Ab initio self-consistent-field studies of the structure, energetics and bonding of small gallium arsenide clusters

Abstract

Ab initio all-electron self-consistent-field calculations are peformed on smallGa _m As _n(m+n≤5) clusters using large basis set. The structure, energetics and bonding are analyzed for all clusters, including the positive and negative charge states. In total 18 species are utilized to give a coherent unified picture. Geometry optimization for all species are performed using analytic energy gradient. For crucial or controversial cases post-self-consistent-field calculations at the second-order Møller-Plesset level are performed. In special, theD _3h geometry ofGa ₂ As ₃ as suggested experimentally from ESR experiment is obtained only after inclusion of electron correlation effects. We suggest an explanation to the experimentally observed mass spectrum of clusters with a given number of atoms. The observed alternating behavior for the ionization potentials and electron affinities is discussed and it is suggested that electron correlation corrections are important for a quantitative theoretical description.