Accurate Simulations of the Vapor−Liquid Equilibrium of Important Organic Solvents and Other Diatomics

Abstract

The vapor-liquid equilibria of 20 substances, most of them widely used as organic solvents, were obtained by means of a Gibbs ensemble Monte Carlo method. All these substances can be represented by linear or angular models with only two bonds. The intermolecular interaction was described by a Kihara potential and, where appropriate, an additional multipolar potential using meaningful microscopic parameters. The results agree excellently with experiment even for ranges of hundreds of kelvin when potential parameters are obtained only from fitting two critical constants. The largest discrepancies are observed for liquids capable of forming hydrogen bonds, especially alcohols, but even in these cases agreement is very fair for temperaturedensity equilibrium bells. Agreement is also very good for vapor pressure up to close to critical pressure, namely 60-80 bar in all cases. The worst agreement is again observed for hydrogen-bonding liquids. Vaporization enthalpies were also calculated for some substances. In this case agreement was only fair but also over a large range of temperatures. Finally, parameters commonly used in chemical engineering, such as the acentric factor and solubility factor, which enable prediction of the mutual solubilities of some hundreds of mixtures, were calculated. Some of these mixtures are not yet apparently measured in spite of their possible industrial interest.

Molecular dynamics simulations of the diffusion coefficients of light n-alkanes in water over a wide range of temperature and pressure

“…Alternative approaches like atomistic simulations have been proven reliable techniques for estimating thermodynamic or transport properties at temperature and pressure conditions that are experimentally unfeasible. To this purpose, various simple, yet efficient force-fields, for the representation of H 2 O (as is discussed in detail in the reviews [30,31]), and n-alkane [32][33][34][35] molecules were developed.…”

A novel orientation-dependent potential model for prolate mesogens

“…4 -6 In spite of the success of the Gay-Berne model, more detailed interaction approaches, such as site-site Lennard-Jones chain models, indicate that the actual core of prolate molecules is significantly better reproduced by a spherocylinder core ͑i.e., a cylinder of height/diameter aspect ratio L*ϭL/, capped at both ends with a hemisphere of the same diameter ͒. 16 Perhaps surprising, it has not been until recently that the ability of the Kihara fluid to form liquid crystals phases has been systematically investigated. 8 Examples of this family of models are the hard spherocylinder ͑HSC͒ fluid and its square-well ͑SWSC͒ or soft repulsive ͑SRS͒ variants, [9][10][11][12][13][14] and the Kihara fluid.…”

A new insight on the structural changes of linear quadrupole liquids

“…16,20 We use 5000 simulation steps for the equilibration cycle and further 45000 to calculate the thermodynamic averages. 16,20 We use 5000 simulation steps for the equilibration cycle and further 45000 to calculate the thermodynamic averages.…”