Non-Gaussian self-diffusion in binary mixtures of highly charged colloids

Abstract

We quantify non-Gaussian diffusion in binary mixtures of dilute, highly charged colloids in three dimensions and compare mean-square displacements ⟨[Δrx(t)]2⟩ and fourth moments ⟨[Δrx(t)]4⟩ obtained from Brownian dynamics with the prediction of multi-component mode-coupling theory (MCT). Using structure factors of systems with a reduced number of effective charges as input, with a rescaled MCT scheme, a quantitative agreement of theoretical predictions for the long-time self-diffusion coefficients DS,x(L) and simulation results is obtained. Rescaled MCT predicts larger non-Gaussian parameters α2,x(t) than those obtained from simulations, which are shifted to shorter times than found in simulations. We observed for the second non-Gaussian parameter α2,x(t) dynamical coupling effects in mixtures of identically charged particles with different short-time diffusion coefficients D0,x.