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-electron, total energy, ab initio DMol molecular method (Density functional theory for Molecular systems). A large cluster of 100 atoms (including 50 oxygen and 50 magnesium) is built to represent the surface. A point charge embedding is used to investigate the electronic properties. The small relaxation of the surface, referred to as rumpling, is exhibited 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 atom adsorption, in good agreement with previous ab initio theoretical studies. The adsorption of a five-ag-atom layer on the MgO(100) surface provides new and interesting results concerning the surface coverage dependence. We have used the unique ability of cluster methods to study the structural effects of the 3% mismatch at the Ag/MgO(100) interface, and we show that Ag atoms are likely to grow on the surface without epitaxy at low coverages.