Dynamical properties of hard-sphere suspensions

We present an alternative approach to the calculation of long-time diffusion coefficients of dense suspensions. The main idea is to approximate friction coefficients rather than the diffusion coefficients. Within this scheme we derive a very simple yet accurate theory of dynamic properties of a hard-sphere suspension: to calculate friction coefficients we keep only the two-particle dynamics while taking the higher-density effects into account via a renormalization of the frequency of the binary encounters by the contact value of the pair-correlation function. Using this theory we calculate the long-time self-friction and self-diffusion coefficients, the time-dependent self-diffusion kernel, and the wave-number-dependent long-time friction coefficients. The explicit results compare reasonably well with Brownian-dynamics simulations.