Structural and topological consequences of anisotropic interactions in clusters

Abstract

A simple model one-parameter anistropic potential-energy function may be constructed from the Lennard-Jones (two-body) and Axilrod–Teller (three-body) forms. Detailed calculations are reported for the resulting potential-energy surfaces of small clusters containing 6–13 atoms as a function of the anisotropy parameter. Within the parameter range studied it is possible to locate minima ranging from deltahedra (with all faces triangular) to rings and chains. The calculations show how the anisotropy affects the order of different stationary points as well as the appearance and disappearance of minima and transition states. The model therefore encompasses aspects of equilibrium and dynamical properties of small clusters comprised of atoms from any parts of the periodic table. A number of the general observations may be rationalised by a theoretical analysis of the potential. Patterns also emerge for the favourability of squashing and folding vibrations of chain and ring molecules as a function of the anisotropy.