TRACER DIFFUSION IN COLLOIDAL MIXTURES

Results for the long-time tracer-diffusion coefficients, from two diff erent theoretical approaches describing tracer diffusion in colloidal mixtures, are presented. The systems studied are binary mixtures of ch arged colloidal particles interacting through Yukawa-type pair potenti als, The effect of bidispersity when different parameters of both spec ies (charges, diameters, relative concentrations, etc.) are varied is discussed, In both theories, the single-exponential approximation and the Fick plus decoupling approximation, the relevant quantities descri bing tracer diffusion at long times, are expressed in terms of integra ls of the static structural properties and the pair interparticle pote ntials of the system, The input static correlation functions are calcu lated within the extended rescaled mean spherical approximation for De rjaguin-Landau-Verwey-Overbeek interactions. In general, both theories predict similar trends for the tracer-diffusion coefficients as the c harge, size, and relative concentration parameters are varied. (C) 199 5 Academic Press, Inc.