Simulated annealing study of neutral and charged clusters: Aln and Gan

Abstract

Density functional calculations with simulated annealing have been performed for clusters of aluminum Al_n and gallium Ga_n up to n=10. There are many local minima in the energy surfaces, with a rich variety of structures and spin multiplicities. With increasing cluster size we find transitions from planar to nonplanar structures at n=5, and to states with minimum spin degeneracy at n=6. Isomers (n≥5) with buckled planar structures reminiscent of the layers in crystalline α‐gallium are generally less stable than ‘‘three‐dimensional’’ isomers. All structures show regular patterns of bond and dihedral angles. Systematic differences between Al and Ga clusters—bonds in the latter are shorter and bond angles closer to 90°—can be understood in terms of atomic properties. Trends in binding and ionization energies are compared with experiment and with the predictions of other calculations.