Crystallization time scales for polydisperse hard-sphere fluids

摘要

We study the evolution of crystallization in dense mono- and polydisperse hard sphere fluids, initially quenchednto an amorphous configuration. We use as signatures of crystallization both the decay of the reduced pressurenZ and the increase in the local and global orientational order parameters ¯Q6. For a given realization of thencrystallization process these parameters show sudden changes, both large and small, separated by long periods ofnquiescence. However, averaging over a large number of realizations, a well-defined scenario for their evolutionnappears.We find an initial fast relaxation to a disordered state, followed by a period of slow variation, associatednto the presence of nucleation events, followed by a fast change, composed of the growth of a few crystalsnwith different orientations, and a final and slow coarsening in a domain-growth process. No clear scaling fornthis whole process was found. We also find that the transition to an stable glassy fluid is quite sharp as thenpolydispersity is increased, showing a probable first-order phase transition behavior. A well-defined boundarynbetween crystallizing and permanently amorphous fluids should exist, at least for a region in packing fractions.nWe looked for segregation at large values of polydispersity, but no effects of this type were found.