Dipped adcluster model study for the end-on chemisorption of O 2 on an Ag surface

Abstract

Theoretical study for the end-on adsorption of an O 2 molecule on an Ag surface is carried out with the use of the dipped adcluster model (DAM). The adcluster of AgO 2 is taken and the highest spin coupling model is employed. Electron transfer from the bulk metal to the adcluster considered by DAM is important for the occurrence of the chemisorption, and this cannot be described by the small-size cluster model. Electron correlations are also quite important and are described by the SD-CI method based on the corresponding parent configurations. In the end-on geometry, the superoxide species is the ground state, and there are no peroxide species in the lower energy region. The calculated adsorption energy compares reasonably with the experimental value. The O—O axis of the superoxide is inclined by 70°–80° from the surface normal. The outside oxygen atom of the adsorbed species seems to be more reactive than the inside one, while the net charge on the former is smaller than that on the latter. Keywords: DAM (dipped adcluster model), silver, superoxide, chemisorption.