PHASE-BEHAVIOR OF HARD-SPHERE MIXTURES

A recent method for treating colloid-polymer mixtures is extended to study the phase behaviour of hard-sphere mixtures. It is shown that, for small size ratios xi = r(2)/r(1), the addition of small spheres (radius r(2)) to a system of large spheres (radius r(1)) induces bulk phase separation in to coexisting crystal and fluid phases. Moreover, prior to inducing bulk crystallization, the small spheres cause crystallization of the large spheres next to a hard wall. The positions of the wall and bulk crystallization phase boundaries calculated for a size ratio of 0.14 compare favourably with a set of recent experimental results.