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The Journal of Chemical Physics Collection


 
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The Journal of Chemical Physics : Intermolecular vibrations of dif...

By: J. Ceponkus, P. Uvdal, and B. Nelander

Description: Far infrared spectra of seven different isotopologs of the water dimer have been measured in neon matrices at 2.8 K. The experiments are interpreted with the aid of density functional theory calculations, in particular the calculated harmonic isotopic shifts were utilized. All six intermolecular vibrational modes of the water dimer and the fully deuterated water dimer are assigned based the isotopic shifts induced. 31 of a total of 42 intermolecular fundamen...

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The Journal of Chemical Physics : Isomorphic classical molecular d...

By: Thomas F. Miller

Description: Ring polymer molecular dynamics (RPMD) is used to directly simulate the dynamics of an excess electron in a supercritical fluid over a broad range of densities. The accuracy of the RPMD model is tested against numerically exact path integral statistics through the use of analytical continuation techniques. At low fluid densities, the RPMD model substantially underestimates the contribution of delocalized states to the dynamics of the excess electron. However...

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The Journal of Chemical Physics : Rovibrational matrix elements of...

By: Adya P. Mishra and T. K. Balasubramanian

Description: The present work pertains to the study of the rotational dynamics of N2 molecules solvated in a matrix of solid para-H2. It is shown that the mixing of the rotational states due to the anisotropic part of the N2–H2 pair potential in the solid gives rise to an additional 5.4% contribution to the intensity of quadrupole-induced double transitions involving N2–H2 pair. Hence the recently reported quadrupole moment matrix element of N2 in a solid para-H2 crystal...

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The Journal of Chemical Physics : Fluids of hard natural and Gauss...

By: Aurélien Perera

Description: The hard Gaussian overlap (HGO) model for ellipsoids is compared to the hard ellipsoid of revolution (HER) model, in the isotropic fluid phase and within the framework of the Percus–Yevick (PY) and hypernetted chain (HNC) integral equation theories. The former model is often used in place of the latter in many approximate theories. Since the HGO model slightly overestimates the contact distance when the two ellipsoids are perpendicular to each other, it lead...

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The Journal of Chemical Physics : Constructing explicit magnetic a...

By: Jacob D. Stevenson, Aleksandra M. Walczak, Randall W. Hall, and Peter G. Wolynes

Description: By defining a spatially varying replica overlap parameter for a supercooled liquid referenced to an ensemble of fiducial liquid state configurations, we explicitly construct a constrained replica free energy functional that maps directly onto an Ising Hamiltonian with both random fields and random interactions whose statistics depend on the liquid structure. Renormalization group results for random magnets when combined with these statistics for the Lennard-...

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The Journal of Chemical Physics : Structural, dynamic, and electro...

By: L. Calderín, D. J. González, L. E. González, and J. M. López

Description: We report on a study of several structural, dynamic, and electronic properties of liquid Sn at a thermodynamic state close to the triple point (573 K) and another one at a higher temperature (1273 K). This study has been performed by ab initio molecular dynamics simulations using 205 atoms and around 20 ps of simulation time. The calculated static structures show a good agreement with the available experimental data. The dynamic structure factors fairly agre...

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The Journal of Chemical Physics : An improved theoretical model fo...

By: Yu Yan, Pablo Blanco, M. Ziad Saghir, and M. Mounir Bou-Ali

Description: Thermal diffusion or Soret effect is a phenomenon of mass transport in fluid mixtures driven by temperature gradients. In this paper, we have studied thermal diffusion coefficients for different binary n-alkane mixtures (equal mass fraction) through both theoretical and experimental methods. The theoretical model is based on the irreversible thermodynamics. Particularly, the nonequilibrium thermodynamic property τ is examined and remodeled with a considerati...

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The Journal of Chemical Physics : High-pressure melting curve of h...

By: Sergio M. Davis, Anatoly B. Belonoshko, Börje Johansson, Natalia V. Skorodumova, and Adri C. van Duin

Description: The melting curve of hydrogen was computed for pressures up to 200 GPa, using molecular dynamics. The inter- and intramolecular interactions were described by the reactive force field (ReaxFF) model. The model describes the pressure-volume equation of state solid hydrogen in good agreement with experiment up to pressures over 150 GPa, however the corresponding equation of state for liquid deviates considerably from density functional theory calculations. Due...

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The Journal of Chemical Physics : Equilibrium and nonequilibrium t...

By: J. B›awzdziewicz and E. Wajnryb

Description: Our recent quasi-two-dimensional thermodynamic description of thin liquid films stabilized by colloidal particles is generalized to describe nonuniform equilibrium states of films in external potentials and nonequilibrium transport processes produced in the film by gradients of thermodynamic forces. Using a Monte Carlo simulation method, we have determined equilibrium equations of state for a film stabilized by a suspension of hard spheres. Employing a multi...

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The Journal of Chemical Physics : Monte Carlo simulations of 1,3,5...

By: Neeraj Rai, Divesh Bhatt, J. Ilja Siepmann, and Laurence E. Fried

Description: The transferable potentials for phase equilibria (TraPPE) force field was extended to nitro and amino substituents for aromatic rings via parametrization to the vapor-liquid coexistence curves of nitrobenzene and aniline, respectively. These groups were then transferred to model 1,3,5-triamino-2,4,6-trinitrobenzene (TATB). Without any further parametrization to solid state data, the TraPPE force field is able to predict TATB’s unit cell lengths and angles at...

