ON ENTROPY AND ORDERING IN BINARY HARD-SPHERE MIXTURES

The configurational entropy of a binary mixture of unequal hard spheres is analysed over a wide range of densities and concentrations as a sum of two contributions: a pair term, s(2), arising from two-body spatial correlations, and a residual term, Delta s, that is due to correlations involving more than two particles. The validity of a one-phase ordering criterion, based on the non-monotonic behaviour of Delta s as a function of the total packing fraction, is investigated in relation to the phase transformations undergone by the model.