Molecular dynamics studies of the properties of small clusters of argon atoms

Abstract

Molecular dynamics calculations have been performed on clusters of 15, 30, 45, 60, 80, and 100 argon atoms at temperatures of up to 75°K. Values of the independent-cluster thermodynamic functions are presented and compared with those obtained from the microcrystal model. This comparison indicates good agreement for values of the Gibbs free energy of formation. The transition from solidlike to fluidlike diffusion in the cluster occurs gradually; no semblance of a phase transition is noted. The radial variation of density in the clusters have maxima and minima reminiscent of those in the radial distribution function for bulk liquids. The temperature dependence of that function indicates that clusters expand quite rapidly as the temperature is increased. The radial distribution of potential energy indicates that there is no region inside the clusters where the environment resembles that in the bulk phases; the properties of the clusters are dominated by the ``surface region'' in which nearly all the atoms exist.