Origin of Low-Energy Peaks in the Ti-K XANES Spectra of SrTiO3 and CaTiO3

Masaki FUJITAa, Hirohide NAKAMATSUb, Sunao SUGIHARAc, Jun-ichi AIHARAa and Rika SEKINEa*

aDepartment of Chemistry, Faculty of Science, Shizuoka University
836 Ohya, Shizuoka 422-8529, Japan
bInstitute for Chemical Research, Kyoto University
Gokasho, Uji, Kyoto 611-0011, Japan
cDepartment of Materials Science and Ceramic Technology, Shonan Institute of Technology
1-1-25 Tsujido Nishikaigan, Fujisawa 251-8511, Japan

(Received: August 11, 2003; Accepted for publication: November 5, 2003; Published on Web: December 24, 2003)

Low-energy parts of the Ti-K XANES spectra for SrTiO3 and CaTiO3 consist of a main peak and pre-edge peaks B and C. We made a characterization of these peaks using the DV Xa cluster model combined with L2 continuum wave functions. This approach with a [TiO6M8(TiO5)6M24]20+ model cluster (M=Sr or Ca) was successful in reproducing the relative positions and intensities of the low-energy peaks. It was found that transitions of the titanium 1s electron to p-type atomic orbitals (AOs) of the same atom are responsible for all these peaks. In general, p-type atomic orbitals (AOs) of the central titanium atom are mixed with various AOs of nearby atoms in the model cluster. Thus, the origin of main and pre-edge peaks for typical perovskite-type titanates has been elucidated consistently within a single theoretical framework.

Keywords: XANES, Pre-edge peaks, Strontium titanate, Calcium titanate, DV-Xa method

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