Density functional study of alkali metals adsorption on the MgO(1 1 1) surface

The adsorption geometry, binding energy and electronic structure of alkali metals overlayers on the MgO(1 1 1) surface have been studied in the framework of the generalized gradient approximation to the density functional theory. Periodic slabs of MgO with Li, Na, and K atoms adsorbed on both surfaces are considered at 0.5 and 1.0 monolayer coverages. It is found that single monolayers of alkali metals stabilize the oxygen-terminated MgO(1 1 1) surface. This effect is rationalized in terms of the large binding energies of the adsorbates and the charge transfer to the surface oxygen layer. We also demonstrate that, deposition of the Li monolayer leads to the transformation of the electronic structure of the MgO(1 1 1) surface from the metallic-like to an insulator-like one with the energy gap of 1.8 eV.