M. Watzlawek et G. Nagele, SELF-DIFFUSION COEFFICIENTS OF CHARGED-PARTICLES - PREDICTION OF NONLINEAR VOLUME FRACTION DEPENDENCE, Physical review. E, Statistical physics, plasmas, fluids, and related interdisciplinary topics, 56(1), 1997, pp. 1258-1261
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.