengeable H{sub 2} yield of 0.15 molecules/100 eV produced before spur expansion, we suggest that the dissociative capture of the so-called vibrationally-relaxing electrons by H{sub 2}O molecules is a possible pathway for the formation of part of the initial H{sub 2} yield. Comparison of recent dissociative-electron-attachment H{sup -}-anion yield-distribution measurements from amorphous H{sub 2}O films with the energy spectrum of vibrationally-relaxing electrons in irradiated liquid water, calculated by Monte Carlo simulations, plays in favor of this hypothesis. (author).

  8. Non-conventional halide oxidation pathways : oxidation by imidazole triplet and surface specific oxidation by ozone

    Science.gov (United States)

    Ammann, Markus; Corral-Arroyo, Pablo; Aellig, Raphael; Orlando, Fabrizio; Lee, Ming-Tao; Artiglia, Luca

    2016-04-01

    Oxidation of halide ions (chloride, bromide, iodide) are the starting point of halogen release mechanisms out of sea water, marine aerosol or other halide containing continental aerosols. Slow oxidation of chloride and bromide by ozone in the bulk aqueous phase is of limited relevance. Faster surface specific oxidation has been suggested based on heterogeneous kinetics experiments. We provide first insight into very efficient bromide oxidation by ozone at the aqueous solution - air interface by surface sensitive X-ray photoelectron spectroscopy indicating significant build-up of an oxidized intermediate at the surface within millisecond time scales. The second source of oxidants in the condensed we have considered is the absorption of light by triplet forming photosensitizers at wavelengths longer than needed for direct photolysis and radical formation. We have performed coated wall flow tube experiments with mixtures of citric acid (CA) and imidazole-2-carboxaldehyde (IC) to represent secondary organic material rich marine aerosol. The halide ions bromide and iodide have been observed to act as efficient electron donors leading to their oxidation, HO2 formation and finally release of molecular halogen compounds. The photosensitization of imidazole-2-carboxaldehyde (IC) involves a well-known mechanism where the triplet excited state of IC is reduced by citric acid to a reduced ketyl radical that reacts with halide ions. A competition kinetics approach has been used to evaluate the rate limiting steps and to assess the significance of this source of halogens to the gas phase.

  9. Liquid flexRIXS: A RIXS endstation for molecular systems at BESSY II

    OpenAIRE

    2016-01-01

    The liquid flexRIXS endstation is dedicated to resonant inelastic x-ray scattering experiments on liquid samples and gasses in the soft x-ray range. The liquids are injected into the chamber via a liquid jet system whereas gasses and also small amounts of liquids can be investigated using a liquid/gas flow cell. The MCP-based RIXS spectrometer allows for a resolving power of better than 1000.

  10. Molecularly imprinted solid-phase extraction combined with ultrasound-assisted dispersive liquid-liquid microextraction for the determination of four Sudan dyes in sausage samples.

    Science.gov (United States)

    Yan, Hongyuan; Qiao, Jindong; Wang, Hui; Yang, Gengliang; Row, Kyung Ho

    2011-06-21

    A simple and highly selective molecularly imprinted solid-phase extraction (MISPE) combined with ultrasound-assisted dispersive liquid-liquid microextraction (DLLME) was developed for the determination of four Sudan dye (I, II, III, and IV) residues in sausage products. The novel molecularly imprinted microspheres (MIMs) synthesized by aqueous suspension polymerization using phenylamine-naphthol as the dummy template show high affinity to the four Sudan dyes and were applied as selective sorbents of MISPE-DLLME to overcome the drawbacks of template leakage in quantitative analysis. Good linearity was obtained in a range of 0.005-2.0 μg g(-1) and the average recoveries of the four Sudan dyes at three spiked levels ranged from 86.3 to 107.5%. The MISPE-DLLME-HPLC protocol significantly improved the purification and enrichment of the analytes and eliminated the template leakage of the conventional MISPE on quantitative analysis.

  11. The interplay between dynamic heterogeneities and structure of bulk liquid water: A molecular dynamics simulation study

    Energy Technology Data Exchange (ETDEWEB)

    Demontis, Pierfranco; Suffritti, Giuseppe B. [Dipartimento di Chimica e Farmacia, Università degli studi di Sassari, Sassari (Italy); Consorzio Interuniversitario Nazionale per la Scienza e Tecnologia dei Materiali (INSTM), Unità di ricerca di Sassari, Via Vienna, 2, I-07100 Sassari (Italy); Gulín-González, Jorge [Grupo de Matemática y Física Computacionales, Universidad de las Ciencias Informáticas (UCI), Carretera a San Antonio de los Baños, Km 21/2, La Lisa, La Habana (Cuba); Masia, Marco [Dipartimento di Chimica e Farmacia, Università degli studi di Sassari, Sassari (Italy); Consorzio Interuniversitario Nazionale per la Scienza e Tecnologia dei Materiali (INSTM), Unità di ricerca di Sassari, Via Vienna, 2, I-07100 Sassari (Italy); Istituto Officina dei Materiali del CNR, UOS SLACS, Via Vienna 2, 07100 Sassari (Italy); Sant, Marco [Dipartimento di Chimica e Farmacia, Università degli studi di Sassari, Sassari (Italy)

    2015-06-28

    In order to study the interplay between dynamical heterogeneities and structural properties of bulk liquid water in the temperature range 130–350 K, thus including the supercooled regime, we use the explicit trend of the distribution functions of some molecular properties, namely, the rotational relaxation constants, the atomic mean-square displacements, the relaxation of the cross correlation functions between the linear and squared displacements of H and O atoms of each molecule, the tetrahedral order parameter q and, finally, the number of nearest neighbors (NNs) and of hydrogen bonds (HBs) per molecule. Two different potentials are considered: TIP4P-Ew and a model developed in this laboratory for the study of nanoconfined water. The results are similar for the dynamical properties, but are markedly different for the structural characteristics. In particular, for temperatures higher than that of the dynamic crossover between “fragile” (at higher temperatures) and “strong” (at lower temperatures) liquid behaviors detected around 207 K, the rotational relaxation of supercooled water appears to be remarkably homogeneous. However, the structural parameters (number of NNs and of HBs, as well as q) do not show homogeneous distributions, and these distributions are different for the two water models. Another dynamic crossover between “fragile” (at lower temperatures) and “strong” (at higher temperatures) liquid behaviors, corresponding to the one found experimentally at T{sup ∗} ∼ 315 ± 5 K, was spotted at T{sup ∗} ∼ 283 K and T{sup ∗} ∼ 276 K for the TIP4P-Ew and the model developed in this laboratory, respectively. It was detected from the trend of Arrhenius plots of dynamic quantities and from the onset of a further heterogeneity in the rotational relaxation. To our best knowledge, it is the first time that this dynamical crossover is detected in computer simulations of bulk water. On the basis of the simulation results, the possible

  12. Molecular dynamics simulation of liquid water confined inside graphite channels: dielectric and dynamical properties.

    Science.gov (United States)

    Martí, J; Nagy, G; Guàrdia, E; Gordillo, M C

    2006-11-30

    Electric and dielectric properties and microscopic dynamics of liquid water confined between graphite slabs are analyzed by means of molecular dynamics simulations for several graphite-graphite separations at ambient conditions. The electric potential across the interface shows oscillations due to water layering, and the overall potential drop is about -0.28 V. The total dielectric constant is larger than the corresponding value for the bulklike internal region of the system. This is mainly due to the preferential orientations of water nearest the graphite walls. Estimation of the capacitance of the system is reported, indicating large variations for the different adsorption layers. The main trend observed concerning water diffusion is 2-fold: on one hand, the overall diffusion of water is markedly smaller for the closest graphite-graphite separations, and on the other hand, water molecules diffuse in interfaces slightly slower than those in the bulklike internal areas. Molecular reorientational times are generally larger than those corresponding to those of unconstrained bulk water. The analysis of spectral densities revealed significant spectral shifts, compared to the bands in unconstrained water, in different frequency regions, and associated to confinement effects. These findings are important because of the scarce information available from experimental, theoretical, and computer simulation research into the dielectric and dynamical properties of confined water.

  13. Nuclear magnetic shielding constants of liquid water: Insights from hybrid quantum mechanics/molecular mechanics models

    Science.gov (United States)

    Kongsted, Jacob; Nielsen, Christian B.; Mikkelsen, Kurt V.; Christiansen, Ove; Ruud, Kenneth

    2007-01-01

    We present a gauge-origin independent method for the calculation of nuclear magnetic shielding tensors of molecules in a structured and polarizable environment. The method is based on a combination of density functional theory (DFT) or Hartree-Fock wave functions with molecular mechanics. The method is unique in the sense that it includes three important properties that need to be fulfilled in accurate calculations of nuclear magnetic shielding constants: (i) the model includes electron correlation effects, (ii) the model uses gauge-including atomic orbitals to give gauge-origin independent results, and (iii) the effect of the environment is treated self-consistently using a discrete reaction-field methodology. The authors present sample calculations of the isotropic nuclear magnetic shielding constants of liquid water based on a large number of solute-solvent configurations derived from molecular dynamics simulations employing potentials which treat solvent polarization either explicitly or implicitly. For both the O17 and H1 isotropic shielding constants the best predicted results compare fairly well with the experimental data, i.e., they reproduce the experimental solvent shifts to within 4ppm for the O17 shielding and 1ppm for the H1 shielding.

  14. Nuclear magnetic shielding constants of liquid water: insights from hybrid quantum mechanics/molecular mechanics models.

    Science.gov (United States)

    Kongsted, Jacob; Nielsen, Christian B; Mikkelsen, Kurt V; Christiansen, Ove; Ruud, Kenneth

    2007-01-21

    We present a gauge-origin independent method for the calculation of nuclear magnetic shielding tensors of molecules in a structured and polarizable environment. The method is based on a combination of density functional theory (DFT) or Hartree-Fock wave functions with molecular mechanics. The method is unique in the sense that it includes three important properties that need to be fulfilled in accurate calculations of nuclear magnetic shielding constants: (i) the model includes electron correlation effects, (ii) the model uses gauge-including atomic orbitals to give gauge-origin independent results, and (iii) the effect of the environment is treated self-consistently using a discrete reaction-field methodology. The authors present sample calculations of the isotropic nuclear magnetic shielding constants of liquid water based on a large number of solute-solvent configurations derived from molecular dynamics simulations employing potentials which treat solvent polarization either explicitly or implicitly. For both the (17)O and (1)H isotropic shielding constants the best predicted results compare fairly well with the experimental data, i.e., they reproduce the experimental solvent shifts to within 4 ppm for the (17)O shielding and 1 ppm for the (1)H shielding.

  15. Molecular dynamics simulations of the structural and thermodynamic properties of imidazolium-based ionic liquid mixtures.

    Science.gov (United States)

    Méndez-Morales, T; Carrete, J; Cabeza, O; Gallego, L J; Varela, L M

    2011-09-29

    In this work, extensive molecular dynamics simulations of mixtures of alcohols of several chain lengths (methanol and ethanol) with the ionic liquids (ILs) composed of the cation 1-hexyl-3-methylimidazolium and several anions of different hydrophobicity degrees (Cl(-), BF(4)(-), PF(6)(-)) are reported. We analyze the influence of the nature of the anion, the length of the molecular chain of the alcohol, and the alcohol concentration on the thermodynamic and structural properties of the mixtures. Densities, excess molar volumes, total and partial radial distribution functions, coordination numbers, and hydrogen bond degrees are reported and analyzed for mixtures of the ILs with methanol and ethanol. The aggregation process is shown to be highly dependent on the nature of the anion and the size of the alcohol, since alcohol molecules tend to interact predominantly with the anionic part of the IL, especially in mixtures of the halogenated IL with methanol. Particularly, our results suggest that the formation of an apolar network similar to that previously reported in mixtures of ILs with water does not take place in mixtures with alcohol when the chloride anion is present, the alcohol molecules being instead homogeneously distributed in the polar network of IL. Moreover, the alcohol clusters formed in mixtures of [HMIM][PF(6)] with alcohol were found to have a smaller size than in mixtures with water. Additionally, we provide a semiquantitative analysis of the dependence of the hydrogen bonding degree of the mixtures on the alcohol concentration. © 2011 American Chemical Society

  16. Simulations of the flipping images and microparameters of molecular orientations in liquids according to the molecule string model

    Institute of Scientific and Technical Information of China (English)

    Wang Li-Na; Zhao Xing-Yu; Zhang Li-Li; Huang Yi-Neng

    2012-01-01

    The relaxation dynamics of liquids is one of the fundamental problems in liquid physics,and it is also one of the key issues to understand the glass transition mechanism.It will undoubtedly provide enlightenment on understanding and calculating the relaxation dynamics if the molecular orientation flipping images and relevant microparameters of liquids are studied.In this paper,we first give five microparameters to describe the individual molecular string (MS) relaxation based on the dynamical Hamiltonian of the MS model,and then simulate the images of individual MS ensemble,and at the same time calculate the parameters of the equilibrium state.The results show that the main molecular orientation flipping image in liquids (including supercooled liquid) is similar to the random walk.In addition,two pairs of the parameters are equal,and one can be ignored compared with the other.This conclusion will effectively reduce the difficulties in calculating the individual MS relaxation based on the single-molecule orientation flipping rate of the general Glauber type,and the computer simulation time of interaction MS relaxation.Moreover,the conclusion is of reference significance for solving and simulating the multi-state MS model.

  17. Selective extraction of triazine herbicides from food samples based on a combination of a liquid membrane and molecularly imprinted polymers.

    Science.gov (United States)

    Mhaka, Byron; Cukrowska, Ewa; Bui, Bernadette Tse Sum; Ramström, Olof; Haupt, Karsten; Tutu, Hlanganani; Chimuka, Luke

    2009-10-02

    A selective extraction technique based on the combination of liquid membrane (microporous membrane liquid-liquid extraction) and molecularly imprinted polymers (MIP) was applied to triazines herbicides in food samples. Simazine, atrazine and propazine were extracted from aqueous food samples through the hydrophobic porous membrane that was impregnated with toluene, which also formed part of the acceptor phase. In the acceptor phase, the compounds were re-extracted onto MIP particles. The extraction technique was optimised for the amount of molecularly imprinted polymers particles in the organic acceptor phase, extraction time, and type of organic acceptor solvent and desorption solvent. An extraction time of 90 min and 50mg of MIP were found to be optimum parameters. Toluene as the acceptor phase was found to give higher triazines binding onto MIP particles compared to hexane and combinations of diethyl ether and hexane. 90% methanol in water was found to be the best desorption solvent compared to acetonitrile, methanol and water. The selectivity of the technique was demonstrated by extracting spiked lettuce and apple extracts where clean chromatograms were obtained compared to liquid membrane extraction alone or to the microporous membrane liquid-liquid extraction - non-imprinted polymer combination. The MIP showed a certain degree of group specificity and the extraction efficiency in lettuce extract was 79% (0.72) for simazine, 98% (1.55) for atrazine and 86% (3.08) for propazine.

  18. Controlling the color of cholesteric liquid-crystalline films by photoirradiation of a chiroptical molecular switch used as dopant

    NARCIS (Netherlands)

    van Delden, RA; Huck, NPM; Feringa, BL; Delden, Richard A. van; Gelder, Marc B. van; Huck, Nina P.M.

    2003-01-01

    Using thin films of a cholesteric mixture of acrylates 2 and 3 doped with the chiroptical molecular switch (M)-trans-1, photo-control of the reflection color between red and green is possible. This doped liquid-crystal (LC) film can be used for photoinduced writing, color reading, and photoinduced l

  19. Efficient analysis of highly complex nuclear magnetic resonance spectra of flexible solutes in ordered liquids by using molecular dynamics

    NARCIS (Netherlands)

    Weber, A.C.J.; Pizzirusso, A.; Muccioli, L.; Zannoni, C.; Meerts, W.L.; Lange, de C.A.; Burnell, E.E.

    2012-01-01

    The NMR spectra of n-pentane as solute in the liquid crystal 5CB are measured at several temperatures in the nematic phase. Atomistic molecular dynamics simulations of this system are carried out to predict the dipolar couplings of the orientationally ordered pentane, and the spectra predicted from

  20. Efficient analysis of highly complex nuclear magnetic resonance spectra of flexible solutes in ordered liquids by using molecular dynamics

    NARCIS (Netherlands)

    Weber, A.C.J.; Pizzirusso, A.; Muccioli, L.; Zannoni, C.; Meerts, W.L.; Lange, de C.A.; Burnell, E.E.

    2012-01-01

    The NMR spectra of n-pentane as solute in the liquid crystal 5CB are measured at several temperatures in the nematic phase. Atomistic molecular dynamics simulations of this system are carried out to predict the dipolar couplings of the orientationally ordered pentane, and the spectra predicted from

  1. Accommodative Behavior of Non-porous Molecular crystal at Solid-Gas and Solid-Liquid Interface

    OpenAIRE

    Mande, Hemant M.; Ghalsasi, Prasanna S.

    2015-01-01

    Molecular crystals demonstrate drastically different behavior in solid and liquid state, mainly due to their difference in structural frameworks. Therefore, designing of unique structured molecular compound which can work at both these interfaces has been a challenge. Here, we present remarkable ‘molecular’ property by non-porous molecular solid crystal, dinuclear copper complex (C6H5CH(X)NH2)2CuCl2, to reversibly ‘adsorb’ HCl gas at solid-gas interface as well as ‘accommodate’ azide anion at...

  2. Variable Charge and Electrical Double Layer of Mineral-Water Interfaces: Silver Halides versus Metal (Hydr)Oxides

    NARCIS (Netherlands)

    Hiemstra, T.

    2012-01-01

    Classically, silver (Ag) halides have been used to understand thermodynamic principles of the charging process and the corresponding development of the electrical double layer (EDL). A mechanistic approach to the processes on the molecular level has not yet been carried out using advanced surface co

  3. Rapid Microwave-Assisted Copper-Catalyzed Nitration of Aromatic Halides with Nitrite Salts

    Energy Technology Data Exchange (ETDEWEB)

    Paik, Seung Uk; Jung, Myoung Geun [Keimyung University, Daegu (Korea, Republic of)

    2012-02-15

    A rapid and efficient copper-catalyzed nitration of aryl halides has been established under microwave irradiation. The catalytic systems were found to be the most effective with 4-substituted aryl iodides leading to nearly complete conversions. Nitration of aromatic compounds is one of the important industrial processes as underlying intermediates in the manufacture of a wide range of chemicals such as dyes, pharmaceuticals, agrochemicals and explosives. General methods for the nitration of aromatic compounds utilize strongly acidic conditions employing nitric acid or a mixture of nitric and sulfuric acids, sometimes leading to problems with poor regioselectivity, overnitration, oxidized byproducts and excess acid waste in many cases of functionalized aromatic compounds. Several other nitrating agents or methods avoiding harsh reaction conditions have been explored using metal nitrates, nitrite salts, and ionic liquid-mediated or microwave-assisted nitrations. Recently, copper or palladium compounds have been successfully used as efficient catalysts for the arylation of amines with aryl halides under mild conditions.

  4. Identical extraction behavior and coordination of trivalent or hexavalent f-element cations using ionic liquid and molecular solvents.

    Science.gov (United States)

    Cocalia, Violina A; Jensen, Mark P; Holbrey, John D; Spear, Scott K; Stepinski, Dominique C; Rogers, Robin D

    2005-06-07

    The extraction of both UO2(2+) and trivalent lanthanide and actinide ions (Am3+, Nd3+, Eu3+) by dialkylphosphoric or dialkylphosphinic acids from aqueous solutions into the ionic liquid, 1-decyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imide has been studied and compared to extractions into dodecane. Radiotracer partitioning measurements show comparable patterns of distribution ratios for both the ionic liquid/aqueous and dodecane/aqueous systems, and the limiting slopes at low acidity indicate the partitioning of neutral complexes in both solvent systems. The metal ion coordination environment, elucidated from EXAFS and UV-visible spectroscopy measurements, is equivalent in the ionic liquid and dodecane solutions with coordination of the uranyl cation by two hydrogen-bonded extractant dimers, and of the trivalent cations by three extractant dimers. This is the first definitive report of a system where both the biphasic extraction equilibria and metal coordination environment are the same in an ionic liquid and a molecular organic solvent.

  5. Molecular dynamics study on evaporation and condensation of n-dodecane at liquid-vapor phase equilibria.

    Science.gov (United States)

    Cao, Bing-Yang; Xie, Jian-Fei; Sazhin, Sergei S

    2011-04-28

    Molecular dynamics simulations are performed to study the evaporation and condensation of n-dodecane (C(12)H(26)) at temperatures in the range 400-600 K. A modified optimized potential for liquid simulation model is applied to take into account the Lennard-Jones, bond bending and torsion potentials with the bond length constrained. The equilibrium liquid-vapor n-dodecane interface thickness is predicted to be ~1.2-2.0 nm. It is shown that the molecular chains lie preferentially parallel to the interface in the liquid-vapor transition region. The predicted evaporation/condensation coefficient decreased from 0.9 to 0.3 when temperature increased from 400 to 600 K. These values can be used for the formulation of boundary conditions in the kinetic modeling of droplet heating and evaporation processes; they are noticeably different from those predicted by the transition state theory. We also present the typical molecular behaviors in the evaporation and condensation processes. The molecular exchange in condensation, typical for simple molecules, has never been observed for n-dodecane molecular chains.

  6. Halo- and azidodediazoniation of arenediazonium tetrafluoroborates with trimethylsilyl halides and trimethylsilyl azide and sandmeyer-type bromodediazoniation with Cu(I)Br in [BMIM][PF6] ionic liquid.

    Science.gov (United States)

    Hubbard, Abigail; Okazaki, Takao; Laali, Kenneth K

    2008-01-04

    Reaction of [ArN(2)][BF(4)] salts immobilized in [BMIM][PF(6)] ionic liquid (IL) with TMSX (X = I, Br) and TMSN(3) represents an efficient method for the preparation of iodo-, bromo-, and azido-derivatives via dediazoniation. The reactions can also be effected starting with ArNH(2) by in situ diazotization with [NO][BF(4)] followed by reaction with TMSX or TMSN(3). Depending on the substituents on the benzenediazonium cation, competing fluorodediazoniation (ArF formation) and hydrodediazoniation (ArH formation) were observed. Dediazoniation with TMSN(3) and with TMSI generally gave the highest chemoselectivity toward ArN(3) and ArI formation. The IL was recycled and reused up to 5 times with no appreciable decrease in the conversions. Multinuclear NMR monitoring of the interaction of [ArN(2)][BF(4)]/TMSX, [BMIM][PF6]/TMSX, and [BMIM][PF(6)]/TMSX/[ArN(2)][BF(4)] indicated that TMSF is formed primarily via [ArN(2)][BF(4)]/TMSX, generating [ArN(2)][X] in situ, which gives ArX on dediazoniation. Competing formation of ArF in Sandmeyer-type bromodediazoniation of [ArN(2)][BF(4)] with Cu(I)Br immobilized in the IL points to significant involvement of heterolytic dediazoniation.

  7. Experimental and ab initio molecular dynamics study of the structure and physical properties of liquid GeTe

    Science.gov (United States)

    Weber, Hans; Schumacher, Mathias; Jóvári, Pál; Tsuchiya, Yoshimi; Skrotzki, Werner; Mazzarello, Riccardo; Kaban, Ivan

    2017-08-01

    GeTe is a prototypical phase-change material employed in data storage devices. In this work, the atomic structure of liquid GeTe is studied by x-ray and neutron diffraction in the temperature range from 1197 to 998 K. The dynamic viscosity is measured from 1273 to 953 K, which is 55 K below the solidification point, using an oscillating-cup viscometer. The density of liquid GeTe between 1293 and 973 K is determined by the high-energy γ -ray attenuation method. The experiments are complemented with ab initio molecular dynamics (AIMD) simulations based on density functional theory (DFT). Compatibility of the AIMD-DFT models with the diffraction data is proven by simultaneous fitting of all data sets in the frame of the reverse Monte Carlo simulation technique. It is shown that octahedral order dominates in liquid GeTe, although tetrahedral structures are also present. The viscosity of the equilibrium and weakly undercooled liquid GeTe obeys the Arrhenius law with a small activation energy of the order of 0.3 eV, which is indicative of a highly fragile liquid. The calculated density of states and electronic wave functions point to the existence of a pseudogap and localized electron states within the gap in the equilibrium liquid near the melting point as well as in the undercooled liquid.

  8. Metal Hydride and Alkali Halide Opacities in Extrasolar Giant Planets and Cool Stellar Atmospheres

    Science.gov (United States)

    Weck, Philippe F.; Stancil, Phillip C.; Kirby, Kate; Schweitzer, Andreas; Hauschildt, Peter H.

    2006-01-01

    The lack of accurate and complete molecular line and continuum opacity data has been a serious limitation to developing atmospheric models of cool stars and Extrasolar Giant Planets (EGPs). We report our recent calculations of molecular opacities resulting from the presence of metal hydrides and alkali halides. The resulting data have been included in the PHOENIX stellar atmosphere code (Hauschildt & Baron 1999). The new models, calculated using spherical geometry for all gravities considered, also incorporate our latest database of nearly 670 million molecular lines, and updated equations of state.

  9. Probing molecular interaction in ionic liquids by low frequency spectroscopy: Coulomb energy, hydrogen bonding and dispersion forces.

    Science.gov (United States)

    Fumino, Koichi; Reimann, Sebastian; Ludwig, Ralf

    2014-10-28

    Ionic liquids are defined as salts composed solely of ions with melting points below 100 °C. These remarkable liquids have unique and fascinating properties and offer new opportunities for science and technology. New combinations of ions provide changing physical properties and thus novel potential applications for this class of liquid materials. To a large extent, the structure and properties of ionic liquids are determined by the intermolecular interaction between anions and cations. In this perspective we show that far infrared and terahertz spectroscopy are suitable methods for studying the cation-anion interaction in these Coulomb fluids. The interpretation of the measured low frequency spectra is supported by density functional theory calculations and molecular dynamics simulations. We present results for selected aprotic and protic ionic liquids and their mixtures with molecular solvents. In particular, we focus on the strength and type of intermolecular interaction and how both parameters are influenced by the character of the ions and their combinations. We show that the total interaction between cations and anions is a result of a subtle balance between Coulomb forces, hydrogen bonds and dispersion forces. For protic ionic liquids we could measure distinct vibrational modes in the low frequency spectra indicating clearly the cation-anion interaction characterized by linear and medium to strong hydrogen bonds. Using isotopic substitution we have been able to dissect frequency shifts related to pure interaction strength between cations and anions and to different reduced masses only. In this context we also show how these different types of interaction may influence the physical properties of ionic liquids such as the melting point, viscosity or enthalpy of vaporization. Furthermore we demonstrate that low frequency spectroscopy can also be used for studying ion speciation. Low vibrational features can be assigned to contact ion pairs and solvent separated

  10. Thermodynamic scaling of molecular dynamics in supercooled liquid state of pharmaceuticals: Itraconazole and ketoconazole

    Energy Technology Data Exchange (ETDEWEB)

    Tarnacka, M., E-mail: mtarnacka@us.edu.pl; Madejczyk, O.; Kamiński, K.; Paluch, M. [Institute of Physics, University of Silesia, ul. Uniwersytecka 4, 40-007 Katowice (Poland); Silesian Center of Education and Interdisciplinary Research, University of Silesia, ul. 75 Pulku Piechoty 1A, 41-500 Chorzow (Poland); Adrjanowicz, K. [NanoBioMedical Centre, ul. Umultowska 85, 61-614 Poznan (Poland); Pionteck, J. [Leibniz Institute of Polymer Research Dresden, Hohe Strasse 6, D-01069 Dresden (Germany); Kaminska, E. [Department of Pharmacognosy and Phytochemistry, School of Pharmacy and Division of Laboratory Medicine in Sosnowiec, Medical University of Silesia, ul. Jagiellonska 4, 41-200 Sosnowiec (Poland)

    2015-06-14

    Pressure-Volume-Temperature (PVT) measurements and broadband dielectric spectroscopy were carried out to investigate molecular dynamics and to test the validity of thermodynamic scaling of two homologous compounds of pharmaceutical activity: itraconazole and ketoconazole in the wide range of thermodynamic conditions. The pressure coefficients of the glass transition temperature (dT{sub g}/dp) for itraconazole and ketoconazole were determined to be equal to 183 and 228 K/GPa, respectively. However, for itraconazole, the additional transition to the nematic phase was observed and characterized by the pressure coefficient dT{sub n}/dp = 258 K/GPa. From PVT and dielectric data, we obtained that the liquid-nematic phase transition is governed by the relaxation time since it occurred at constant τ {sub α} = 10{sup −5} s. Furthermore, we plotted the obtained relaxation times as a function of T{sup −1}v{sup −γ}, which has revealed that the validity of thermodynamic scaling with the γ exponent equals to 3.69 ± 0.04 and 3.64 ± 0.03 for itraconazole and ketoconazole, respectively. Further analysis of the scaling parameter in itraconazole revealed that it unexpectedly decreases with increasing relaxation time, which resulted in dramatic change of the shape of the thermodynamic scaling master curve. While in the case of ketoconazole, it remained the same within entire range of data (within experimental uncertainty). We suppose that in case of itraconazole, this peculiar behavior is related to the liquid crystals’ properties of itraconazole molecule.

