Hard-sphere mixture in the colloidal range: a critical analysis of approximate virial pressure binodals

Abstract

Highly asymmetric binary mixtures of hard spheres are known to exhibit a metastable fluid–fluid phase separation. The route using the virial pressure is the simplest way to compute the binodal, provided that accurate contact values of the pair distribution functions are known. To this end, various empirical modifications of the Boublik–Mansoori–Carnahan–Starling–Leland equation of state have been proposed that take into account some self-consistency rules or constraints, especially in the colloidal range. The present comparative study shows that binodals can be obtained from a variety of equations of state but emphasises the difficulty to correlate the occurrence of the binodal with specific constraints on the pair distribution functions at contact.