On the critical non-additivity driving segregation of asymmetric binary hard sphere fluids

Per Sillrén (1) , Jean-Pierre Hansen (2)

1 Applied Physics
2 Chemistry

A previously proposed version of thermodynamic perturbation theory, appropriate for singular pair interactions between particles, is applied to binary mixtures of hard spheres with non-additive diameters. The critical non-additivity ∆C required to drive fluid-fluid phase separation is determined as a function of the ratio ξ ≤ 1 of the diameters of the two species. ∆C (ξ) is found to decrease with ξ and to go through a minimum for ξ ≃ 0.015 before increasing sharply as ξ → 0, irrespective of the total packing-fraction η of the mixture. These results are the basis of an estimate of the range of size ratios for which a binary mixture of additive hard spheres exhibit a fluid-fluid miscibility gap. This range is conjectured to be 0.01 < ξ < 0.1.

Mots clés: Physical Sciences

Per Sillrén, Jean-Pierre Hansen. On the critical non-additivity driving segregation of asymmetric binary hard sphere fluids. Molecular Physics, 2010, 108 (01), pp.97-104. ⟨10.1080/00268970903514561⟩. ⟨hal-00565914⟩