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

Abstract

We have used ab initio MO as well as MNDO, AM1 and PM3 semiempirical methods with large (ZnO) 60 clusters to study the H 2 and CO adsorption, 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 gaps, and bonding distances. The calculated SCF orbital energies, density of states and stretch frequencies are compared with infrared and ultraviolet photoelectron experiments. We analyse the effect of cluster size on our calculations, hydrogen bonding, and heterolytic dissociation, as well as the diversity and stability of the bonding sites, and compare our results obtained using both ab initio and semiempirical methods.