An ab initio study of the O1s and Mg1s, Mg2s, Mg2p core electron binding energies in bulk MgO

Embedded cluster models combined with wavefunction based quantum chemical ab initio methods were used to calculate the O1s and Mg1s, Mg2s, Mg2p core electron binding energies (CEBEs) of bulk MgO. The calculations were performed at three levels of theory: Koopmans' theorem (KT, initial state effects), Delta SCF (relaxation of the electronic wavefunction after core ionization, final state effects, with inclusion of scalar relativistic effects), and approximate coupled cluster (CC) approach to account for electron correlation. Several basis sets as well as MgO clusters of various design and size were employed to study their influence on the CEBEs. The contribution of electron correlation being in the order of 1 eV, but very much different for the different core levels, was analyzed in detail. Our final results are 529.5 eV for the O1s CEBE and 1303.5, 87.7 and 48.8 eV for Mg1s, Mg2s, Mg2p, respectively (all relative to the Fermi level). They agree with recent experimental XPS data within about 0.5 eV.