  11. Evaluation of molecular dynamics simulation methods for ionic liquid electric double layers

    Science.gov (United States)

    Haskins, Justin B.; Lawson, John W.

    2016-05-01

    We investigate how systematically increasing the accuracy of various molecular dynamics modeling techniques influences the structure and capacitance of ionic liquid electric double layers (EDLs). The techniques probed concern long-range electrostatic interactions, electrode charging (constant charge versus constant potential conditions), and electrolyte polarizability. Our simulations are performed on a quasi-two-dimensional, or slab-like, model capacitor, which is composed of a polarizable ionic liquid electrolyte, [EMIM][BF4], interfaced between two graphite electrodes. To ensure an accurate representation of EDL differential capacitance, we derive new fluctuation formulas that resolve the differential capacitance as a function of electrode charge or electrode potential. The magnitude of differential capacitance shows sensitivity to different long-range electrostatic summation techniques, while the shape of differential capacitance is affected by charging technique and the polarizability of the electrolyte. For long-range summation techniques, errors in magnitude can be mitigated by employing two-dimensional or corrected three dimensional electrostatic summations, which led to electric fields that conform to those of a classical electrostatic parallel plate capacitor. With respect to charging, the changes in shape are a result of ions in the Stern layer (i.e., ions at the electrode surface) having a higher electrostatic affinity to constant potential electrodes than to constant charge electrodes. For electrolyte polarizability, shape changes originate from induced dipoles that soften the interaction of Stern layer ions with the electrode. The softening is traced to ion correlations vertical to the electrode surface that induce dipoles that oppose double layer formation. In general, our analysis indicates an accuracy dependent differential capacitance profile that transitions from the characteristic camel shape with coarser representations to a more diffuse

  12. Molecular catalytic coal liquid conversion. Quarterly progress report, [January--March 1993

    Energy Technology Data Exchange (ETDEWEB)

    Stock, L.M.; Cheng, C.; Ettinger, M.

    1993-03-31

    Last quarter, substantial progress has been made in the two general tasks advanced in our research proposal. The first task consists of the development of molecular homogeneous catalysts that can be used in the hydrogenation of coal liquids and in coal conversion processes. The second task concerns the activation of dihydrogen by basic catalysts in homogeneous reaction systems. With regards to the first task, we have prepared two organometallic rhodium (1) catalysts. These are the dimer of dichloropentamethylcyclopentadienylrhodium, [RhCl{sub 2}(C{sub 5}Me{sub 5})], and the dimer of chloro(1,5-hexadiene)rhodium We have subsequently investigated the hydrogenation of various aromatic organic compounds using these organometallic reagents as catalysts. Results showed that both catalysts effected the hydrogenation of the aromatic portions of a wide range of organic compounds, including aromatic hydrocarbons and aromatic compounds containing the ether group, alkyl groups, amino and carbonyl groups. However, both compounds were totally ineffective in catalyzing the hydrogenation of sulfur-containing aromatic organic compounds. Nevertheless, both rhodium catalysts successfully catalyzed the hydrogenation of naphthalene even in the presence of the coal liquids. With regards to base-activated hydrogenation of organic compounds, we have found that hydroxide and alkoxide bases are capable of activating,dihydrogen, thereby leading to the hydrogenation of phenyl-substituted alkenes. More specifically, tetrabutylammonium hydroxide, potassium tert-butoxide and potassium phenoxide were successfully used to activate dihydrogen and induce the hydrogenation of trans-stilbene. Potassium tert-butoxide was found to be slightly more effective than the other two bases in accomplishing this chemistry.

  13. Accurate schemes for calculation of thermodynamic properties of liquid mixtures from molecular dynamics simulations

    Science.gov (United States)

    Caro, Miguel A.; Laurila, Tomi; Lopez-Acevedo, Olga

    2016-12-01

    We explore different schemes for improved accuracy of entropy calculations in aqueous liquid mixtures from molecular dynamics (MD) simulations. We build upon the two-phase thermodynamic (2PT) model of Lin et al. [J. Chem. Phys. 119, 11792 (2003)] and explore new ways to obtain the partition between the gas-like and solid-like parts of the density of states, as well as the effect of the chosen ideal "combinatorial" entropy of mixing, both of which have a large impact on the results. We also propose a first-order correction to the issue of kinetic energy transfer between degrees of freedom (DoF). This problem arises when the effective temperatures of translational, rotational, and vibrational DoF are not equal, either due to poor equilibration or reduced system size/time sampling, which are typical problems for ab initio MD. The new scheme enables improved convergence of the results with respect to configurational sampling, by up to one order of magnitude, for short MD runs. To ensure a meaningful assessment, we perform MD simulations of liquid mixtures of water with several other molecules of varying sizes: methanol, acetonitrile, N, N-dimethylformamide, and n-butanol. Our analysis shows that results in excellent agreement with experiment can be obtained with little computational effort for some systems. However, the ability of the 2PT method to succeed in these calculations is strongly influenced by the choice of force field, the fluidicity (hard-sphere) formalism employed to obtain the solid/gas partition, and the assumed combinatorial entropy of mixing. We tested two popular force fields, GAFF and OPLS with SPC/E water. For the mixtures studied, the GAFF force field seems to perform as a slightly better "all-around" force field when compared to OPLS+SPC/E.

  14. Molecular Simulation on Microstructure of Ionic Liquids in Capture of CO2

    Institute of Scientific and Technical Information of China (English)

    YUE Zhen-uo; LIU Xiao-min; ZHAO Yu-ling; ZHANG Xiao-chun; LU Xing-mei; ZHANG Suo-jiang

    2011-01-01

    Molecular dynamic simulation is used to study the microstructure of four kinds of ionic liquids (ILs),[Emim]PF6,[Emim][Tf2N],[PC6,6,6,14]PF6 and [PC6,6,6,14][Tf2N] in the capture process of CO2.Radial distribution function (RDF) and spatial distribution function (SDF) are used to analyze the microscopic properties of these systems.The calculated results show that the space distribution of CO2 around ILs determines the capability of ionic liquids for capturing CO2.Based on the analysis of SDF,CO2 and PF6- are overlapped partially around [Emim]+ in [Emim]PF6-CO2 mixture.When the anion is [Tf2N]-,cations are mainly distributed on one side of [Tf2N]- near N atom,and CO2 is concentrated on two sides near the fluoroalkylgroup (-CF3),and there is little overlapped district between cation and CO2.In [PC6,6,6,14]PF6-CO2 mixture,layered structure is found and CO2 is much nearer to PF6- than [PC6,6,6,14]+.Based on the analysis of RDF,in the phosphonium-based ILs,the highest distribution densities of anions and CO2 around cations are about 6 and 3 times as their average ones respectively,while in the imidazolium-based ILs,they are about 3 and 2 respectively,this means that the distributions of CO2 and anions around the imidazolium-based ILs are more evenly distributed than those around the phosphonium-bascd ILs.

  15. Molecular dynamics simulation studies of ionic liquid electrolytes for electric double layer capacitors

    Science.gov (United States)

    Hu, Zongzhi

    Molecular Dynamics (MD) simulation has been performed on various Electric Double Layer Capacitors (EDLCs) systems with different Room Temperature Ionic Liquids (RTILs) as well as different structures and materials of electrodes using a computationally efficient, low cost, united atom (UA)/explicit atom (EA) force filed. MD simulation studies on two 1-butyl-3-methylimidazolium (BMIM) based RTILs, i.e., [BMIM][BF4] and [BMIM][PF6], have been conducted on both atomic flat and corrugated graphite as well as (001) and (011) gold electrode surfaces to understand the correlations between the Electric Double Layer (EDL) structure and their corresponding differential capacitance (DC). Our MD simulations have strong agreement with some experimental data. The structures of electrodes also have a strong effect on the capacitance of EDLCs. MD simulations have been conducted on RTILs of N-methyl-N- propylpyrrolidinium [pyr13] and bis(fluorosulfonyl)imide (FSI) as well as [BMIM][PF6] on both curvature electrodes (fullerenes, nanotube, nanowire) and atomic flat electrode surfaces. It turns out that the nanowire electrode systems have the largest capacitance, following by fullerene systems. Nanotube electrode systems have the smallest capacitance, but they are still larger than that of atomically flat electrode system. Also, RTILs with slightly different chemical structure such as [Cnmim], n = 2, 4, 6, and 8, FSI and bis(trifluoromethylsulfonyl)imide (TFSI), have been examined by MD simulation on both flat and nonflat graphite electrode surfaces to study the effect of cation and anion's chemical structures on EDL structure and DC. With prismatic (nonflat) graphite electrodes, a transition from a bell-shape to a camel-shape DC dependence on electrode potential was observed with increase of the cation alkyl tail length for FSI systems. In contrast, the [Cnmim][TFSI] ionic liquids generated only a camel-shape DC on the rough surface regardless of the length of alkyl tail.

  16. Resolving dispersion and induction components for polarisable molecular simulations of ionic liquids

    Science.gov (United States)

    Pádua, Agílio A. H.

    2017-05-01

    One important development in interaction potential models, or atomistic force fields, for molecular simulation is the inclusion of explicit polarisation, which represents the induction effects of charged or polar molecules on polarisable electron clouds. Polarisation can be included through fluctuating charges, induced multipoles, or Drude dipoles. This work uses Drude dipoles and is focused on room-temperature ionic liquids, for which fixed-charge models predict too slow dynamics. The aim of this study is to devise a strategy to adapt existing non-polarisable force fields upon addition of polarisation, because induction was already contained to an extent, implicitly, due to parametrisation against empirical data. Therefore, a fraction of the van der Waals interaction energy should be subtracted so that the Lennard-Jones terms only account for dispersion and the Drude dipoles for induction. Symmetry-adapted perturbation theory is used to resolve the dispersion and induction terms in dimers and to calculate scaling factors to reduce the Lennard-Jones terms from the non-polarisable model. Simply adding Drude dipoles to an existing fixed-charge model already improves the prediction of transport properties, increasing diffusion coefficients, and lowering the viscosity. Scaling down the Lennard-Jones terms leads to still faster dynamics and densities that match experiment extremely well. The concept developed here improves the overall prediction of density and transport properties and can be adapted to other models and systems. In terms of microscopic structure of the ionic liquids, the inclusion of polarisation and the down-scaling of Lennard-Jones terms affect only slightly the ordering of the first shell of counterions, leading to small decreases in coordination numbers. Remarkably, the effect of polarisation is major beyond first neighbours, significantly weakening spatial correlations, a structural effect that is certainly related to the faster dynamics of

  17. Dielectric relaxation in ionic liquid/dipolar solvent binary mixtures: A semi-molecular theory

    Science.gov (United States)

    Daschakraborty, Snehasis; Biswas, Ranjit

    2016-03-01

    A semi-molecular theory is developed here for studying dielectric relaxation (DR) in binary mixtures of ionic liquids (ILs) with common dipolar solvents. Effects of ion translation on DR time scale, and those of ion rotation on conductivity relaxation time scale are explored. Two different models for the theoretical calculations have been considered: (i) separate medium approach, where molecularities of both the IL and dipolar solvent molecules are retained, and (ii) effective medium approach, where the added dipolar solvent molecules are assumed to combine with the dipolar ions of the IL, producing a fictitious effective medium characterized via effective dipole moment, density, and diameter. Semi-molecular expressions for the diffusive DR times have been derived which incorporates the effects of wavenumber dependent orientational static correlations, ion dynamic structure factors, and ion translation. Subsequently, the theory has been applied to the binary mixtures of 1-butyl-3-methylimidazolium tetrafluoroborate ([Bmim][BF4]) with water (H2O), and acetonitrile (CH3CN) for which experimental DR data are available. On comparison, predicted DR time scales show close agreement with the measured DR times at low IL mole fractions (xIL). At higher IL concentrations (xIL > 0.05), the theory over-estimates the relaxation times and increasingly deviates from the measurements with xIL, deviation being the maximum for the neat IL by almost two orders of magnitude. The theory predicts negligible contributions to this deviation from the xIL dependent collective orientational static correlations. The drastic difference between DR time scales for IL/solvent mixtures from theory and experiments arises primarily due to the use of the actual molecular volume ( Vmol dip ) for the rotating dipolar moiety in the present theory and suggests that only a fraction of Vmol dip is involved at high xIL. Expectedly, nice agreement between theory and experiments appears when experimental

  18. Dielectric relaxation in ionic liquid/dipolar solvent binary mixtures: A semi-molecular theory.

    Science.gov (United States)

    Daschakraborty, Snehasis; Biswas, Ranjit

    2016-03-14

    A semi-molecular theory is developed here for studying dielectric relaxation (DR) in binary mixtures of ionic liquids (ILs) with common dipolar solvents. Effects of ion translation on DR time scale, and those of ion rotation on conductivity relaxation time scale are explored. Two different models for the theoretical calculations have been considered: (i) separate medium approach, where molecularities of both the IL and dipolar solvent molecules are retained, and (ii) effective medium approach, where the added dipolar solvent molecules are assumed to combine with the dipolar ions of the IL, producing a fictitious effective medium characterized via effective dipole moment, density, and diameter. Semi-molecular expressions for the diffusive DR times have been derived which incorporates the effects of wavenumber dependent orientational static correlations, ion dynamic structure factors, and ion translation. Subsequently, the theory has been applied to the binary mixtures of 1-butyl-3-methylimidazolium tetrafluoroborate ([Bmim][BF4]) with water (H2O), and acetonitrile (CH3CN) for which experimental DR data are available. On comparison, predicted DR time scales show close agreement with the measured DR times at low IL mole fractions (x(IL)). At higher IL concentrations (x(IL) > 0.05), the theory over-estimates the relaxation times and increasingly deviates from the measurements with x(IL), deviation being the maximum for the neat IL by almost two orders of magnitude. The theory predicts negligible contributions to this deviation from the x(IL) dependent collective orientational static correlations. The drastic difference between DR time scales for IL/solvent mixtures from theory and experiments arises primarily due to the use of the actual molecular volume (V(mol)(dip)) for the rotating dipolar moiety in the present theory and suggests that only a fraction of V(mol)(dip) is involved at high x(IL). Expectedly, nice agreement between theory and experiments appears when

  19. Infrared spectra of FHF - in alkali halides

    Science.gov (United States)

    Chunnilall, C. J.; Sherman, W. F.

    1982-03-01

    The bifluoride ion, FHF -, has been substitutionally isolated within single crystal samples of several different alkali halides. Infrared spectra of these crystals have been studied for sample temperatures down to 8K when half-bandwidths of less than 1 cm -1 have been observed. (Note that at room temperature ν 3 is observed to have a half-bandwidth of about 40 cm -1). The frequency shifts and half-bandwidth changes caused by cooling are considered together with the frequency shifts caused by pressures up to 10 k bar. The low temperature spectra clearly indicate that FHF - is a linear symmetrical ion when substitutionally isolated within alkali halides of either the NaCl or CsCl structure.

  20. Chiral Alkyl Halides: Underexplored Motifs in Medicine

    Directory of Open Access Journals (Sweden)

    Bálint Gál

    2016-11-01

    Full Text Available While alkyl halides are valuable intermediates in synthetic organic chemistry, their use as bioactive motifs in drug discovery and medicinal chemistry is rare in comparison. This is likely attributable to the common misconception that these compounds are merely non-specific alkylators in biological systems. A number of chlorinated compounds in the pharmaceutical and food industries, as well as a growing number of halogenated marine natural products showing unique bioactivity, illustrate the role that chiral alkyl halides can play in drug discovery. Through a series of case studies, we demonstrate in this review that these motifs can indeed be stable under physiological conditions, and that halogenation can enhance bioactivity through both steric and electronic effects. Our hope is that, by placing such compounds in the minds of the chemical community, they may gain more traction in drug discovery and inspire more synthetic chemists to develop methods for selective halogenation.

  1. Lanthanide-halide based humidity indicators

    Science.gov (United States)

    Beitz, James V.; Williams, Clayton W.

    2008-01-01

    The present invention discloses a lanthanide-halide based humidity indicator and method of producing such indicator. The color of the present invention indicates the humidity of an atmosphere to which it is exposed. For example, impregnating an adsorbent support such as silica gel with an aqueous solution of the europium-containing reagent solution described herein, and dehydrating the support to dryness forms a substance with a yellow color. When this substance is exposed to a humid atmosphere the water vapor from the air is adsorbed into the coating on the pore surface of the silica gel. As the water content of the coating increases, the visual color of the coated silica gel changes from yellow to white. The color change is due to the water combining with the lanthanide-halide complex on the pores of the gel.

  2. Anharmonic properties of potassium halide crystals

    OpenAIRE

    RAJU, Krishna Murti

    2011-01-01

    An effort has been made to obtain the anharmonic properties of potassium halides starting from primary physical parameters viz. nearest neighbor distance and hardness parameters assuming long- and short- range potentials at elevated temperatures. The elastic energy density for a deformed crystal can be expanded as power series of strains for obtaining coefficients of quadratic, cubic and quartic terms which are known as the second, third and fourth order elastic constants respectively...

  3. Investigation of the local structure of mixtures of an ionic liquid with polar molecular species through molecular dynamics: cluster formation and angular distributions.

    Science.gov (United States)

    Carrete, Jesús; Méndez-Morales, Trinidad; Cabeza, Óscar; Lynden-Bell, Ruth M; Gallego, Luis J; Varela, Luis M

    2012-05-24

    In this work, we used molecular dynamics simulations to analyze in detail the spatial distributions of the different constituents in mixtures of 1-butyl-3-methylimidazolium tetrafluoroborate with three polar molecular species: water and two alcohols of different chain lengths (methanol and ethanol). In particular, we report results regarding the influence of the chosen species and its concentration on the formation of ionic and molecular clusters over the whole miscibility range, as well as on the angular distribution of polar molecules around the anion and the cation in these systems. Both analyses showed that addition of a molecular species breaks down the polar network of the pure ionic liquid in clusters whose mean size decreases progressively as more molecules are added. At very high concentrations of the molecular species, the ions are found to be isolated in mixtures with water and methanol, but they tend to form pairs in ethanol. In mixtures with water we identified large clusters that form a water network at very high water concentrations, while at low water concentrations polar molecules tend to form smaller aggregates. In contrast, in mixtures with alkanols there is no evidence of the formation of large alcohol clusters at any concentration. Spatial order in alcohol was also studied by means of the Kirkwood G factor, reaching the conclusion that the angular correlations which appear in pure alcohols due to dipole interactions are destroyed by the ionic liquid, even when present only in tiny amounts.

  4. Molecular dynamics simulations of hydrophobous ions at the liquid-liquid interfaces: case of dicarbollide anions as synergy agents and of ionic liquids as extracting medium; Simulations par dynamique moleculaire d'ions hydrophobes aux interfaces liquide - liquide: le cas des anions dicarbollides comme agents de synergie et celui des liquides ioniques comme milieu extractant

    Energy Technology Data Exchange (ETDEWEB)

    Chevrot, G

    2008-01-15

    Based on molecular dynamics simulations, we first describe the distribution of dicarbollide salts (CCD{sup -}, Mn{sup +}) in concentrated monophasic solutions (water, chloroform, octanol, nitrobenzene) and in the corresponding biphasic 'oil' - water solutions. We point to the importance of surface activity of the CCD{sup -}s and of their self-aggregation in water, with marked counterions effects, and we explain the synergistic effect of CCD{sup -}s in the Eu{sup 3+} extraction by BTP ligands. In the second part of the thesis we report exploratory simulations on the extraction of Sr{sup 2+} by 18-crown-6 to an hydrophobic ionic liquid ([BMI][PF6]), focusing on the liquid - liquid interface. Analogies and differences with a classical aqueous interface are outlined. (author)

  5. Neutron Scattering of Residual Hydrogen in 1,4-Dioxane-D8 Liquid. Understanding Measurements with Molecular Dynamics Simulations

    Energy Technology Data Exchange (ETDEWEB)

    de Almeida, Valmor F. [Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States); Liu, Hongjun [Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States); Herwig, Kenneth W. [Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States); Kidder, Michelle [Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States)

    2016-01-25

    That incoherent scattering from protiated molecular liquids adds a constant background to the measured scattering intensity is well known, but less appreciated is the fact that coherent scattering is also induced by the presence of hydrogen in a deuterated liquid. In fact, the scattering intensity can be very sensitive, in the small-q region, with respect to the amounts and distribution of residual H in the system. We used 1,4-dioxane liquid to demonstrate that the partial structure factors of the HD and DD atom pairs contribute significantly to inter-molecular scattering and that uncertainty in the extent of deuteration account for discrepancies between simulations and measurements. Both contributions to uncertainty have similar magnitudes: scattering interference of the hydrogen-deuterium pair, and complementary interference from the deuterium-deuterium pair by virtue of chemical inhomogeneity. This situation arises in practice since deuteration of liquids is often 99% or less. A combined experimental and extensive computational study of static thermal neutron scattering of 1,4-dioxane demonstrates the foregoing. We show, through simulations, that the reason for the differences is the content of protiated dioxane (vendors quote 1%). We estimate that up to 5% (at 298K and at 343K) protiated mole fraction may be involved in generating the scattering differences. Finally, we find that the particular distribution of hydrogen in the protiated molecules affects the results significantly; here we considered molecules to be either fully protiated or fully deuterated. This scenario best reconciles the computational and experimental results, and leads us to speculate that the deuteration synthesis process tends to leave a molecule either fully deuterated or fully protiated. Although we have used 1,4-dioxane as a model liquid, the effects described in this study extend to similar liquids and similar systematic experimental/computational studies can be performed to either

  6. Lanthanide doped strontium-barium cesium halide scintillators

    Science.gov (United States)

    Bizarri, Gregory; Bourret-Courchesne, Edith; Derenzo, Stephen E.; Borade, Ramesh B.; Gundiah, Gautam; Yan, Zewu; Hanrahan, Stephen M.; Chaudhry, Anurag; Canning, Andrew

    2015-06-09

    The present invention provides for a composition comprising an inorganic scintillator comprising an optionally lanthanide-doped strontium-barium, optionally cesium, halide, useful for detecting nuclear material.

  7. Molecular dynamics studies of a generalised multipole model of molecular asymmetry in apolar and polar liquid crystals

    Energy Technology Data Exchange (ETDEWEB)

    Johnston, S.J

    2001-11-01

    Results are presented from molecular dynamics simulations in the NPT ensemble of novel bent-core liquid crystal systems with the aim of determining the effect of both the bent-core shape and the addition of a transverse electric dipole upon the phase behaviour. The design of these molecules has been prompted by the realisation that ferroelectric phases need not consist of chiral molecules, since in the case of bent-core systems, selective steric shape packing results in a reduced system symmetry and ferroelectric properties without the need for chirality. A simple apolar model of the interaction employed a two-site Gay-Berne potential with the sites separated by {+-}0.5 reduced units for all models investigated. The angle between the sites, 180 deg - {gamma}, and thus the steric dipole was varied in a range {gamma} = 0 deg to {gamma} = 70 deg suggested by real molecules, and was seen to influence the phase behaviour markedly. The rod-like model formed isotropic, nematic, smectic A and smectic B phases. As the angle {gamma} increased the transition temperature to the ordered phase decreased; the nematic phase was first destabilised and then stabilised with respect to the smectic phase. Increasing {gamma} had subtle effects on layer packing in the {gamma} = 10 deg and {gamma} = 20 deg models. The {gamma} = 20 deg model was seen to undergo a transition from the smectic A phase to a tilted smectic B phase. For {gamma} = 40 deg a 'TGB-like' phase similar to the Blue phase seen in real materials was identified as the system cooled whereas for {gamma} = 70 deg no ordered phase formed. The study was repeated with the addition of a transverse electric dipole of {mu}* = 1.5 which was seen to stabilise a range of smectic phases. The nematic phase was destabilised in the rod-like model with a transition directly to a smectic B phase then to a ferroelectric crystal. As the angle {gamma} increased the transition temperature to the first ordered phase decreased more

  8. Segregation of ions at the interface: molecular dynamics studies of the bulk and liquid-vapor interface structure of equimolar binary mixtures of ionic liquids.

    Science.gov (United States)

    Palchowdhury, Sourav; Bhargava, B L

    2015-08-14

    The structures of three different equimolar binary ionic liquid mixtures and their liquid-vapor interface have been studied using atomistic molecular dynamics simulations. Two of these binary mixtures were composed of a common cation 1-n-butyl-3-methylimidazolium and varying anions (chloride and hexafluorophosphate in one of the mixtures and chloride and trifluoromethanesulfonate in the other) and the third binary mixture was composed of a common anion, trifluoromethanesulfonate and two imidazolium cations with ethyl and octyl side chains. Binary mixtures with common cations are found to be homogeneous. The anions are preferentially located near the ring hydrogen atoms due to H-bonding interactions. Segregation of ions is observed at the interface with an enrichment of the liquid-vapor interface layer by longer alkyl chains and bigger anions with a distributed charge. The surface composition is drastically different from that of the bulk composition, with the longer alkyl tail groups and bigger anions populating the outermost layer of the interface. The longer alkyl chains of the cations and trifluoromethanesulfonate anions with a smaller charge density show orientational ordering at the liquid-vapor interface.

  9. Origin of heterogeneous dynamics in local molecular structures of ionic liquids.

    Science.gov (United States)

    Sha, Maolin; Liu, Yusheng; Dong, Huaze; Luo, Fabao; Jiang, Fangling; Tang, Zhongfeng; Zhu, Guanglai; Wu, Guozhong

    2016-11-04

    Room-temperature ionic liquids (ILs) are generally considered as structurally heterogeneous with inherent polar/apolar phase separation. However, even after a decade of research, local dynamics in the heterogeneous structures of ILs remain neglected. Such local dynamics may influence the ion transport of electrolytes, as well as the reaction rate of solvents. In this study, we performed molecular dynamics simulation to analyze the local dynamics for the structural heterogeneity of ILs. Calculations of the diffusion, reorientation, and association dynamics showed a distinct heterogeneous dynamics between the polar and apolar regions of ILs. Further studies demonstrated that such local dynamic differences originate from local structural heterogeneity. Different energy barriers determine a predominant fast reorientation dynamics in apolar regions and a locally vibrating behavior in polar regions. Additionally, we suggested a new jumping mechanism to clarify the dynamic heterogeneity of ions in the polar regions. The results will help determine the origin of the heterogeneous dynamics in IL local structures and provide a theoretical basis for tuning the dynamic properties of ILs used as electrolytes or reaction solvents.

  10. Molecular dynamics simulation of nanomanipulation based on AFM in liquid ambient

    Science.gov (United States)

    Korayem, M. H.; Hefzabad, R. N.; Homayooni, A.; Aslani, H.

    2016-11-01

    Environmental factor is one of the most fundamental parameters in analyzing nanorobots and nanoassemblies. This study focuses on analyzing the manipulation process in a liquid environment using molecular dynamics simulation method. For this purpose, extended simple point-charge water model has been used to model an aqueous media. The effects of different conditions such as substrate material, submerging, electrical charge, and adhesion have been investigated on the manipulation force. In the water media, performing the manipulation process can reduce the manipulation force and increase the possibility of manipulation on the substrates with high adhesion. The manipulation results illustrate that these forces have extremum values in dry (vacuum) and partially submerged nanomanipulations. When the manipulation is carried out in the aqueous media, the interaction of nanoparticle and substrate reduces and leads to decrease the damage of targeted nanoparticle. The RMS criterion confirms this result. The results indicate the adhesion and attraction forces between the tip and nanoparticle reduce in the aqueous media. This reason leads to occur no pulling mode manipulation in the water. Due to dipolar property of water molecules, charge plays a significant role in the manipulation for aqueous ambient. The comparison of manipulation results by charged and chargeless tip shows a larger manipulation force while the charged tip is used.

  11. Adsorption and solvation of ethanol at the water liquid-vapor interface: a molecular dynamics study

    Science.gov (United States)

    Wilson, M. A.; Pohorille, A.

    1997-01-01

    The free energy profiles of methanol and ethanol at the water liquid-vapor interface at 310K were calculated using molecular dynamics computer simulations. Both alcohols exhibit a pronounced free energy minimum at the interface and, therefore, have positive adsorption at this interface. The surface excess was computed from the Gibbs adsorption isotherm and was found to be in good agreement with experimental results. Neither compound exhibits a free energy barrier between the bulk and the surface adsorbed state. Scattering calculations of ethanol molecules from a gas phase thermal distribution indicate that the mass accommodation coefficient is 0.98, and the molecules become thermalized within 10 ps of striking the interface. It was determined that the formation of the solvation structure around the ethanol molecule at the interface is not the rate-determining step in its uptake into water droplets. The motion of an ethanol molecule in a water lamella was followed for 30 ns. The time evolution of the probability distribution of finding an ethanol molecule that was initially located at the interface is very well described by the diffusion equation on the free energy surface.

  12. Macroscopic birefringence in liquid crystals from novel cyanobacterial polysaccharide with an extremely high molecular weight

    Science.gov (United States)

    Okajima-Kaneko, Maiko; Hayasaka-Kaneko, Daisaku; Miyazato, Shinji; Kaneko, Tatsuo

    2007-05-01

    We report an efficient method for extraction of anionic polysaccharides (PS) from cyanobacteria, Aphanothece sacrum; we used a hot alkaline solution (0.01 N NaOH) as an elution solvent in the first step of the extraction and isopropanol as a precipitation solvent in the last step. Thin fibers of PS were obtained at a high yield (50-80 % to the weight of the raw cyanobacterial sample). The spectroscopy and elemental analyses indicated the PS contains fucose, uronic acids (14.2 % by a carbazole-sulfuric acid method), a sugar unit containing amides. The solution of PS with a concentration of 1 wt% showed a very high viscosity (80 000cps) implying a high molecular weight, and a strong macroscopic birefringence with a texture typical of nematic liquid crystals was confirmed by crossed-polarizing microscopy (more than 0.5 wt%). The PS from A. sacrum may form a special structure rigid-rod enough to show LC phase and macroscopic birefringence.

