Density functional study of the interaction of molecular oxygen with small neutral and charged silver clusters

O-2 adsorption on small neutral, anionic and cationic silver clusters Ag-n (n = 1-7) has been studied by using the PW91PW91 density functional method. The adsorption energies of O-2 on the anionic and neutral clusters have an odd-even alternation pattern clearly, and our calculations give the same adsorption behavior of O-2 on silver cluster anions as the experimental measurements. The adsorption energies on the cationic clusters, instead, are generally smaller than those on the anionic and neutral clusters, and reach a local maximum at Ag4O2+. Natural bond orbital analyses show that electrons mostly transfer from silver atoms to molecular O-2 except for the smallest silver cluster cations (n = 1-3). (c) 2006 Elsevier B.V. All rights reserved.