CALCULATION OF BAND STRUCTURES FOR PEROVSKITE-TYPE CRYSTALS USING DISCRETE VARIATIONAL X-ALPHA METHOD

Electronic structures of perovskite-type oxides were calculated using the discrete variational X(alpha) method. First, band structures and densities of states (DOS) were calculated for SrTiO3 and tetragonal BaTiO3. The calculated band structures agreed well with the previous reports and the DOS explained the XPS spectra measured well. Furthermore, band structures of SrTiO3/SrZrO3 superlattices with double period of SrTiO3 along [001], [011] and [111] directions were calculated. As a result, it was confirmed that the SrTiO3 and the [001] superlattice showed an indirect transition between the conduction band at the GAMMA point and valence band at the M or R point, while the [011] or the [111] superlattice showed a direct transition at the GAMMA point.