  13. Molecular dynamics in rod-like liquid crystals probed by muon spin resonance spectroscopy.

    Science.gov (United States)

    McKenzie, Iain; Scheuermann, Robert; Sedlak, Kamil; Stoykov, Alexey

    2011-08-01

    Muoniated spin probes were produced by the addition of muonium (Mu) to two rod-like liquid crystals: N-(4-methoxybenzylidene)-4'-n-butylaniline (MBBA) and cholesteryl nonanoate (CN). Avoided level crossing muon spin resonance spectroscopy was used to characterize the muoniated spin probes and to probe dynamics at the molecular level. In MBBA Mu adds predominantly to the carbon of the bridging imine group and the muon and methylene proton hyperfine coupling constants (hfccs) of the resulting radical shift in the nematic phase due to the dipolar hyperfine coupling, the ordering of the molecules along the applied magnetic field and fluctuations about the local director. The amplitude of these fluctuations in in the nematic phase of MBBA is determined from the temperature dependence of the methylene proton hfcc. Mu adds to the double bond of the steroidal ring system of CN and the temperature dependence of the Δ(1) line width provides information about the amplitude of the fluctuations about the local director in the chiral nematic phase and the slow isotropic reorientation in the isotropic phase.

  14. Molecular monitoring of the intestinal flora by denaturing high performance liquid chromatography.

    Science.gov (United States)

    Goldenberg, Oliver; Herrmann, Stefanie; Marjoram, Gina; Noyer-Weidner, Mario; Hong, George; Bereswill, Stefan; Göbel, Ulf B

    2007-01-01

    Gut flora analysis is hampered by the complexity of the intestinal microbiota and by inherent limitations of culture-based approaches. Therefore, culture-independent molecular methods based upon 16S rRNA gene analysis were applied successfully for the analysis of complex microbial communities. However, generally accepted and validated profiling methods such as denaturing and temperature gradient gel electrophoresis (DGGE/TGGE) are still laborious and time consuming. Thus, we adapted the separation of amplified bacterial 16S rRNA gene fragments by denaturing high performance liquid chromatography (DHPLC) using the WAVE Microbial Analysis System as a rapid and convenient means to display complex intestinal bacterial communities and to monitor changes in the gut flora. The separation of 16S rRNA gene fragments amplified from reference strains representing main gut bacterial populations and from human stool samples revealed that DHPLC analysis effectively detects bacterial groups predominant in the human gut flora. The investigation of faecal samples from hospitalized patients before, during and after antibiotic therapy showed that PCR-based DHPLC can be used to monitor gut flora changes. Results from DHPLC analysis were comparable with DGGE profiles generated from the same samples, demonstrating that the adapted DHPLC protocol is well suited for the analysis of complex microbial communities.

  15. Molecular dynamics calculation of thermophysical properties for a highly reactive liquid.

    Science.gov (United States)

    Wang, H P; Luo, B C; Wei, B

    2008-10-01

    In order to further understand the physical characteristics of liquid silicon, the thermophysical properties are required over a broad temperature range. However, its high reactivity brings about great difficulties in the experimental measurement. Here we report the thermophysical properties by molecular dynamics calculation, including density, specific heat, diffusion coefficient, and surface tension. The calculation is performed with a system consisting of 64,000 atoms, and employing the Stillinger-Weber (SW) potential model and the modified embedded atom method (MEAM) potential model. The results show that the density increases as a quadratic function of undercooling, and the value calculated by SW potential model is only 2-4 % smaller than the reported experimental data. The specific heat is obtained to be 30.95 J mol;{-1}K;{-1} by SW potential model and 32.50 J mol;{-1}K;{-1} by MEAM potential model, both of which are constants in the corresponding ranges of temperature. The self-diffusion coefficient is exponentially dependent on the temperature and consistent with the Arrhenius equation. The surface tension increases linearly with the rise of undercooling and agrees well with the reported experimental results. This work provides reasonable data in much wider temperature range, especially for the undercooled metastable state.

  16. Steady-state molecular dynamics simulation of vapour to liquid nucleation with McDonald's daemon

    CERN Document Server

    Horsch, Martin; Vrabec, Jadran

    2009-01-01

    The most interesting step of condensation is the cluster formation up to the critical size. In a closed system, this is an instationary process, as the vapour is depleted by the emerging liquid phase. This imposes a limitation on direct molecular dynamics (MD) simulation of nucleation by affecting the properties of the vapour to a significant extent so that the nucleation rate varies over simulation time. Grand canonical MD with McDonald's daemon is discussed in the present contribution and applied for sampling both nucleation kinetics and steady-state properties of a supersaturated vapour. The idea behind that approach is to simulate the production of clusters up to a given size for a specified supersaturation. In that way, nucleation is studied by a steady-state simulation. A series of simulations is conducted for the truncated and shifted Lennard-Jones fluid which accurately describes the fluid phase coexistence of noble gases and methane. The classical nucleation theory is found to overestimate the free e...

  17. Molecular sieve supported ionic liquids as efficient adsorbent for CO2 capture

    Directory of Open Access Journals (Sweden)

    Yang Na

    2015-01-01

    Full Text Available [NH3e-mim][BF4], [OHe-mim][BF4] and [HOEAm] were selected and supported onto molecular sieves NaY, USY, SAPO-34 and MCM-41, to prepare supported ionic liquids. It was found that [NH3e-mim][BF4]/NaY has excellent CO2 adsorption performance, with adsorption capacity of 0.108 mmolCO2/g. This paper investigates the optimal adsorption conditions and recyclability of [NH3e-mim][BF4]/NaY. The results show that [NH3e-mim][BF4]/NaY has good CO2 adsorption under the condition of 20°C and 20% ILs loading amount. By vacuum heating, CO2 adsorption capacity reaches 0.451mmolCO2/g at fifth runs and reduces to 0.29mmolCO2/g at tenth runs. The structure and characterization of the [NH3e-mim][BF4]/NaY was examined by FT-IR, XRD, SEM and TG-DSC. TG-DSC also shows that it has good thermostability below 50°C.

  18. Thermophysical properties of energetic ionic liquids/nitric acid mixtures: Insights from molecular dynamics simulationsa)

    Science.gov (United States)

    Hooper, Justin B.; Smith, Grant D.; Bedrov, Dmitry

    2013-09-01

    Molecular dynamics (MD) simulations of mixtures of the room temperature ionic liquids (ILs) 1-butyl-4-methyl imidazolium [BMIM]/dicyanoamide [DCA] and [BMIM][NO3-] with HNO3 have been performed utilizing the polarizable, quantum chemistry based APPLE&P® potential. Experimentally it has been observed that [BMIM][DCA] exhibits hypergolic behavior when mixed with HNO3 while [BMIM][NO3-] does not. The structural, thermodynamic, and transport properties of the IL/HNO3 mixtures have been determined from equilibrium MD simulations over the entire composition range (pure IL to pure HNO3) based on bulk simulations. Additional (non-equilibrium) simulations of the composition profile for IL/HNO3 interfaces as a function of time have been utilized to estimate the composition dependent mutual diffusion coefficients for the mixtures. The latter have been employed in continuum-level simulations in order to examine the nature (composition and width) of the IL/HNO3 interfaces on the millisecond time scale.

  19. Adsorption and solvation of ethanol at the water liquid-vapor interface: a molecular dynamics study

    Science.gov (United States)

    Wilson, M. A.; Pohorille, A.

    1997-01-01

    The free energy profiles of methanol and ethanol at the water liquid-vapor interface at 310K were calculated using molecular dynamics computer simulations. Both alcohols exhibit a pronounced free energy minimum at the interface and, therefore, have positive adsorption at this interface. The surface excess was computed from the Gibbs adsorption isotherm and was found to be in good agreement with experimental results. Neither compound exhibits a free energy barrier between the bulk and the surface adsorbed state. Scattering calculations of ethanol molecules from a gas phase thermal distribution indicate that the mass accommodation coefficient is 0.98, and the molecules become thermalized within 10 ps of striking the interface. It was determined that the formation of the solvation structure around the ethanol molecule at the interface is not the rate-determining step in its uptake into water droplets. The motion of an ethanol molecule in a water lamella was followed for 30 ns. The time evolution of the probability distribution of finding an ethanol molecule that was initially located at the interface is very well described by the diffusion equation on the free energy surface.

  20. Thermodynamic, Structural and Transport Properties of Lennard-Jones Liquid Systems. A Molecular Dynamics Simulations of Liquid Helium, Neon, Methane and Nitrogen

    Directory of Open Access Journals (Sweden)

    F. Ould Kadour

    2003-12-01

    Full Text Available Abstract: Molecular dynamics calculations are carried out in order to find the properties of Lennard Jones liquids in different state points of their phase diagram. The spherical shape and the stability of the helium, neon, methane and nitrogen make the liquids easily accessible to numerical simulation. Thermodynamic, structural, and transport properties are studied and compared with both experimental data and recent theoretical investigations. In the present work, up to 22 state points are covered, some of which are near or at the triple point. It will be shown that the classical approach leads to data that are in very good agreement with experiments and other types of calculations. At high temperatures and low densities, we observe a decrease in the uncertainties in the stress autocorrelation function by increasing the number of iterations.

  1. Volumetric properties, viscosity and refractive index of the protic ionic liquid, pyrrolidinium octanoate, in molecular solvents

    Energy Technology Data Exchange (ETDEWEB)

    Anouti, Meriem, E-mail: meriem.anouti@univ-tours.f [Universite Francois Rabelais de Tours, Laboratoire PCMB (EA 4244), equipe Chimie-physique des Interfaces et des Milieux Electrolytiques (CIME), parc de Grandmont, 37200 Tours (France); Vigeant, Annie; Jacquemin, Johan; Brigouleix, Catherine; Lemordant, Daniel [Universite Francois Rabelais de Tours, Laboratoire PCMB (EA 4244), equipe Chimie-physique des Interfaces et des Milieux Electrolytiques (CIME), parc de Grandmont, 37200 Tours (France)

    2010-07-15

    Densities (rho) and viscosities (eta) of binary mixtures containing the Protic Ionic Liquid (PIL), pyrrolidinium octanoate with five molecular solvents: water, methanol, ethanol, n-butanol, and acetonitrile are determined at the atmospheric pressure as a function of the temperature and within the whole composition range. The refractive index of all mixtures (n{sub D}) is measured at 298.15 K. The excess molar volumes V{sup E} and deviation from additivity rules of viscosities eta{sup E} and refractive index DELTA{sub p}hin, of pyrrolidinium octanoate solutions were then deduced from the experimental results as well as apparent molar volumes Vphi{sub i}, partial molar volumes V-bar{sub m,i} and thermal expansion coefficients alpha{sub p}. The excess molar volumes V{sup E} are negative over the entire mole fraction range for mixture with water, acetonitrile, and methanol indicating strong hydrogen-bonding interaction for the entire mole fraction. In the case of longest carbon chain alcohols (such as ethanol and n-butanol) + pyrrolidinium octanoate solutions, the V{sup E} variation as a function of the composition describes an S shape. The deviation from additivity rules of viscosities is negative over the entire composition range for the acetonitrile, methanol, ethanol, and butanol, and becomes less negative with increasing temperature. Whereas, eta{sup E} of the left brace[Pyrr][C{sub 7}CO{sub 2}] + waterright brace binary mixtures is positive in the whole mole fraction range and decreases with increasing temperature. the excess Gibbs free energies of activation of viscous flow (DELTAG*{sup E}) for these systems were calculated. The deviation from additivity rules of refractive index DELTA{sub p}hin are positive over the whole composition range and approach a maximum of 0.25 in PIL mole fraction for all systems. The magnitude of deviation for DELTA{sub p}hin describes the following order: water > methanol > acetonitrile > ethanol. Results have been discussed in

  2. POLY-ANIONS IN LIQUID CSPB - AN AB-INITIO MOLECULAR-DYNAMICS SIMULATION

    NARCIS (Netherlands)

    DEWIJS, GA; PASTORE, G; SELLONI, A; VANDERLUGT, W

    1994-01-01

    Most alkali-group-IV liquid alloys exhibit strong chemical effects leading to well-defined equiatomic compounds. This is generally explained by the survival of particular clusters of lead-''Zintl'' ions-in the liquid state. We report on an ab initio simulation of liquid CsPb, for which the chemical

  3. Making and Breaking of Lead Halide Perovskites

    KAUST Repository

    Manser, Joseph S.

    2016-02-16

    A new front-runner has emerged in the field of next-generation photovoltaics. A unique class of materials, known as organic metal halide perovskites, bridges the gap between low-cost fabrication and exceptional device performance. These compounds can be processed at low temperature (typically in the range 80–150 °C) and readily self-assemble from the solution phase into high-quality semiconductor thin films. The low energetic barrier for crystal formation has mixed consequences. On one hand, it enables inexpensive processing and both optical and electronic tunability. The caveat, however, is that many as-formed lead halide perovskite thin films lack chemical and structural stability, undergoing rapid degradation in the presence of moisture or heat. To date, improvements in perovskite solar cell efficiency have resulted primarily from better control over thin film morphology, manipulation of the stoichiometry and chemistry of lead halide and alkylammonium halide precursors, and the choice of solvent treatment. Proper characterization and tuning of processing parameters can aid in rational optimization of perovskite devices. Likewise, gaining a comprehensive understanding of the degradation mechanism and identifying components of the perovskite structure that may be particularly susceptible to attack by moisture are vital to mitigate device degradation under operating conditions. This Account provides insight into the lifecycle of organic–inorganic lead halide perovskites, including (i) the nature of the precursor solution, (ii) formation of solid-state perovskite thin films and single crystals, and (iii) transformation of perovskites into hydrated phases upon exposure to moisture. In particular, spectroscopic and structural characterization techniques shed light on the thermally driven evolution of the perovskite structure. By tuning precursor stoichiometry and chemistry, and thus the lead halide charge-transfer complexes present in solution, crystallization

  4. Making and Breaking of Lead Halide Perovskites.

    Science.gov (United States)

    Manser, Joseph S; Saidaminov, Makhsud I; Christians, Jeffrey A; Bakr, Osman M; Kamat, Prashant V

    2016-02-16

    A new front-runner has emerged in the field of next-generation photovoltaics. A unique class of materials, known as organic metal halide perovskites, bridges the gap between low-cost fabrication and exceptional device performance. These compounds can be processed at low temperature (typically in the range 80-150 °C) and readily self-assemble from the solution phase into high-quality semiconductor thin films. The low energetic barrier for crystal formation has mixed consequences. On one hand, it enables inexpensive processing and both optical and electronic tunability. The caveat, however, is that many as-formed lead halide perovskite thin films lack chemical and structural stability, undergoing rapid degradation in the presence of moisture or heat. To date, improvements in perovskite solar cell efficiency have resulted primarily from better control over thin film morphology, manipulation of the stoichiometry and chemistry of lead halide and alkylammonium halide precursors, and the choice of solvent treatment. Proper characterization and tuning of processing parameters can aid in rational optimization of perovskite devices. Likewise, gaining a comprehensive understanding of the degradation mechanism and identifying components of the perovskite structure that may be particularly susceptible to attack by moisture are vital to mitigate device degradation under operating conditions. This Account provides insight into the lifecycle of organic-inorganic lead halide perovskites, including (i) the nature of the precursor solution, (ii) formation of solid-state perovskite thin films and single crystals, and (iii) transformation of perovskites into hydrated phases upon exposure to moisture. In particular, spectroscopic and structural characterization techniques shed light on the thermally driven evolution of the perovskite structure. By tuning precursor stoichiometry and chemistry, and thus the lead halide charge-transfer complexes present in solution, crystallization

  5. Liquid-liquid-solid microextraction based on membrane-protected molecularly imprinted polymer fiber for trace analysis of triazines in complex aqueous samples.

    Science.gov (United States)

    Hu, Yuling; Wang, Yangyang; Hu, Yufei; Li, Gongke

    2009-11-20

    A novel liquid-liquid-solid microextraction (LLSME) technique based on porous membrane-protected molecularly imprinted polymer (MIP)-coated silica fiber has been developed. In this technique, a MIP-coated silica fiber was protected with a length of porous polypropylene hollow fiber membrane which was filled with water-immiscible organic phase. Subsequently the whole device was immersed into aqueous sample for extraction. The LLSME technique was a three-phase microextraction approach. The target analytes were firstly extracted from the aqueous sample through a few microliters of organic phase residing in the pores and lumen of the membrane, and were then finally extracted onto the MIP fiber. A terbutylazine MIP-coated silica fiber was adopted as an example to demonstrate the feasibility of the novel LLSME method. The extraction parameters such as the organic solvent, extraction and desorption time were investigated. Comparison of the LLSME technique was made with molecularly imprinted polymer based solid-phase microextraction (MIP-SPME) and hollow fiber membrane-based liquid-phase microextraction (HF-LPME), respectively. The LLSME, integrating the advantages of high selectivity of MIP-SPME and enrichment and sample cleanup capability of the HF-LPME into a single device, is a promising sample preparation method for complex samples. Moreover, the new technique overcomes the problem of disturbance from water when the MIP-SPME fiber was exposed directly to aqueous samples. Applications to analysis of triazine herbicides in sludge water, watermelon, milk and urine samples were evaluated to access the real sample application of the LLSME method by coupling with high-performance liquid chromatography (HPLC). Low limits of detection (0.006-0.02 microg L(-1)), satisfactory recoveries and good repeatability for real sample (RSD 1.2-9.6%, n = 5) were obtained. The method was demonstrated to be a fast, selective and sensitive pretreatment method for trace analysis of triazines

  6. π(+)-π(+) stacking of imidazolium cations enhances molecular layering of room temperature ionic liquids at their interfaces.

    Science.gov (United States)

    Tang, Fujie; Ohto, Tatsuhiko; Hasegawa, Taisuke; Bonn, Mischa; Nagata, Yuki

    2017-01-25

    The interfacial structure of room temperature ionic liquids (RTILs) controls many of the unique properties of RTILs, such as the high capacitance of RTILs and the efficiency of charge transport between RTILs and electrodes. RTILs have been experimentally shown to exhibit interfacial molecular layering structures over a 10 Å length scale. However, the driving force behind the formation of these layered structures has not been resolved. Here, we report ab initio molecular dynamics simulations of imidazolium RTIL/air and RTIL/graphene interfaces along with force field molecular dynamics simulations. We find that the π(+)-π(+) interaction of imidazolium cations enhances the layering structure of RTILs, despite the electrostatic repulsion. The length scales of the molecular layering at the RTIL/air and RTIL/graphene interfaces are very similar, manifesting the limited effect of the substrate on the interfacial organization of RTILs.

  7. Liquid Water through Density-Functional Molecular Dynamics: Plane-Wave vs Atomic-Orbital Basis Sets

    CERN Document Server

    Miceli, Giacomo; Pasquarello, Alfredo

    2016-01-01

    We determine and compare structural, dynamical, and electronic properties of liquid water at near ambient conditions through density-functional molecular dynamics simulations, when using either plane-wave or atomic-orbital basis sets. In both frameworks, the electronic structure and the atomic forces are self-consistently determined within the same theoretical scheme based on a nonlocal density functional accounting for van der Waals interactions. The overall properties of liquid water achieved within the two frameworks are in excellent agreement with each other. Thus, our study supports that implementations with plane-wave or atomic-orbital basis sets yield equivalent results and can be used indiscriminately in study of liquid water or aqueous solutions.

  8. Multi-scale coarse-graining of non-conservative interactions in molecular liquids

    Energy Technology Data Exchange (ETDEWEB)

    Izvekov, Sergei, E-mail: sergiy.izvyekov.civ@mail.mil; Rice, Betsy M. [U.S. Army Research Laboratory, Aberdeen Proving Ground, Maryland 21005 (United States)

    2014-03-14

    A new bottom-up procedure for constructing non-conservative (dissipative and stochastic) interactions for dissipative particle dynamics (DPD) models is described and applied to perform hierarchical coarse-graining of a polar molecular liquid (nitromethane). The distant-dependent radial and shear frictions in functional-free form are derived consistently with a chosen form for conservative interactions by matching two-body force-velocity and three-body velocity-velocity correlations along the microscopic trajectories of the centroids of Voronoi cells (clusters), which represent the dissipative particles within the DPD description. The Voronoi tessellation is achieved by application of the K-means clustering algorithm at regular time intervals. Consistently with a notion of many-body DPD, the conservative interactions are determined through the multi-scale coarse-graining (MS-CG) method, which naturally implements a pairwise decomposition of the microscopic free energy. A hierarchy of MS-CG/DPD models starting with one molecule per Voronoi cell and up to 64 molecules per cell is derived. The radial contribution to the friction appears to be dominant for all models. As the Voronoi cell sizes increase, the dissipative forces rapidly become confined to the first coordination shell. For Voronoi cells of two and more molecules the time dependence of the velocity autocorrelation function becomes monotonic and well reproduced by the respective MS-CG/DPD models. A comparative analysis of force and velocity correlations in the atomistic and CG ensembles indicates Markovian behavior with as low as two molecules per dissipative particle. The models with one and two molecules per Voronoi cell yield transport properties (diffusion and shear viscosity) that are in good agreement with the atomistic data. The coarser models produce slower dynamics that can be appreciably attributed to unaccounted dissipation introduced by regular Voronoi re-partitioning as well as by larger

  9. Efficient analysis of highly complex nuclear magnetic resonance spectra of flexible solutes in ordered liquids by using molecular dynamics.

    Science.gov (United States)

    Weber, Adrian C J; Pizzirusso, Antonio; Muccioli, Luca; Zannoni, Claudio; Meerts, W Leo; de Lange, Cornelis A; Burnell, E Elliott

    2012-05-07

    The NMR spectra of n-pentane as solute in the liquid crystal 5CB are measured at several temperatures in the nematic phase. Atomistic molecular dynamics simulations of this system are carried out to predict the dipolar couplings of the orientationally ordered pentane, and the spectra predicted from these simulations are compared with the NMR experimental ones. The simulation predictions provide an excellent starting point for analysis of the experimental NMR spectra using the covariance matrix adaptation evolutionary strategy. This shows both the power of atomistic simulations for aiding spectral analysis and the success of atomistic molecular dynamics in modeling these anisotropic systems.

  10. Line emissions from sonoluminescence in aqueous solutions of halide salts without noble gases

    Energy Technology Data Exchange (ETDEWEB)

    Liang, Jinfu, E-mail: liang.shi2007@163.com [The Key Laboratory of Modern Acoustics, Ministry of Education, Institution of Acoustics, Nanjing University, Nanjing 210093 (China); School of Physics and Electronic Science, Guizhou Normal University, Guiyang 550001 (China); Chen, Weizhong, E-mail: wzchen@nju.edu.cn [The Key Laboratory of Modern Acoustics, Ministry of Education, Institution of Acoustics, Nanjing University, Nanjing 210093 (China); Zhou, Chao; Cui, Weicheng; Chen, Zhan [The Key Laboratory of Modern Acoustics, Ministry of Education, Institution of Acoustics, Nanjing University, Nanjing 210093 (China)

    2015-02-20

    Line emissions of trivalent terbium (Tb{sup 3+}) ion were observed from single-bubble sonoluminescence (SL) in an aqueous solution of terbium chloride (TbCl{sub 3}) that contained no noble gas. In addition, sodium (Na) lines were observed in multi-bubble SL in aqueous solutions of various halide salts that contained no noble gas. These observations show that the halide ions, such as Cl{sup −}, Br{sup −}, and I{sup −}, help for line emissions as the noble gases. The intensity of a line emission depends on both the chemical species produced by cavitation bubbles and the temperature of SL bubble that responds to the driving ultrasound pressure. With the increase of driving pressure, some line emissions attached to the continuous spectrum may become increasingly clear, while other line emissions gradually become indistinct. - Highlights: • Line emissions of Tb(III) ions were observed without the presence of noble gases. • The halide ions help to generate a line emission during sonoluminescence. • The intensity of a line emission mainly depends on the bubble's temperature. • The definition of a line emission is related to the temperature of caviation bubble and the kind of host liquid.

  11. The "ionic" to "molecular" transitions in AlCl3 and FeCl3 as predicted by an ionic interaction model

    Science.gov (United States)

    Hutchinson, Francis; Walters, Malcolm K.; Rowley, Adrian J.; Madden, Paul A.

    1999-03-01

    A polarizable ionic interaction model for AlCl3 and FeCl3, constructed from potentials similar to those used for a variety of ionic halides by simply scaling the cation radius, is found to give a semi-quantitative account of the structural and dynamical properties of the liquid and solid phases of AlCl3 and FeCl3. This indicates that the "covalent" interactions responsible for the remarkable, quasi-molecular nature of these two liquids are contained within the ionic model.

  12. The influence of halides in polyoxotitanate cages; dipole moment, splitting and expansion of d-orbitals and electron-electron repulsion.

    Science.gov (United States)

    Hanf, Schirin; Matthews, Peter D; Li, Ning; Luo, He-Kuan; Wright, Dominic S

    2017-01-03

    Metal-doped polyoxotitanate (M-POT) cages have been shown to be efficient single-source precursors to metal-doped titania [TiO2(M)] (state-of-the-art photocatalytic materials) as well as molecular models for the behaviour of dopant metal ions in bulk titania. Here we report the influence halide ions have on the optical and electronic properties of a series of halide-only, and cobalt halide-'doped' POT cages. In this combined experimental and computational study we show that halide ions can have several effects on the band gaps of halide-containing POT cages, influencing the dipole moment (hole-electron separation) and the structure of the valance band edge. Overall, the band gap behaviour stems from the effects of increasing orbital energy moving from F to I down Group 17, as well as crystal-field splitting of the d-orbitals, the potential effects of the Nephelauxetic influence of the halides and electron-electron repulsion.

  13. A Facile Ionic Liquid Promoted Synthesis, Cholinesterase Inhibitory Activity and Molecular Modeling Study of Novel Highly Functionalized Spiropyrrolidines

    Directory of Open Access Journals (Sweden)

    Abdulrahman I. Almansour

    2015-01-01

    Full Text Available A series of novel dimethoxyindanone embedded spiropyrrolidines were synthesized in ionic liquid, [bmim]Br and were evaluated for their inhibitory activities towards cholinesterases. Among the spiropyrrolidines, compound 4f exhibited the most potent activity with an IC50 value of 1.57 µM against acethylcholinesterase (AChE. Molecular docking simulation for the most active compound was employed with the aim of disclosing its binding mechanism to the active site of AChE receptor.

  14. Isobaric Molecular Dynamics Version of the Generalized Replica Exchange Method (gREM): Liquid-Vapor Equilibrium.

    Science.gov (United States)

    Małolepsza, Edyta; Secor, Maxim; Keyes, Tom

    2015-10-22

    A prescription for sampling isobaric generalized ensembles with molecular dynamics is presented and applied to the generalized replica exchange method (gREM), which was designed to simulate first-order phase transitions. The properties of the isobaric gREM ensemble are discussed, and a study is presented for the liquid-vapor equilibrium of the guest molecules given for gas hydrate formation with the mW water model. Phase diagrams, critical parameters, and a law of corresponding states are obtained.

  15. Base stable quaternary ammonium ionic liquids

    OpenAIRE

    Lethesh, Kallidanthiyil Chellappan; Dehaen, Wim; Binnemans, Koen

    2014-01-01

    Ionic liquids with the bis(2-ethylhexyl)dimethylammonium cation, [BEDMA]+, were prepared by a halide-free route starting from the readily available secondary amine bis(2-ethylhexyl)amine. The following anions were considered: chloride, bromide, iodide, nitrate, hydrogensulphate, dihydrogenphosphate, formate, acetate, propionate, trifluoroacetate, methyl sulphate, methanesulphonate, tosylate, isonicotinate, nicotinate and picolinate. Several of the compounds are room-temperature ionic liquids,...

  16. TIME-DEPENDENT PROPERTIES OF LIQUID WATER: A COMPARISON OF CAR-PARRINELLO AND BORN-OPPENHIEMER MOLECULAR DYNAMICS SIMULATIONS

    Energy Technology Data Exchange (ETDEWEB)

    Kuo, I W; Mundy, C; McGrath, M; Siepmann, J I

    2005-12-29

    A series of 30 ps first principles molecular dynamics simulations in the microcanonical ensemble were carried out to investigate transport and vibrational properties of liquid water. To allow for sufficient sampling, the thermodynamic constraints were set to an elevated temperature of around 423 K and a density of 0.71 g/cm{sup 3} corresponding to the saturated liquid density for the Becke-Lee-Yang-Parr (BLYP) representation of water. Four simulations using the Car-Parrinello molecular dynamics (CPMD) technique with varying values of the fictitious electronic mass ({mu}) and two simulations using the Born-Oppenheimer molecular dynamics (BOMD) technique are analyzed to yield structural and dynamical information. At the selected state point, the simulations are found to exhibit non-glassy dynamics and yield consistent results for the liquid structure and the self-diffusion coefficient, although the statistical uncertainties in the latter quantity are quite large. Consequently, it can be said that the CPMD and BOMD methods produce equivalent results for these properties on the time scales reported here. However, it was found that the choice of {mu} affects the frequency spectrum of the intramolecular modes, shifting them slightly to regions of lower frequency. Using a value of {mu} = 400 a.u. results in a significant drift in the electronic kinetic energy of the system over the course of 30 ps and a downward drift in the ionic temperature. Therefore, for long trajectories at elevated temperatures, lower values of this parameter are recommended for CPMD simulations of water.

