Density functional calculations were performed for V10O3H12 and V9WO31H12 cluster models. The effects of external potential perturbation and cluster reduction on their electronic properties were analyzed. The influence of such perturbations on the activity of the (0 0 1) surface in a hypothetical process of nucleophile attack on V(W) Lewis acid-sites was considered. The analysis focused on global and local reactivity descriptors. W atoms were found to be more accessible for nucleophilic attack than V atoms. It was shown that the electronic chemical potential increases much faster with reduction for the V9WO31H12 than for the V10O31H12 cluster due to a difference in hardness data. Such behavior favors dissociative adsorption on V9WO31H12 (C) 2003 Elsevier Science B.V. All rights reserved.