AB-INITIO AND SEMIEMPIRICAL MO STUDIES USING LARGE CLUSTER-MODELS OF CO AND H-2 ADSORPTION AND DISSOCIATION ON ZNO SURFACES WITH THE FORMATION OF ZNH AND OH SPECIES

We have used ab initio MO as well as MNDO, AM1 and PM3 semiempirical m ethods with large (ZnO)(60) clusters to study the H-2 and CO adsorptio n, as well as the H-2 dissociation, on ZnO surfaces with the formation of ZnH and OH species. From the optimized adsorption and dissociation geometries, we analyse Mulliken populations, binding energies, band g aps, and bonding distances. The calculated SCF orbital energies, densi ty of states and stretch frequencies are compared with infrared and ul traviolet photoelectron experiments. We analyse the effect of cluster size on our calculations, hydrogen bonding, and heterolytic dissociati on, as well as the diversity and stability of the bonding sites, and c ompare our results obtained using both ab initio and semiempirical met hods. (C) 1997 Elsevier Science B.V.