MSA for segregating liquid mixtures: Crossover from mean-spherical to mean-field exponents

The critical exponents , , and of a binary mixture of equal-sized hard spheres with repulsive Yukawa interactions for unlike-atom pairs and attractive Yukawa interactions for like-atom pairs are calculated from analytical solutions in the mean spherical approximation. For strong to moderate screening we find the expected mean spherical values of the critical exponents; for weak screening the system shows a mean field behaviour. For an intermediate range of the potential, the system displays a crossover from mean-field behaviour to mean-spherical behaviour in the immediate vicinity of the critical point. The domain over which the mean-spherical exponents describe the critical behaviour shrinks as the range of the interatomic potential increases.