ELECTRONIC-STRUCTURE OF NICKEL, IRON, AND COBALT IMPURITIES IN MAGNESIUM-OXIDE

We present theoretical results for the electronic structure of nickel, iron, and cobalt impurities in MgO, calculated using a linear muffin-tin-orbital Green's-function method. We investigate the ground states and the localization properties of these defects, where lattice relaxations are not taken into account. With the help of a method from Fazzio, Caldas, and Zunger we analyze the optical properties of these systems to some extent, showing that they cannot be described within a one-electron picture. Furthermore, we take a close look at the so-called Mott-Hubbard parameter. Here, we analyze two major definitions and show that they lead to quite different results.