Electronic structure of Mn acceptor impurity incorporated SrTiO3 using embedded cluster method

We have performed atomic-level first principle electronic structure calculations on doped grain boundaries (GB) in SrTiO3. This was motivated by the electron holography experiments, which were able to quantify the electrostatic potential and the associated space charge distribution across the Mn-doped GB in this material. The embedded cluster Discrete Variational (DV)-X alpha method was used to determine the charge and the densities of states for several idealized models of a single crystal and symmetrical tilt grain boundaries in SrTiO3. Special attention was given to the role of Mn+2 and Mn+3 accepters substituting for Ti+4 resulting in charge segregation across the grain boundaries, which was shown in the electron holography experiments. We have found that Mn replacing Ti prefers to have valence charge around +2 and this picture agrees with the experimental observation of negative grain boundary charges in the GB core.