Phase behavior of nonadditive hard-sphere mixtures

We show the existence of a fluid-fluid demixing transition in binary mixtures of nonadditive asymmetric hard-sphere mixtures by performing Gibbs ensemble Monte Carlo simulations for a size ratio of 0.1 and varying degrees of nonadditivity. We compare our results with the theoretical binodals obtained from the equation of state proposed by Barboy and Gelbart [J. Chem. Phys. 71, 3053 (1979)] and we find reasonable agreement for sufficiently large values of the nonadditivity parameter. Upon decreasing the nonadditivity parameter, we find that the fluid-fluid demixing region shifts to higher pressures and becomes narrower. For sufficiently small nonadditivities, we do not find a fluid-fluid demixing transition for total packing fractions <0.5.