Molecular dynamics of dense gases: Effects of continuous potentials

Abstract

Molecular-dynamics simulations of dense gases at 297 K (reduced temperature ${T}^{*}=\frac{T}{\ensuremath{\epsilon}}=1.47$) have been carried out using a Lennard-Jones (LJ) (6-12) pair potential and a truncated LJ potential. Our objective was to study the effects of continuous potentials, with and without attractive forces, on density fluctuations in dense fluids, and to interpret recent neutron scattering measurements on krypton gases which revealed significant deviations from results for hard-sphere fluids. We compare our results with experiments and other studies using molecular dynamics and kinetic theory, but which employed hard-sphere potentials. In particular, predictions of the full width at half maximum for $S(q,w)$ show improved agreement with experiments for values of $q<{q}_{0}$ where ${q}_{0}$ is the position of the first diffraction peak in $S(q)$, when the full potential is used. This satisfactory agreement verifies the sensitivity of the width of $S(q,w)$ to potential-dependent effects.