Direct Simulation of the Phase Behavior of Binary Hard-Sphere Mixtures: Test of the Depletion Potential Description

Abstract

We study the phase behavior of additive binary hard-sphere mixtures by direct computer simulation, using a new technique which exploits an analog of the Gibbs adsorption equation. The resulting phase diagrams, for size ratios $q\phantom{\rule{0ex}{0ex}}=\phantom{\rule{0ex}{0ex}}0.2,0.1$, and 0.05, are in remarkably good agreement with those obtained from an effective one-component Hamiltonian based on pairwise additive depletion potentials, even in regimes of high packing (solid phases) and for relatively large size ratios ( $q\phantom{\rule{0ex}{0ex}}=\phantom{\rule{0ex}{0ex}}0.2$) where one might expect the approximation of pairwise additivity to fail. Our results show that the depletion potential description accounts for the key features of the phase equilibria for $q\ensuremath{\le}0.2$.