ATOMIC-STRUCTURE STUDY OF THE AG MGO(100) SURFACE BY AN AB-INITIO, TOTAL-ENERGY MOLECULAR CLUSTER METHOD USING DENSITY-FUNCTIONAL THEORY/

The clean and Ag-covered MgO(100) surface is investigated by an all-el ectron, total energy, ab initio DMol molecular method (Density functio nal theory for Molecular systems). A large cluster of 100 atoms (inclu ding 50 oxygen and 50 magnesium) is built to represent the surface. A point charge embedding is used to investigate the electronic propertie s. The small relaxation of the surface, referred to as rumpling, is ex hibited and shown to have barely no effect on the adsorption of Ag on the surface. The oxygen site is found to be the most stable for Ag ato m adsorption, in good agreement with previous ab initio theoretical st udies. The adsorption of a five-ag-atom layer on the MgO(100) surface provides new and interesting results concerning the surface coverage d ependence. We have used the unique ability of cluster methods to study the structural effects of the 3% mismatch at the Ag/MgO(100) interfac e, and we show that Ag atoms are likely to grow on the surface without epitaxy at low coverages.