Critical properties of non-spherical molecule fluids from the virial expansion

Critical constants of pure fluids (as important reference data in construct ing vapour-liquid phase diagrams and basic input of various estimation meth ods) were determined for systems of non-spherical Kihara molecules; values of the critical temperature, density, compression factor and pressure of fl uids composed of prolate and oblate molecules were evaluated from the fourt h-order virial expansion. The second and third virial coefficients of the K ihara molecules were determined by applying the recently proposed method in which the effect of molecular core geometry and functional dependence of a pair interaction on the surface-surface distance are factorized and the fo rmer contribution determined from a formula for the corresponding hard conv ex body virial coefficient. The virial expansion for non-spherical Kihara m olecules is applied to determine the critical constants of n-alkanes (metha ne to octane) and cyclic hydrocarbons (cyclopentane, cyclohexane, benzene a nd naphthalene); a fair agreement with experimental data was found.