  17. Hydrogen storage and ionic mobility in amide-halide systems.

    Science.gov (United States)

    Anderson, Paul A; Chater, Philip A; Hewett, David R; Slater, Peter R

    2011-01-01

    We report the results of a systematic study of the effect of halides on hydrogen release and uptake in lithium amide and lithium imide, respectively. The reaction of lithium amide and lithium imide with lithium or magnesium chloride, bromide and iodide resulted in a series of amide-halide and imide-halide phases, only two of which have been reported previously. On heating with LiH or MgH2, the amide-halides synthesised all released hydrogen more rapidly than lithium amide itself, accompanied by much reduced, or in some cases undetectable, release of ammonia by-product. The imide-halides produced were found to hydrogenate more rapidly than lithium imide, reforming related amide-halide phases. The work was initiated to test the hypothesis that the incorporation of halide anions might improve the lithium ion conductivity of lithium amide and help maintain high lithium ion mobility at all stages of the de/rehydrogenation process, enhancing the bulk hydrogen storage properties of the system. Preliminary ionic conductivity measurements indicated that the most conducting amide- and imide-halide phases were also the quickest to release hydrogen on heating and to hydrogenate. We conclude that ionic conductivity may be an important parameter in optimising the materials properties of this and other hydrogen storage systems.

  18. Sub-millimeter Spectroscopy of Astrophysically Important Molecules and Ions: Metal Hydrides, Halides, and Cyanides

    Science.gov (United States)

    Ziurys, L. M.; Flory, M. A.; Halfen, D. T.

    2006-01-01

    With the advent of SOFIA, Herschel, and SAFIR, new wavelength regions will become routinely accessible for astronomical spectroscopy, particularly at submm frequencies (0.5-1.1 THz). Molecular emission dominates the spectra of dense interstellar gas at these wavelengths. Because heterodyne detectors are major instruments of these missions, accurate knowledge of transition frequencies is crucial for their success. The Ziurys spectroscopy laboratory has been focusing on the measurement of the pure rotational transitions of astrophysically important molecules in the sub-mm regime. Of particular interest have been metal hydride species and their ions, as well as metal halides and cyanides. A new avenue of study has included metal bearing molecular ions.

  19. Preparation of molecularly imprinted polymers using anacardic acid monomers derived from cashew nut shell liquid.

    Science.gov (United States)

    Philip, Joseph Y N; Buchweishaija, Joseph; Mkayula, Lupituko L; Ye, Lei

    2007-10-31

    The objective of this work was to use monomers from cashew ( Anacardium occidentale L.) nut shells to develop molecularly imprinted polymers. Cashew nut shell liquid (CNSL) is a cheap and renewable agro byproduct consisting of versatile monomers. Solvent-extracted CNSL contains over 80% anacardic acid (AnAc) with more than 90% degree of unsaturation in its C 15 side chain. From AnAc monomer, anacardanyl acrylate (AnAcr) and anacardanyl methacrylate (AnMcr) monomers were synthesized and their chemical structures were characterized by Fourier transform IR and NMR. Different imprinted bulk polymers based on AnAc, AnAcr, and AnMcr functional monomers have been prepared. In the present study, each functional monomer was separately copolymerized in toluene with ethylene glycol dimethacrylate and divinylbenzene as cross-linkers, using racemic propranolol as a model template. While the AnAc based polymer revealed a meager rebinding ability, the imprinted polymers made from AnAcr and AnMcr displayed highly specific propranolol binding. At a polymer concentration of 2 mg/mL, AnAcr and AnMcr based imprinted polymers were able to bind over 50% of trace propranolol (initial concentration 1.2 nM). Under the same condition propranolol uptake by the two nonimprinted control polymers was less than 20%. Chiral recognition properties of these polymers were further confirmed using tritium-labeled (S)-propranolol as a tracer in displacement experiments, suggesting that the apparent affinity of the imprinted chiral sites for the correct enantiomer is at least 10 times that of the mismatched (R)-propranolol. Moreover, cross reactivity studies of these polymers showed that the (S)-imprinted sites have higher cross-reactivity toward (R, S)-metoprolol than (R)-propranolol and (R)-timolol.

  20. Interface between platinum(111) and liquid isopropanol (2-propanol): a model for molecular dynamics studies.

    Science.gov (United States)

    Tarmyshov, Konstantin B; Müller-Plathe, Florian

    2007-02-21

    A molecular dynamics model and its parametrization procedure are devised and used to study adsorption of isopropanol on platinum(111) (Pt(111)) surface in unsaturated and oversaturated coverages regimes. Static and dynamic properties of the interface between Pt(111) and liquid isopropanol are also investigated. The magnitude of the adsorption energy at unsaturated level increases at higher coverages. At the oversaturated coverage (multilayer adsorption) the adsorption energy reduces, which coincides with findings by Panja et al. in their temperature-programed desorption experiment [Surf. Sci. 395, 248 (1998)]. The density analysis showed a strong packing of molecules at the interface followed by a depletion layer and then by an oscillating density profile up to 3 nm. The distribution of individual atom types showed that the first adsorbed layer forms a hydrophobic methyl "brush." This brush then determines the distributions further from the surface. In the second layer methyl and methine groups are closer to the surface and followed by the hydroxyl groups; the third layer has exactly the inverted distribution. The alternating pattern extends up to about 2 nm from the surface. The orientational structure of molecules as a function of distance of molecules is determined by the atom distribution and surprisingly does not depend on the electrostatic or chemical interactions of isopropanol with the metal surface. However, possible formation of hydrogen bonds in the first layer is notably influenced by these interactions. The surface-adsorbate interactions influence the mobility of isopropanol molecules only in the first layer. Mobility in the higher layers is independent of these interactions.

  1. Impact of ionic liquids in aqueous solution on bacterial plasma membranes studied with molecular dynamics simulations.

    Science.gov (United States)

    Lim, Geraldine S; Zidar, Jernej; Cheong, Daniel W; Jaenicke, Stephan; Klähn, Marco

    2014-09-04

    The impact of five different imidazolium-based ionic liquids (ILs) diluted in water on the properties of a bacterial plasma membrane is investigated using molecular dynamics (MD) simulations. Cations considered are 1-octyl-3-methylimidazolium (OMIM), 1-octyloxymethyl-3-methylimidazolium (OXMIM), and 1-tetradecyl-3-methylimidazolium (TDMIM), as well as the anions chloride and lactate. The atomistic model of the membrane bilayer is designed to reproduce the lipid composition of the plasma membrane of Gram-negative Escherichia coli. Spontaneous insertion of cations into the membrane is observed in all ILs. Substantially more insertions of OMIM than of OXMIM occur and the presence of chloride reduces cation insertions compared to lactate. In contrast, anions do not adsorb onto the membrane surface nor diffuse into the bilayer. Once inserted, cations are oriented in parallel to membrane lipids with cation alkyl tails embedded into the hydrophobic membrane core, while the imidazolium-ring remains mostly exposed to the solvent. Such inserted cations are strongly associated with one to two phospholipids in the membrane. The overall order of lipids decreased after OMIM and OXMIM insertions, while on the contrary the order of lipids in the vicinity of TDMIM increased. The short alkyl tails of OMIM and OXMIM generate voids in the bilayer that are filled by curling lipids. This cation induced lipid disorder also reduces the average membrane thickness. This effect is not observed after TDMIM insertions due to the similar length of cation alkyl chain and the fatty acids of the lipids. This lipid-mimicking behavior of inserted TDMIM indicates a high membrane affinity of this cation that could lead to an enhanced accumulation of cations in the membrane over time. Overall, the simulations reveal how cations are inserted into the bacterial membrane and how such insertions change its properties. Moreover, the different roles of cations and anions are highlighted and the fundamental

  2. Molecular Simulations of the Vapor-Liquid Phase Interfaces of Pure Water Modeled with the SPC/E and the TIP4P/2005 Molecular Models

    Science.gov (United States)

    Vinš, Václav; Celný, David; Planková, Barbora; Němec, Tomáš; Duška, Michal; Hrubý, Jan

    2016-03-01

    In our previous study [Planková et al., EPJWeb. Conf. 92, 02071 (2015)], several molecular simulations of vapor-liquid phase interfaces for pure water were performed using the DL_POLY Classic software. The TIP4P/2005 molecular model was successfully used for the modeling of the density profile and the thickness of phase interfaces together with the temperature dependence of the surface tension. In the current study, the extended simple point charge (SPC/E) model for water was employed for the investigation of vapor-liquid phase interfaces over a wide temperature range from 250 K to 600 K. The TIP4P/2005 model was also used with the temperature step of 25 K to obtain more consistent data compared to our previous study. Results of the new simulations are in a good agreement with most of the literature data. TIP4P/2005 provides better results for the saturated liquid density with its maximum close to 275 K, while SPC/E predicts slightly better saturated vapor density. Both models give qualitatively correct representation for the surface tension of water. The maximum absolute deviation from the IAPWS standard for the surface tension of ordinary water is 10.4 mN · m-1 and 4.1 mN · m-1 over the temperature range from 275 K to 600 K in case of SPC/E and TIP4P/2005, respectively.

  3. Free-surface molecular command systems for photoalignment of liquid crystalline materials.

    Science.gov (United States)

    Fukuhara, Kei; Nagano, Shusaku; Hara, Mitsuo; Seki, Takahiro

    2014-01-01

    The orientation of liquid crystal molecules is very sensitive towards contacting surfaces, and this phenomenon is critical during the fabrication of liquid crystal display panels, as well as optical and memory devices. To date, research has focused on designing and modifying solid surfaces. Here we report an approach to control the orientation of liquid crystals from the free (air) surface side: a skin layer at the free surface was prepared using a non-photoresponsive liquid crystalline polymer film by surface segregation or inkjet printing an azobenzene-containing liquid crystalline block copolymer. Both planar-planar and homoeotropic-planar mode patterns were readily generated. This strategy is applicable to various substrate systems, including inorganic substrates and flexible polymer films. These versatile processes require no modification of the substrate surface and are therefore expected to provide new opportunities for the fabrication of optical and mechanical devices based on liquid crystal alignment.

  4. Photophysics of Hybrid Lead Halide Perovskites: The Role of Microstructure.

    Science.gov (United States)

    Srimath Kandada, Ajay Ram; Petrozza, Annamaria

    2016-03-15

    Since the first reports on high efficiency, solution processed solar cells based on hybrid lead halide perovskites, there has been an explosion of activities on these materials. Researchers with interests spanning the full range from conventional inorganic to emerging organic and hybrid optoelectronic technologies have been contributing to the prolific research output. This has led to solar cell power conversion efficiencies now exceeding 20% and the demonstration of proofs of concept for electroluminescent and lasing devices. Hybrid perovskites can be self-assembled by a simple chemical deposition of the constituent units, with the possibility of integrating the useful properties of organic and inorganic compounds at the molecular scale within a single crystalline material, thus enabling a fine-tuning of the electronic properties. Tellingly, the fundamental properties of these materials may make us think of a new, solution processable, GaAs-like semiconductor. While this can be true to a first approximation, hybrid perovskites are intrinsically complex materials, where the presence of various types of interactions and structural disorder may strongly affect their properties. In particular, a clear understanding and control of the relative interactions between the organic and inorganic moieties is of paramount importance to properly disentangle their innate physics. In this Account we review our recent studies which aim to clarify the relationship between structural and electronic properties from a molecular to mesoscopic level. First we identify the markers for local disorder at the molecular level by using Raman spectroscopy as a probe. Then, we exploit such a tool to explore the role of microstructure on the absorption and luminescence properties of the semiconductor. Finally we address the controversy surrounding electron-hole interactions and excitonic effects. We show that in hybrid lead-halide perovskites dielectric screening also depends on the local

  5. Molecular dynamics simulations on specific heat capacity and glass transition tempera-ture of liquid silver

    Institute of Scientific and Technical Information of China (English)

    2001-01-01

    The embedded-atom method is adopted to simulate the specific heat capacity of liquid silver. The relationship between the specific heat capacity and the temperature above and below melting point is derived. The results show that there exists an anormaly of the specific heat capacity of liquid silver near 950 K. Simulated pair distribution functions show that the liquid-to-glass transition takes place at this temperature.

  6. Salting-out assisted liquid-liquid extraction and partial least squares regression to assay low molecular weight polycyclic aromatic hydrocarbons leached from soils and sediments

    Science.gov (United States)

    Bressan, Lucas P.; do Nascimento, Paulo Cícero; Schmidt, Marcella E. P.; Faccin, Henrique; de Machado, Leandro Carvalho; Bohrer, Denise

    2017-02-01

    A novel method was developed to determine low molecular weight polycyclic aromatic hydrocarbons in aqueous leachates from soils and sediments using a salting-out assisted liquid-liquid extraction, synchronous fluorescence spectrometry and a multivariate calibration technique. Several experimental parameters were controlled and the optimum conditions were: sodium carbonate as the salting-out agent at concentration of 2 mol L- 1, 3 mL of acetonitrile as extraction solvent, 6 mL of aqueous leachate, vortexing for 5 min and centrifuging at 4000 rpm for 5 min. The partial least squares calibration was optimized to the lowest values of root mean squared error and five latent variables were chosen for each of the targeted compounds. The regression coefficients for the true versus predicted concentrations were higher than 0.99. Figures of merit for the multivariate method were calculated, namely sensitivity, multivariate detection limit and multivariate quantification limit. The selectivity was also evaluated and other polycyclic aromatic hydrocarbons did not interfere in the analysis. Likewise, high performance liquid chromatography was used as a comparative methodology, and the regression analysis between the methods showed no statistical difference (t-test). The proposed methodology was applied to soils and sediments of a Brazilian river and the recoveries ranged from 74.3% to 105.8%. Overall, the proposed methodology was suitable for the targeted compounds, showing that the extraction method can be applied to spectrofluorometric analysis and that the multivariate calibration is also suitable for these compounds in leachates from real samples.

  7. How specific halide adsorption varies hydrophobic interactions.

    Science.gov (United States)

    Stock, Philipp; Müller, Melanie; Utzig, Thomas; Valtiner, Markus

    2016-03-11

    Hydrophobic interactions (HI) are driven by the water structure around hydrophobes in aqueous electrolytes. How water structures at hydrophobic interfaces and how this influences the HI was subject to numerous studies. However, the effect of specific ion adsorption on HI and hydrophobic interfaces remains largely unexplored or controversial. Here, the authors utilized atomic force microscopy force spectroscopy at well-defined nanoscopic hydrophobic interfaces to experimentally address how specific ion adsorption of halide ions as well as NH4 (+), Cs(+), and Na(+) cations alters interaction forces across hydrophobic interfaces. Our data demonstrate that iodide adsorption at hydrophobic interfaces profoundly varies the hydrophobic interaction potential. A long-range and strong hydration repulsion at distances D > 3 nm, is followed by an instability which could be explained by a subsequent rapid ejection of adsorbed iodides from approaching hydrophobic interfaces. In addition, the authors find only a weakly pronounced influence of bromide, and as expected no influence of chloride. Also, all tested cations do not have any significant influence on HI. Complementary, x-ray photoelectron spectroscopy and quartz-crystal-microbalance with dissipation monitoring showed a clear adsorption of large halide ions (Br(-)/I(-)) onto hydrophobic self-assembled monolayers (SAMs). Interestingly, iodide can even lead to a full disintegration of SAMs due to specific and strong interactions of iodide with gold. Our data suggest that hydrophobic surfaces are not intrinsically charged negatively by hydroxide adsorption, as it was generally believed. Hydrophobic surfaces rather interact strongly with negatively charged large halide ions, leading to a surface charging and significant variation of interaction forces.

  8. Development of novel growth methods for halide single crystals

    Science.gov (United States)

    Yokota, Yuui; Kurosawa, Shunsuke; Shoji, Yasuhiro; Ohashi, Yuji; Kamada, Kei; Yoshikawa, Akira

    2017-03-01

    We developed novel growth methods for halide scintillator single crystals with hygroscopic nature, Halide micro-pulling-down [H-μ-PD] method and Halide Vertical Bridgman [H-VB] method. The H-μ-PD method with a removable chamber system can grow a single crystal of halide scintillator material with hygroscopicity at faster growth rate than the conventional methods. On the other hand, the H-VB method can grow a large bulk single crystal of halide scintillator without a quartz ampule. CeCl3, LaBr3, Ce:LaBr3 and Eu:SrI2 fiber single crystals could be grown by the H-μ-PD method and Eu:SrI2 bulk single crystals of 1 and 1.5 inch in diameter could be grown by the H-VB method. The grown fiber and bulk single crystals showed comparable scintillation properties to the previous reports using the conventional methods.

  9. SYNTHESIS AND SUPRAMOLECULAR CHEMISTRY OF NOVEL LIQUID-CRYSTALLINE CROWN ETHER-SUBSTITUTED PHTHALOCYANINES - TOWARD MOLECULAR WIRES AND MOLECULAR IONOELECTRONICS

    NARCIS (Netherlands)

    VANNOSTRUM, CF; PICKEN, SJ; SCHOUTEN, AJ; NOLTE, RJM

    1995-01-01

    The synthesis of the metal-free and the dihydroxysilicon derivatives of tetrakis[4',5'-bis(decoxy)benzo-18-crown-6]phthalocyanine is described. The metal-free phthalocyanine is liquid crystalline and exhibits a crystalline phase to mesophase transition at 148 degrees C. The structures of the crystal

  10. Synthesis and Supramolecular Chemistry of Novel Liquid Crystalline Crown Ether-Substituted Phthalocyanines : Toward Molecular Wires and Molecular Ionoelectronics

    NARCIS (Netherlands)

    Nostrum, Cornelus F. van; Picken, Stephen J.; Schouten, Arend-Jan; Nolte, Roeland J.M.

    1995-01-01

    The synthesis of the metal-free and the dihydroxysilicon derivatives of tetrakis[4’,5’-bis(decoxy)benzo-18-crown-6]phthalocyanine is described. The metal-free phthalocyanine is liquid crystalline and exhibits a crystalline phase to mesophase transition at 148 °C. The structures of the crystalline ph

  11. Synthesis and Supramolecular Chemistry of Novel Liquid Crystalline Crown Ether-Substituted Phthalocyanines : Toward Molecular Wires and Molecular Ionoelectronics

    NARCIS (Netherlands)

    Nostrum, Cornelus F. van; Picken, Stephen J.; Schouten, Arend-Jan; Nolte, Roeland J.M.

    1995-01-01

    The synthesis of the metal-free and the dihydroxysilicon derivatives of tetrakis[4’,5’-bis(decoxy)benzo-18-crown-6]phthalocyanine is described. The metal-free phthalocyanine is liquid crystalline and exhibits a crystalline phase to mesophase transition at 148 °C. The structures of the crystalline

  12. Synthesis and Supramolecular Chemistry of Novel Liquid Crystalline Crown Ether-Substituted Phthalocyanines : Toward Molecular Wires and Molecular Ionoelectronics

    NARCIS (Netherlands)

    Nostrum, Cornelus F. van; Picken, Stephen J.; Schouten, Arend-Jan; Nolte, Roeland J.M.

    1995-01-01

    The synthesis of the metal-free and the dihydroxysilicon derivatives of tetrakis[4’,5’-bis(decoxy)benzo-18-crown-6]phthalocyanine is described. The metal-free phthalocyanine is liquid crystalline and exhibits a crystalline phase to mesophase transition at 148 °C. The structures of the crystalline ph

  13. SYNTHESIS AND SUPRAMOLECULAR CHEMISTRY OF NOVEL LIQUID-CRYSTALLINE CROWN ETHER-SUBSTITUTED PHTHALOCYANINES - TOWARD MOLECULAR WIRES AND MOLECULAR IONOELECTRONICS

    NARCIS (Netherlands)

    VANNOSTRUM, CF; PICKEN, SJ; SCHOUTEN, AJ; NOLTE, RJM

    1995-01-01

    The synthesis of the metal-free and the dihydroxysilicon derivatives of tetrakis[4',5'-bis(decoxy)benzo-18-crown-6]phthalocyanine is described. The metal-free phthalocyanine is liquid crystalline and exhibits a crystalline phase to mesophase transition at 148 degrees C. The structures of the crystal

  14. Research Update: Luminescence in lead halide perovskites

    Directory of Open Access Journals (Sweden)

    Ajay Ram Srimath Kandada

    2016-09-01

    Full Text Available Efficiency and dynamics of radiative recombination of carriers are crucial figures of merit for optoelectronic materials. Following the recent success of lead halide perovskites in efficient photovoltaic and light emitting technologies, here we review some of the noted literature on the luminescence of this emerging class of materials. After outlining the theoretical formalism that is currently used to explain the carrier recombination dynamics, we review a few significant works which use photoluminescence as a tool to understand and optimize the operation of perovskite based optoelectronic devices.

  15. Research Update: Luminescence in lead halide perovskites

    Science.gov (United States)

    Srimath Kandada, Ajay Ram; Petrozza, Annamaria

    2016-09-01

    Efficiency and dynamics of radiative recombination of carriers are crucial figures of merit for optoelectronic materials. Following the recent success of lead halide perovskites in efficient photovoltaic and light emitting technologies, here we review some of the noted literature on the luminescence of this emerging class of materials. After outlining the theoretical formalism that is currently used to explain the carrier recombination dynamics, we review a few significant works which use photoluminescence as a tool to understand and optimize the operation of perovskite based optoelectronic devices.

  16. Nanoscale investigation of organic - inorganic halide perovskites

    Science.gov (United States)

    Cacovich, S.; Divitini, G.; Vrućinić, M.; Sadhanala, A.; Friend, R. H.; Sirringhaus, H.; Deschler, F.; Ducati, C.

    2015-10-01

    Over the last few years organic - inorganic halide perovskite-based solar cells have exhibited a rapid evolution, reaching certified power conversion efficiencies now surpassing 20%. Nevertheless the understanding of the optical and electronic properties of such systems on the nanoscale is still an open problem. In this work we investigate two model perovskite systems (based on iodine - CH3NH3PbI3 and bromine - CH3NH3PbBr3), analysing the local elemental composition and crystallinity and identifying chemical inhomogeneities.

  17. Static and dynamic length scales in supercooled liquids: insights from molecular dynamics simulations of water and tri-propylene oxide.

    Science.gov (United States)

    Klameth, F; Henritzi, P; Vogel, M

    2014-04-14

    We perform molecular dynamics simulations to study static and dynamic length scales in molecular supercooled liquids, in particular, water. For a determination of these scales, we use equilibrium configurations and pin appropriate subsets of molecules so as to obtain random matrices, cylindrical pores, and slit confinements. Static length scales ξ(s) are determined by analyzing overlap correlation functions for various fractions of pinned molecules or distances to the confining walls. For water in all confinements and for propylene oxide trimers in random geometry, a linear increase of ξ(s) with inverse temperature is found. Dynamic length scales ξ(d) are determined by analogous analysis of fraction-dependent or position-resolved correlation times of structural relaxation. While ξ(d) continuously grows upon cooling in the cylindrical and slit confinements, we find no evidence for a temperature dependence in random matrices, implying that molecular dynamics in parsed volumes is qualitatively different from that in bulk liquids. Finally, we study possible connections between the growth of the static and dynamic length scales and the slowdown of the structural relaxation of the supercooled bulk liquids. For water, we observe a linear relation between ln τ(α) and ξ(s)²/T in the whole accessible range down to the critical temperature of mode-coupling theory, T(c). In the weakly supercooled regime, the same relation holds also for ξ(d), as obtained from cylindrical and slit confinements, but deviations from this behavior are observed near T(c). The results are discussed in connection with random first-order theory and experimental studies of liquid dynamics in nanoscopic confinements and binary mixtures.

  18. Path Integral Molecular Dynamics within the Grand Canonical-like Adaptive Resolution Technique: Quantum-Classical Simulation of Liquid Water

    CERN Document Server

    Agarwal, Animesh

    2015-01-01

    Quantum effects due to the spatial delocalization of light atoms are treated in molecular simulation via the path integral technique. Among several methods, Path Integral (PI) Molecular Dynamics (MD) is nowadays a powerful tool to investigate properties induced by spatial delocalization of atoms; however computationally this technique is very demanding. The abovementioned limitation implies the restriction of PIMD applications to relatively small systems and short time scales. One possible solution to overcome size and time limitation is to introduce PIMD algorithms into the Adaptive Resolution Simulation Scheme (AdResS). AdResS requires a relatively small region treated at path integral level and embeds it into a large molecular reservoir consisting of generic spherical coarse grained molecules. It was previously shown that the realization of the idea above, at a simple level, produced reasonable results for toy systems or simple/test systems like liquid parahydrogen. Encouraged by previous results, in this ...

  19. Quantification of triacylglycerol molecular species in cocoa butter using high-performance liquid chromatography equipped with nano quantity analyte detector.

    Science.gov (United States)

    Beppu, Fumiaki; Nagai, Toshiharu; Yoshinaga, Kazuaki; Mizobe, Hoyo; Kojima, Koichi; Gotoh, Naohiro

    2013-01-01

    Triacylglycerol (TAG) molecular species were quantified through high-performance liquid chromatography (HPLC) equipped with a nano quantity analyte detector (NQAD). TAG standard compounds, i.e., 1,3-dipalmitoyl-2-oleoylglycerol (β-POP), 1-palmitoyl-2-oleoyl-3-stearoyl-rac-glycerol (β-POS), and 1,3-distearoyl-2-oleoylglycerol (β-SOS), and natural cocoa butter were used for analyses. NQAD gave the first order equation passing through the origin for all TAG standard compounds. TAG molecular species in cocoa butter were quantified using the calibration curves and the obtained values were almost the same as the reported ones of conventional cocoa butter. Furthermore, a recovery test was also carried out and the values were almost 100. Therefore, HPLC-NQAD can be successfully used for the quantification of TAG molecular species in natural fats and oils.

  20. Steric engineering of metal-halide perovskites with tunable optical band gaps.

    Science.gov (United States)

    Filip, Marina R; Eperon, Giles E; Snaith, Henry J; Giustino, Feliciano

    2014-12-15

    Owing to their high energy-conversion efficiency and inexpensive fabrication routes, solar cells based on metal-organic halide perovskites have rapidly gained prominence as a disruptive technology. An attractive feature of perovskite absorbers is the possibility of tailoring their properties by changing the elemental composition through the chemical precursors. In this context, rational in silico design represents a powerful tool for mapping the vast materials landscape and accelerating discovery. Here we show that the optical band gap of metal-halide perovskites, a key design parameter for solar cells, strongly correlates with a simple structural feature, the largest metal-halide-metal bond angle. Using this descriptor we suggest continuous tunability of the optical gap from the mid-infrared to the visible. Precise band gap engineering is achieved by controlling the bond angles through the steric size of the molecular cation. On the basis of these design principles we predict novel low-gap perovskites for optimum photovoltaic efficiency, and we demonstrate the concept of band gap modulation by synthesising and characterising novel mixed-cation perovskites.

  1. Finding New Perovskite Halides via Machine learning

    Directory of Open Access Journals (Sweden)

    Ghanshyam ePilania

    2016-04-01

    Full Text Available Advanced materials with improved properties have the potential to fuel future technological advancements. However, identification and discovery of these optimal materials for a specific application is a non-trivial task, because of the vastness of the chemical search space with enormous compositional and configurational degrees of freedom. Materials informatics provides an efficient approach towards rational design of new materials, via learning from known data to make decisions on new and previously unexplored compounds in an accelerated manner. Here, we demonstrate the power and utility of such statistical learning (or machine learning via building a support vector machine (SVM based classifier that uses elemental features (or descriptors to predict the formability of a given ABX3 halide composition (where A and B represent monovalent and divalent cations, respectively, and X is F, Cl, Br or I anion in the perovskite crystal structure. The classification model is built by learning from a dataset of 181 experimentally known ABX3 compounds. After exploring a wide range of features, we identify ionic radii, tolerance factor and octahedral factor to be the most important factors for the classification, suggesting that steric and geometric packing effects govern the stability of these halides. The trained and validated models then predict, with a high degree of confidence, several novel ABX3 compositions with perovskite crystal structure.

  2. Intriguing Optoelectronic Properties of Metal Halide Perovskites.

    Science.gov (United States)

    Manser, Joseph S; Christians, Jeffrey A; Kamat, Prashant V

    2016-11-09

    A new chapter in the long and distinguished history of perovskites is being written with the breakthrough success of metal halide perovskites (MHPs) as solution-processed photovoltaic (PV) absorbers. The current surge in MHP research has largely arisen out of their rapid progress in PV devices; however, these materials are potentially suitable for a diverse array of optoelectronic applications. Like oxide perovskites, MHPs have ABX3 stoichiometry, where A and B are cations and X is a halide anion. Here, the underlying physical and photophysical properties of inorganic (A = inorganic) and hybrid organic-inorganic (A = organic) MHPs are reviewed with an eye toward their potential application in emerging optoelectronic technologies. Significant attention is given to the prototypical compound methylammonium lead iodide (CH3NH3PbI3) due to the preponderance of experimental and theoretical studies surrounding this material. We also discuss other salient MHP systems, including 2-dimensional compounds, where relevant. More specifically, this review is a critical account of the interrelation between MHP electronic structure, absorption, emission, carrier dynamics and transport, and other relevant photophysical processes that have propelled these materials to the forefront of modern optoelectronics research.

