Comparative First-Principles Calculations of SrTiO3, BaTiO3, PbTiO3 and CaTiO3 (001), (011) and (111) Surfaces

I present the results of my ab initio calculations for SrTiO3, BaTiO3, PbTiO3 and CaTiO3 neutral (001), as well as for polar (011) and (111) surfaces using the hybrid description of exchange and correlation. AO and BO2-terminations for the nonpolar (001) surface and A, BO, and O terminations of the polar (011) surface, as well as B and AO(3)-terminations of the polar (111) surface were calculated. In the case of the neutral AO-terminated (001) surface for SrTiO3, BaTiO3, PbTiO3 and CaTiO3 perovskites, all upper-layer A atoms relax inward towards the bulk, while all second layer atoms relax outwards. For the BO2-terminated (001) surface, in most cases, the largest relaxations are on the second-layer metal atoms. For practically all ABO(3) perovskites, the surface rumpling is considerably larger for the AO-terminated than for the BO2-terminated (001) surface, but their surface energies always are almost equal. Just opposite, different terminations of the (011) ABO(3) surface lead to very different surface energies for the O-terminated, A-terminated, and BO-terminated (011) surface, respectively. The surface energies for all calculated (111) surfaces are considerably larger than even for (011) surfaces. A considerable increase in the Ti-O chemical bond covalency near the (011) surface as compared to the bulk and to the (111) and (001) surfaces in considered ABO(3) perovskites were predicted.