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

The (100) surface of magnesium oxide has been studied theoretically with th e semi-empirical SCF-MO method MSINDO using embedded clusters as surface mo dels. The reliability of this approach and its applicability for further in vestigations of chemical reactions on the MgO surface have been tested by c alculating a variety of bulk and surface properties and comparing the resul ts with accurate data from the literature. In particular, the lattice param eter, heat of atomization, and electronic structure of bulk MgO, and the ge ometrical structure and defect formation energies of the MgO(100) surface w ere 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 optimiz ation technique has been investigated and possible ways for minimizing arti facts 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.