Single-processor PC-based molecular dynamics simulations of the orientational motion of liquids: Chloroform at 298 and 220 K

Rothschild, Walter G.

doi:10.1016/s0167-7322(02)00126-5

Cited by 12 publications

(19 citation statements)

References 8 publications

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“…The systems of concern here are benzene solutions of each of the two halomethanes dichloro-and trichloromethane, its constituent components having previously yielded simulated thermodynamic, spectroscopic, static, and molecular-dynamic properties in satisfactory agreement with experiment [9,12]. We therefore can expect that our present findings, specific to the equimolar solution system of chloroform and benzene, and to a lesser extent of dichloromethane and benzene, describe some selected characteristics of these solutions on the molecular level at useful accuracy.…”

Section: Discussionsupporting

confidence: 71%

“…The appropriate information is tabulated in table 1, together with a comparison of simulated and experimental enthalpies of vaporization. The procedures of the calculations, using a microcanonical ensemble (constant volume, particle number, and energy), were as previously reported [2,9,10,12], yet benzene posed some initial difficulties for the simulations (besides program changes to accommodate a 12-atom molecule with its fractional atomic charges). In fact, the equilibration procedure failed until greatly reduced step sizes-time intervals as low as Át ¼ 0.1 fs (instead of the usual 5 fs) and temperature-scaling at each simulation step (instead of at each fifth)-were applied [13].…”

Section: Methodsmentioning

confidence: 99%

See 1 more Smart Citation

Solvation by benzene: molecular dynamics simulation of orientational motion, translational diffusion, and site–site radial distributions of the solutes di- and trichloromethane (chloroform)

Rothschild

2007

Molecular Physics

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By a standard, proven molecular dynamics procedure we generated individual equilibrium systems of dichloromethane and trichloromethane (chloroform) in benzene, each at equimolar concentration, as well as those of the neat components. We analysed the orientational dynamics of the C-H bond direction of chloroform in benzene-solvated and neat chloroform by the tumbling motion of its l ¼ 1 and l ¼ 2 Legendre polynomial auto-correlations between 250 and 438 K at iso-density conditions specific to the solution and neat system, respectively. We find that solvent benzene exerts a hindering effect on the orientational motion of chloroform over its neat state under an activation energy of 3.8 kJ mol À1 , although the density of the solution is less than that of the neat solute. The hindering effect diminishes with increasing kinetic energy to eventually disappear near the critical region. Probing benzene as solute within an equimolar solution with chloroform does not show a correspondingly increased hindering of the orientational motion of the (in-plane) C 0 2 axes of benzene. The short-time rotational regimes at ambient conditions were examined by simulating the auto-correlation functions of the three components of angular velocity, the results implying that the coherence in the correlation of the primary rotational variable is rather short-lived. The long-time translational-diffusional characteristics were examined by the mean-square distance of chloroform travelled during 100 ps, establishing that chloroform diffuses slightly faster in equimolar solution with benzene than in its neat state-most likely on account of more favourable free volume conditions in the solution. From various site-site radial distribution functions between solute and solvent species and from appropriate atom-atom distances between nearest-neighbour molecules, we found that chloroform aggregates, to a minimum, with two nearest-neighbour benzene shells in a three-member configuration. We conjecture that the hindering effect by benzene on the chloroform solute is caused by its temporary entrapment, on time scales of the order of 0.2 ps, in cages from momentary perpendicular and parallel configurations of nearest-and near-neighbour benzene molecules. We find no convincing evidence for the existence of a stable, symmetric-top 1:1 chloroform-benzene complex. Solute species dichloromethane in benzene exhibits similar, but less pronounced, solution dynamics.

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Section: Discussionsupporting

confidence: 71%

Section: Methodsmentioning

confidence: 99%

Solvation by benzene: molecular dynamics simulation of orientational motion, translational diffusion, and site–site radial distributions of the solutes di- and trichloromethane (chloroform)

Rothschild

2007

Molecular Physics

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“…4 From the comparison between these two spectra, they found that the slowest Debye mode of the dielectric spectrum is absent in the depolarized light scattering, but other high-frequency processes of the dielectric relaxation are observed in the light-scattering spectrum, after dividing the time constants of the former by three to correct the difference in the reorientational relaxation times of the rank-1 (dipole) and the rank-2 (tensor) modes. 41 Based on the correspondence, they proposed that the dielectric and depolarized light-scattering spectra observe the same dynamic modes except for the slowest Debye mode of the former. The comparison between the dielectric and depolarized light-scattering spectra was performed on supercooled 1propanol by Gabriel and co-workers.…”

Section: Thementioning

confidence: 99%

“…The spectrum of the depolarized light scattering is given by the time correlation function of the anisotropic part of the polarizability tensor, 41 which possesses the d-type symmetry as the shear stress tensor does. Therefore, the microscopic dynamics coupled to the depolarized light scattering is expected to be similar to the viscoelastic relaxation, and different from the dielectric relaxation, contrary to the experimental results described above.…”

