Virial coefficients and demixing of athermal nonadditive mixtures.
We compute the fourth virial coefficient of a binary nonadditive, hard-sphere mixture over a wide range of deviations 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 coexistence lines, which we then compare with the available Gibbs-ensemble Monte Carlo data and with the estimates obtained through two refined integral-equation theories of the fluid state. We find that in a regime of moderately negative nonadditivity and largely asymmetric diameters, relevant to the modeling of sterically and electrostatically stabilized colloidal mixtures, the fluid-fluid critical point is unstable with respect to crystallization.
Pellicane
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Dipartimento di Fisica, Università degli Studi di Messina, Contrada Papardo, 98166 Messina, Italy. giuseppe.pellicane@unime.it
Caccamo
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C
Giaquinta
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Saija
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