#### Abstract

A system of 864 particles interacting with a Lennard-Jones potential and obeying classical equations of motion has been studied on a digital computer (CDC 3600) to simulate molecular dynamics in liquid argon at 94.4°K and a density of 1.374 g ${\mathrm{cm}}^{-3\mathrm{}}$. The pair-correlation function and the constant of self-diffusion are found to agree well with experiment; the latter is 15% lower than the experimental value. The spectrum of the velocity autocorrelation function shows a broad maximum in the frequency region $\omega =0.25\left(\frac{{k}_{B}T}{\hslash}\right)$. The shape of the Van Hove function ${G}_{s}(r,t)$ attains a maximum departure from a Gaussian at about $t=3.0\mathrm{}\times {10}^{-12\mathrm{}}$ sec and becomes a Gaussian again at about ${10}^{-11\mathrm{}}$ sec. The Van Hove function ${G}_{d}(r,t)$ has been compared with the convolution approximation of Vineyard, showing that this approximation gives a too rapid decay of ${G}_{d}(r,t)$ with time. A delayed-convolution approximation has been suggested which gives a better fit with ${G}_{d}(r,t)$; this delayed convolution makes ${G}_{d}(r,t)$ decay as ${t}^{4}$ at short times and as $t$ at long times.

DOI: http://dx.doi.org/10.1103/PhysRev.136.A405

- Received 6 May 1964
- Published in the issue dated October 1964

© 1964 The American Physical Society