Non-equilibrium molecular dynamics simulations were used to calculate the self-diffusion coefficient of a Lennard-Jones fluid over wide ranges of density and temperature. The change in self-diffusion coefficient with temperature decreased with increasing density. For a density of 0.84, a peak was observed in the value of the self-diffusion coefficient and the critical temperature, 1.25. The value of the self-diffusion coefficient depended strongly upon system size. The data on the self-diffusion coefficient were fitted to a simple analytical relationship based upon hydrodynamic arguments. This correction scaled as N−α, where α was an adjustable parameter and N was the number of particles. It was observed that values of α < 1 provided quite a good correction to the simulation data. The system size dependence was very strong for lower densities, but it was not as strong for higher densities. The self-diffusion coefficient calculated with non-equilibrium molecular dynamic simulations at different temperatures and densities was in good agreement with other calculations from the literature.

Critical Anomaly and Finite Size Scaling of the Self-Diffusion Coefficient for Lennard—Jones Fluids by Non-Equilibrium Molecular Dynamic Simulation. Asad, A., Wu, J.T.: Chinese Physics B, 2011, 20[10], 106601