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

Published

July 1, 2003

Author(s)

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

Abstract

K_1-xLi_xTaO₃ (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

Pub Type

Journals

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 25, 2024)