Title :
Computer modelling of KTN solid solutions
Author :
Borstel, G. ; Eglitis, R.I. ; Kotomin, E.A.
Author_Institution :
Fachbereich Phys., Osnabruck Univ., Germany
Abstract :
The results of quantum chemical modelling of perovskite solid solutions KNbxTa1-xO3 are presented and compared with recent full-potential LMTO calculations. We show that Nb atoms in KTaO3 reveal off-center displacements along both the [100] and [111] axes at as low concentrations as x=0.125, which is in much better agreement with XAFS experiments than full potential LMTO calculations. The analysis of the optimized atomic and electronic structure clearly demonstrates that several nearest Nb impurities in KTaO3 are able for self-ordering and reveal a cooperative behaviour. This probably triggers the KTN ferroelectric phase transition. In contrast, Ta impurities in KNbO3 reveal no self-ordering. The qualitatively different behaviour of Nb and Ta atoms could be caused by a small difference in their chemical bonding with other atoms, first of all oxygens
Keywords :
INDO calculations; bonds (chemical); ferroelectric materials; ferroelectric transitions; impurities; linear muffin-tin orbital method; potassium compounds; total energy; KNbxTa1-xO3; KNbO3TaO3; KTN solid solutions; Ta impurities; chemical bonding; computer modelling; cooperative behaviour; electronic structure; ferroelectric phase transition; full-potential LMTO calculations; off-center displacements; optimized atomic structure; perovskite solid solutions; quantum chemical modelling; self-ordering; several nearest Nb impurities; Bonding; Chemicals; Crystalline materials; Crystals; Ferroelectric materials; Impurities; Niobium; Optical materials; Photorefractive materials; Solid modeling;
Conference_Titel :
Applications of Ferroelectrics, 2000. ISAF 2000. Proceedings of the 2000 12th IEEE International Symposium on
Conference_Location :
Honolulu, HI
Print_ISBN :
0-7803-5940-2
DOI :
10.1109/ISAF.2000.942409
