Radial Distribution Functions of Fluid Argon

Abstract

The purpose of the present work is twofold. In the first place, we have deduced from theoretical considerations which of the two integral equations [the Percus-Yevick (PY) and convolution hypernetted chain (CHNC) equations] will yield a better distribution function ($g$) under different conditions of temperature and density, and for different interaction potentials. In the second place, we have computed the $g\text{'}\mathrm{s}$ of fluid argon at several values of temperature (all below the critical temperature) and density. The computed $g\text{'}\mathrm{s}$ from the PY and CHNC integral equations using the two different interaction potentials (the Lennard-Jones and Guggenheim-McGlashan potentials) between the argon atoms are compared among themselves as well as with the experimental curves of Eisenstein and Gingrich. The computed $g\text{'}\mathrm{s}$ for liquid argon at $T=126.7\mathrm{}°$K and $n=1.66\mathrm{}\times {10}^{-2\mathrm{}}$ particles/${\mathrm{\AA }}^3$ have also been compared with the Monte-Carlo $g$ of Wood, Parker, and Jacobson. From the computed $g\text{'}\mathrm{s}$ we have calculated energies, pressures, and compressibilities. We have shown that the PY and the CHNC equations can be considered as two different approximations to an exact integral equation. On the basis of this way of looking at the PY and CHNC equations and from the comparison of the computed results we have drawn some conclusions.