A Monte Carlo study of liquid benzene (original) (raw)
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Monte Carlo simulations of pure liquid substituted benzenes with OPLS potential functions
Journal of Computational Chemistry, 1993
Intermolecular potential functions have been developed for use in computer simulations of substituted benzenes. Previously reported optimized potentials for liquid simulations (OPLS) for benzene and organic functional groups were merged and tested in Monte Carlo statistical mechanics simulations for the pure liquids of toluene, m‐cresol, anisole, aniline, and benzonitrile at 25°C at 1 atm. The merged potential functions yielded acceptable thermodynamic results for the liquids except in the case of aniline, for which the error in the heat of vaporization was 12%. This was remedied by enhancing the polarity of the model to be more consistent with the observed dipole moment of aniline. Overall, the average errors in computed heats of vaporization and densities were then 2 and 1%, respectively. The structures of the liquids were characterized through energy and radial distribution functions. For m‐cresol and aniline, the molecules participate in averages of 1.6 and 1.4 hydrogen bonds, r...
Condensed Matter Physics, 2007
The inhomogeneous Monte Carlo technique is used in studying the vapor-liquid interface of benzene in a broad range of temperatures using the TraPPE potential field. The obtained values of the VLE parameters are in good agreement with the experimental values as well as with the results from GEMC simulations. In contrast to the GEMC, within one simulation box the inhomogeneous MC technique also yields information on the structural properties of the interphase between the two phases. The values of the vaporization enthalpy and the vapor pressure very well satisfy the Clausius-Clapeyron equation.
On the structure and dynamics of liquid benzene
Chemical Physics, 1982
The structure and dynamics of liquid benzene are analysed on the basis of a molecular-dynamics experiment involving 216 molecules and lasting 20 ps. Benzene molecules are modelled as rigid hexagons interacting by a six-centre Lennard-Jones potential. The rwulting spatial and time correlation functions are compared to X-ray, neutron. NMR and light scattering data. Selected expansion coefficients of g(R, fl ,, $, D,2) are used in a critical examination of the applied potential. 1. Motivation Although the field of polar liquids has been extensively investigated by computer simulation only a few papers exist [l-4]? which are at least qualitatively correct. This comes from the long-range interactions which must be carefully summed in order to avoid spurious artefacts [5,6]. On the contrary. mere trimcation of the pair potential turned out to be sufficient for non-polar liquids being governed by short-range interactions: As a consequence highly accurate results can be obtained from the simulation of "small-number systems". For this reason a large variety of systems has been published since the pioneering work of Singer et al. [7], who studied two-centre Lennard-Jones molecules. At present more complex molecules like benzene seem to be tractable. Apart from a preliminary paper of Kushick and Beme [S] representing benzene molecules by rotational ellipsoids the only computer-simulation study taking into account the six-fold symmetry of the benzene ring is due to Evans and Watts [9]. However, their Monte Carlo study is restricted to static properties. Even in this respect their analysis is not complete. For example the atom-atom correlation functions g
Simulated structure, dynamics, and vibrational spectra of liquid benzene
Chemical Physics, 2000
A classical molecular dynamics simulation of liquid benzene is performed, using a potential model which allows for full molecular flexibility. The short range intermolecular radial distribution function is on average reminiscent of the crystalline structure, although practically no preferential orientation can be found for the molecules in the first coordination shell. The average cage lifetime and its vibrational dynamics are obtained from appropriate time correlation functions. The intramolecular vibrations are investigated by calculating the vibrational density of states and the infrared and Raman spectra, achieving an excellent agreement with the experimental data. Finally, the dephasing of the 1 (A 1g ) ring breathing mode and of the 6 (E 2g ) in-plane bending mode is analyzed on the basis of the Kubo dephasing function. For 1 mode the Kubo correlation time of 516 fs agrees with the experimental value, and is consistent with a relaxation mechanism involving the cage reorganization. In contrast, 6 has a practically pure Lorentzian line shape, with a width of 7.16 cm Ϫ1 in perfect agreement with the experimental value of 7.2 cm Ϫ1 .
