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Energetics of Li Atom Displacements in K1-xLixTa03: First-Principles Calculations

Published

Author(s)

S A. Prosandeev, Eric J. Cockayne, Benjamin P. Burton

Abstract

K1-xLixTaO3 (KLT) solid solutions exhibit a variety of interesting physical phenomena related to large local displacements of Li-ions from ideal perovskite A-site positions. First-principles calculations for KLT supercells were used to investigate these phenomena. Lettice dynamics calculations show that KLT has a Li off-centering instability. The energetics of Li-displacements for isolated Li-ions and for Li-Li pairs up to 4th neighbors were calculated. The interaction between nearest neighbor Li-ions strongly favors ferroelectric alignment along their mutual axis. Such Li-Li pairs can be considered as seeds for polar nanoclusters in KLT. Electrostriction, local oxygen relaxation, coupling to the KT soft-mode, and an interaction with neighboring Li-ions all enhance the polarization arising from Li off-centering. Calculated hopping barriers for isolated Li-ions and for nearest neighbor Li-Li pairs are in good agreement with Arrhenius fits to experimental dielectric data.
Citation
Physical Review B (Condensed Matter and Materials Physics)
Volume
68
Issue
No. 1

Keywords

dynamical charges, first-principles computations, lattice dynamics, perovskites, solid solutions

Citation

Prosandeev, S. , Cockayne, E. and Burton, B. (2003), Energetics of Li Atom Displacements in K1-xLixTa03: First-Principles Calculations, Physical Review B (Condensed Matter and Materials Physics) (Accessed April 16, 2024)
Created July 1, 2003, Updated February 19, 2017