| dc.description |
The structural properties and the band structures of the charge-transfer insulating oxides SrO, MgO and SrTiO<sub>3</sub> are computed both within density functional theory in the local density approximation (LDA) and in Hedin's GW -scheme for self-energy corrections, by using a model dielectric function, which approximately includes local field and dynamical effects. The deep valence states are shifted by the GW -method to higher binding energies, in very good agreement with photoemission spectra. Since in all of these oxides the direct gaps at high-symmetry points of the Brillouin zone may be very sensitive to the actual value of the lattice parameter a already at the LDA level, self-energy corrections are computed both at the theoretical and the experimental a . For MgO and SrO, the values of the energies of transition between the valence and the conduction bands are improved by GW -corrections, while for SrTiO<sub>3</sub> they are overestimated. The results are discussed in relation to the importance of local field effects and to the nature of the electronic states in these insulating oxides. |
