Chemical Trends of Surface Reconstruction and Band Positions of Nonmetallic Perovskite Oxides from First Principles

High Resolution Image Download MS PowerPoint Slide An evolutionary algorithm search in combination with first-principles calculations is performed to systematically predict the reconstructed surface structures of nonmetallic perovskite oxides. Four types of lowest-energy reconstruction patterns are obtained for the macroscopically stoichiometric (001) surfaces of NaTaO 3, KTaO 3, CaTiO 3, SrTiO 3, YAlO 3, and LaAlO 3 as representatives of A + B 5+ O 3, A 2+ B 4+ O 3, and A 3+ B 3+ O 3 systems. We explain chemical trends in the surface energies and band positions of 10 perovskite oxides, additionally including KNbO 3, BaTiO 3, BaZrO 3, and LaGaO 3, in terms of the atomic environments at the outermost reconstructed surface layers. Regaining A –O ( B –O) coordination numbers and bond lengths at the surfaces is found to stabilize the A 2+ B 4+ O 3 and A 3+ B 3+ O 3 ( A + B 5+ O 3 ) surfaces. Decreasing the coordination number of cation A ( B ) leads to shallow (deep) valence band maxima and conduction band minima relative to the vacuum level. Our study provides general insights into the surface reconstruction and band alignment of nonmetallic perovskite oxides.