Hybrid DFT calculations of the atomic and electronic structure for ABO3 perovskite (0 0 1) surfaces

We present the results of first-principles calculations on two possible terminations of the (0 0 1) surfaces of SrTiO3, BaTiO3, and PbTiO3 perovskite crystals. Atomic structure and the electronic configurations were calculated for different 2D slabs, both stoichiometric and non-stoichiometric, using hybrid (B3PW) exchange-correlation technique and re-optimized basis sets of atomic (Gaussian) orbitals. Results are compared with previous calculations and available experimental data. The electronic density distribution near the surface and covalency effects are discussed in details for all three perovskites. Both SrTiO3 and BaTiO3 (0 0 1) surfaces demonstrate reduction of the optical gap with respect to the bulk, especially for the TiO2-terminated surfaces, whereas PbTiO3 surfaces show a slight increase of the gap. The top of the PbTiO3 valence band lies at X point of the Brillouin Zone, unlike the M point for SrTiO3 and BaTiO3.