DETERMINATION OF THE GROUND-STATE GEOMETRIES OF COPPER CLUSTERS BY SIMULATED ANNEALING WITHIN AN EQUIVALENT CRYSTAL APPROACH

Abstract

We determine the lowest energy structures of small (11–20 atoms) copper clusters. The semi-empirical Equivalent Crystal Theory (ECT) is used in conjunction with the Metropolis Monte Carlo algorithm to determine the equilibrium geometry of each cluster via simulated annealing. The optimum structures of the clusters in this size range are found to be derived from icosahedral structures. The 13-atom cluster is an icosahedron and the 19-atom is a double-icosahedron. The other sizes show structures related to these. The 11-atom clusters, however, show somewhat different structures. We propose the ECT as an efficient tool for developing starting structures for more chemically accurate, first principles and therefore computationally very demanding, approaches.