Ab initio phonon dispersion curves and interatomic force constants of barium titanate
Abstract
The phonon dispersion curves of cubic BaTiO_3 have been computed within a first-principles approach and the results compared to the experimental data. The curves obtained are very similar to those reported for KNbO_3 by Yu and Krakauer [Phys. Rev. Lett. 74, 4067 (1995)]. They reveal that correlated atomic displacements along <100> chains are at the origin of the ferroelectric instability. A simplified model illustrates that spontaneous collective displacements will occur when a dozen of aligned atoms are coupled. The longitudinal interatomic force constant between nearest neighbour Ti and O atoms is relatively weak in comparison to that between Ti atoms in adjacent cells. The small coupling between Ti and O displacements seems however necessary to reproduce a ferroelectric instability.
Keywords
Cite
@article{arxiv.cond-mat/9706294,
title = {Ab initio phonon dispersion curves and interatomic force constants of barium titanate},
author = {Ph. Ghosez and X. Gonze and J. -P. Michenaud},
journal= {arXiv preprint arXiv:cond-mat/9706294},
year = {2008}
}
Comments
12 pages, 4 figures