Theoretical active impurity levels of iron, chromium, and manganese for photorefractive effects in barium titanate

Using the self-consistent field multiple-scattering Xα method, we calculate and discuss the 3d energy levels, which are potentially photorefractively active for substitutional iron, chromium, and manganese ions in BaTiO3 relative to the valence band edge. Moreover, we examine the almost intrinsic defect formed by an oxygen vacancy associated with titanium.