UNIVERSAL SELF-DIFFUSION AND SUBDIFFUSION IN COLLOIDS AT FREEZING

We provide a theoretical explanation for the observed quasiuniversality of the ratio of the long-time to short-time self-diffusion coefficients in colloidal liquids at freezing. We also predict that the mean-squared displacement at freezing, plotted against a suitably renormalized time, yields a universal curve showing a short-time subdiffusive regime and a long-time caged diffusion. We obtain C(s) (k, t), the intermediate scattering function, for all (k, t) and show that it implies strong non-Gaussian behavior in the probability distribution of the single-particle displacement at short times.