Influence of the atom–atom interaction anisotropy on the structure and stability of ArnCl2 clusters

Global potential energy minima have been characterized for ArnCl2 clusters (n = 2 to 25) using a simple sum of Ar–Ar and Ar–Cl2 potentials. We compare the results for a fully anisotropic (double-minimum) Ar–Cl2 interaction, obtained from scaled high-level ab initio calculations, with those for an approximate (single-minimum) form involving equivalent isotropic ArCl terms. Many of the global minima, with some interesting exceptions, can be understood in terms of low-lying minima of Arn+2. In particular, several global minima exhibit unusual six-fold axial symmetry for the more realistic fully anisotropic form. The approximate isotropic potential does not support some global minima which the fully anisotropic form predicts to have high relative stability. The effect of three-body forces between Ar atoms is shown to be generally unimportant.