Physical properties of model colloidal liquids using Brownian dynamics simulation

Some aspects of the equilibrium and non-Newtonian behaviour of a free draining (Rouse level) Brownian Dynamics, BD, model colloidal liquids have been computed. Simulations have been carried out of spherical particles using the r(-n) inverse power repulsive and hard-sphere interaction. The self-diffusion coefficients, linear dynamic viscosities, non-Newtonian viscosity behaviour and associated restructuring of the assembly have been computed. Despite the very simple nature of the model, many of the computed properties follow closely the experimental data, giving at worst qualitative agreement. The model also obeys the Cox-Merz rule on rescaling either the frequency or shear rate. Where the model does show significant differences from the experimental data, we can attribute this to the absence of many-body hydrodynamics in the model. For example, the long-time self-diffusion coefficient decreases with increasing volume fraction, but to a smaller extent than for the experimental systems. The magnitude of the viscosity and also the extent of liquid restructuring at high shear rates are other aspects of the model which probably suffer from the absence of many-body hydrodynamics.