  3. Finding New Perovskite Halides via Machine learning

    Science.gov (United States)

    Pilania, Ghanshyam; Balachandran, Prasanna V.; Kim, Chiho; Lookman, Turab

    2016-04-01

    Advanced materials with improved properties have the potential to fuel future technological advancements. However, identification and discovery of these optimal materials for a specific application is a non-trivial task, because of the vastness of the chemical search space with enormous compositional and configurational degrees of freedom. Materials informatics provides an efficient approach towards rational design of new materials, via learning from known data to make decisions on new and previously unexplored compounds in an accelerated manner. Here, we demonstrate the power and utility of such statistical learning (or machine learning) via building a support vector machine (SVM) based classifier that uses elemental features (or descriptors) to predict the formability of a given ABX3 halide composition (where A and B represent monovalent and divalent cations, respectively, and X is F, Cl, Br or I anion) in the perovskite crystal structure. The classification model is built by learning from a dataset of 181 experimentally known ABX3 compounds. After exploring a wide range of features, we identify ionic radii, tolerance factor and octahedral factor to be the most important factors for the classification, suggesting that steric and geometric packing effects govern the stability of these halides. The trained and validated models then predict, with a high degree of confidence, several novel ABX3 compositions with perovskite crystal structure.

  4. Molecular dynamics investigation of dynamical heterogeneity and local structure in the supercooled liquid and glass states of Al

    Energy Technology Data Exchange (ETDEWEB)

    Li, M.; Wang, C. Z.; Mandelev, M.; Ho, K. M.

    2008-05-13

    Molecular dynamics simulations are performed to study the structure and dynamical heterogeneity in the liquid and glass states of Al using a frequently employed embedded atom potential. While the pair correlation function of the glass and liquid states displays only minor differences, the icosahedral short-range order (ISRO) and the dynamics of the two states are very different. The ISRO is much stronger in the glass than in the liquid. It is also found that both the most mobile and the most immobile atoms in the glass state tend to form clusters, and the clusters formed by the immobile atoms are more compact. In order to investigate the local environment of each atom in the liquid and glass states, a local density is defined to characterize the local atomic packing. There is a strong correlation between the local packing density and the mobility of the atoms. These results indicate that dynamical heterogeneity in glasses is directly correlated to the local structure. We also analyze the diffusion mechanisms of atoms in the liquid and glass states. It is found that for the mobile atoms in the glass state, initially they are confined in the cages formed by their nearest neighbors and vibrating. On the time scale of {beta} relaxation, the mobile atoms try to break up the cage confinement and hop into new cages. In the supercooled liquid states, however, atoms continuously diffuse. Furthermore, it is found that on the time scale of {beta} relaxation, some of the mobile atoms in the glass state cooperatively hop, which is facilitated by the stringlike cluster structures. On the longer time scale, it is found that a certain fraction of atoms can simultaneously hop, although they are not nearest neighbors. Further analysis shows that these hopping atoms form big and more compact clusters than the characterized most mobile atoms. The cooperative rearrangement of these big compact clusters might facilitate the simultaneous hopping of atoms in the glass states on the long

  5. Separation of phenolic acids from natural plant extracts using molecularly imprinted anion-exchange polymer confined ionic liquids.

    Science.gov (United States)

    Bi, Wentao; Tian, Minglei; Row, Kyung Ho

    2012-04-06

    Polymer-confined ionic liquids were used for the separation of phenolic acids from natural plant extract by utilizing an anion-exchange mechanism. They were synthesized using molecular imprinting technique to reduce non-directional ion-ion interactions during anion-exchange and other interactions with interference substances that could decrease selectivity. A suitable sorbent for phenolic acid separation could be identified based on the adsorption behaviors of phenolic acids on different polymer-confined ionic liquids. Thus, the developed ionic liquid-based molecularly imprinted anion-exchange polymer (IMAP) achieved high recovery rates by solid-phase extraction of phenolic acids from Salicornia herbacea L. extract: 90.1% for protocatechuic acid, 95.5% for ferulic acid and 96.6% for caffeic acid. Moreover, the phenolic acids were separable from each other by repeated solid phase extraction cycles. The proposed method could be used to separate other phenolic acids or organic acids from complex samples. Copyright © 2011 Elsevier B.V. All rights reserved.

  6. Pressure-dependent morphology of trihexyl(tetradecyl)phosphonium ionic liquids: A molecular dynamics study

    Science.gov (United States)

    Sharma, Shobha; Gupta, Aditya; Dhabal, Debdas; Kashyap, Hemant K.

    2016-10-01

    In the present molecular dynamics study, we investigate the effects of increasing pressure on the structural morphology of trihexyl(tetradecyl)phosphonium bromide (P666,14+/Br-) and trihexyl(tetradecyl)phosphonium dicyanamide (P666,14+/DCA-) ionic liquids (ILs). Special attention was paid to how charge and polarity orderings, which are present in the microscopic structure of these ILs at ambient conditions, respond to very high external pressure. The simulated X-ray scattering structure functions, S(q)s, of the two systems reveal that both the characteristic orderings show appreciable responsiveness towards the applied pressure change. At a given pressure, a slight difference between the polarity ordering (PO), charge ordering (CO), and adjacency correlations (AC) for both the systems points towards different microscopic structure of the two ILs due to change in anion. Beyond a certain pressure, we observe emergence of a new low-q peak in the S(q)s of both the systems. The new peak is associated with formation of crystalline order in these systems at higher pressures and the real space length-scale corresponding to the crystalline order lies in between those of polarity- and charge-ordering. Beyond the transition pressure, the crystallinity of both the systems increases with increasing pressure and the corresponding length-scale shifts towards smaller values upon increasing pressure. We also observe that the extent of the usual polarity ordering decreases upon increasing pressure for both the P666,14+/Br- and P666,14+/DCA- systems. We demonstrate that the disappearance of the usual polarity peak is due to decreased polar-polar and apolar-apolar correlations and enhanced correlations between the charged and uncharged groups of the ions. This scenario is completely reversed for the components corresponding to the crystalline order, the polar-polar and apolar-apolar correlations are enhanced and polar-apolar correlations are diminished at higher pressure. In addition

  7. Molecular dynamics studies and quantification of the effect of chirality on the formation of liquid crystal mesophases

    Energy Technology Data Exchange (ETDEWEB)

    Solymosi, Miklos

    2002-07-01

    Results are presented from theoretical studies and from a series of molecular dynamics simulations undertaken to quantify the effect of chirality on the formation of liquid crystal mesophases. In the theoretical studies we have proposed a scaled chiral index with a formulation which allows comparison to be made between molecules comprising different numbers of atoms. We have undertaken chirality calculations utilizing the proposed scaled chiral index, G{sub 0S}, for one optimized static molecular geometry for a range of liquid crystal chiral dopants and ferroelectric liquid crystal molecules. The scaled chiral index, G{sub 0S}, allows a rapid calculation to be made of a pseudoscalar quantity which shows a good correlation with the helical twisting power of liquid crystal chiral dopants in a nematic liquid crystal solvent. This could prove a powerful aid in the design of novel dopant molecules where the dopant is rigid and the helical twisting is predominantly a steric effect. The same scaled chirality index, G{sub 0S}, calculation for ferroelectric liquid crystal molecules hints at an inverse correlation with spontaneous polarization agreeing with some experimental results. The scaled chiral index is a chemically useful index that can also be decomposed into atomic or functional group contributions, thereby creating a new measure of the asymmetric potential of functional groups and their different possible substitution positions. In the molecular dynamics simulation studies we have investigated two three-site Gay-Berne models, one chiral and the other achiral, each with a rotated central site forming a zigzag shape. In the chiral model one of the end site was additionally rotated out of the plane of the other two sites by a chiral angle {theta}{sub c}. Results from the achiral phase simulations support the theory that steric molecular shape can be associated with a driving force that leads to the smectic A - smectic C phase transition since such a transition was

  8. Pair Potential That Reproduces the Shape of Isochrones in Molecular Liquids

    DEFF Research Database (Denmark)

    Veldhorst, Arno; Schrøder, Thomas; Dyre, Jeppe C.

    2016-01-01

    Many liquids have curves (isomorphs) in their phase diagrams along which structure, dynamics, and some thermodynamic quantities are invariant in reduced units. A substantial part of their phase diagrams is thus effectively one dimensional. The shapes of these isomorphs are described by a material......-dependent function of density, h(ρ), which for real liquids is well approximated by a power law, ργ. However, in simulations, a power law is not adequate when density changes are large; typical models, such as Lennard-Jones liquids, show that γ(ρ) ≡ d ln h(ρ)/d ln ρ is a decreasing function of density. This article...

  9. Formation of reactive halide species by myeloperoxidase and eosinophil peroxidase.

    Science.gov (United States)

    Spalteholz, Holger; Panasenko, Oleg M; Arnhold, Juergen

    2006-01-15

    The formation of chloro- and bromohydrins from 1-palmitoyl-2-oleoyl-sn-glycero-3-phosphocholine following incubation with myeloperoxidase or eosinophil peroxidase in the presence of hydrogen peroxide, chloride and/or bromide was analysed by matrix-assisted laser desorption/ionisation time-of-flight mass spectrometry. These products were only formed below a certain pH threshold value, that increased with increasing halide concentration. Thermodynamic considerations on halide and pH dependencies of reduction potentials of all redox couples showed that the formation of a given reactive halide species in halide oxidation coupled with the reduction of compound I of heme peroxidases is only possible below a certain pH threshold that depends on halide concentration. The comparison of experimentally derived and calculated data revealed that Cl(2), Br(2), or BrCl will primarily be formed by the myeloperoxidase-H(2)O(2)-halide system. However, the eosinophil peroxidase-H(2)O(2)-halide system forms directly HOCl and HOBr.

  10. Structural transformation between long and short-chain form of liquid sulfur from \\textit{ab initio} molecular dynamics

    CERN Document Server

    Plašienka, Dušan; Martoňák, Roman

    2014-01-01

    We present results of \\textit{ab initio} molecular dynamics study of a structural transformation occurring in hot liquid sulfur under high pressure, which corresponds to the chain-breakage phenomenon recently observed experimentally by Liu \\textit{et al.} [1] and to the electronic transition reported by Brazhkin \\textit{et al.} [2,3]. We performed an extensive \\textit{ab initio} study and confirmed the existence of one transformation separating two distinct liquid polymeric phases: one composed of short chain-like fragments and another one with very long chains. We have not observed additional transformations reported in Refs. [2,3] and in the recent theoretical study by Zhao and Mu [4] and our findings are in agreement with the most recent experiment [1]. We offer a structural description of this liquid-liquid transformation in terms of chain lengths, cross-linking and geometry and investigate several physical properties. We conclude that the transformation is accompanied by changes in configurational energy...

  11. Synthesis, Reactivity and Stability of Aryl Halide Protecting Groups towards Di-Substituted Pyridines

    Directory of Open Access Journals (Sweden)

    Ptoton Mnangat Brian

    2016-03-01

    Full Text Available This paper reports the synthesis and reactivity of different Benzyl derivative protecting groups. The synthesis and stability of Benzyl halides, 4-methoxybenzyl halides, 3,5-dimethoxybenzyl halides, 3,4-dimethoxybenzyl halides, 3,4,5-trimethoxybenzyl halide protecting groups and their reactivity towards nitrogen atom of a di-substituted pyridine ring in formation of pyridinium salts is also reported.

  12. Path integral molecular dynamics within the grand canonical-like adaptive resolution technique: Simulation of liquid water

    Energy Technology Data Exchange (ETDEWEB)

    Agarwal, Animesh, E-mail: animesh@zedat.fu-berlin.de; Delle Site, Luigi, E-mail: dellesite@fu-berlin.de [Institute for Mathematics, Freie Universität Berlin, Berlin (Germany)

    2015-09-07

    Quantum effects due to the spatial delocalization of light atoms are treated in molecular simulation via the path integral technique. Among several methods, Path Integral (PI) Molecular Dynamics (MD) is nowadays a powerful tool to investigate properties induced by spatial delocalization of atoms; however, computationally this technique is very demanding. The above mentioned limitation implies the restriction of PIMD applications to relatively small systems and short time scales. One of the possible solutions to overcome size and time limitation is to introduce PIMD algorithms into the Adaptive Resolution Simulation Scheme (AdResS). AdResS requires a relatively small region treated at path integral level and embeds it into a large molecular reservoir consisting of generic spherical coarse grained molecules. It was previously shown that the realization of the idea above, at a simple level, produced reasonable results for toy systems or simple/test systems like liquid parahydrogen. Encouraged by previous results, in this paper, we show the simulation of liquid water at room conditions where AdResS, in its latest and more accurate Grand-Canonical-like version (GC-AdResS), is merged with two of the most relevant PIMD techniques available in the literature. The comparison of our results with those reported in the literature and/or with those obtained from full PIMD simulations shows a highly satisfactory agreement.

  13. Path integral molecular dynamics within the grand canonical-like adaptive resolution technique: Simulation of liquid water

    Science.gov (United States)

    Agarwal, Animesh; Delle Site, Luigi

    2015-09-01

    Quantum effects due to the spatial delocalization of light atoms are treated in molecular simulation via the path integral technique. Among several methods, Path Integral (PI) Molecular Dynamics (MD) is nowadays a powerful tool to investigate properties induced by spatial delocalization of atoms; however, computationally this technique is very demanding. The above mentioned limitation implies the restriction of PIMD applications to relatively small systems and short time scales. One of the possible solutions to overcome size and time limitation is to introduce PIMD algorithms into the Adaptive Resolution Simulation Scheme (AdResS). AdResS requires a relatively small region treated at path integral level and embeds it into a large molecular reservoir consisting of generic spherical coarse grained molecules. It was previously shown that the realization of the idea above, at a simple level, produced reasonable results for toy systems or simple/test systems like liquid parahydrogen. Encouraged by previous results, in this paper, we show the simulation of liquid water at room conditions where AdResS, in its latest and more accurate Grand-Canonical-like version (GC-AdResS), is merged with two of the most relevant PIMD techniques available in the literature. The comparison of our results with those reported in the literature and/or with those obtained from full PIMD simulations shows a highly satisfactory agreement.

  14. Interplay between the structure and dynamics in liquid and undercooled boron: An ab initio molecular dynamics simulation study

    Energy Technology Data Exchange (ETDEWEB)

    Jakse, N.; Pasturel, A. [Sciences et Ingénierie des Matériaux et Procédés, UMR CNRS 5266, Grenoble INP, BP 75, 38402 Saint-Martin d’Hères Cedex (France)

    2014-12-21

    In the present work, the structural and dynamic properties of liquid and undercooled boron are investigated by means of ab initio molecular dynamics simulation. Our results show that both liquid and undercooled states present a well pronounced short-range order (SRO) mainly due to the formation of inverted umbrella structural units. Moreover, we observe the development of a medium-range order (MRO) in the undercooling regime related to the increase of inverted umbrella structural units and of their interconnection as the temperature decreases. We also evidence that this MRO leads to a partial crystallization in the β-rhombohedral crystal below T = 1900 K. Finally, we discuss the role played by the SRO and MRO in the nearly Arrhenius evolution of the diffusion and the non-Arrhenius temperature dependence of the shear viscosity, in agreement with the experiment.

  15. Isomerization reaction dynamics and equilibrium at the liquid-vapor interface of water. A molecular-dynamics study

    Science.gov (United States)

    Benjamin, Ilan; Pohorille, Andrew

    1993-01-01

    The gauche-trans isomerization reaction of 1,2-dichloroethane at the liquid-vapor interface of water is studied using molecular-dynamics computer simulations. The solvent bulk and surface effects on the torsional potential of mean force and on barrier recrossing dynamics are computed. The isomerization reaction involves a large change in the electric dipole moment, and as a result the trans/gauche ratio is considerably affected by the transition from the bulk solvent to the surface. Reactive flux correlation function calculations of the reaction rate reveal that deviation from the transition-state theory due to barrier recrossing is greater at the surface than in the bulk water. This suggests that the system exhibits non-Rice-Ramsperger-Kassel-Marcus behavior due to the weak solvent-solute coupling at the water liquid-vapor interface.

  16. Molecular dynamics simulation of the behaviour of water in nano-confined ionic liquid-water mixtures

    Science.gov (United States)

    Docampo-Álvarez, B.; Gómez-González, V.; Montes-Campos, H.; Otero-Mato, J. M.; Méndez-Morales, T.; Cabeza, O.; Gallego, L. J.; Lynden-Bell, R. M.; Ivaništšev, V. B.; Fedorov, M. V.; Varela, L. M.

    2016-11-01

    This work describes the behaviour of water molecules in 1-butyl-3-methylimidazolium tetrafluoroborate ionic liquid under nanoconfinement, between graphene sheets. By means of molecular dynamics simulations, the adsorption of water molecules at the graphene surface is studied. A depletion of water molecules in the vicinity of the neutral and negatively charged graphene surfaces, and their adsorption at the positively charged surface are observed in line with the preferential hydration of the ionic liquid anions. The findings are appropriately described using a two-level statistical model. The confinement effect on the structure and dynamics of the mixtures is thoroughly analyzed using the density and the potential of mean force profiles, as well as by the vibrational densities of the states of water molecules near the graphene surface. The orientation of water molecules and the water-induced structural transitions in the layer closest to the graphene surface are also discussed.

  17. Isomerization reaction dynamics and equilibrium at the liquid-vapor interface of water. A molecular-dynamics study

    Science.gov (United States)

    Benjamin, Ilan; Pohorille, Andrew

    1993-01-01

    The gauche-trans isomerization reaction of 1,2-dichloroethane at the liquid-vapor interface of water is studied using molecular-dynamics computer simulations. The solvent bulk and surface effects on the torsional potential of mean force and on barrier recrossing dynamics are computed. The isomerization reaction involves a large change in the electric dipole moment, and as a result the trans/gauche ratio is considerably affected by the transition from the bulk solvent to the surface. Reactive flux correlation function calculations of the reaction rate reveal that deviation from the transition-state theory due to barrier recrossing is greater at the surface than in the bulk water. This suggests that the system exhibits non-Rice-Ramsperger-Kassel-Marcus behavior due to the weak solvent-solute coupling at the water liquid-vapor interface.

  18. Alkali metal and alkali earth metal gadolinium halide scintillators

    Energy Technology Data Exchange (ETDEWEB)

    Bourret-Courchesne, Edith; Derenzo, Stephen E.; Parms, Shameka; Porter-Chapman, Yetta D.; Wiggins, Latoria K.

    2016-08-02

    The present invention provides for a composition comprising an inorganic scintillator comprising a gadolinium halide, optionally cerium-doped, having the formula A.sub.nGdX.sub.m:Ce; wherein A is nothing, an alkali metal, such as Li or Na, or an alkali earth metal, such as Ba; X is F, Br, Cl, or I; n is an integer from 1 to 2; m is an integer from 4 to 7; and the molar percent of cerium is 0% to 100%. The gadolinium halides or alkali earth metal gadolinium halides are scintillators and produce a bright luminescence upon irradiation by a suitable radiation.

  19. Temperature Sensitive Optical Phenomena in Heavy Metal Halide Films.

    Science.gov (United States)

    1979-01-08

    Heavy - metal halides such as Pb!2 and HgI2 exhibit a strongly tempera- ture dependent absorption edge at visible frequencies. The shift in the absorption...AOb9 537 ROCKWELL INTERNATIONAL ANAHEIM CA ELECTRONICS RESEAR—— ETC FIG L u G TEMPERATURE SENSITIVE OPTICAL PHENOMENA IN HEAVY METAL HALIDE F—— ETC (U...PHENOMENA IN HEAVY METAL HALIDE F — ET C( U) ,JAN 79 J D MC*LLEN, D M HEINZ. F S STEARNS DAAK7O— 77—C—01 6 5 UNCLASSIFIED C79 1501 _ _ U SB

  20. Comparing an ionic liquid to a molecular solvent in the cesium cation extraction by a calixarene: a molecular dynamics study of the aqueous interfaces.

    Science.gov (United States)

    Sieffert, Nicolas; Wipff, Georges

    2006-10-01

    We report a molecular dynamics (MD) study of the interfacial behavior of key partners involved in the Cs(+) cation extraction by a calix[4]arene-crown-6 host (L), comparing an ionic liquid (IL) to a classical molecular solvent (chloroform) as receiving "oil" phase. The IL is composed of hydrophobic 1-butyl-3-methylimidazolium cations (BMI(+)) and bis(trifluoromethylsulfonyl)imide anions (Tf(2)N(-)) and forms a biphasic system with water. The simulations reveal similarities but also interesting differences between the two types of interfaces. Much longer times are needed to "equilibrate" IL systems, compared to classical liquid mixtures, and there is more intersolvent mixing with the IL than with chloroform, especially concerning the water-in-oil content. There is also some excess of the BMI(+) cations over the Tf(2)N(-) anions in the aqueous phase. Simulations on the Na(+)NO(3)(-) and Cs(+)NO(3)(-) ions show that they sometimes interact at the interface with the IL ions, forming hydrated intimate ion pairs, whereas they are "repelled" by the classical interface. The LCs(+) complex and L ligand also behave differently, depending on the "oil phase". They are better solvated by the IL than by chloroform and thus poorly attracted at the IL interface, whereas they adsorb at the chloroform interface, adopting well-defined amphiphilic orientations. The results are discussed in the context of assisted ion transfer and provide a number of arguments explaining the specificity and efficiency of IL based, compared to classical extraction systems.

  1. Double-Diffusive Convection During Growth of Halides and Selenides

    Science.gov (United States)

    Singh, N. B.; Su, Ching-Hua; Duval, Walter M. B.

    2015-01-01

    Heavy metal halides and selenides have unique properties which make them excellent materials for chemical, biological and radiological sensors. Recently it has been shown that selenohalides are even better materials than halides or selenides for gamma-ray detection. These materials also meet the strong needs of a wide band imaging technology to cover ultra-violet (UV), midwave infrared wavelength (MWIR) to very long wavelength infrared (VLWIR) region for hyperspectral imager components such as etalon filters and acousto-optic tunable filters (AO). In fact AOTF based imagers based on these materials have some superiority than imagers based on liquid crystals, FTIR, Fabry-Perot, grating, etalon, electro-optic modulation, piezoelectric and several other concepts. For example, broadband spectral and imagers have problems of processing large amount of information during real-time observation. Acousto-Optic Tunable Filter (AOTF) imagers are being developed to fill the need of reducing processing time of data, low cost operation and key to achieving the goal of covering long-wave infrared (LWIR). At the present time spectral imaging systems are based on the use of diffraction gratings are typically used in a pushbroom or whiskbroom mode. They are mostly used in systems and acquire large amounts of hyperspectral data that is processed off-line later. In contrast, acousto-optic tunable filter spectral imagers require very little image processing, providing new strategies for object recognition and tracking. They are ideally suited for tactical situations requiring immediate real-time image processing. But the performance of these imagers depends on the quality and homogeneity of acousto-optic materials. In addition for many systems requirements are so demanding that crystals up to sizes of 10 cm length are desired. We have studied several selenides and halide crystals for laser and AO imagers for MWIR and LWIR wavelength regions. We have grown and fabricated crystals of

  2. Experimental and molecular dynamics simulation study of structure of liquid and amorphous Ni62Nb38 alloy

    Science.gov (United States)

    Zhang, Y.; Ashcraft, R.; Mendelev, M. I.; Wang, C. Z.; Kelton, K. F.

    2016-11-01

    The state-of-the-art experimental and atomistic simulation techniques were utilized to study the structure of the liquid and amorphous Ni62Nb38 alloy. First, the ab initio molecular dynamics (AIMD) simulation was performed at rather high temperature where the time limitations of the AIMD do not prevent to reach the equilibrium liquid structure. A semi-empirical potential of the Finnis-Sinclair (FS) type was developed to almost exactly reproduce the AIMD partial pair correlation functions (PPCFs) in a classical molecular dynamics simulation. This simulation also showed that the FS potential well reproduces the bond angle distributions. The FS potential was then employed to elongate the AIMD PPCFs and determine the total structure factor (TSF) which was found to be in excellent agreement with X-ray TSF obtained within the present study demonstrating the reliability of the AIMD for the simulation of the structure of the liquid Ni-Nb alloys as well as the reliability of the developed FS potential. The glass structure obtained with the developed potential was also found to be in excellent agreement with the X-ray data. The analysis of the structure revealed that a network of the icosahedra clusters centered on Ni atoms is forming during cooling the liquid alloy down to Tg and the Nb Z14, Z15, and Z16 clusters are attached to this network. This network is the main feature of the Ni62Nb38 alloy and further investigations of the properties of this alloy should be based on study of the behavior of this network.

  3. Unraveling the Role of Monovalent Halides in Mixed-Halide Organic-Inorganic Perovskites.

    Science.gov (United States)

    Deepa, Melepurath; Ramos, F Javier; Shivaprasad, S M; Ahmad, Shahzada

    2016-03-16

    The performance of perovskite solar cells is strongly influenced by the composition and microstructure of the perovskite. A recent approach to improve the power conversion efficiencies utilized mixed-halide perovskites, but the halide ions and their roles were not directly studied. Unraveling their precise location in the perovskite layer is of paramount importance. Here, we investigated four different perovskites by using X-ray photoelectron spectroscopy, and found that among the three studied mixed-halide perovskites, CH3 NH3 Pb(I0.74 Br0.26 )3 and CH3 NH3 PbBr3-x Clx show peaks that unambiguously demonstrate the presence of iodide and bromide in the former, and bromide and chloride in the latter. The CH3 NH3 PbI3-x Clx perovskite shows anomalous behavior, the iodide content far outweighs that of the chloride; a small proportion of chloride, in all likelihood, resides deep within the TiO2 /absorber layer. Our study reveals that there are many distinguishable structural differences between these perovskites, and that these directly impact the photovoltaic performances. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  4. Modeling reactive scattering of F(2P) at a liquid squalane interface: a hybrid QM/MM molecular dynamics study.

    Science.gov (United States)

    Radak, Brian K; Yockel, Scott; Kim, Dongwook; Schatz, George C

    2009-07-01

    To better understand the reactivity of gases with liquid surfaces, experimentalists have recently probed the reactive scattering of atomic fluorine at the surface of liquid squalane (C(30)H(62)). In this paper we further this research by simulating this scattering process at collision energies of 0.5 and 1.0 eV using a hybrid QM/MM molecular dynamics scheme. To model the structure of the liquid surface, classical molecular dynamics calculations were performed utilizing the OPLS-AA force field. During the F + squalane molecular dynamics simulation, QM/MM calculations are performed at every trajectory step by combining the MSINDO semiempirical Hamiltonian with OPLS-AA and using a dynamic partitioning of the atoms in the QM or MM regions via a "seed atom" method. This computational model provides a type of "on-the-fly" direct dynamics applicable to larger scale chemical processes that include the making/breaking of chemical bonds not available in standard force field models. Our results show that H abstraction is the only reactive scattering pathway and that most trajectories result in reactive scattering. Reaction statistics at the squalane surface are discussed, including variation of the results with incident angle and collision energy, and the probability of reaction as a function of carbon atom type, collision depth, and residence time. Product states, including angular distributions and final translational and rovibrational energies, are also considered and found to be significantly affected by the exothermic reaction energy for H abstraction. The vibrational distributions are in good agreement with recent experiments, but the rotational distributions are dominated by a nonthermal component while the experiments, which involve thermal incident energies, show comparable thermal and nonthermal contributions. Results for O + squalane at 1.0 eV, which we also present, show analogous comparisons with experiment, with OH vibrational distributions which are cold and

  5. Orbital free ab initio molecular dynamics simulation study of some static and dynamic properties of liquid noble metals

    Directory of Open Access Journals (Sweden)

    G.M. Bhuiyan

    2012-10-01

    Full Text Available Several static and dynamic properties of liquid Cu, Ag and Au at thermodynamic states near their respective melting points, have been evaluated by means of the orbital free ab-initio molecular dynamics simulation method. The calculated static structure shows good agreement with the available X-ray and neutron diffraction data. As for the dynamic properties, the calculated dynamic structure factors point to the existence of collective density excitations along with a positive dispersion for l-Cu and l-Ag. Several transport coefficients have been obtained which show a reasonable agreement with the available experimental data.

  6. Structure and dynamics of Ni2+ in liquid ammonia: A quantum mechanical charge field molecular dynamics (QMCF-MD) study

    Science.gov (United States)

    Saleh, Muhammad; Hofer, Thomas S.

    2016-09-01

    An investigation of structural and dynamical properties of Ni2+ in liquid ammonia has been carried out via Quantum Mechanical Charge Field Molecular Dynamics. By extending the quantum mechanical region to include first and second solvation shell, a more realistic representation of the system was achieved yielding improved results on present computational facilities. The structural results obtained from the 16 ps trajectory agree well with experimental investigations for various nitrogen-containing Ni2+ systems. Detailed analysis of mean residence time and vibrational properties highlights a rather flexible structure of the first and second shells compared to Ni2+ in aqueous solution.