Section: Thementioning

confidence: 99%

Coupling between Structural and Dielectric Relaxations of Methanol and Ethanol Studied by Molecular Dynamics Simulation

Yamaguchi

2020

J. Phys. Chem. B

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The microscopic origin of the fast dielectric relaxation modes and the integrated dielectric relaxation times of methanol and ethanol was investigated by means of cross-correlation analysis of molecular dynamics simulation. Random force on the fluctuation of collective dipole moment was correlated with the two-body density mode in both real and reciprocal spaces. A strong coupling was observed with the OH alternation mode at 30 nm–1, suggesting that alternating switching of the hydrogen bond within a hydrogen-bonding chain is the principal origin of the retarded friction on the collective dipole moment. The relaxation of the coupling was much slower than that of the partial intermediate scattering functions at the corresponding wavenumber, which suggests the breakdown of the factorization approximation employed in the mode-coupling theory. Although the prepeak structure is strongly coupled to the viscoelastic relaxation, its coupling with the dielectric relaxation is relatively weak. The difference between the viscoelastic and the dielectric relaxations was discussed in terms of the different symmetries of the shear stress tensor and the collective dipole moment.

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“…O tratamento do problema considerando o meio em que o oscilador se encontra torna-se muito mais complicado, mas é essencial para compreender o espectro vibracional, principalmente em fase condensada, em que o ambiente pode alterar consideravelmente o espectro obtido, [35][36][37][38] seja no desvio de frequências vibracionais, ou na forma de linha das bandas do espectro. 20,39,40 Os desvios nos valores de frequência envolvem características de equilíbrio do sistema, enquanto que a análise de forma de linha necessita da descrição da dinâmica do sistema e como este relaxa após ser excitado vibracionalmente. 20,40 No contexto da espectroscopia vibracional em fases condensadas, o papel da anarmonicidade do oscilador é fundamental, pois permite acoplar os graus de liberdade intra e intermoleculares e, portanto, observar as mudanças espectrais causadas pela fase condensada no oscilador sonda analisado.…”

Section: Espectroscopia Vibracional Em Fase Condensadaunclassified

Espectroscopia vibracional e propriedades termodinâmicas de líquidos iônicos em alta pressão

Penna¹

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The aim of this thesis is the quantitative treatment of the vibrational frequency shifts of ionic liquids under pressure. The study of the ionic liquids 1-butyl-3-methylimidazolium, 1-hexyl-3methylimidazolium and 1-octyl-3-methylimidazolium tetrafluoroborate under high pressure were made under a simultaneous approach of simulation, spectroscopy and liquid theories. The equations of state of such systems are obtained with data in the MPa range and are necessary in the analysis of spectroscopic data obtained in the GPa range. It becomes necessary to obtain the density data in a larger pressure range, and to develop a methodology that selects through equations of state proposed in literature that extrapolate very differently in the GPa range. Two proposals to validate such equations of state, and obtain high pressure density data, are made. The first one consists in comparing the extrapolations with classic Molecular Dynamics results. This becomes a problem because the force field is not parametrized for this region. However, a good agreement between the simulation curve and the equation of Domanska are obtained which implicates that this equation could be considered better to describe this system under pressure. This finding is in agreement with the second strategy, in which the different equations of state are used to analyze quantitatively the frequency shift data of the totally symmetric stretching mode of the tetrafluoroborate anion using the Schweizer and Chandler model. The equation of Domanska provides a better linear fit of the attractive frequency shift component, as predicted by the model of Schweizer and Chandler. Moreover, the frequency shift data for the three systems colapse in a master curve when they are plotted versus the reduced density, and the overall fit to the model is the best through all equations of state tested. Ab initio molecular dynamics simulations of the 1butyl-3-methylimidazolium tetrafluoroborate under pressure were made and show that this methodology is accurate to describe quantitatively describe the experimental frequency shift, but the Raman spectrum presents an intense band which is not observed experimentally.

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Single-processor PC-based molecular dynamics simulations of the orientational motion of liquids: Chloroform at 298 and 220 K

Cited by 12 publications

References 8 publications

Solvation by benzene: molecular dynamics simulation of orientational motion, translational diffusion, and site–site radial distributions of the solutes di- and trichloromethane (chloroform)

Solvation by benzene: molecular dynamics simulation of orientational motion, translational diffusion, and site–site radial distributions of the solutes di- and trichloromethane (chloroform)

Coupling between Structural and Dielectric Relaxations of Methanol and Ethanol Studied by Molecular Dynamics Simulation

Espectroscopia vibracional e propriedades termodinâmicas de líquidos iônicos em alta pressão

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