Cluster modeling of metal oxides: the influence of the surrounding point charges on the embedded cluster

An ab initio study has been performed to investigate the influence of the surrounding point charges on the calculated electronic properties of the embedded NiO cluster. The employment of the nominal charges ±2.0 would cause overestimation of the crystal potential even for the so-called ionic oxide NiO. Several criteria, namely, the charge, potential, dipole moment and charge density consistence for determining the magnitude of point charges self-consistently have been proposed and examined. When the embedding point charges are spherically expanded, giving the embedding point charges a continuous distribution of charge density, a good agreement is reached between the calculated properties of the embedded cluster model and those of the bulk solid after charge density consistence is fulfilled.