| Abstract
| - We compute the fourth virial coefficient of a binary nonadditive, hard-sphere mixture over a wide range ofdeviations from diameter additivity and size ratios. Hinging on this knowledge, we build up a y expansion(Barboy, B.; Gelbart, W. N. J. Chem. Phys.1979, 71, 3053) in order to trace the fluid−fluid coexistencelines, which we then compare with the available Gibbs-ensemble Monte Carlo data and with the estimatesobtained through two refined integral-equation theories of the fluid state. We find that in a regime of moderatelynegative nonadditivity and largely asymmetric diameters, relevant to the modeling of sterically andelectrostatically stabilized colloidal mixtures, the fluid−fluid critical point is unstable with respect tocrystallization.
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