Diffusion of concentrated neutral hard-sphere colloidal suspensions

We evaluate theoretical expressions for the long-time wave-number-dependent self-diffusion and collective diffusion coefficients D-S(L)(k, phi) and D- L(k, phi), respectively, as a function of volume fraction phi and wave vect or k for neutral monodisperse hard-sphere colloidal suspensions over the en tire fluid range. The theory is based on the Smoluchowski equation with mea n-field-like hydrodynamic interactions, cage diffusion, and is free of adju stable parameters. The basic physical mechanisms underlying our formulas ar e discussed and the results are compared with recent experimental results b y Segre and Pusey.