LONG-TIME SELF-DIFFUSION COEFFICIENTS OF SUSPENSIONS

We present a theory for calculation of the long-time self-diffusion coefficient of suspensions of interacting colloidal particles without hydrodynamic interactions. The theory follows the idea put forward in the preceding paper [Jan A. Leegwater and Grzegorz Szamel, Phys. Rev. A 46, 4999 (1992)]: The self-friction coefficient is calculated approximately and the self-diffusion coefficient can be obtained using the Einstein relation. To calculate the friction coefficient, we retain the part of the three-particle dynamical correlations that can be expressed in terms of the two-particle dynamical correlations. In this way we renormalize the two-particle dynamics. To get explicit results for hard spheres, we introduce a decoupling approximation for the long-time contributions to the friction coefficient. For intermediate densities the predictions of our theory agree very well with Brownian-dynamics simulation.