MgO(100) surface relaxation and vacancy defects: a semi-empirical quantum-chemical study

The (100) surface of magnesium oxide has been studied theoretically with the semi-empirical SCF-MO method MSINDO using embedded clusters as surface models. The reliability of this approach and its applicability for further investigations of chemical reactions on the MgO surface have been tested by calculating a variety of bulk and surface properties and comparing the results with accurate data from the literature. In particular, the lattice parameter, heat of atomization, and electronic structure of bulk MgO, and the geometrical structure and defect formation energies of the MgO(100) surface were considered. Reasonable agreement with results of recent experiments and high-level theoretical calculations was found for most of the properties. The dependence of calculated surface relaxation and rumpling on the optimization technique has been investigated and possible ways for minimizing artifacts from cluster boundary effects are presented. The calculated energies of isolated O, O2-, Mg, Mg2+, and MgO vacancy formation depend strongly on the optimization of nearest and second-nearest neighbor atoms.