Electronic structure and lattice relaxation related to Fe in MgO

The electronic structure of Fe impurity in MgO was calculated by the linear muffin-tin-orbital–full-potential method within the conventional local-density approximation (LDA) and making use of the LDA+U formalism. The importance of introducing different potentials, depending on the screened Coulomb integral U, is emphasized for obtaining a physically reasonable ground state of the ${\mathrm{Fe}}^{2+}$ ion configuration. The symmetry lowering of the ion electrostatic field leads to the observed Jahn-Teller effect; related ligand relaxation confined to tetragonal symmetry has been optimized based on the full-potential total-energy results. The electronic structure of the ${\mathrm{Fe}}^{3+}$ ion is also calculated and compared with that of ${\mathrm{Fe}}^{2+}$.