Comparative B3PW and B3LYP Calculations of ABO3 (A = Ba, Sr, Pb, Ca; B = Sn, Ti, Zr) Neutral (001) and Polar (111) Surfaces

Abstract

We completed B3LYP and B3PW computations for AO- and BO2-terminated (001) as well as AO3- and B-terminated (111) surfaces of BSO, BTO, STO, PTO, CTO, BZO, SZO, and CZO perovskites. In particular, we performed the first B3LYP computations for polar BSO (111) surfaces. We observed that most of the upper-layer atoms for AO- and BO2-terminated ABO perovskite (001) surfaces relax inward. In contrast, practically all second-layer atoms relax upward. Lastly, almost all third-layer atoms relax inward. This tendency is less pronounced for atomic relaxation of first, second, and third layer atoms for AO3- and B-terminated ABO perovskite (111) surfaces. For almost all ABO perovskites, their (001) surface rumplings s are considerably larger for AO-terminated compared to BO2-terminated surfaces. On the contrary, the ABO perovskite (001) surface energies, for both AO and BO2-terminations, are essentially equivalent. The ABO perovskite polar (111) surface energies are always substantially larger than their neutral (001) surface energies. In most cases, the surface energies of AO3-terminated ABO perovskite polar (111) surfaces are considerably larger than their B-terminated surface energies. Our computations illustrate a noticeable boost in the B-O bond covalency near the BO2-terminated (001) surface related to the bulk. Our computed ABO perovskite bulk Γ-Γ band gaps are almost always reduced near the AO- and BO2-terminated neutral (001) surfaces as well as in most cases also near the AO3- and B-terminated polar (111) surfaces.