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.