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8 August 2003 Quantum-chemical study of excitons in tetragobnal BaTiO3 and SrTiO3 crystals
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Proceedings Volume 5122, Advanced Organic and Inorganic Optical Materials; (2003)
Event: 2003 Chapter books, 2003, Bellingham, WA, United States
Using a quantum-chemical INDO method based on the Hartree-Fock formalism and the periodic large unit cell (LUC) model we present a theoretical interpretation of the structural and electronic properties of triplet excitons in the tetragonal BaTiO3 and SrTiO3 crystals. Our study demonstrates that the exciton structure has particularities in each material. In the BaTiO3 the defect structure corresponds to the so-called Mott-Wannier-type exciton having a considerable separation, 7.0 Å, between the hole and the electron. Meanwhile, in SrTiO3 the structural and electronic features of the triplet exciton are quite different. The hole-electron distance is about 2.14 Å and the defect is well localized in two contiguous atoms: the hole on one of the O atoms and the electron on the neighbor Ti atom. The calculated luminescence energy using the so-called ΔSCF method is found to be equal to 0.94 eV and 1.13 eV for BaTiO3 and SrTiO3, respectively. Since it falls within the infrared part of the spectrum, the experimentally detected green luminescence due to photo-excited states should be attributed to the singlet excitons.
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Ricardo Viteri, Luis Miguel Procel, Francisco Tipan, Diego Fernando Ortiz, and Arvids Stashans "Quantum-chemical study of excitons in tetragobnal BaTiO3 and SrTiO3 crystals", Proc. SPIE 5122, Advanced Organic and Inorganic Optical Materials, (8 August 2003);


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