Wave vector dependence of the effective diffusion coefficient of Brownian particles

Abstract

On the basis of a density relaxation equation of Felderhof, the wave vector dependence of the effective diffusion coefficient is calculated for Brownian particles under the influence of thermodynamic and hydrodynamicinteractions. The calculations are correct to first order in the density and show that in the large wave vector limit the diffusion coefficient has to be connected with self‐diffusion. For three different model potentials (the hard sphere potential, the triangle potential, and the screened Coulomb potential), numerical results are given. It is shown that long range repulsion has a large effect on the effective diffusion coefficient especially at small values of the wave vector.