Molecular and Brownian Dynamics Simulations of Self-Diffusion in Inverse Power Fluids

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Abstract
We compare the structural, thermodynamic and dynamical behaviour of a model colloidal system with that of the equivalent atomic system using the simulation techniques of brownian dynamics and molecular dynamics. In the process we establish the important role made by solvent mediated many-body hydrodynamics on colloidal single particle motion on “short” and “long” time scales. The short and long-time self-diffusion coefficients of model stabilised colloidal particles were calculated at solids volume fractions up to 0.527 using a hydrodynamics-free Brownian Dynamics, BD technique with model colloidal particles interacting through a r −36 repulsive pair potential. We have improved the simulation technique to follow the self-diffusion process over several molecular diameters, required for the evaluation of the long-time diffusion coefficient. The simulation long-time diffusion coefficient follows closely the behaviour of the experimental short-time diffusion coefficient for volume fractions below ca. 0.4.