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Computer Modeling of Point Defects, Impurity Self-Ordering Effects and Surfaces in Advanced Perovskite Ferroelectrics

100%

Borstel G., Kotomin E. A., Eglitis R. I., Heifets E.

Acta Physica Polonica A

2000

vol. 98

issue 5

469-481

The calculated optical properties of basic point defects - F-type centers and hole polarons - in KNbO_{3} perovskite crystals are used for the interpretation of available experimental data. The results of quantum chemical calculations for perovskite KNb_{x}Ta_{1-x}O_{3} solid solutions are presented for x=0, 0.125, 0.25, 0.75, and 1. An analysis of the optimized atomic and electronic structure clearly demonstrates that several nearest Nb atoms substituting for Ta in KTaO_{3} - unlike Ta impurities in KNbO_{3} - reveal a self-ordering effect, which probably triggers the ferroelectricity observed in KNb_{x}Ta_{1-x}O_{3}. Lastly, the (110) surface relaxations are calculated for SrTiO_{3} and BaTiO_{3} perovskites. The positions of atoms in 16 near-surface layers placed atop a slab of rigid ions are optimized using the classical shell model. Strong surface rumpling and surface-induced dipole moments perpendicular to the surface are predicted for both the O-terminated and Ti-terminated surfaces.

X-Ray Photoemission Spectra of Dy(Co_{1-x}Al_{x})_{2} Systems

76%

Szajek A., Jezierski A., Kowalczyk A., Baszyński J., Bartkowski S., Neumann M., Borstel G.

Acta Physica Polonica A

1997

vol. 91

issue 2

439-442

The electronic structure of Dy(Co_{1-x}Al_{x})_{2} compounds (Laves phase - MgCu_{2}, C15) for Al concentrations x = 0.0, 0.1, 0.2 was investigated by X-ray photoelectron spectroscopy. The results were compared with the ab initio band structure calculations.

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2 Acta Physica Polonica A

1 2000

1 1997

2 Borstel G.

1 Bartkowski S.

1 Baszyński J.

1 Eglitis R. I.

1 Heifets E.

1 Jezierski A.

1 Kotomin E. A.

1 Kowalczyk A.

1 Neumann M.

1 Szajek A.

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Computer Modeling of Point Defects, Impurity Self-Ordering Effects and Surfaces in Advanced Perovskite Ferroelectrics

X-Ray Photoemission Spectra of Dy(Co_{1-x}Al_{x})_{2} Systems