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The Journal of Chemical Physics : Equilibrium fluctuations of the ...

By: D. I. Zhukhovitskii

Description: Spectra of the cluster surface equilibrium fluctuations are treated by decomposition into the bulk and net capillary ones. The bulk fluctuations without capillary ones are simulated by the surface of a cluster truncated by a sphere. The bulk fluctuation spectrum is shown to be generated primarily by the discontinuity in the spatial distribution of cluster internal particles. The net capillary fluctuation slice spectrum is obtained in molecular dynamics simul...

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The Journal of Chemical Physics : A first principles theoretical s...

By: Bhabani S. Mallik, A. Semparithi, and Amalendu Chandra

Description: A theoretical study of vibrational spectral diffusion and hydrogen bond dynamics in aqueous ionic solutions is presented from first principles without employing any empirical potential models. The present calculations are based on ab initio molecular dynamics for trajectory generation and wavelet analysis of the simulated trajectories for time dependent frequency calculations. Results are obtained for two different deuterated aqueous solutions: the first one...

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The Journal of Chemical Physics : Glassy properties and viscous sl...

By: Kristine Niss, Cécile Dalle-Ferrier, Valentina M. Giordano, Giulio Monaco, Bernhard Frick et al

Description: We present an extensive analysis of the proposed relationship [ T. Scopigno et al., Science 302, 849 (2003) ] between the fragility of glass-forming liquids and the nonergodicity factor as measured by inelastic x-ray scattering. We test the robustness of the correlation through the investigation of the relative change under pressure of the speed of sound, nonergodicity factor, and broadening of the acoustic exitations of a molecular glass former, cumene, and...

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The Journal of Chemical Physics : Pair correlation functions of si...

By: Arieh Ben-Naim and Vincent K. Shen

Description: We have calculated the pair correlation functions for several binary mixtures composed of simple solutes in a Lennard-Jones solvent. In particular, we have studied the solute-solute pair correlation functions and their dependence on the total density, the solvent Lennard-Jones parameters, and on the solute-solute energy parameter. All the results were obtained from solving the Percus–Yevick equations, as well as from Monte Carlo simulations. The relevance of...

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The Journal of Chemical Physics : Effect of solvent polarization o...

By: Egor Vladimirov, Anela Ivanova, and Notker Rösch

Description: The solvent contribution λs to the reorganization energy of electron transfer can be estimated from averages of the potential energy gaps between neutral-pair and ion-pair states over an ensemble of structures generated from molecular dynamics simulations. Invoking a Marcus-type two-sphere model for charge separation and recombination in an aqueous environment, we explored the effect of a polarizable force field and noted a strong reduction of λs (by ∼ 45%) ...

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The Journal of Chemical Physics : Spontaneous charging and crystal...

By: Joost de Graaf, Jos Zwanikken, Markus Bier, Arjen Baarsma, Yasha Oloumi et al

Description: We study the spontaneous charging and the crystallization of spherical micron-sized water droplets dispersed in oil by numerically solving, within a Poisson–Boltzmann theory in the geometry of a spherical cell, for the density profiles of the cations and anions in the system. We take into account screening, ionic Born self-energy differences between oil and water, and partitioning of ions over the two media. We find that the surface charge density of the dro...

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The Journal of Chemical Physics : Molecular dynamics simulation of...

By: Hossein Eslami, Farkhondeh Mozaffari, Jalil Moghadasi, and Florian Müller-Plathe

Description: A method for the simulation of fluids confined between surfaces is developed. The molecular dynamics, with coupling to an external bath, simulation method of Berendsen et al. [J. Chem. Phys. 81, 3684 (1984) ] is extended for this purpose. We keep the temperature and the parallel component of pressure fixed and change the box length in the perpendicular direction with respect to the confining surfaces to archive equilibrium. The simulation is easy to perform,...

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The Journal of Chemical Physics : Dissipation in molecular junctions

By: Ryan Jorn and Tamar Seideman

Description: A recently developed theory that formulates the phenomena of inelastic transport and current-driven dynamics in molecular-scale electronics within a time-dependent scattering approach is extended to account for dissipation of the current-induced excitation through coupling to electrode phonons and electron-hole pairs. Our approach treats the electronic transport, the nuclear dynamics, and the energy and phase exchange between the electronic and the vibration...

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The Journal of Chemical Physics : First-principles study of crysta...

By: Sheng Ju and Guang-Yu Guo

Description: Within the density functional theory with the generalized gradient approximation, we present a systematic ab initio investigation of crystal structure, electronic structure, and linear and nonlinear optical responses in a polar double perovskite Bi2ZnTiO6. The effect of B-site ordering is explored by comparing three possible configurations: A-type with alternative Zn and Ti layers stacking along the c axis; C-type with Zn and Ti c axis chains; and G-type wit...

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The Journal of Chemical Physics : Quantum-state resolved reactive ...

By: Alexander M. Zolot, Paul J. Dagdigian, and David J. Nesbitt

Description: Exothermic chemical reaction dynamics at the gas-liquid interface have been investigated by colliding a supersonic beam of F atoms [Ecom = 0.7(3) kcal/mol] with a continuously refreshed liquid hydrocarbon (squalane) surface under high vacuum conditions. Absolute HF(v,J) product densities are determined by infrared laser absorption spectroscopy, with velocity distributions along the probe axis derived from high resolution Dopplerimetry. Nascent HF(v ⩽ 3) prod...

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