Accurate simulations of the vapor-liquid equilibrium of important organic solvents and other diatomics

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 temperature - density 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.