Oxgen-vacancy defects in PbTiO3 and BaTiO3 crystals: a quantum chemical study

Sheyla Serrano; Carlos Duque; Paul Medina; Arvids Stashans

doi:10.1117/12.515777

8 August 2003 Oxgen-vacancy defects in PbTiO₃ and BaTiO₃ crystals: a quantum chemical study

Sheyla Serrano, Carlos Duque, Paul Medina, Arvids Stashans

Proceedings Volume 5122, Advanced Organic and Inorganic Optical Materials; (2003) https://doi.org/10.1117/12.515777
Event: 2003 Chapter books, 2003, Bellingham, WA, United States

Abstract

We study effects produced by an O vacancy and F center in cubic and tetragonal lead titanate (PbTiO₃) crystals as well as barium titanate (BaTiO₃) (001) surface. Displacements and charges of defect-surrounding atoms, lattice distortion and relaxation energies are carefully analyzed. It is found that the predominant cause of atomic movements in PbTiO₃ around an O vacancy in the Coulomb interaction while in the case of F center also changes in the chemical bonding within the atomic planes should be taken into consideration in order to explain atomic movements. We also observe a phenomenon known as bi-stability of the fundamental state, which occurs due to the rotation of some cationic planes. The obtained vibronic energy barriers for bi-stability are found to be around 1.0 eV. In the case of the BaTiO₃ crystal the computed average atomic movements around the O vacancies are around 0.12 Å and 0.15 Å for the cubic and tetragonal lattices, respectively. In the case of F center we observe somewhat smaller lattice distortion. In the latter case, however, we find a considerable redistribution of electronic charge leading to a polarization of the defect-surrounding lattice, especially if the F center is situated within the Ti-O₂ plane. In general, there is a reduction of the ferroelectric dipole moment for the tetragonal phase of the crystal due to the F center presence on BaTiO₃ (001) surface.

Citation Download Citation

Sheyla Serrano, Carlos Duque, Paul Medina, and Arvids Stashans "Oxgen-vacancy defects in PbTiO₃ and BaTiO₃ crystals: a quantum chemical study", Proc. SPIE 5122, Advanced Organic and Inorganic Optical Materials, (8 August 2003); https://doi.org/10.1117/12.515777

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