Comparison of size effects in aluminum and silicon clusters

Abstract

Semiempirical molecular orbital calculations by the SINDO1 method are used as the basis for a comparative study of medium size Aln and Sin clusters (n=13,14,19,23,35,43). Particular emphasis is placed on the differences between metallic and semiconductor properties in dependence on cluster size. Optimized structures of crystalline and noncrystalline forms are compared with respect to average bondlengths, binding energies per atom, ionization potentials, energy gaps between highest occupied and lowest unoccupied molecular orbitals, densities of states, and charge distributions. Solid state properties begin to show up at cluster size of n=43, but more clearly for aluminum than for silicon.