Two-fluid corresponding states model: a new mixing rule approximation

A semi-empirical approximation of the generalised Percus-Yevick (PY) equation for a mixture of hard spheres by Lebowitz (1964) is used to improve the reprentation of the thermodynamic properties of dense fluid mixtures. The radial distribution function obtained by Lebowitz has been used to derive mixing rules in which a difference of the size of the constituent molecules has a direct effect. The performance of the new approximation is illustrated by comparing the results obtained from it with those from two earlier models for fluid mixtures with different molecular sizes within the framework of the principle of corresponding states. In order to separate the examination of the effect of changes in the mixing rules from the effects of uncertainties in the pair potential for real fluids, the tests conducted here make use of the results of computer simulation for prescribed and simple intermolecular potential models.