Effects of Long-Range Interactions on the Structure of Supercritical Fluid Mercury: Large-Scale Molecular-Dynamics Simulations

Abstract

We have carried out large-scale and long-time molecular-dynamics simulations for fluid mercury near the critical point using Lennard-Jones-type effective pair potential derived by the inverse method from the observed structure factor near the critical point. We have investigated the dependence of the structure on the system size and cut-off distance of the effective pair potential, and found that the static structure depends strongly on the system size and cut-off distance, when the system is close to the critical point. In particular, the long-wavelength density fluctuation increases drastically with increasing the cut-off distance of the potential near the critical point. Therefore very weak interatomic interaction at very long distance is important near the critical point. We have also obtained the critical exponents for the structure factor and the correlation length of the density fluctuation and shown that they approach the theoretical values when the system size and the cut-off distance increase.