The approach to the Brownian limit in particulate dispersions

We present results for the velocity autocorrelation functions, self diffusion coefficients, memory functions, viscosity and related quantities for binary systems consisting of particles with identical Lennard-Jones interaction parameters but different masses. By varying the mass ratio and the solute concentration, we are able to study the behaviour of the properties of this binary system as it approaches the Brownian limit. We observe that the relationship between the infinite dilution solute self diffusion coefficient and the solvent viscosity approaches Stokes-Einstein behaviour as the mass ratio is increased, and that the solute self diffusion coefficient and the total viscosity are linear functions of the solute concentration. We also find that at high values of the mass ratio, the dispersion becomes shear-thinning in the range of shear rates at which the solvent is Newtonian.