Molecular dynamics simulation of dense gases

Abstract

A system of 500 Lennard-Jones particles has been simulated by computer molecular dynamics. Calculations were made at three densities and three temperatures ranging from below the critical density at high temperature to the triple-point density and temperature. Besides the equilibrium pair-correlation function the dynamical quantities calculated were: the time dependence of the moments <X ²> and <X ⁴> of the displacement, velocity autocorrelation function and test particle correlation functions: F _s(k, t) and S _s(k, ω). Both the full potential and a truncated one (i.e. without the attractive part) have been used in the calculation to investigate the effects of the attractive part on the above quantities. The results are then compared with the recently developed generalized hard-sphere Enskog theory of dense gases. At low density and without the attractive part the results are in good agreement with theory; however, this is not so in the presence of the attractive part which modifies the detailed dynamical behaviour of the test particle to a considerable extent. At high densities the attractive part is much less important but, as expected, the results do not agree with theory.