Binary Yukawa mixtures: comments on the compressibility-energy thermodynamic inconsistency in the mean spherical approximation

Abstract

The thermodynamic properties of a binary Yukawa mixture are calculated within the mean spherical approximation (MSA) using both the energy and compressibility routes. Two types of binary mixtures are considered: (a) a mixture, denoted by M1, that exhibits a tendency to homocoordination; and (b) another, denoted by M2, that exhibits a tendency to heterocoordination. Also, two types of calculations are carried out: one in which the thermodynamic states are specified by the concentration c, the number denisty p and the temperature T; the other in which c, T and the pressure P are specified. The results of the calculations suggest that for mixture M1 the energy route tends to exacerbate the tendency to a phase transition. In particular, it is found that, at the prescribed P, the MSA results using the energy route exhibit a miscibility gap at certain concentration and over a wide range of temperatures, which does not show up in the compressibility route. In the case of mixture M2 both routes are reasonably con...