STATISTICAL ENTROPY OF A BINARY HARD-SPHERE MIXTURE - THE LOW-DENSITYLIMIT

We have studied the virial expansion of the configurational entropy of a binary mixture of unequal hard spheres as a function of the diamete r ratio and of the relative concentration of the two species. The entr opy was analysed as a sum of two terms: a pair term, which arises from two-particle spatial correlations, and a residual contribution that i s associated with correlations involving more than two particles. We d iscuss the behaviour of this last quantity in the regime of strongly a symmetric sizes and concentrations with specific regard to the onset o f the mechanism leading to phase separation at a thermodynamic level.