Liquid argon: The influence of three-body interactions on atomic correlations

Abstract

Molecular dynamics calculations on a two-dimensional argon liquid at 96\ifmmode^\circ\else\textdegree\fi{}K have been performed taking into account three-body interactions. The three-body forces were assumed to have the Axilrod-Teller form. For the pair interaction the Lennard-Jones potential was chosen. The differences between structural and dynamical correlations which arise from calculations with and without the presence of three-body interactions have been studied. Whereas the differences between distribution functions (pair correlation function and triplet correlation function) due to the three-body forces are not significant, time correlation functions (veloci$\stackrel{\mathrm{\ifmmode\acute\else\textasciiacute\fi{}}}{\mathrm{t}}$y autocorrelation function and intermediate scattering function) show systematic deviations. For example, in the case of the velocity autocorrelation function, deviations up to 25% have been observed. Furthermore, the fourth moment of the scattering law is calcualted for wave numbers $0.234\ensuremath{\le}k\ensuremath{\le}2.34$ ${\mathrm{\AA{}}}^{\ensuremath{-}1}$. Here, also, the deviations (up to 12%) from the pair-theory values are systematic. The results indicate that the determination of pair potentials from the fourth moment (a recent method by Rahman) does not give unique pair potentials for argon and argonlike systems since three-body forces are clearly reflected in the fourth moment.