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

The electronic structures of a series of (MgO)(x) (x = 2-16) clusters cut o ut from MgO solid have been calculated by means of ab initio method. The co nvergence of the electronic properties and the adsorption properties of (Mg O)(x) clusters with the increase of cluster size has been investigated. The calculation results demonstrated a good correlation of the topologic param eters N-d (the total amount of dangling bonds of a cut-out cluster) and bet a (the average dangling bonds on each in-cluster atom) with the stability o f clusters, which not only provides an efficient way to set up a good clust er model of a given size without paying for the high cost of derailed preli minary calculations, but also ensures a good convergence from the cluster t o 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 m odels. The calculation results show the adsorption is more site dependent t han size dependent and the cubic (MgO)(x) models provide a convergent descr iption 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.