Solid solutions of KTaO3 and KNbO3 (KTN) exhibit unusual dielectric properties at ferroelectric phase transitions, which are usually associated with a Nb instability that is often explained by the large Nb dynamical charge in oxides. Using non-self-consistent VASP computations, we showed earlier that the Nb dynamical charge in layerd KTN strongly depends on the local environment of Nb. In the present study, we have performed self-consistent first-principles computations for fixed composition KTa7/8Nb1/8O3 in different configurations shown. We computed the equilibrium ionic positions, Born charges, force constants, vibration frequencies and modes. We also discuss the question whether Nb has a multi-well potential, and the field dependence of susceptibility.
@article{arxiv.cond-mat/0401039,
title = {First-Principles Computations for KTN},
author = {S. Prosandeev and E. Cockayne and B. Burton and A. Turik},
journal= {arXiv preprint arXiv:cond-mat/0401039},
year = {2007}
}
Comments
2 pages, 1 figure, Fundamental Physics of Ferrorlectrics, Williamsburg 2004