The nonadditive hard-sphere mixture as a reference system in equation-of-state calculations

Abstract

A new reference system is presented for equation-of-state calculations for highly asymmetric mixtures: a mixture of hard spheres with nonadditive diameters. This system allows the introduction of an adjustable binary parameter in the reference term of the EOS while preserving the Boublik-Mansoori mixed-hard-sphere form which is advantageous for mixtures whose components differ greatly in size. The new reference term is tested against a one-fluid reference term of the Carnahan-Starling form; in each case the EOS uses one adjustable parameter in the reference term and one in the perturbation term. For binary systems, the new method offers little improvement over the one-fluid theory. However, when binary parameters are used to predict multicomponent vapor-liquid equilibria, the new method may have some advantages.