A comparison between the absorption properties of the regular and Fs-defected MgO (100) surface

The electron density, the electrostatic potential and the electric field of the MgO (100) surface, both regular and containing an oxygen vacancy (Fs center), are compared in order to understand the modifications induced in the surface-absorbate interaction by the presence of the defect, with particular attention to the metal-oxide case. The spindensity for a gold atom absorbing on the most characteristic sites of the regular and Fs-defected surface is also shown. It is found that in the defected surface the electron pair in the vacancy protrudes appreciably out of the surface, thus shifting the electrostatic potential to negative values (but producing a similar electric field) and being able to chemically interact with neighboring absorbed species. These results rationalize the rotational invariance and double frustration effects previously described for the metal/Fs-defected MgO (100) surface.