Influence of intermolecular potential parameters on orthobaric properties of fluids consisting of spherical and linear molecules

Abstract

Model fluids consisting of spherical n/6 molecules and of linear two-centre Lennard-Jones molecules are considered. The orthobaric densities and the vapour pressures are calculated by using perturbation theory at liquid densities and second virial coefficients at gas densities. In order to classify the results the deviations from corresponding states principle are investigated. For spherical molecules, a steeper repulsive potential lowers the vapour pressure considerably but hardly effects the liquid saturation density. For linear molecules, an increasing elongation lowers the vapour pressure and increases the liquid saturation density. Finally, comparison with real Ar, CH₄, N₂, F₂, C₂H₆, and CO₂ is made.