Phase behavior of nonadditive hard-sphere mixtures

We show the existence of a fluid-fluid demixing transition in binary mixtur es of nonadditive asymmetric hard-sphere mixtures by performing Gibbs ensem ble Monte Carlo simulations for a size ratio of 0.1 and varying degrees of nonadditivity. We compare our results with the theoretical binodals obtaine d from the equation of state proposed by Barboy and Gelbart [J. Chem. Phys. 71, 3053 (1979)] and we find reasonable agreement for sufficiently large v alues of the nonadditivity parameter. Upon decreasing the nonadditivity par ameter, we find that the fluid-fluid demixing region shifts to higher press ures and becomes narrower. For sufficiently small nonadditivities, we do no t find a fluid-fluid demixing transition for total packing fractions <0.5. [S1063-651X(98)02412-X].