Short-time transport properties in dense suspensions: From neutral to charge-stabilized colloidal spheres

Abstract

We present a detailed study of short-time dynamic properties in concentrated suspensions ofcharge-stabilized and of neutral colloidal spheres. The particles in many of these systems are subjectto significant many-body hydrodynamic interactions. A recently developed accelerated Stokesiandynamics (ASD) simulation method is used to calculate hydrodynamic functions,wave-number-dependent collective diffusion coefficients, self-diffusion and sedimentationcoefficients, and high-frequency limiting viscosities. The dynamic properties are discussed independence on the particle concentration and salt content. Our ASD simulation results are comparedwith existing theoretical predictions, notably those of the renormalized density fluctuation expansionmethod of Beenakker and Mazur [Physica A 126, 349 (1984)], and earlier simulation data on hardspheres. The range of applicability and the accuracy of various theoretical expressions for short-timeproperties are explored through comparison with the simulation data. We analyze, in particular, thevalidity of generalized Stokes?Einstein relations relating short-time diffusion properties to thehigh-frequency limiting viscosity, and we point to the distinctly different behavior of de-ionizedcharge-stabilized systems in comparison to hard spheres.