Ab initio theory of magnetic interactions at surfaces

Abstract

The low to high spin energy transition of Ni adsorbed on regular and defective sites ofMgO(100) and the relative strengths of bulk and surface magnetic coupling constants offirst row transition metal oxides (MnO, FeO, CoO, NiO and CuO) are taken as examples toillustrate some deficiencies of density functional theory (DFT). For these ionic systems acluster/periodic comparison within the same computational method (either DFT orHartree–Fock) is used to establish that embedded cluster models provide an adequaterepresentation. The cluster model approach is then used to obtain accurate values forthe magnetic properties of interest by using explicitly correlated wavefunctionmethods which handle the electronic open shell rigorously as spin eigenfunctions.