The energetics and structures of metal clusters are studied by the Car-Parrinello method with Al chosen as a paradigm. For the 13- and 55-atom clusters which can assume perfect icosahedral and cubic structures, the distortions from these ideal structures are substantial. For the 55-atom cluster, several inequivalent but energetically nearly degenerate structures are found. The origin of this near-degeneracy is traced to the short range of the effective interatomic interactions, which provides an ab initio justification for their parametrization in terms of short-range potentials.

• Received 15 May 1991

DOI:https://doi.org/10.1103/PhysRevLett.67.1594