Non-hydrodynamic contribution to the concentration dependence of the self diffusion of interacting brownian macroparticles

Abstract

The generalized Langevin equation and the stationary requirement for an equilibrium system are used to calculate the modification of the self (tracer) diffusion coefficient by direct interactions. In the absence of hydrodynamics, this modification of D??? is equal to the previously predicted modification of the mutual-diffusion coefficient Dm by the same effect, though Dm is also modified by direct interactions in another way. The effect treated here may be viewed as being a change in the generalized Smoluchowski equation in which the free-particle diffusion coefficient Do is replaced by a dressed diffusion coefficient, and not as being a memory-function effect in the conventional generalized Smoluchowski equation.