Convergence from clusters to the bulk solid: Ab initio calculations of (MgO)(x) (x=2-16) clusters

Abstract

The electronic structures of a series of (MgO)(x) (x = 2-16) clusters cut out from MgO solid have been calculated by means of ab initio method. The convergence of the electronic properties and the adsorption properties of (MgO)(x) clusters with the increase of cluster size has been investigated. The calculation results demonstrated a good correlation of the topologic parameters N-d (the total amount of dangling bonds of a cut-out cluster) and beta (the average dangling bonds on each in-cluster atom) with the stability of clusters, which not only provides an efficient way to set up a good cluster model of a given size without paying for the high cost of derailed preliminary calculations, but also ensures a good convergence from the cluster to the surface. Atomic O adsorption on differently coordinated pair sites of O-XC-Mg-YC has been considered with cubic (MgO)(x) (x = 4, 6, 8) cluster models. The calculation results show the adsorption is more site dependent than size dependent and the cubic (MgO)(x) models provide a convergent description of the reactivity in the order of O-3C-Mg-3C > O-4C-Mg-3C > O-3C-Mg-4C > O-4C-Mg-4C. (C) 1999 John Wiley & Sons, Inc. Int J Quant Chem 73: 377-386, 1999.