Ab initio molecular orbital theory study of GaAs clusters: The geometry

We have studied the structure and geometry of neutral and charged atomic clusters consisting of Ga and As atoms via ab initio Hartree-Fock (HF) and second-order Mowller-Plesset methods. The GamAsn cluster with m not equal n composition prefers a nontetrahedral geometry in the charge neutral (q = 0) state. These clusters tend to be stable in tetrahedral geometry when appropriately charged. The GamAsn cluster with m = n composition (1:1 ratio of Ga to As atoms) tends to be stable in a tetrahedral geometry in the charge neutral (q = 0) state. With increasing size of the cluster, the geometry of GanAsn cluster approaches the zinc-belende-type crystalline structure. (C) 2000 John Wiley & Sons, Inc.