Correlations in the Motion of Atoms in Liquid Argon

Phys. Rev. 136, A405 – Published 19 October 1964
A. Rahman


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 cm-3. 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 ω=0.25(kBT). The shape of the Van Hove function Gs(r, t) attains a maximum departure from a Gaussian at about t=3.0×10-12 sec and becomes a Gaussian again at about 10-11 sec. The Van Hove function Gd(r, t) has been compared with the convolution approximation of Vineyard, showing that this approximation gives a too rapid decay of Gd(r, t) with time. A delayed-convolution approximation has been suggested which gives a better fit with Gd(r, t); this delayed convolution makes Gd(r, t) decay as t4 at short times and as t at long times.


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

© 1964 The American Physical Society

Authors & Affiliations

A. Rahman

  • Argonne National Laboratory, Argonne, Illinois

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