DYNAMICS OF SELF-DIFFUSION PROCESS IN CONCENTRATED HARD-SPHERE SUSPENSIONS OF INTERACTING BROWNIAN PARTICLES

A Statistical Physics theory of concentrated hard-sphere suspensions of interacting Brownian particles is presented, in which both hydrodynamic and direct interactions between particles are taken into account. A new macroscopic equation for the particle number density is derived to study the self-diffusion process. For short and long times the asymptotic behavior of this equation are investigated analytically. The volume fraction dependence of the short- and long-time self-diffusion coefficients are thus explored from a new standpoint. The long-range hydrodynamic interactions due to the Oseen tenser are shown to play a crucial role in both coefficients, while the short-range hydrodynamic interactions and the direct interactions just lead to corrections. Results are in excellent agreement with available experimental data.