Long-time self-diffusion coefficient in colloidal suspensions: theory versus simulation

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Abstract
The long-time self-diffusion coefficient of a colloidal fluid interacting via a Yukawa potential and obeying Brownian dynamics is calculated by computer simulations for different parameters of the Yukawa potential over a broad range of densities. As two extreme cases, the hard sphere and the unscreened Coulomb interaction are also included. The simulation results are compared with different theoretical expressions. In general, it is found that a kinetic-like theory that incorporates both the exact short-time behaviour of the friction kernel and the two-particle dynamics describes the simulational data best. Also, simulations and theories for the self-diffusion in two-dimensional Brownian Yukawa fluids are compared, where the same qualitative behaviour is found.