Abstract
Under GGA, the cleavage energy, surface energy, surface grand potential, surface relaxation, and surface electronic structure have been calculated for five different terminations of PbTiO3 (1 1 0) surface by using PAW method implemented in VASP. Taking into account the results of two neutral PbTiO3 (1 0 0) surfaces, the favorable PbTiO3 (1 1 0) and (1 0 0) surfaces are the TiO2-terminated (1 0 0) surface, the PbO-terminated (1 0 0) surface, and the O-terminated (1 1 0) surface successively in view of surface energy minimization. The surface grand potential calculations show that two neutral PbO- and TiO2-terminated (1 0 0) surfaces are favored in the moderate Pb and O chemical potentials, two mutual complementary TiO- and Pb-(1 1 0) terminations are stable in Pb-poor environment and in O- and Pb-rich conditions, respectively. A non-negligible rumpling of O-terminated (1 1 0) surface is found in the third O2 layer and large lateral displacements between Ti and O atoms on the PbTiO layer lead to the initial O-Ti-O alignment broken. Different from the Fermi levels of the three nonstoichiometric TiO-, Pb- and O-terminations which are located in the band gap, the Fermi level of the PbTiO- termination is located at the bottom of the conduction band and that of the O2-termination is located at the top of the valence band due to increment and decrement of the occupation states for polarity compensation.
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