  7. Orbital free ab initio molecular dynamics simulation study of some static and dynamic properties of liquid noble metals

    CERN Document Server

    Bhuiyan, G M; González, D J; 10.5488/CMP.15.33604

    2012-01-01

    Several static and dynamic properties of liquid Cu, Ag and Au at thermodynamic states near their respective melting points, have been evaluated by means of the orbital free ab-initio molecular dynamics simulation method. The calculated static structure shows good agreement with the available X-ray and neutron diffraction data. As for the dynamic properties, the calculated dynamic structure factors point to the existence of collective density excitations along with a positive dispersion for l-Cu and l-Ag. Several transport coefficients have been obtained which show a reasonable agreement with the available experimental data.

  8. Liquid-crystalline rigid-core semiconductor oligothiophenes: influence of molecular structure on phase behaviour and thin-film properties.

    Science.gov (United States)

    Melucci, Manuela; Favaretto, Laura; Bettini, Christian; Gazzano, Massimo; Camaioni, Nadia; Maccagnani, Piera; Ostoja, Paolo; Monari, Magda; Barbarella, Giovanna

    2007-01-01

    The design, synthesis and properties of liquid-crystalline semiconducting oligothiophenes containing dithienothiophene (DTT), benzothiadiazole (BTZ) and carbazole (CBZ) rigid cores are described. The effect of molecular structure (shape, size and substitution) on their thermal behaviour and electrical properties has been investigated. Polarised optical microscopy (POM) and differential scanning calorimetry (DSC) analyses have revealed highly ordered smectic mesophases for most of the newly synthesised compounds. X-ray diffraction (XRD) studies performed at various temperatures have shown that the smectic order is retained in the crystalline state upon cooling across the transition temperature, affording cast films with a more favourable morphology for FET applications.

  9. Configurational entropy of protein: A combined approach based on molecular simulation and integral-equation theory of liquids

    Science.gov (United States)

    Chong, Song-Ho; Ham, Sihyun

    2011-03-01

    We report the recent development of a theoretical method to calculate the protein configurational entropy in explicit solvent from statistical properties of the solvent-averaged protein potential energy surface. This method can be implemented by combining molecular simulation and integral-equation theory of liquids. Our method does not assume Gaussian distribution of protein configurations, and can be applied to unfolded or misfolded states of protein in which an average protein structure is not well defined. An illustrative application is made to misfolded state of 42-residue amyloid beta protein in water.

  10. Molecular scale track structure simulations in liquid water using the Geant4-DNA Monte-Carlo processes

    Energy Technology Data Exchange (ETDEWEB)

    Francis, Z., E-mail: ziad.francis@gmail.co [Institut de Radioprotection et de Surete Nucleaire, Laboratoire de Dosimetrie des Rayonnements Ionisants, BP 17, 92262 Fontenay-aux-Roses Cedex (France); Incerti, S. [Universite Bordeaux 1, CNRS/IN2P3, Centre d' Etudes Nucleaires de Bordeaux Gradignan, CENBG, Chemin du Solarium, BP120, 33175 Gradignan (France); Capra, R. [Via Niella 12, 17100 Savona (Italy); Mascialino, B. [Department of Medical Radiation Physics, Stockholm University, Box 260, 17176 Stockholm (Sweden); Montarou, G. [Laboratoire de Physique Corpusculaire, 24 avenue des Landais, 63177 Aubiere (France); Stepan, V. [Nuclear Physics Institute ASCR, Na Truhlarce 39/64, Praha 8 (Czech Republic); Villagrasa, C. [Institut de Radioprotection et de Surete Nucleaire, Laboratoire de Dosimetrie des Rayonnements Ionisants, BP 17, 92262 Fontenay-aux-Roses Cedex (France)

    2011-01-15

    This paper presents a study of energy deposits induced by ionising particles in liquid water at the molecular scale. Particles track structures were generated using the Geant4-DNA processes of the Geant4 Monte-Carlo toolkit. These processes cover electrons (0.025 eV-1 MeV), protons (1 keV-100 MeV), hydrogen atoms (1 keV-100 MeV) and alpha particles (10 keV-40 MeV) including their different charge states. Electron ranges and lineal energies for protons were calculated in nanometric and micrometric volumes.

  11. Thermodynamics of liquids: standard molar entropies and heat capacities of common solvents from 2PT molecular dynamics.

    Science.gov (United States)

    Pascal, Tod A; Lin, Shiang-Tai; Goddard, William A

    2011-01-07

    We validate here the Two-Phase Thermodynamics (2PT) method for calculating the standard molar entropies and heat capacities of common liquids. In 2PT, the thermodynamics of the system is related to the total density of states (DoS), obtained from the Fourier Transform of the velocity autocorrelation function. For liquids this DoS is partitioned into a diffusional component modeled as diffusion of a hard sphere gas plus a solid component for which the DoS(υ) → 0 as υ→ 0 as for a Debye solid. Thermodynamic observables are obtained by integrating the DoS with the appropriate weighting functions. In the 2PT method, two parameters are extracted from the DoS self-consistently to describe diffusional contributions: the fraction of diffusional modes, f, and DoS(0). This allows 2PT to be applied consistently and without re-parameterization to simulations of arbitrary liquids. We find that the absolute entropy of the liquid can be determined accurately from a single short MD trajectory (20 ps) after the system is equilibrated, making it orders of magnitude more efficient than commonly used perturbation and umbrella sampling methods. Here, we present the predicted standard molar entropies for fifteen common solvents evaluated from molecular dynamics simulations using the AMBER, GAFF, OPLS AA/L and Dreiding II forcefields. Overall, we find that all forcefields lead to good agreement with experimental and previous theoretical values for the entropy and very good agreement in the heat capacities. These results validate 2PT as a robust and efficient method for evaluating the thermodynamics of liquid phase systems. Indeed 2PT might provide a practical scheme to improve the intermolecular terms in forcefields by comparing directly to thermodynamic properties.

  12. Metal halide perovskites for energy applications

    Science.gov (United States)

    Zhang, Wei; Eperon, Giles E.; Snaith, Henry J.

    2016-06-01

    Exploring prospective materials for energy production and storage is one of the biggest challenges of this century. Solar energy is one of the most important renewable energy resources, due to its wide availability and low environmental impact. Metal halide perovskites have emerged as a class of semiconductor materials with unique properties, including tunable bandgap, high absorption coefficient, broad absorption spectrum, high charge carrier mobility and long charge diffusion lengths, which enable a broad range of photovoltaic and optoelectronic applications. Since the first embodiment of perovskite solar cells showing a power conversion efficiency of 3.8%, the device performance has been boosted up to a certified 22.1% within a few years. In this Perspective, we discuss differing forms of perovskite materials produced via various deposition procedures. We focus on their energy-related applications and discuss current challenges and possible solutions, with the aim of stimulating potential new applications.

  13. Tellurium halide IR fibers for remote spectroscopy

    Science.gov (United States)

    Zhang, Xhang H.; Ma, Hong Li; Blanchetiere, Chantal; Le Foulgoc, Karine; Lucas, Jacques; Heuze, Jean; Colardelle, P.; Froissard, P.; Picque, D.; Corrieu, G.

    1994-07-01

    The new family of IR transmitting glasses, the TeX glasses, based on the association of tellurium and halide (Cl, Br, or I) are characterized by a wide optical window extending from 2 to 18 micrometers and a strong stability towards devitrification. Optical fibers drawn from these glasses exhibit low losses in the 7 - 10 micrometers range (less than 1 dB/m for single index fibers, 1 - 2 dB/m for fibers having a core-clad structure). The TeX glass fibers have been used in a remote analysis set-up which is mainly composed of a FTIR spectrometer coupled with a HgCdTe detector. This prototype system permits qualitative and quantitative analysis in a wide wavelength region lying from 3 to 13 micrometers , covering the fundamental absorption of more organic species. The evolution of a lactic and an alcoholic fermentation has been monitored by means of this set-up.

  14. Thermoluminescence of alkali halides and its implications

    Energy Technology Data Exchange (ETDEWEB)

    Gartia, R.K., E-mail: rkgartia02@yahoo.in [Physics Department, Manipur University, Imphal 795003 (India); Rey, L. [Aerial-CRT-parc d' Innovation, B.P. 40443, F-67412 Illkirch Cedex (France); Tejkumar Singh, Th. [Physics Department, Manipur University, Imphal 795003 (India); Basanta Singh, Th. [Luminescence Dating Laboratory, Manipur University, Imphal 795003 (India)

    2012-03-01

    Trapping levels present in some alkali halides namely NaCl, KCl, KBr, and KI are determined by deconvolution of the thermoluminescence (TL) curves. Unlike most of the studies undertaken over the last few decades, we have presented a comprehensive picture of the phenomenon of TL as an analytical technique capable of revealing the position of the trapping levels present in the materials. We show that for all practical purposes, TL can be described involving only the three key trapping parameters, namely, the activation energy (E), the frequency factor (s), and the order of kinetics (b) even for complex glow curves having a number of TL peaks. Finally, based on these, we logically infer the importance of TL in development and characterization of materials used in dosimetry, dating and scintillation.

  15. Synthesis, spectroscopic and molecular docking studies of imidazolium and pyridinium based ionic liquids with HSA as potential antimicrobial agents

    Science.gov (United States)

    Trush, Maria M.; Semenyuta, Ivan V.; Vdovenko, Sergey I.; Rogalsky, Sergiy P.; Lobko, Evgeniya O.; Metelytsia, Larisa O.

    2017-06-01

    The interaction between human serum albumin (HSA) and synthesized imidazolium and pyridinium based ionic liquids (ILs), as good potential microbial growth inhibitors, was investigated by spectroscopic techniques combined with molecular docking analysis. All compounds were significant active against the tested bacterial and fungal strains. FT-IR spectroscopy indicated that the interaction of HSA with ILs generates considerable changes in protein secondary structure. The results of the molecular docking study showed that the studied ILs are able to firmly bind in the subdomain IIA of HSA with almost equal binding affinity (about -6.23 kcal/mol). Investigated HSA-ILs complex binds through hydrogen bonding or/and cation-π interactions. This study provides a better understanding of the binding of imidazolium and pyridinium based ILs to HSA and opens the way for their further biological and pharmaceutical investigations as candidates with antimicrobial properties.

  16. Substitution Reactions by Azide and Thiocyanide Anions in Room Temperature Ionic Liquids

    Institute of Scientific and Technical Information of China (English)

    2003-01-01

    Conducted in the ionic liquids, activated and inactivated halides, acyl chlorides, tosylate, and bezotriazolyl acylates were converted to corresponding azide and thiocyanide compounds in high yields under mild conditions.

  17. Electronic and Ionic Transport Dynamics in Organolead Halide Perovskites.

    Science.gov (United States)

    Li, Dehui; Wu, Hao; Cheng, Hung-Chieh; Wang, Gongming; Huang, Yu; Duan, Xiangfeng

    2016-07-26

    Ion migration has been postulated as the underlying mechanism responsible for the hysteresis in organolead halide perovskite devices. However, the electronic and ionic transport dynamics and how they impact each other in organolead halide perovskites remain elusive to date. Here we report a systematic investigation of the electronic and ionic transport dynamics in organolead halide perovskite microplate crystals and thin films using temperature-dependent transient response measurements. Our study reveals that thermally activated ionic and electronic conduction coexist in perovskite devices. The extracted activation energies suggest that the electronic transport is easier, but ions migrate harder in microplates than in thin films, demonstrating that the crystalline quality and grain boundaries can fundamentally modify electronic and ionic transport in perovskites. These findings offer valuable insight on the electronic and ionic transport dynamics in organolead halide perovskites, which is critical for optimizing perovskite devices with reduced hysteresis and improved stability and efficiency.

  18. On the molecular anisotropy of liquid crystalline and flexible polymer systems

    Science.gov (United States)

    van Horn, Brett L.

    The demand for products of ever increasing quality or for novel applications has required increasing attention to or manipulation of the anisotropy of manufactured parts. Oriented plastics are used everywhere from recording film to automotive body parts to monofilament fishing line. Liquid crystals are also used in a wide array of applications including their dominance in the flat panel display industry, color changing temperature sensors, and woven bullet resistant fabrics. Anisotropy can also be detrimental, for instance sometimes leading to poor fracture resistance or low yield stress along specific directions. Controlling and measuring anisotropy of materials has become increasingly important, but doing so is wrought with challenges. Measuring physical properties of isotropic liquids, such as water or most oils can be done in a straightforward fashion. Their viscosities and densities, for example, have unique values under a given set of conditions. With anisotropic fluids, like liquid crystals, the viscosity, for instance, will not only depend upon temperature, concentration, etc. but also upon the direction of observation, degree of anisotropy, source of anisotropy, and so forth. This added degree of complexity complicates our ability to define the state of the material at which the measurements are made and generally necessitates the use of more sophisticated measurement strategies or techniques. This work presents techniques and tools for investigating anisotropy in liquid crystalline and stretched polymeric systems. Included are the use of conoscopy for the determination of birefringence and orientation of nematic liquid crystals and stretched polymers, the shear response of flow aligning nematic liquid crystal monodomains, and the design of a novel linear rheometer that allows for in situ optical or scattering investigations.

  19. Synthesis and characterization of liquid-crystalline supramolecular architecture by a combination of molecular recognition and polymerization reaction

    Science.gov (United States)

    Ahn, Cheol-Hee

    for polymers with controlled cylindrical and spherical shapes which assemble into thermotropic liquid crystalline phase. The molecular design, synthesis, characterization and polymerization of these bulky monomers and polymers requires a combination of supramolecular chemistry, liquid crystallinity and polymer science. This thesis will provide an entry into the design of visualizable polymeric materials with dramatically different properties which are determined by their shape. Cylindrical and spherical polymers obtained from flexible backbones jacketed with dendritic coats will access a mechanism to control the conformation and rigidity of their flexible chains. The rigidity of cylindrical polymers can be manipulated via their diameter, internal structure and conformational restrictions. Mechanisms to change in a reversible and controlled way to change the shape of the polymer from rod-like to spherical is elaborated and this work can open a new technological concepts in areas such as fibers, films, membranes, electronic, photonic and controlled release systems.

  20. Optical study of the molecular alignment in a nematic liquid crystal in an oblique magnetic field

    OpenAIRE

    Oldano, C.; Miraldi, E.; Strigazzi, A.; Taverna Valabrega, P.; Trossi, L.

    1984-01-01

    The light intensity I transmitted through a homeotropically oriented nematic liquid crystal slab held between crossed polarizers, as a function of the angle θH of an applied magnetic field, is calculated for oblique light incidence. The presence of singular points in the I vs. θ H curve which are related to the elastic constants of the liquid crystal is demonstrated One of these points, found here for the first time, for small angles of incidence depends only on the ratio K33/Χ a, and allows ...

  1. International Symposium on Halide Glasses (2nd) (Extended Abstracts).

    Science.gov (United States)

    1983-08-05

    method in which Pyrex 7740 is the standard material. These results will be compared with our earlier results on a fluorozirconate glass ( ZBLAN glass ...AliS 215 INTERNATIONAL SYMPOSIUM ON HALIDE GLASSES 12ND) 1/1 (EXTENDED ABSTRACTS) (U) RENSSELAER POLY’TECHNIC INST TROY NY DEPT OF MATERIALS ENGINEE...Classification) Second International Symposium on Halide Glasses (Extended Abstracts) (U) 12. PERSONAL AUTHOR(S) Cornelius T. Moynihan Chairman 13a

  2. A spectroscopic and molecular dynamic approach on the interaction between ionic liquid type gemini surfactant and human serum albumin.

    Science.gov (United States)

    Maurya, Jitendra Kumar; Mir, Muzaffar Ul Hassan; Maurya, Neha; Dohare, Neeraj; Ali, Anwar; Patel, Rajan

    2016-10-01

    The interactions of imidazolium bashed ionic liquid-type cationic gemini surfactant ([C12-4-C12im]Br2) with HSA were studied by fluorescence, time-resolved fluorescence, UV-visible, circular dichroism, molecular docking and molecular dynamic simulation methods. The results showed that the [C12-4-C12im]Br2 quenched the fluorescence of HSA through dynamic quenching mechanism as confirmed by time-resolved spectroscopy. The Stern-Volmer quenching constant (Ksv) and relevant thermodynamic parameters such as enthalpy change (ΔH), Gibbs free energy change (ΔG) and entropy change (ΔS) for interaction system were calculated at different temperatures. The results revealed that hydrophobic forces played a major role in the interactions process. The results of synchronous fluorescence, UV-visible and CD spectra demonstrated that the binding of [C12-4-C12im]Br2 with HSA induces conformational changes in HSA. Inquisitively, the molecular dynamics study contribute towards understanding the effect of binding of [C12-4-C12im]Br2 on HSA to interpret the conformational change in HSA upon binding in aqueous solution. Moreover, the molecular modelling results show the possible binding sites in the interaction system.

  3. Vibrational circular dichroism from ab initio molecular dynamics and nuclear velocity perturbation theory in the liquid phase.

    Science.gov (United States)

    Scherrer, Arne; Vuilleumier, Rodolphe; Sebastiani, Daniel

    2016-08-28

    We report the first fully ab initio calculation of dynamical vibrational circular dichroism spectra in the liquid phase using nuclear velocity perturbation theory (NVPT) derived electronic currents. Our approach is rigorous and general and thus capable of treating weak interactions of chiral molecules as, e.g., chirality transfer from a chiral molecule to an achiral solvent. We use an implementation of the NVPT that is projected along the dynamics to obtain the current and magnetic dipole moments required for accurate intensities. The gauge problem in the liquid phase is resolved in a twofold approach. The electronic expectation values are evaluated in a distributed origin gauge, employing maximally localized Wannier orbitals. In a second step, the gauge invariant spectrum is obtained in terms of a scaled molecular moments, which allows to systematically include solvent effects while keeping a significant signal-to-noise ratio. We give a thorough analysis and discussion of this choice of gauge for the liquid phase. At low temperatures, we recover the established double harmonic approximation. The methodology is applied to chiral molecules ((S)-d2-oxirane and (R)-propylene-oxide) in the gas phase and in solution. We find an excellent agreement with the theoretical and experimental references, including the emergence of signals due to chirality transfer from the solute to the (achiral) solvent.

  4. Stokes shift dynamics in (non-dipolar ionic liquid + dipolar solvent) binary mixtures: A semi-molecular theory

    Science.gov (United States)

    Pal, Tamisra; Biswas, Ranjit

    2014-10-01

    A semi-molecular theory for studying composition dependent Stokes shift dynamics of a dipolar solute in binary mixtures of (non-dipolar ionic liquid + common dipolar solvent) is developed here. The theory provides microscopic expressions for solvation response functions in terms of static and dynamic structure factors of the mixture components and solute-solvent static correlations. In addition, the theory provides a framework for examining the interrelationship between the time dependent solvation response in and frequency dependent dielectric relaxation of a binary mixture containing electrolyte. Subsequently, the theory has been applied to predict ionic liquid (IL) mole fraction dependent dynamic Stokes shift magnitude and solvation energy relaxation for a dipolar solute, C153, in binary mixtures of an ionic liquid, trihexyltetradecylphosphonium chloride ([P14,666][Cl]) with a common dipolar solvent, methanol (MeOH). In the absence of suitable experimental data, necessary input parameters have been obtained from approximate methods. Dynamic shifts calculated for these mixtures exhibit a linear increase with IL mole fraction for the most part of the mixture composition, stressing the importance of solute-IL dipole-ion interaction. Average solvation rates, on the other hand, show a nonlinear IL mole fraction dependence which is qualitatively similar to what has been observed for such binary mixtures with imidazolium (dipolar) ILs. These predictions should be re-examined in suitable experiments.

  5. Vibrational circular dichroism from ab initio molecular dynamics and nuclear velocity perturbation theory in the liquid phase

    Science.gov (United States)

    Scherrer, Arne; Vuilleumier, Rodolphe; Sebastiani, Daniel

    2016-08-01

    We report the first fully ab initio calculation of dynamical vibrational circular dichroism spectra in the liquid phase using nuclear velocity perturbation theory (NVPT) derived electronic currents. Our approach is rigorous and general and thus capable of treating weak interactions of chiral molecules as, e.g., chirality transfer from a chiral molecule to an achiral solvent. We use an implementation of the NVPT that is projected along the dynamics to obtain the current and magnetic dipole moments required for accurate intensities. The gauge problem in the liquid phase is resolved in a twofold approach. The electronic expectation values are evaluated in a distributed origin gauge, employing maximally localized Wannier orbitals. In a second step, the gauge invariant spectrum is obtained in terms of a scaled molecular moments, which allows to systematically include solvent effects while keeping a significant signal-to-noise ratio. We give a thorough analysis and discussion of this choice of gauge for the liquid phase. At low temperatures, we recover the established double harmonic approximation. The methodology is applied to chiral molecules ((S)-d2-oxirane and (R)-propylene-oxide) in the gas phase and in solution. We find an excellent agreement with the theoretical and experimental references, including the emergence of signals due to chirality transfer from the solute to the (achiral) solvent.

  6. Synthesis of methyl halides from biomass using engineered microbes.

    Science.gov (United States)

    Bayer, Travis S; Widmaier, Daniel M; Temme, Karsten; Mirsky, Ethan A; Santi, Daniel V; Voigt, Christopher A

    2009-05-13

    Methyl halides are used as agricultural fumigants and are precursor molecules that can be catalytically converted to chemicals and fuels. Plants and microorganisms naturally produce methyl halides, but these organisms produce very low yields or are not amenable to industrial production. A single methyl halide transferase (MHT) enzyme transfers the methyl group from the ubiquitous metabolite S-adenoyl methionine (SAM) to a halide ion. Using a synthetic metagenomic approach, we chemically synthesized all 89 putative MHT genes from plants, fungi, bacteria, and unidentified organisms present in the NCBI sequence database. The set was screened in Escherichia coli to identify the rates of CH(3)Cl, CH(3)Br, and CH(3)I production, with 56% of the library active on chloride, 85% on bromide, and 69% on iodide. Expression of the highest activity MHT and subsequent engineering in Saccharomyces cerevisiae results in productivity of 190 mg/L-h from glucose and sucrose. Using a symbiotic co-culture of the engineered yeast and the cellulolytic bacterium Actinotalea fermentans, we are able to achieve methyl halide production from unprocessed switchgrass (Panicum virgatum), corn stover, sugar cane bagasse, and poplar (Populus sp.). These results demonstrate the potential of producing methyl halides from non-food agricultural resources.

  7. Molecular dynamics study on the effect of boundary heating rate on the phase change characteristics of thin film liquid

    Science.gov (United States)

    Hasan, Mohammad Nasim; Morshed, A. K. M. Monjur; Rabbi, Kazi Fazle; Haque, Mominul

    2016-07-01

    In this study, theoretical investigation of thin film liquid phase change phenomena under different boundary heating rates has been conducted with the help of molecular dynamics simulation. To do this, the case of argon boiling over a platinum surface has been considered. The study has been conducted to get a better understanding of the nano-scale physics of evaporation/boiling for a three phase system with particular emphasis on the effect of boundary heating rate. The simulation domain consisted of liquid and vapor argon atoms placed over a platinum wall. Initially the whole system was brought to an equilibrium state at 90K with the help of equilibrium molecular dynamics and then the temperature of the bottom wall was increased to a higher temperature (250K/130K) over a finite heating period. Depending on the heating period, the boundary heating rate has been varied in the range of 1600×109 K/s to 8×109 K/s. The variations of argon region temperature, pressure, net evaporation number with respect to time under different boundary heating rates have been determined and discussed. The heat fluxes normal to platinum wall for different cases were also calculated and compared with theoretical upper limit of maximum possible heat transfer to elucidate the effect of boundary heating rate.

  8. Molecular structure of the discotic liquid crystalline phase of hexa-peri-hexabenzocoronene/oligothiophene hybrid and their charge transport properties

    Energy Technology Data Exchange (ETDEWEB)

    Bag, Saientan; Maingi, Vishal; Maiti, Prabal K., E-mail: maiti@physics.iisc.ernet.in [Department of Physics, Center for Condensed Matter Theory, Indian Institute of Science, Bangalore 560012 (India); Yelk, Joe; Glaser, Matthew A.; Clark, Noel A. [Department of Physics, University of Colorado, Boulder, Colorado 80309 (United States); Walba, David M. [Department of Chemistry and Biochemistry, University of Colorado, Boulder, Colorado 80309 (United States)

    2015-10-14

    Using atomistic molecular dynamics simulation, we study the discotic columnar liquid crystalline (LC) phases formed by a new organic compound having hexa-peri-Hexabenzocoronene (HBC) core with six pendant oligothiophene units recently synthesized by Nan Hu et al. [Adv. Mater. 26, 2066 (2014)]. This HBC core based LC phase was shown to have electric field responsive behavior and has important applications in organic electronics. Our simulation results confirm the hexagonal arrangement of columnar LC phase with a lattice spacing consistent with that obtained from small angle X-ray diffraction data. We have also calculated various positional and orientational correlation functions to characterize the ordering of the molecules in the columnar arrangement. The molecules in a column are arranged with an average twist of 25° having an average inter-molecular separation of ∼5 Å. Interestingly, we find an overall tilt angle of 43° between the columnar axis and HBC core. We also simulate the charge transport through this columnar phase and report the numerical value of charge carrier mobility for this liquid crystal phase. The charge carrier mobility is strongly influenced by the twist angle and average spacing of the molecules in the column.

  9. On the influence of hydrated imidazolium-based ionic liquid on protein structure stability: A molecular dynamics simulation study

    Science.gov (United States)

    Shao, Qiang

    2013-09-01

    The structure stability of three α-helix bundle (the B domain of protein A) in an imidazolium-based ionic liquid (1-butyl-3-methylimidazolium chloride (BMIM-Cl)) is studied by molecular dynamics simulations. Consistent with previous experiments, the present simulation results show that the native structure of the protein is consistently stabilized in BMIM-Cl solutions with different concentrations. It is observed that BMIM+ cations have a strong tendency to accumulate on protein surface whereas Cl- anions are expelled from protein. BMIM+ cations cannot only have electrostatic interactions with the carbonyl groups on backbone and the carboxylate groups on negatively charged side chains, but also have hydrophobic interactions with the side chains of non-polar residues. In the meanwhile, the accumulation of large-size BMIM+ cations on protein surface could remove the surrounding water molecules, reduce the hydrogen bonding from water to protein, and thus stabilize the backbone hydrogen bonds. In summary, the present study could improve our understanding of the molecular mechanism of the impact of water-miscible ionic liquid on protein structure.

  10. Molecular orientation of carboxylic acids adsorbed on graphite from the liquid

    Energy Technology Data Exchange (ETDEWEB)

    Clarke, Stuart M. [Department of Chemistry and BP Institute, Madingley Rise, Cambridge (United Kingdom); Inabe, Akira [Department of Chemistry and Research Center for Molecular Thermodynamics, Graduate School of Science, Osaka Univ., Osaka (Japan); Thomas, Robert K.; Fish, Joe [Physical and Theoretical Chemistry Laboratory, Oxford (United Kingdom)

    2001-03-01

    We present incoherent elastic neutron scattering and calorimetry data from simple monocarboxylic acids, C9, C14 and C16, adsorbed from their liquids to the graphite surface which indicate the formation of solid monolayers with molecules which are predominantly upright. (author)

  11. Visualizing Molecular Chirality in the Organic Chemistry Laboratory Using Cholesteric Liquid Crystals

    Science.gov (United States)

    Popova, Maia; Bretz, Stacey Lowery; Hartley, C. Scott

    2016-01-01

    Although stereochemistry is an important topic in second-year undergraduate organic chemistry, there are limited options for laboratory activities that allow direct visualization of macroscopic chiral phenomena. A novel, guided-inquiry experiment was developed that allows students to explore chirality in the context of cholesteric liquid crystals.…

  12. Evidencing molecular associations in binary liquid mixtures via photothermal measurements of thermophysical parameters

    NARCIS (Netherlands)

    Neamtu, C.; Dadarlat, D.; Chirtoc, M.; Sahraoui, A.H.; Longuemart, S.; Bicanic, D.D.

    2006-01-01

    The back photopyroelectric (PPE) configuration, with opaque sample and thermally thick sample and sensor, was applied in order to obtain room temperature values of the thermal diffusivity of some liquid mixtures. The methodology is based on a sample's thickness scan, and not on a frequency scan as i

  13. Step free energies at faceted solid-liquid interfaces from equilibrium molecular dynamics simulations.

    Science.gov (United States)

    Frolov, T; Asta, M

    2012-12-07

    In this work a method is proposed for computing step free energies for faceted solid-liquid interfaces based on atomistic simulations. The method is demonstrated in an application to (111) interfaces in elemental Si, modeled with the classical Stillinger-Weber potential. The approach makes use of an adiabatic trapping procedure, and involves simulations of systems with coexisting solid and liquid phases separated by faceted interfaces containing islands with different sizes, for which the corresponding equilibrium temperatures are computed. We demonstrate that the calculated coexistence temperature is strongly affected by the geometry of the interface. We find that island radius is inversely proportional to superheating, allowing us to compute the step free energy by fitting simulation data within the formalism of classical nucleation theory. The step free energy value is computed to be γ(st) = 0.103 ± 0.005 × 10(-10) J/m. The approach outlined in this work paves the way to the calculation of step free energies relevant to the solidification of faceted crystals from liquid mixtures, as encountered in nanowire growth by the vapor-liquid-solid mechanism and in alloy casting. The present work also shows that at low undercoolings the Stillinger-Weber interatomic potential for Si tends to crystallize in the wurtzite, rather than the diamond-cubic structure.

