Brownian motion in asymmetric two-dimensional colloidal mixtures

In this paper we report some aspects of our work on the description of tracer-diffusion phenomena in model two-dimensional binary colloidal mixtures. Here we study the effects of asymmetries between the two brownian species. In particular, we consider the effects of the dynamic asymmetry produced when the free-diffusion mobility of one of the species is reduced, thus resembling a sluggish porous matrix permeated by a colloidal liquid (the species with a ''normal'' free-diffusion mobility). This study consists mostly of Brownian dynamics simulations, but a theoretical interpretation of the results is also attempted, with the assistance of an approximate theory of tracer-diffusion in equilibrium colloidal mixtures (the single exponential approximation). (C) 1997 Elsevier Science B.V.