SELF-DIFFUSION COEFFICIENTS OF CHARGED-PARTICLES - PREDICTION OF NONLINEAR VOLUME FRACTION DEPENDENCE

We report on calculations of the translational and rotational short-ti me self-diffusion coefficients D-s(t) and D-s(t) for suspensions of ch arge-stabilized colloidal spheres. These diffusion coefficients are af fected by electrostatic forces and many-body hydrodynamic interactions (HI). Our computations account for both two-body and three-body HI. F or strongly charged particles, we predict interesting nonlinear scalin g relations D-s(t) proportional to 1-a(t) phi(4/3) and D-s(r) proporti onal to 1-a(r) phi(2) depending on volume fraction phi, with essential ly charge-independent parameters a(t) and a(r). These scaling relation s are strikingly different from the corresponding results for hard sph eres. Our numerical results can be explained using a model of effectiv e hard spheres. Moreover, we perceptibly improve the known result for D-s(t) of hard-sphere suspensions.