  14. A pair potential that reproduces the shape of isochrones in molecular liquids

    CERN Document Server

    Veldhorst, Arno A; Dyre, Jeppe C

    2016-01-01

    Many liquids have curves (isomorphs) in their phase diagram along which structure, dynamics and some thermodynamic quantities are invariant in reduced units. A substantial part of their phase diagram is thus effectively one dimensional. The shape of these isomorphs is described by a material-dependent function of density $h(\\rho)$, which for many liquids is well approximated by a power law $\\rho^\\gamma$. When density changes are large, however, this often fails; simulations of typical models such as the Lennard-Jones system show that $\\gamma(\\rho) \\equiv \\,\\mathrm{d} \\ln h(\\rho)/\\,\\mathrm{d} \\ln \\rho$ is a decreasing function of the density, while experimental results on organic liquids show the opposite. This paper presents results from computer simulations using a new pair potential that diverges at a non-zero distance and has $\\gamma(\\rho)$ increasing with density. Our results indicate that the finite size of molecules should be taken into account when modeling liquids over a large density range.

  15. Relation between the electroforming voltage in alkali halide-polymer diodes and the bandgap of the alkali halide

    Energy Technology Data Exchange (ETDEWEB)

    Bory, Benjamin F.; Wang, Jingxin; Janssen, René A. J.; Meskers, Stefan C. J., E-mail: s.c.j.meskers@tue.nl [Molecular Materials and Nanosystems and Institute for Complex Molecular Systems, Eindhoven University of Technology, P.O. Box 513, 5600 MB Eindhoven (Netherlands); Gomes, Henrique L. [Instituto de Telecomunicações, Av. Rovisco, Pais 1, 1049-001 Lisboa, Portugal and Universidade do Algarve, Campus de Gambelas, 8005-139 Faro (Portugal); De Leeuw, Dago M. [Max-Planck Institute for Polymer Research, Ackermannweg 10, 55128 Mainz, Germany and King Abdulaziz University, Jeddah (Saudi Arabia)

    2014-12-08

    Electroforming of indium-tin-oxide/alkali halide/poly(spirofluorene)/Ba/Al diodes has been investigated by bias dependent reflectivity measurements. The threshold voltages for electrocoloration and electroforming are independent of layer thickness and correlate with the bandgap of the alkali halide. We argue that the origin is voltage induced defect formation. Frenkel defect pairs are formed by electron–hole recombination in the alkali halide. This self-accelerating process mitigates injection barriers. The dynamic junction formation is compared to that of a light emitting electrochemical cell. A critical defect density for electroforming is 10{sup 25}/m{sup 3}. The electroformed alkali halide layer can be considered as a highly doped semiconductor with metallic transport characteristics.

  16. The molecular assembly of the ionic liquid/aliphatic carboxylic acid/aliphatic amine as effective and safety transdermal permeation enhancers.

    Science.gov (United States)

    Kubota, Koji; Shibata, Akira; Yamaguchi, Toshikazu

    2016-04-30

    In spite of numerous advantages, transdermal drug delivery systems are unfeasible for most drugs because of the barrier effect of the stratum corneum. Ionic liquids were recently used to enhance transdermal drug delivery by improving drug solubility. In the present study, safe and effective ionic liquids for transdermal absorption were obtained as salts generated by a neutralization reaction between highly biocompatible aliphatic carboxylic acids (octanoic acid or isostearic acid) and aliphatic amines (diisopropanolamine or triisopropanolamine) (Medrx Co., Ltd., 2009). The mechanism of skin permeability enhancement by ionic liquids was investigated by hydrophilic phenol red and hydrophobic tulobuterol. Further, the skin permeation enhancing effect was remarkably superior in the acid excess state rather than the neutralization state. Infrared absorption spectrum analysis confirmed that ionic liquids/aliphatic carboxylic acid/aliphatic amine are coexisting at all mixing states. In the acid excess state, ionic liquids interact with aliphatic carboxylic acids via hydrogen bonds. Thus, the skin permeation enhancing effect is not caused by the ionic liquid alone. The "liquid salt mixture," referred to as a complex of ingredients coexisting with ionic liquids, forms a molecular assembly incorporating hydrophilic drug. This molecular assembly was considered an effective and safety enhancer of transdermal drug permeation.

  17. Molecular dynamics simulations of the aqueous interface with the [BMI][PF6] ionic liquid: Comparison of different solvent models.

    Science.gov (United States)

    Chevrot, G; Schurhammer, R; Wipff, G

    2006-09-28

    We report a Molecular Dynamics (MD) study of the interface between water and the hygroscopic room temperature Ionic Liquid "IL" [BMI][PF6] (1-butyl-3-methyl-imidazolium hexafluorophosphate), comparing the TIP3P, SPC/E and TIP5P models for water and two IL models where the ions are +/-1 or +/-0.9 charged. A recent MD study (A. Chaumont, R. Schurhammer and G. Wipff, J. Phys. Chem. B, 2005, 109, 18964) showed that using TIP3P water in conjunction with the IL(+/-1) model led to water-IL mixing without forming an interface, whereas a biphasic system could be obtained with the IL(+/-0.9) model. With the TIP5P and SPC/E models, the juxtaposed aqueous and IL phases are found to remain distinct for at least 20 ns. The resulting IL humidity, exaggerated with the IL(+/-1) model, is in better agreement with experiment using the IL(+/-0.9) model. We also report demixing simulations on the "randomly mixed" liquids, using the IL(+/-0.9) model for the ionic liquid. With the three tested water models, the phases separate very slowly ( approximately 20 ns or more) compared to "classical" chloroform-water mixtures (less than 1 ns), leading to biphasic systems similar to those obtained after equilibration of the juxtaposed liquids. The characteristics of the interface (size, polarity, ion orientation, electrostatic potential) are compared with the different models. Possible reasons why, among the three tested water models, the widely-used TIP3P model exaggerates the inter-solvent mixing, are analyzed. The difficulty in computationally and experimentally equilibrating water-IL mixtures is attributed to the slow dynamics and micro-heterogeneity of the IL and to the different states of water in the IL phase.

  18. Solvation structure of the halides from x-ray absorption spectroscopy

    Science.gov (United States)

    Antalek, Matthew; Pace, Elisabetta; Hedman, Britt; Hodgson, Keith O.; Chillemi, Giovanni; Benfatto, Maurizio; Sarangi, Ritimukta; Frank, Patrick

    2016-07-01

    Three-dimensional models for the aqueous solvation structures of chloride, bromide, and iodide are reported. K-edge extended X-ray absorption fine structure (EXAFS) and Minuit X-ray absorption near edge (MXAN) analyses found well-defined single shell solvation spheres for bromide and iodide. However, dissolved chloride proved structurally distinct, with two solvation shells needed to explain its strikingly different X-ray absorption near edge structure (XANES) spectrum. Final solvation models were as follows: iodide, 8 water molecules at 3.60 ± 0.13 Å and bromide, 8 water molecules at 3.40 ± 0.14 Å, while chloride solvation included 7 water molecules at 3.15 ± 0.10 Å, and a second shell of 7 water molecules at 4.14 ± 0.30 Å. Each of the three derived solvation shells is approximately uniformly disposed about the halides, with no global asymmetry. Time-dependent density functional theory calculations simulating the chloride XANES spectra following from alternative solvation spheres revealed surprising sensitivity of the electronic state to 6-, 7-, or 8-coordination, implying a strongly bounded phase space for the correct structure during an MXAN fit. MXAN analysis further showed that the asymmetric solvation predicted from molecular dynamics simulations using halide polarization can play no significant part in bulk solvation. Classical molecular dynamics used to explore chloride solvation found a 7-water solvation shell at 3.12 (-0.04/+0.3) Å, supporting the experimental result. These experiments provide the first fully three-dimensional structures presenting to atomic resolution the aqueous solvation spheres of the larger halide ions.

  19. Semiquantal molecular dynamics simulations of hydrogen-bond dynamics in liquid water using multi-dimensional Gaussian wave packets.

    Science.gov (United States)

    Ono, Junichi; Ando, Koji

    2012-11-01

    A semiquantal (SQ) molecular dynamics (MD) simulation method based on an extended Hamiltonian formulation has been developed using multi-dimensional thawed gaussian wave packets (WPs), and applied to an analysis of hydrogen-bond (H-bond) dynamics in liquid water. A set of Hamilton's equations of motion in an extended phase space, which includes variance-covariance matrix elements as auxiliary coordinates representing anisotropic delocalization of the WPs, is derived from the time-dependent variational principle. The present theory allows us to perform real-time and real-space SQMD simulations and analyze nuclear quantum effects on dynamics in large molecular systems in terms of anisotropic fluctuations of the WPs. Introducing the Liouville operator formalism in the extended phase space, we have also developed an explicit symplectic algorithm for the numerical integration, which can provide greater stability in the long-time SQMD simulations. The application of the present theory to H-bond dynamics in liquid water is carried out under a single-particle approximation in which the variance-covariance matrix and the corresponding canonically conjugate matrix are reduced to block-diagonal structures by neglecting the interparticle correlations. As a result, it is found that the anisotropy of the WPs is indispensable for reproducing the disordered H-bond network compared to the classical counterpart with the use of the potential model providing competing quantum effects between intra- and intermolecular zero-point fluctuations. In addition, the significant WP delocalization along the out-of-plane direction of the jumping hydrogen atom associated with the concerted breaking and forming of H-bonds has been detected in the H-bond exchange mechanism. The relevance of the dynamical WP broadening to the relaxation of H-bond number fluctuations has also been discussed. The present SQ method provides the novel framework for investigating nuclear quantum dynamics in the many

  20. Molecular dynamics analysis of the friction between a water-methanol liquid mixture and a non-polar solid crystal surface

    Science.gov (United States)

    Nakaoka, Satoshi; Yamaguchi, Yasutaka; Omori, Takeshi; Joly, Laurent

    2017-05-01

    We performed molecular dynamics analysis of the momentum transfer at the solid-liquid interface for a water-methanol liquid mixture between parallel non-polar solid walls in order to understand the strong decrease of the friction coefficient (FC) induced by the methanol adsorption at the surface observed in our previous work [S. Nakaoka et al., Phys. Rev. E 92, 022402 (2015)]. In particular, we extracted the individual contributions of water and methanol molecules to the total FC and found that the molecular FC for methanol was larger than that for water. We further showed that the reduction of the total solid-liquid FC upon the increase of the methanol molar fraction in the first adsorption layer occurred as a result of a decrease in the molecular number density as well as a decrease in the molecular FCs of both molecules. Analysis of the molecular orientation revealed that the decrease of the molecular FC of methanol resulted from changes of the contact feature onto the solid surface. Specifically, methanol molecules near the solid surface had their C-O bond parallel to the surface with both CH3 and O sites contacting the solid at low methanol molar fraction, while they had their C-O bond outward from the surface with only the CH3 site contacting the solid at higher methanol molar fraction. The mechanisms discussed in this work could be used to search for alternative water additives to further reduce the solid-liquid friction.

  1. Molecular transport into and out of ionic-liquid filled block copolymer vesicles in water

    Science.gov (United States)

    Lodge, Timothy; Yao, Letitia; So, Soonyong

    We have developed a method to prepare stable, size-controlled block copolymer vesicles that contain ionic liquid in the interior, but that are dispersed in water. Such nanoemulsions are of interest as nanoreactors, because the mass transfer and cost limitations of ionic liquids are circumvented. However, a crucial question is whether target molecules (e . g ., reagents and products) can enter and leave the vesicles, respectively, on a useful time scale (i . e ., seconds or shorter). In this talk we will briefly describe methods to prepare such vesicles with narrow size distributions, using poly(styrene)-block-poly(ethylene oxide) and poly(butadiene)-block-poly(ethylene oxide) copolymers of various compositions. We will then present results of pulsed-field gradient NMR measurements of probe diffusion that yield independent measurements of the entry and escape rates for selected small molecules, as a function of membrane thickness and temperature.

  2. Molecular dynamics studies of a generalised multipole model of molecular asymmetry in apolar and polar liquid crystals

    CERN Document Server

    Johnston, S J

    2001-01-01

    was identified as the system cooled whereas for gamma = 70 deg no ordered phase formed. The study was repeated with the addition of a transverse electric dipole of mu* = 1.5 which was seen to stabilise a range of smectic phases. The nematic phase was destabilised in the rod-like model with a transition directly to a smectic B phase then to a ferroelectric crystal. As the angle gamma increased the transition temperature to the first ordered phase decreased more markedly than for the apolar models. Smectic A, tilted smectic B and a spontaneously polarised smectic B phase were observed in the gamma = 10 deg bent-core model. The gamma = 20 deg model showed smectic A and tilted antiferroelectric smectic B phases. The gamma = 40 deg model showed an antiferroelectric phase that exhibited unusual packing behaviour. Both the gamma = 20 deg and gamma = 40 deg models showed a significant phase biaxiality in the smectic B phases. This study has successfully reproduced some of the complex features seen in real molecular p...

  3. Thermal Diffusion in Liquid Mixtures and Polymer Solutions by Molecular Dynamics Simulations

    OpenAIRE

    2007-01-01

    This thesis is focused on simulating the transport processes of heat and matter under a sufficiently weak temperature gradient where the system linearly responds. The systems we are interested in are binary isotropic liquids with no convection and no viscous flows. Four related transport coefficients of the systems, the thermal conductivity of heat conduction, the diffusion coefficient of matter transfer, the Soret coefficient and the thermal diffusion coefficient of the cross effect between ...

  4. Dendritic Liquid Crystals:Self-organization and Nuclear Magnetic Relaxation Investigation of Their Molecular Dynamics

    Institute of Scientific and Technical Information of China (English)

    A.Van-quynh; P.J.Sebasti■o; D.Apreutesei; G.H.Mehl

    2007-01-01

    1 Results Liquid crystalline dendrimers and structurally related multipodes are supermolecules consisting of an amorphous hyper-branched core at the periphery of which are attached mesogenic groups capable of self-organization.Two opposite tendencies compete in these systems: the internal dendrimer tends to adopt a pseudo-spherical architecture that has a disordering influence on the packing of the mesogenic parts whose tend to self-organize into partially ordered structures.These kinds of systems show ...

  5. First principles molecular dynamics simulation of a task-specific ionic liquid based on silver-olefin complex: atomistic insight into separation process

    CERN Document Server

    Jiang, De-en

    2008-01-01

    First principles molecular dynamics based on density functional theory is applied to a hypothetical ionic liquid whose cations and anions are silver-ethylene complex [Ag(C2H4)2+] and tetrafluoroborate [BF4-], respectively. This ionic liquid represents a group of task-specific silver complex-based ionic liquids synthesized recently. Molecular dynamics simulations at two temperatures are performed for five picoseconds. Events of association, dissociation, exchange, and recombination of ethylene with silver cation are observed. A mechanism of ethylene transfer similar to the Grotthus type of proton transfer in water is identified, where a silver cation accepts one ethylene molecule and donates another to a neighboring silver cation. This mechanism may contribute to fast transport of olefins through ionic liquid membranes based on silver complexes for olefin/paraffin separation.

  6. First principles molecular dynamics simulation of a task-specific ionic liquid based on silver-olefin complex: atomistic insights into a separation process.

    Science.gov (United States)

    Jiang, De-en; Dai, Sheng

    2008-08-21

    First principles molecular dynamics based on density functional theory is applied to a hypothetical ionic liquid whose cations and anions are silver-ethylene complex [Ag(C2H4)2+] and tetrafluoroborate [BF4-], respectively. This ionic liquid represents a group of task-specific silver complex-based ionic liquids synthesized recently. Molecular dynamics simulations at two temperatures are performed for five picoseconds. Events of association, dissociation, exchange, and recombination of ethylene with silver cation are found. A mechanism of ethylene transfer similar to the Grotthus type of proton transfer in water is identified, where a silver cation accepts one ethylene molecule and donates another to a neighboring silver cation. This mechanism may contribute to fast transport of olefins through ionic liquid membranes based on silver complexes for olefin/paraffin separation.

  7. Molecular simulation of the thermodynamic, structural, and vapor-liquid equilibrium properties of neon.

    Science.gov (United States)

    Vlasiuk, Maryna; Frascoli, Federico; Sadus, Richard J

    2016-09-14

    The thermodynamic, structural, and vapor-liquid equilibrium properties of neon are comprehensively studied using ab initio, empirical, and semi-classical intermolecular potentials and classical Monte Carlo simulations. Path integral Monte Carlo simulations for isochoric heat capacity and structural properties are also reported for two empirical potentials and one ab initio potential. The isobaric and isochoric heat capacities, thermal expansion coefficient, thermal pressure coefficient, isothermal and adiabatic compressibilities, Joule-Thomson coefficient, and the speed of sound are reported and compared with experimental data for the entire range of liquid densities from the triple point to the critical point. Lustig's thermodynamic approach is formally extended for temperature-dependent intermolecular potentials. Quantum effects are incorporated using the Feynman-Hibbs quantum correction, which results in significant improvement in the accuracy of predicted thermodynamic properties. The new Feynman-Hibbs version of the Hellmann-Bich-Vogel potential predicts the isochoric heat capacity to an accuracy of 1.4% over the entire range of liquid densities. It also predicts other thermodynamic properties more accurately than alternative intermolecular potentials.

  8. Molecular simulation of the thermodynamic, structural, and vapor-liquid equilibrium properties of neon

    Science.gov (United States)

    Vlasiuk, Maryna; Frascoli, Federico; Sadus, Richard J.

    2016-09-01

    The thermodynamic, structural, and vapor-liquid equilibrium properties of neon are comprehensively studied using ab initio, empirical, and semi-classical intermolecular potentials and classical Monte Carlo simulations. Path integral Monte Carlo simulations for isochoric heat capacity and structural properties are also reported for two empirical potentials and one ab initio potential. The isobaric and isochoric heat capacities, thermal expansion coefficient, thermal pressure coefficient, isothermal and adiabatic compressibilities, Joule-Thomson coefficient, and the speed of sound are reported and compared with experimental data for the entire range of liquid densities from the triple point to the critical point. Lustig's thermodynamic approach is formally extended for temperature-dependent intermolecular potentials. Quantum effects are incorporated using the Feynman-Hibbs quantum correction, which results in significant improvement in the accuracy of predicted thermodynamic properties. The new Feynman-Hibbs version of the Hellmann-Bich-Vogel potential predicts the isochoric heat capacity to an accuracy of 1.4% over the entire range of liquid densities. It also predicts other thermodynamic properties more accurately than alternative intermolecular potentials.

  9. The Vibrational Spectra of the Boron Halides and Their Molecular ...

    African Journals Online (AJOL)

    NICO

    of matrix isolation spectroscopy in solid noble gas or nitrogen matrices is that of ... on the distribution of the charge densities and their topologies was derived using .... all shift to lower wavenumber, while for complexes 1, 3 and 4 these modes ...

  10. Molecular dynamics simulation of liquid phase adsorption of alkaloid on graphite surface

    Energy Technology Data Exchange (ETDEWEB)

    Suzuki, M.; Wang, D.; Sakoda, A. [The University of Tokyo, Tokyo (Japan). Institute of Industrial Science

    1997-10-20

    A methodology for molecular dynamics simulation of alkaloid adsorption onto solid surfaces from solutions is developed by employing berberine as a model alkaloid, and water, methanol and N,N-dimethylformamide (DMF) as model solvents. A single berberine molecule and a salvation shell around it are considered as the solution model. The behavior of berberine at the vacuum-solid interface and at the solution-solid interface were simulated, and it is found that a berberine molecule adsorbed with its molecular plane parallel to the graphite surface is most stable, and the molecular conformation does not change considerably during dissolution in the solvents and adsorption onto the graphite. Also, the solvent effects on the adsorption are focused on by analyzing the potential energy change of berberine molecule being adsorbed onto the graphite surface from the solutions by molecular dynamics calculations, and discussed quantitatively by combining solvophobic theory and calculations of the potential energy by molecular simulation. It is known that the presence of water or methanol has little effect on the adsorption of berberine onto the graphite surface, and that the presence of DMF inhibits the adsorption of berberine significantly. It can be said that the methodology developed in this work is useful for studying the solvent effects on adsorption, and for choosing proper solvents in adsorptive separation and purification processes for alkaloids. 31 refs., 9 figs., 4 tabs.

  11. Molecular dynamics study of response of liquid N,N-dimethylformamide to externally applied electric field using a polarizable force field

    Energy Technology Data Exchange (ETDEWEB)

    Gao, Weimin; Niu, Haitao; Lin, Tong; Wang, Xungai; Kong, Lingxue [Institute for Frontier Materials, Deakin University, Waurn Ponds VIC 3216 (Australia)

    2014-01-28

    The behavior of Liquid N,N-dimethylformamide subjected to a wide range of externally applied electric fields (from 0.001 V/nm to 1 V/nm) has been investigated through molecular dynamics simulation. To approach the objective the AMOEBA polarizable force field was extended to include the interaction of the external electric field with atomic partial charges and the contribution to the atomic polarization. The simulation results were evaluated with quantum mechanical calculations. The results from the present force field for the liquid at normal conditions were compared with the experimental and molecular dynamics results with non-polarizable and other polarizable force fields. The uniform external electric fields of higher than 0.01 V/nm have a significant effect on the structure of the liquid, which exhibits a variation in numerous properties, including molecular polarization, local cluster structure, rotation, alignment, energetics, and bulk thermodynamic and structural properties.

  12. Molecular Diagnosis Using Residual Liquid-Based Cytology Materials for Patients with Nondiagnostic or Indeterminate Thyroid Nodules.

    Science.gov (United States)

    Kwon, Hyemi; Kim, Won Gu; Eszlinger, Markus; Paschke, Ralf; Song, Dong Eun; Kim, Mijin; Park, Suyeon; Jeon, Min Ji; Kim, Tae Yong; Shong, Young Kee; Kim, Won Bae

    2016-12-01

    Molecular analysis for common somatic mutations in thyroid cancer can improve diagnostic accuracy of fine-needle aspiration cytology (FNAC) in the nondiagnostic or indeterminate category of thyroid nodules. In this study, we evaluated the feasibility of molecular diagnosis from residual liquid-based cytology (LBC) material after cytological diagnosis. This prospective study enrolled 53 patients with thyroid nodules diagnosed as nondiagnostic, atypia of undetermined significance (AUS), or follicular lesion of undetermined significance (FLUS) after FNAC. DNAs and RNAs were isolated from residual LBC materials. BRAF(V600E) and RAS point mutations, PAX8/peroxisome proliferator-activated receptor γ (PPARγ), RET/PTC1, and RET/PTC3 rearrangements were evaluated by real-time polymerase chain reaction and pyrosequencing. All DNAs from 53 residual LBC samples could be analysed and point mutations were detected in 10 samples (19%). In 17 AUS nodules, seven samples (41%) had point mutations including BRAF (n=4), NRAS (n=2), and KRAS (n=1). In 20 FLUS nodules, three samples (15%) had NRAS point mutations. RNA from only one FLUS nodule could be analysed for rearrangements and there was no abnormality. Molecular analysis for BRAF and RAS mutations was feasible in residual LBC materials and might be useful for diagnosis of indeterminate thyroid nodules.

  13. Molecular investigation of the interaction between ionic liquid type gemini surfactant and lysozyme: A spectroscopic and computational approach.

    Science.gov (United States)

    Maurya, Jitendra Kumar; Mir, Muzaffar Ul Hassan; Singh, Upendra Kumar; Maurya, Neha; Dohare, Neeraj; Patel, Seema; Ali, Anwar; Patel, Rajan

    2015-07-01

    Herein, we are reporting the interaction of ionic liquid type gemini surfactant, 1,4-bis(3-dodecylimidazolium-1-yl) butane bromide ([C12-4-C12 im]Br2) with lysozyme by using Steady state fluorescence, UV-visible, Time resolved fluorescence, Fourier transform-infrared (FT-IR) spectroscopy techniques in combination with molecular modeling and docking method. The steady state fluorescence spectra suggested that the fluorescence of lysozyme was quenched by [C12-4-C12 im]Br2 through static quenching mechanism as confirmed by time resolved fluorescence spectroscopy. The binding constant for lysozyme-[C12-4-C12 im]Br2 interaction have been measured by UV-visible spectroscopy and found to be 2.541 × 10(5) M(-1). The FT-IR results show conformational changes in the secondary structure of lysozyme by the addition of [C12-4-C12 im]Br2. Moreover, the molecular docking study suggested that hydrogen bonding and hydrophobic interactions play a key role in the protein-surfactant binding. Additionally, the molecular dynamic simulation results revealed that the lysozyme-[C12-4-C12 im]Br2 complex reaches an equilibrium state at around 3 ns.

  14. Enantioseparations by high-performance liquid chromatography using molecularly imprinted polymers.

    Science.gov (United States)

    Spivak, David A

    2013-01-01

    Molecularly imprinted polymers (MIPs) are becoming increasingly useful as chromatographic adsorbents for molecular separations, especially chiral separations, because they can be tailored to specifically recognize the target molecule including its stereochemistry. Traditionally formed MIPs (as described here) are stable under ambient conditions for years, take only days to make, and use relatively inexpensive components, with the possible exception of the template in some cases which can be reused after it is removed from the polymer to keep costs down. In addition to providing experimental details for typical synthetic methods to fabricate MIPs and pack them into HPLC columns, this chapter also gives an overview of the concepts of molecular imprinting method and discusses important factors for designing an effective imprinted polymer.

  15. Development and application of gas diffusion denuder sampling techniques with in situ derivatization for the determination of hydrogen halides in volcanic plumes

    Science.gov (United States)

    Gutmann, Alexandra; Rüdiger, Julian; Bobrowski, Nicole; Hoffmann, Thorsten

    2017-04-01

    Volcanoes emit large amounts of gases into the atmosphere. The gas composition in volcanic plumes vary, driven by subsurface processes (such as magma rising) as well as by chemical reactions within the plume after mixing with ambient air. The knowledge of the gas composition can be a useful tool to monitor volcanic activity changes. However, to use the plume composition as a monitoring parameter, it is essential to understand the chemical reactions inside volcanic plumes, in particular when interpretation of volcanic activity changes is based on reactive gas species, such as bromine monoxide or molecular halogens. Changes in BrO/SO2-ratios, measured by UV spectrometers, have already been interpreted in connection with increasing volcanic activity prior to eruptions. But the abundance of BrO changes as a function of the reaction time, and therefore with distance from the vent, as well as the spatial position in the plume. Actually model and field studies assume a non-direct emission of BrO, but its formation due to photochemical and multiphase reactions involving gas and particle phase of volcanic emission mixed with the surrounding atmosphere. However, same models presume HBr as initially emitted species. Therefore, HBr is an important species linking BrO to geophysical processes in volcanic systems. Due to the lack of analytical methods for the accurate speciation of certain halogens (HBr, Br2, Br, BrCl, HOBr, etc.) there are still large uncertainties about the magnitude of volcanic halogen emissions, and in the understanding of the bromine chemistry in volcanic plumes. Since the concentrations of hydrogen halides are not directly accesable by remote sensing techniques, an in situ method with coated gas diffusion denuder was developed. The method uses selective derivatization reaction of gaseous hydrogen halides with an organic compound for the enrichment and immobilization. For this task 5,6-Epoxy-5,6-dihydro-1,10-phenanthrolin was identified as a suitable

  16. Perspectives on organolead halide perovskite photovoltaics

    Science.gov (United States)

    Hariz, Alex

    2016-07-01

    A number of photovoltaic technologies have been developed for large-scale solar-power production. The single-crystal first-generation photovoltaic devices were followed by thin-film semiconductor absorber layers layered between two charge-selective contacts, and more recently, by nanostructured or mesostructured solar cells that utilize a distributed heterojunction to generate charge carriers and to transport holes and electrons in spatially separated conduits. Even though a number of materials have been trialed in nanostructured devices, the aim of achieving high-efficiency thin-film solar cells in such a manner as to rival the silicon technology has yet to be attained. Organolead halide perovskites have recently emerged as a promising material for high-efficiency nanoinfiltrated devices. An examination of the efficiency evolution curve reveals that interfaces play a paramount role in emerging organic electronic applications. To optimize and control the performance in these devices, a comprehensive understanding of the contacts is essential. However, despite the apparent advances made, a fundamental theoretical analysis of the physical processes taking place at the contacts is still lacking. However, experimental ideas, such as the use of interlayer films, are forging marked improvements in efficiencies of perovskite-based solar cells. Furthermore, issues of long-term stability and large-area manufacturing have some way to go before full commercialization is possible.

  17. Preparation and Evaluation of Molecularly Imprinted Monolithic Column for Felodipine in Micro-liquid Chromatography

    Institute of Scientific and Technical Information of China (English)

    Qi Liang DENG; Zhi Hong LUN; Chao YAN; Ru Yu GAO

    2005-01-01

    This study concentrated on the production of molecularly imprinted polymers (MIPs) as highly selective sorbents for felodipine (FLD), a representive dihydropyridine calcium antagonists.Demonstrated chromatographically through a selection factor, these MIPs showed high selectivity for the template molecule among a group of structurally similar compounds. The recognition was found to correlate with structural similarity to the template compound.

