Determination of the Ground-State Geometries of Copper Clusters by Simulated Annealing within an Equivalent Crystal Approach.

We determine the lowest energy structures of small (11-20 atoms) copper clusters. The semi-empirica1 Equivalent Crysta1 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 icosahedra1 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. [ABSTRACT FROM AUTHOR]