Dodecahedral and smaller arsenic clusters: Asn, n=2, 4, 12, 20

Abstract
Ab initio all-electron quantum mechanical methods, including the Hartree–Fock (HF), second-order perturbation theory, configuration interaction with single and double excitations (CISD), and coupled cluster with single and double excitations (CCSD) methods, have been applied to four arsenic clusters, diatomic As2, tetrahedral As4, cagelike As12 belonging to the D3d point group, and dodecahedral As20. Several basis sets were used. The double-zeta plus polarization (DZP) includes both d and f polarization functions, while the triple-zeta plus double polarization basis includes two sets of f functions on each atom. From the most reliable theoretical results, As12 is energetically lowest among the clusters considered, and As20 is energetically comparable to As4.