Journal of the American Chemical Society, 2004
Molecular dynamics atomistic simulations of solid and liquid benzene have been performed, employing a model intermolecular potential derived from quantum mechanical calculations. The ab initio database includes approximately 200 geometries of the benzene dimer with interaction energies computed at the MP2 level of theory. The accuracy of the modeled force field results is satisfactory. The thermodynamic and structural properties, calculated in the condensed phases, are compared with experimental data and previous simulation results. Single particle and collective dynamical properties are also investigated through the calculation of translational and rotational diffusion coefficients, reorientational dynamics, and viscosities. The agreement of these data with experimental measurements confirms the reliability of the proposed force field.
Monte Carlo simulation of liquid n‐alkanes. I. Intramolecular structure and thermodynamics
ChemInform, 1992
The conformational properties of liquid n-alkanes (ranging from n-pentane to n-decane) have been investigated using Monte Carlo computer simulation techniques. The method of simulation combines the "reptation" method with a scheme of preferential sampling, which leads to an improvement of the simulation efficiency. The change of internal properties and structure as an effect of the density is studied.
The fast dynamics of benzene in the liquid phase. Part II. A molecular dynamics simulation
Physical Chemistry Chemical Physics, 2001
A molecular dynamics simulation is performed for liquid benzene in the rigid body approximation. The results concerning the structural and dynamical properties of the system provide the basis for the interpretation of recent experimental data. In particular, it is shown that the system is characterised by a well deÐned cage structure, and that the average dynamics of the cages describe the main dynamical features of the bulk liquid. The calculated mean lifetime of the cages is in good agreement with the value of the Kubo correlation time derived from the experiments. In the picture emerging both from experiments and calculations, the fast intermolecular dynamics of liquid benzene is characterised by an inhomogeneously broadened distribution of intermolecular vibrational frequencies, whose dephasing is primarily due to the relaxation of the local structures. In particular, this mechanism is responsible for the dephasing of the low frequency librations giving rise to the intermediate quasi-exponential relaxation observed in the optical Kerr e †ect experiments.
Dynamics of liquid benzene: A cage analysis
The Journal of Chemical Physics, 2005
Dynamics of single molecules in liquids, inspected in the picosecond time scale by means of spectroscopic measurements or molecular-dynamics ͑MD͒ simulations, reveals a complex behavior which can be addressed as due to local confinement ͑cage͒. This work is devoted to the analysis of cage structures in liquid benzene, obtained from MD simulations. According to a paradigm proposed for previous analysis of atomic and molecular liquids ͓see, for example, A. Polimeno, G. J. Moro, and J. H. Freed, J. Chem. Phys. 102, 8094 ͑1995͔͒, the istantaneous cage structure is specified by the frame of axes which identifies the molecular configuration at the closest minimum on the potential-energy landscape. In addition, the modeling of the interaction potential between probe molecule and molecular environment, based on symmetry considerations, and its parametrization from the MD trajectories, allows the estimation of the structural parameters which quantify the strength of molecular confinement. Roto-translational dynamics of probe and related cage with respect to a laboratory frame, dynamics of the probe within the cage ͑vibrations, librations, re-orientational motions͒, and the restructuring processes of the cage itself are analyzed in terms of selected time self-correlation functions. A time-scale separation between the processes is established. Moreover, by exploiting the evidence of fast vibrational motions of the probe with respect to the cage center, an orientational effective potential is derived to describe the caging in the time scale longer than ϳ0.2 ps.
Journal of Molecular Liquids, 2010
The development of new effective intermolecular potential models of benzene and hexafluororbenzene, capable in reproducing the thermodynamic and structural properties of molecular systems in a wide range of thermodynamic state points has been presented and discussed. Subsequently, the properties of the fluids have been investigated by employing molecular dynamics and Monte Carlo simulation techniques. The main purpose of this study was to reveal information concerning the liquid state, vapor-liquid equilibrium and supercritical phase properties of these fluids. In the case of the supercritical phase, we mainly focused on the behavior of local density inhomogeneities and related properties. Our calculations reveal that the local density augmentation is much more pronounced in the case of hexafluorobenzene. The origins of possible resemblances and discrepancies with available experimental data have been also systematically discussed and related to our conclusions reported in previous publications. The local density reorganization dynamics as a function of the bulk density and the size of the local region have been also studied, revealing a significant density and length scale dependence similar to the ones presented for other pure supercritical fluids in previous publication of our group.