Electronic structure of a grain-boundary model in SrTiO3

It is known that grain boundaries (GB's) in strontium titanate (SrTiO3) play an important and often a controlling role in determining the material's electrical properties. To understand how their electronic structures are related to the GB structures, we have examined two structure models of the Sigma 5 GB in SrTiO3 obtained by first-principles pseudopotential total energy calculations. The electronic structure of bulk crystal and the relaxed GB models are then studied by using the orthogonalized linear combination of atomic orbitals method. Results are presented for the ground-state structural properties and band structure of bulk SrTiO3, the total density of states (DOS), the atom and orbital-resolved partial DOS, effective charges, bond order, charge-density distribution, and near-edge structure of electron energy-loss spectroscopy. It is shown that the GB structures have smaller values of fundamental band gaps, effective charges, and bond orders relative to bulk SrTiO3. There are no GB-induced electronic states within or at the edge of the fundamental band gap. The 100-atom GB model with buckled Sr columns in the GB con is found to be a more likely model. It is also shown that the electron charge distribution across the GB line in SrTiO3 is almost balanced.