  18. Simulation of macromolecular liquids with the adaptive resolution molecular dynamics technique

    Science.gov (United States)

    Peters, J. H.; Klein, R.; Delle Site, L.

    2016-08-01

    We extend the application of the adaptive resolution technique (AdResS) to liquid systems composed of alkane chains of different lengths. The aim of the study is to develop and test the modifications of AdResS required in order to handle the change of representation of large molecules. The robustness of the approach is shown by calculating several relevant structural properties and comparing them with the results of full atomistic simulations. The extended scheme represents a robust prototype for the simulation of macromolecular systems of interest in several fields, from material science to biophysics.

  19. Shock Hugoniots of molecular liquids and the principle of corresponding states

    Energy Technology Data Exchange (ETDEWEB)

    Chisolm, Eric D [Los Alamos National Laboratory; Crockett, Scott D [Los Alamos National Laboratory; Shaw, Milton S [Los Alamos National Laboratory

    2009-01-01

    We observe that the shock velocity-particle velocity Hugoniots for various liquids (e.g. nitrogen, oxygen, carbon dioxide, argon) lie almost on top of one another. Recalling the work of Ross and Ree [J. Chem. Phys. 73, 6146-6152 (1980)], we hypothesize that these materials obey a principle of corresponding states. We use the principle to deduce how the Hugoniots of two corresponding materials should be related, and we compare the results with data and find good agreement. We suggest this as a method for estimating the Hugoniot of a material of the appropriate type in the absence of shock data, and we illustrate with fluorine.

  20. Hydrogen bonding discotic liquid crystals: Synthesis, self-assembly, and molecular recognition

    Science.gov (United States)

    Bushey, Mark Lawrence

    The triamides shown below form discotic liquid crystalline phases with intermolecular hydrogen bonding stabilizing the columnar structure, A and B. The mesomorphic orientations of the columns are dependent on the amide side chain. Three mesophasic orientations are described: columns aligned perpendicular to the surface, columns aligned parallel to the surface in a radial pattern, and columns aligned parallel to the surface in a parallel or aligned pattern. The aggregation of the tridodecyloxy-triamides show N-H shifting in the IR at elevated temperatures, an indication that hydrogen bonding is important in the association of liquid crystalline mesophases. Powder X-ray diffraction studies indicate packing of the columns into a hexagonal lattice.* Studies on triamides with chiral side chains result in molecules stacking into columns displaying a helical pitch. In concentrated solutions of dodecane, molecules with chiral side chains display behavior consistent with chiral nematic liquid crystals; a super helical packing of the chiral columns. These superhelical packed systems show temperature dependent selective reflection of visible light and fingerprint textures. Atomic force microscopy (AFM) confirms in sub-monolayer films, that molecules preferring an edge-on orientation form long columns on highly ordered pyrolytic graphite (HOPG), those that prefer a face-on orientation form large amorphous domains. Electrostatic force microscopy (EFM) images of the domains of molecules in the edge-on orientation provides no discernible polarity, imaging of the domains of molecules in the face-on orientation indicates a negative polar orientation. Scanning probe measurements (SPM) of the tridodecynyl-triamide have shown similar edge-on orientations of other tridodecyloxy-triamides. Powder X-ray diffraction of these liquid crystalline phases shows a hexagonal packing of the columnar assembly. Electro-optic switching studies indicate a piezoelectric switching mechanism, possibly

  1. Structural and chemical analysis of gadolinium halides encapsulated within WS2 nanotubes

    Science.gov (United States)

    Anumol, E. A.; Enyashin, Andrey N.; Batra, Nitin M.; Costa, Pedro M. F. J.; Deepak, Francis Leonard

    2016-06-01

    The hollow cavities of nanotubes serve as templates for the growth of size- and shape-confined functional nanostructures, giving rise to novel materials and properties. In this work, considering their potential application as MRI contrast agents, gadolinium halides are encapsulated within the hollow cavities of WS2 nanotubes by capillary filling to obtain GdX3@WS2 nanotubes (where X = Cl, Br or I and @ means encapsulated in). Aberration corrected scanning/transmission electron microscopy (S/TEM) and spectroscopy is employed to understand the morphology and composition of the GdI3@WS2 nanotubes. The three dimensional morphology is studied with STEM tomography but understanding the compositional information is non-trivial due to the presence of multiple high atomic number elements. Therefore, energy dispersive X-ray spectroscopy (EDS) tomography was employed revealing the three dimensional chemical composition. Molecular dynamics simulations of the filling procedure shed light into the mechanics behind the formation of the confined gadolinium halide crystals. The quasi-1D system employed here serves as an example of a TEM-based chemical nanotomography method that could be extended to other materials, including beam-sensitive soft materials.The hollow cavities of nanotubes serve as templates for the growth of size- and shape-confined functional nanostructures, giving rise to novel materials and properties. In this work, considering their potential application as MRI contrast agents, gadolinium halides are encapsulated within the hollow cavities of WS2 nanotubes by capillary filling to obtain GdX3@WS2 nanotubes (where X = Cl, Br or I and @ means encapsulated in). Aberration corrected scanning/transmission electron microscopy (S/TEM) and spectroscopy is employed to understand the morphology and composition of the GdI3@WS2 nanotubes. The three dimensional morphology is studied with STEM tomography but understanding the compositional information is non-trivial due to the

  2. A hybrid framework of first principles molecular orbital calculations and a three-dimensional integral equation theory for molecular liquids: Multi-center molecular Ornstein–Zernike self-consistent field approach

    Energy Technology Data Exchange (ETDEWEB)

    Kido, Kentaro, E-mail: kido.kentaro@jaea.go.jp [Nuclear Safety Research Center, Japan Atomic Energy Agency, 2-4 Shirane, Shirakata, Tokai-mura, Naka-gun, Ibaraki 319-1195 (Japan); Kasahara, Kento [Department of Molecular Engineering, Graduate School of Engineering, Kyoto University, Nishikyo-ku, Kyoto 615-8510 (Japan); Yokogawa, Daisuke [Department of Chemistry, Graduate School of Science, Nagoya University, Chikusa, Nagoya 464-8602 (Japan); Institute of Transformative Bio-Molecules (WPI-ITbM), Nagoya University, Chikusa, Nagoya 464-8062 (Japan); Sato, Hirofumi [Department of Molecular Engineering, Graduate School of Engineering, Kyoto University, Nishikyo-ku, Kyoto 615-8510 (Japan); Elements Strategy Institute for Catalysts and Batteries (ESICB), Kyoto University, Katsura, Kyoto 615-8520 (Japan)

    2015-07-07

    In this study, we reported the development of a new quantum mechanics/molecular mechanics (QM/MM)-type framework to describe chemical processes in solution by combining standard molecular-orbital calculations with a three-dimensional formalism of integral equation theory for molecular liquids (multi-center molecular Ornstein–Zernike (MC-MOZ) method). The theoretical procedure is very similar to the 3D-reference interaction site model self-consistent field (RISM-SCF) approach. Since the MC-MOZ method is highly parallelized for computation, the present approach has the potential to be one of the most efficient procedures to treat chemical processes in solution. Benchmark tests to check the validity of this approach were performed for two solute (solute water and formaldehyde) systems and a simple S{sub N}2 reaction (Cl{sup −} + CH{sub 3}Cl → ClCH{sub 3} + Cl{sup −}) in aqueous solution. The results for solute molecular properties and solvation structures obtained by the present approach were in reasonable agreement with those obtained by other hybrid frameworks and experiments. In particular, the results of the proposed approach are in excellent agreements with those of 3D-RISM-SCF.

  3. A Biomass-Derived Non-Noble Cobalt Catalyst for Selective Hydrodehalogenation of Alkyl and (Hetero)Aryl Halides.

    Science.gov (United States)

    Sahoo, Basudev; Surkus, Annette-Enrica; Pohl, Marga-Martina; Radnik, Jörg; Schneider, Matthias; Bachmann, Stephan; Scalone, Michelangelo; Junge, Kathrin; Beller, Matthias

    2017-09-04

    Hydrodehalogenation is a straightforward approach for detoxifications of harmful anthropogenic organohalide-based pollutants, as well as removal of halide protecting groups used in multistep syntheses. A novel sustainable catalytic material was prepared from biowaste (chitosan) in combination with an earth-abundant cobalt salt. The heterogeneous catalyst was fully characterized by transmission electron microscope, X-ray diffraction, and X-ray photoelectron spectroscopy measurements, and successfully applied to hydrodehalogenation of alkyl and (hetero)aryl halides with broad scope (>40 examples) and excellent chemoselectivity using molecular hydrogen as a reductant. The general usefulness of this method is demonstrated by successful detoxification of non-degradable pesticides and fire retardants. Moreover, the potential of the catalyst as a deprotection tool is demonstrated in a multistep synthesis of (±)-peronatin B (alkaloid). © 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

  4. 基于混合液晶分子动力学模拟比较液晶分子旋转黏度大小∗%Rotational viscosity comparison of liquid crystals based on the molecular dynamics of mixtures

    Institute of Scientific and Technical Information of China (English)

    王启东; 彭增辉; 刘永刚; 姚丽双; 任淦; 宣丽

    2015-01-01

    It is critical to improve the response speed of a liquid crystal wavefront corrector in order to increase the band-width of a liquid crystal adaptive optics system. The design of liquid crystal molecules with small rotational viscosity becomes a basic method of increasing the response speed of a liquid crystal wavefront corrector. Various phases of liquid crystal from molecular dynamics simulation are given in this paper, and the detailed computational methods of order parameter and rotational viscosity are also presented. Rotational viscosities of liquid crystals are compared based on the molecular dynamics of mixtures. The data fluctuation is reduced effectively through several simulations and the multiple analysis of original data. A detailed process of molecular dynamics of mixtures is given in this paper and the result is greatly satisfactory. We believe that one can perform a better molecular design using this process and obtain a better understanding of molecular interactions of LCs.

  5. Polarization transfer kinetics in a binary system of molecular luminescense centers in nanopores with a liquid crystal filler

    Science.gov (United States)

    Kucherenko, M. G.; Palem, A. A.

    2008-04-01

    We have studied the anisotropic activated luminescence of molecular centers introduced into spherical nanopores filled with a nematic liquid crystal possessing a homeotropic texture. The kinetics of the anisotropy of emission from these centers is traced during selective pulsed activation of the donor subsystem by a linearly polarized light in the case where the long-range nonradiative transfer of the electron excitation energy to the acceptor molecules takes place in a radially aligned two-component luminescent system. A theoretical model is proposed that takes into account the migration of excitations over the system of donor centers. Dependences of the kinetics of the anisotropy of acceptor luminescence on the nanopore radius, the Förster transfer rate, and some other parameters have been determined. A change in the sign of polarization of the activated luminescence signal has been observed.

  6. Temperature effects on the capacitance of an imidazolium-based ionic liquid on a graphite electrode: a molecular dynamics simulation.

    Science.gov (United States)

    Liu, Xiaohong; Han, Yining; Yan, Tianying

    2014-08-25

    Temperature-dependent electric double layer (EDL) and differential capacitance-potential (C(d)-U) curves of the ionic liquid 1-butyl-3-methylimidazolium hexafluorophosphate (BMIM(+)/PF6(-)) were studied on a graphite electrode by molecular dynamics simulations. It was found that all C(d)-U curves were asymmetric camel-shaped with higher C(d) at negative polarization, attributed to the specific adsorption of BMIM(+). In addition, the maxima of Cd at the negative polarization decrease monotonically with temperature due to the thicker EDL, whereas at the positive polarization they gradually increase from 450 to 550 K and decrease at 600 K. Such temperature effects at positive polarization may be understood in terms of the competition between two aspects: the weakening specific adsorption of BMIM(+) allows more effective screening to the positive charge and overall increasing EDL thickness. Although the former dominates from 450 to 550 K, the latter becomes dominant at 600 K.

  7. Cross-linked agarose for separation of low molecular weight natural products in hydrophilic interaction liquid chromatography.

    Science.gov (United States)

    Tan, Tianwei; Su, Zhi-Guo; Gu, Ming; Xu, Jun; Janson, Jan-Christer

    2010-05-01

    Following its market introduction in 1982, the cross-linked 12% agarose gel media Superose 12 has become widely known as a tool for size exclusion chromatography of proteins and other biological macromolecules. In this review it is shown that, when appropriate mobile phases are used, Superose possesses adsorption properties similar to that of traditional media for hydrophilic interaction liquid chromatography (HILIC). This is illustrated by the separation and purification of low molecular weight compounds such as polyphenols including active components of traditional Chinese medicinal herbs and green tea. Structural features of the cross-linked agarose that likely cause the observed adsorption effects are discussed as well. These are identified as being primarily ether bonds acting as strong hydrogen bond acceptors as well as hydrophobic residues originating from the cross-linking reagents.

  8. Ionic liquid mediated synthesis and molecular docking study of novel aromatic embedded Schiff bases as potent cholinesterase inhibitors.

    Science.gov (United States)

    Abd Razik, Basma M; Osman, Hasnah; Basiri, Alireza; Salhin, Abdussalam; Kia, Yalda; Ezzat, Mohammed Oday; Murugaiyah, Vikneswaran

    2014-12-01

    Novel aromatic embedded Schiff bases have been synthesized in ionic liquid [bmim]Br and evaluated in vitro for their acetylcholinesterase (AChE) and butyrylcholinesterase (BChE) enzymes inhibitory activities. Among the newly synthesized compounds, 5f, 5h and 7j displayed higher AChE enzyme inhibitory activities than standard drug, galanthamine, with IC50 values of 1.88, 2.05 and 2.03μM, respectively. Interestingly, all the compounds except for compound 5c displayed higher BChE inhibitories than standard with IC50 values ranging from 3.49 to 19.86μM. Molecular docking analysis for 5f and 7j possessing the most potent AChE and BChE inhibitory activities, disclosed their binding interaction templates to the active site of AChE and BChE enzymes, respectively.

  9. A hybrid molecular dynamics/fluctuating hydrodynamics method for modelling liquids at multiple scales in space and time

    Energy Technology Data Exchange (ETDEWEB)

    Korotkin, Ivan, E-mail: i.korotkin@qmul.ac.uk; Karabasov, Sergey; Markesteijn, Anton [The School of Engineering and Material Science, Queen Mary University of London, Mile End Road, E1 4NS London (United Kingdom); Nerukh, Dmitry; Scukins, Arturs [Institute of Systems Analytics, Aston University, Birmingham B4 7ET (United Kingdom); Farafonov, Vladimir [Department of Physical Chemistry, V. N. Karazin Kharkiv National University, Svobody Square 4, 61022 Kharkiv (Ukraine); Pavlov, Evgen [Institute of Systems Analytics, Aston University, Birmingham B4 7ET (United Kingdom); Faculty of Physics, Kiev National Taras Shevchenko University, Prospect Acad. Glushkova 4, Kiev 03127 (Ukraine)

    2015-07-07

    A new 3D implementation of a hybrid model based on the analogy with two-phase hydrodynamics has been developed for the simulation of liquids at microscale. The idea of the method is to smoothly combine the atomistic description in the molecular dynamics zone with the Landau-Lifshitz fluctuating hydrodynamics representation in the rest of the system in the framework of macroscopic conservation laws through the use of a single “zoom-in” user-defined function s that has the meaning of a partial concentration in the two-phase analogy model. In comparison with our previous works, the implementation has been extended to full 3D simulations for a range of atomistic models in GROMACS from argon to water in equilibrium conditions with a constant or a spatially variable function s. Preliminary results of simulating the diffusion of a small peptide in water are also reported.

  10. Focus: Phase-resolved nonlinear terahertz spectroscopy—From charge dynamics in solids to molecular excitations in liquids

    Science.gov (United States)

    Elsaesser, Thomas; Reimann, Klaus; Woerner, Michael

    2015-06-01

    Intense terahertz (THz) electric field transients with amplitudes up to several megavolts/centimeter and novel multidimensional techniques are the key ingredients of nonlinear THz spectroscopy, a new area of basic research. Both nonlinear light-matter interactions including the non-perturbative regime and THz driven charge transport give new insight into the character and dynamics of low-energy excitations of condensed matter and into quantum kinetic phenomena. This article provides an overview of recent progress in this field, combining an account of technological developments with selected prototype results for liquids and solids. The potential of nonlinear THz methods for future studies of low-frequency excitations of condensed-phase molecular systems is discussed as well.

  11. Molecular dynamics determination of the surface tension of silver-gold liquid alloys and the Tolman length of nanoalloys

    Science.gov (United States)

    Calvo, F.

    2012-04-01

    Using molecular dynamics simulations, an embedded-atom model potential, and the mechanistic route, we have computed the pressure tensor and the surface tension γ of Ag-Au liquid alloys. Although the model generally underestimates γ for pure metals, calculations for a bulk planar slab exhibit nonlinear variations of γ with increasing gold concentration, which agree with experiments and can be accounted for by a perfect solution model. Calculations for various nanoscale droplets containing between 100 and 3200 atoms show a systematic decrease of γ with increasing droplet radius R. The positive Tolman length of the alloy determined from these size variations is estimated to vary slightly with gold concentration. The effects of temperature in the range 1300-1700 K are discussed.

  12. Algorithms for GPU-based molecular dynamics simulations of complex fluids: Applications to water, mixtures, and liquid crystals.

    Science.gov (United States)

    Kazachenko, Sergey; Giovinazzo, Mark; Hall, Kyle Wm; Cann, Natalie M

    2015-09-15

    A custom code for molecular dynamics simulations has been designed to run on CUDA-enabled NVIDIA graphics processing units (GPUs). The double-precision code simulates multicomponent fluids, with intramolecular and intermolecular forces, coarse-grained and atomistic models, holonomic constraints, Nosé-Hoover thermostats, and the generation of distribution functions. Algorithms to compute Lennard-Jones and Gay-Berne interactions, and the electrostatic force using Ewald summations, are discussed. A neighbor list is introduced to improve scaling with respect to system size. Three test systems are examined: SPC/E water; an n-hexane/2-propanol mixture; and a liquid crystal mesogen, 2-(4-butyloxyphenyl)-5-octyloxypyrimidine. Code performance is analyzed for each system. With one GPU, a 33-119 fold increase in performance is achieved compared with the serial code while the use of two GPUs leads to a 69-287 fold improvement and three GPUs yield a 101-377 fold speedup.

  13. Kinetics of Heterogeneous Solvent-free Liquid Phase Oxidation of Alcohol Using ZrO2 Catalyst with Molecular Oxygen

    Institute of Scientific and Technical Information of China (English)

    ILYAS Mohammad; SADIQ Mohammad

    2008-01-01

    Clean liquid phase solvent-free oxidation of alcohol to aldehyde/ketone using ZrO2 catalyst with molecular oxygen has been studied.Monoclinic phase ZrO2 has been synthesized and characterized by XRD,SEM,EDX and surface and pore size analyses.Oxidation of alcohol was carded out in a typical batch reactor at different sDeed of agitation(150-1200 r/min),temperature(373-413 K),catalyst loading(50-300 mg)and partial pressure of oxygen(12-101 kPa).These parameters influence alcohol conversion as well as selectivity.A handy touch of kinetics was given to the experimental data and apparent activation energy was calculated.

  14. Communication: molecular dynamics and (1)H NMR of n-hexane in liquid crystals.

    Science.gov (United States)

    Weber, Adrian C J; Burnell, E Elliott; Meerts, W Leo; de Lange, Cornelis A; Dong, Ronald Y; Muccioli, Luca; Pizzirusso, Antonio; Zannoni, Claudio

    2015-07-07

    The NMR spectrum of n-hexane orientationally ordered in the nematic liquid crystal ZLI-1132 is analysed using covariance matrix adaptation evolution strategy (CMA-ES). The spectrum contains over 150 000 transitions, with many sharp features appearing above a broad, underlying background signal that results from the plethora of overlapping transitions from the n-hexane as well as from the liquid crystal. The CMA-ES requires initial search ranges for NMR spectral parameters, notably the direct dipolar couplings. Several sets of such ranges were utilized, including three from MD simulations and others from the modified chord model that is specifically designed to predict hydrocarbon-chain dipolar couplings. In the end, only inaccurate dipolar couplings from an earlier study utilizing proton-proton double quantum 2D-NMR techniques on partially deuterated n-hexane provided the necessary estimates. The precise set of dipolar couplings obtained can now be used to investigate conformational averaging of n-hexane in a nematic environment.

  15. Communication: Molecular dynamics and 1H NMR of n-hexane in liquid crystals

    Science.gov (United States)

    Weber, Adrian C. J.; Burnell, E. Elliott; Meerts, W. Leo; de Lange, Cornelis A.; Dong, Ronald Y.; Muccioli, Luca; Pizzirusso, Antonio; Zannoni, Claudio

    2015-07-01

    The NMR spectrum of n-hexane orientationally ordered in the nematic liquid crystal ZLI-1132 is analysed using covariance matrix adaptation evolution strategy (CMA-ES). The spectrum contains over 150 000 transitions, with many sharp features appearing above a broad, underlying background signal that results from the plethora of overlapping transitions from the n-hexane as well as from the liquid crystal. The CMA-ES requires initial search ranges for NMR spectral parameters, notably the direct dipolar couplings. Several sets of such ranges were utilized, including three from MD simulations and others from the modified chord model that is specifically designed to predict hydrocarbon-chain dipolar couplings. In the end, only inaccurate dipolar couplings from an earlier study utilizing proton-proton double quantum 2D-NMR techniques on partially deuterated n-hexane provided the necessary estimates. The precise set of dipolar couplings obtained can now be used to investigate conformational averaging of n-hexane in a nematic environment.

  16. Two Dimensional Organometal Halide Perovskite Nanorods with Tunable Optical Properties.

    Science.gov (United States)

    Aharon, Sigalit; Etgar, Lioz

    2016-05-11

    Organo-metal halide perovskite is an efficient light harvester in photovoltaic solar cells. Organometal halide perovskite is used mainly in its "bulk" form in the solar cell. Confined perovskite nanostructures could be a promising candidate for efficient optoelectronic devices, taking advantage of the superior bulk properties of organo-metal halide perovskite, as well as the nanoscale properties. In this paper, we present facile low-temperature synthesis of two-dimensional (2D) lead halide perovskite nanorods (NRs). These NRs show a shift to higher energies in the absorbance and in the photoluminescence compared to the bulk material, which supports their 2D structure. X-ray diffraction (XRD) analysis of the NRs demonstrates their 2D nature combined with the tetragonal 3D perovskite structure. In addition, by alternating the halide composition, we were able to tune the optical properties of the NRs. Fast Fourier transform, and electron diffraction show the tetragonal structure of these NRs. By varying the ligands ratio (e.g., octylammonium to oleic acid) in the synthesis, we were able to provide the formation mechanism of these novel 2D perovskite NRs. The 2D perovskite NRs are promising candidates for a variety of optoelectronic applications, such as light-emitting diodes, lasing, solar cells, and sensors.

  17. Halide Perovskites: Poor Man's High-Performance Semiconductors.

    Science.gov (United States)

    Stoumpos, Constantinos C; Kanatzidis, Mercouri G

    2016-07-01

    Halide perovskites are a rapidly developing class of medium-bandgap semiconductors which, to date, have been popularized on account of their remarkable success in solid-state heterojunction solar cells raising the photovoltaic efficiency to 20% within the last 5 years. As the physical properties of the materials are being explored, it is becoming apparent that the photovoltaic performance of the halide perovskites is just but one aspect of the wealth of opportunities that these compounds offer as high-performance semiconductors. From unique optical and electrical properties stemming from their characteristic electronic structure to highly efficient real-life technological applications, halide perovskites constitute a brand new class of materials with exotic properties awaiting discovery. The nature of halide perovskites from the materials' viewpoint is discussed here, enlisting the most important classes of the compounds and describing their most exciting properties. The topics covered focus on the optical and electrical properties highlighting some of the milestone achievements reported to date but also addressing controversies in the vastly expanding halide perovskite literature. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  18. Molecular dynamics and a spectroscopic study of sulfur dioxide absorption by an ionic liquid and its mixtures with PEO.

    Science.gov (United States)

    Hoher, Karina; Cardoso, Piercarlo F; Lepre, Luiz F; Ando, Rômulo A; Siqueira, Leonardo J A

    2016-10-19

    An investigation comprising experimental techniques (absorption capacity of SO2 and vibrational spectroscopy) and molecular simulations (thermodynamics, structure, and dynamics) has been performed for the polymer poly(ethylene oxide) (PEO), the ionic liquid butyltrimethylammonium bis(trifluoromethylsulfonyl)imide ([N4111][Tf2N]) and their mixtures as sulfur dioxide (SO2) absorbing materials. The polymer PEO has higher capacity to absorb SO2 than the neat ionic liquid, whereas the mixtures presented intermediary absorption capacities. The band assigned to the symmetric stretching band of SO2 at ca. 1140 cm(-1), which is considered a spectroscopic probe for the strength of SO2 interactions with its neighborhood, shifts to lower wavenumbers as more negative total interaction energy values of SO2 were evaluated from the simulations. The solvation free energy of SO2, ΔGsol, correlates linearly with the absorption capacity of SO2. The negative values of ΔGsol are due to negative and positive values of enthalpy and entropy, respectively. In the ionic liquid, SO2 weakens the cation-anion interactions, whereas in the mixture with a high content of PEO these interactions are slightly increased. Such effects were correlated with the relative population of cisoid and transoid conformers of Tf2N anions as revealed by Raman spectroscopy. Moreover, the presence of SO2 in the systems provokes the increase of diffusion coefficients of the absorbing species in comparison with the systems without the gas. Proper to the slow dynamics of the polymer, the diffusion coefficient of ions and SO2 diminishes with the increase of the PEO content.

  19. Effect of ion structure on conductivity in lithium-doped ionic liquid electrolytes: A molecular dynamics study

    Science.gov (United States)

    Liu, Hongjun; Maginn, Edward

    2013-09-01

    Molecular dynamics simulations were performed to examine the role cation and anion structure have on the performance of ionic liquid (IL) electrolytes for lithium conduction over the temperature range of 320-450 K. Two model ionic liquids were studied: 1-butyl-3-methylimidazolium bis[(trifluoromethyl)sulfonyl]imide ([bmim][Tf2N]) and 1-butyl-4-methylpyridinium pyrrolide ([bmpyr][pyl]) doped with Li[Tf2N] and Li[pyl], respectively. The results have demonstrated that the Li+ doped IL containing the planar [bmpyr] cation paired with the planar [pyl] anion significantly outperformed the [bmim][Tf2N] IL. The different coordination of Li+ with the [Tf2N]- or [pyl]- anions produces a remarkable change in IL structure with a concomitant effect on the transport of all ions. For the doped [bmim][Tf2N], each Li+ is coordinated by four oxygen atoms from [Tf2N]- anions. Formation of a rigid structure between Li+ and [Tf2N]- induces a decrease in the mobility of all ions. In contrast, for the doped [bmpyr][pyl], each Li+ is coordinated by two nitrogen atoms from [pyl]- anions. The original alternating structure cation|anion|cation in the neat [bmpyr][pyl] is replaced by another alternating structure cation|anion|Li+|anion|cation in the doped [bmpyr][pyl]. Increases of Li+ mole fraction in doped [bmpyr][pyl] affects the dynamics to a much lesser extent compared with [bmim][Tf2N] and leads to reduced diffusivities of cations and anions, but little change in the dynamics of Li+. More importantly, the calculations predict that the Li+ ion conductivity of doped [bmpyr][pyl] is comparable to that observed in organic liquid electrolytes and is about an order of magnitude higher than that of doped [bmim][Tf2N]. Such Li+ conductivity improvement suggests that this and related ILs may be promising candidates for use as electrolytes in lithium ion batteries and capacitors.

  20. Reorientational dynamics in molecular liquids as revealed by dynamic light scattering: From boiling point to glass transition temperature

    Science.gov (United States)

    Schmidtke, B.; Petzold, N.; Kahlau, R.; Rössler, E. A.

    2013-08-01

    We determine the reorientational correlation time τ of a series of molecular liquids by performing depolarized light scattering experiments (double monochromator, Fabry-Perot interferometry, and photon correlation spectroscopy). Correlation times in the range 10-12 s-100 s are compiled, i.e., the full temperature interval between the boiling point and the glass transition temperature Tg is covered. We focus on low-Tg liquids for which the high-temperature limit τ ≅ 10-12 s is easily accessed by standard spectroscopic equipment (up to 440 K). Regarding the temperature dependence three interpolation formulae of τ(T) with three parameters each are tested: (i) Vogel-Fulcher-Tammann equation, (ii) the approach recently discussed by Mauro et al. [Proc. Natl. Acad. Sci. U.S.A. 106, 19780 (2009)], and (iii) our approach decomposing the activation energy E(T) in a constant high temperature value E∞ and a "cooperative part" Ecoop(T) depending exponentially on temperature [Schmidtke et al., Phys. Rev. E 86, 041507 (2012)], 10.1103/PhysRevE.86.041507. On the basis of the present data, approaches (i) and (ii) are insufficient as they do not provide the correct crossover to the high-temperature Arrhenius law clearly identified in the experimental data while approach (iii) reproduces the salient features of τ(T). It allows to discuss the temperature dependence of the liquid's dynamics in terms of a Ecoop(T)/E∞ vs. T/E∞ plot and suggests that E∞ controls the energy scale of the glass transition phenomenon.