Direct simulation of the phase behavior of binary hard-sphere mixtures: Test of the depletion potential description

We study the phase behavior of additive binary hard-sphere mixtures by dire ct computer simulation, using a new technique which exploits an analog of t he Gibbs adsorption equation. The resulting phase diagrams, for size ratios q = 0.2,0.1, and 0.05, are in remarkably good agreement with those obtaine d from an effective one-component Hamiltonian based on pairwise additive de pletion potentials, even in regimes of high packing (solid phases) and for relatively large size ratios (q = 0.2) where one might expect the approxima tion of pairwise additivity to fail. Our results show that the depletion po tential description accounts for the key features of the phase equilibria f or q 0.2. [S0031-9007(98)08128-9].