Memory effects in the self-diffusion of interacting Brownian particles

We study the time-dependent self-diffusion coefficient for suspensions of interacting, spherical Brownian particles. The self-diffusion coefficient exhibits memory effects with a wide range of relaxation times and a long-time tail. An approximate description of the time dependence involving a small number of parameters is proposed. We test the approximation for an exactly solvable model in which the particles interact via a square step or well potential and show that it works satisfactorily.