Freezing of binary hard-sphere mixtures into disordered crystals: a density functional approach

The density functional theory of freezing is extended to the crystallisation of multicomponent Systems into substitutional solid solutions. The forraalism is applied to the case of binary mixtures ofhard sphres. As the ratio ofdiameters a = a^/ai is lowered, thefluidsolid phase diagram evolves from a spindle shape (1 > ar > 0. 94) into an azeotropic diagram (0. 94 > a> 0. 92) and finally into a eutectic diagram (0. 92 > C> 0. 85). The influence of inter-atomic attractions is examined within the van der Waals mean-field approximation. ' The resulting phase diagrams are even richer than for the bare hard-sphere mixtures, and turn out to be very sensitive to the combination rule for the attractive energy between opposite species.