Freezing of polydisperse hard spheres

Freezing of polydisperse hard spheres is studied by Monte Carlo simulation and the results are interpreted with a cell model of the solid. The results supplement an earlier study of freezing of nearly monodisperse hard sphere s and, within the assumption of a substitutionally disordered solid, a comp lete description of the freezing behavior is obtained. The density and poly dispersity of the precipitate are characterized by a single curve, regardle ss of the composition of the fluid from which it is formed. Fractionation e nables a fluid of arbitrary polydispersity to precipitate a solid of small polydispersity, dispeling the long-held notion of a fluid-phase "critical" polydispersity, beyond which it cannot form a solid. Nevertheless, a primar y conclusion from the previous study is confirmed: a solid crystalline phas e of polydispersity exceeding 5.7% of the average sphere diameter cannot be precipitated from a fluid phase. [S1063-651X(98)04312-8].