Electronic structure of the valence band for perovskite-type titanium double oxides studied by XPS and DV-Xα cluster calculations |
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Authors: | Hirohide Nakamatsu Hirohiko Adachi Shigero Ikeda |
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Institution: | Department of Chemistry, Faculty of Science, Osaka University, Toyonaka, Osaka 560 Japan |
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Abstract: | XPS spectra of the valence bands for the perovskite-type titanium double oxides BaTiO3, SrTiO3 and CaTiO3 have been measured and analyzed by means of DV-Xα calculations for the TiO6 embedded cluster model. The theoretical photoelectron spectra modulated by the photoionization cross-sections are in good agreement with experiment. The XPS results show that the O 2p valence band is constructed of two peaks whose spacing becomes larger in the order BaTiO3 < SrTiO3 < CaTiO3. The DV-Xα results indicate that the greater part of the lower-energy peak is attributed to the levels which have O 2p orbitals pointing to Ti cations and are thus stabilized by the electrostatic potential concomitant with a decreased TiO bond distance. The electrostatic potential also reduces the O 2p-Ti 3d mixing and, together with the repulsion of the electron cloud between the Ti and O ions, makes the TiO bond more ionic. |
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