Dense fluid self-diffusion coefficient calculations using perturbation theory and molecular dynamics

A procedure to correlate self-diffusion coefficients in dense fluids by usi ng the perturbation theory (WCA) coupled with the smooth-hard-sphere theory is presented and tested against molecular simulations and experimental dat a. This simple algebraic expression correlates well the self-diffusion coef ficients of carbon dioxide, ethane, propane, ethylene, and sulfur hexafluor ide. We have also performed canonical ensemble molecular dynamics simulatio ns by using the Hoover-Nose thermostat and the mean-square displacement for mula to compute self-diffusion coefficients for the reference WCA intermole cular potential. The good agreement obtained from both methods, when compar ed with experimental data, suggests that the smooth-effective-sphere theory is a useful procedure to correlate diffusivity of pure substances.