Lattice dynamics of BaTiO3, PbTiO3 and PbZrO3: a comparative first-principles study

TL;DR

This study compares the lattice dynamics of BaTiO3, PbTiO3, and PbZrO3 using first-principles calculations, revealing how compositional changes affect phonon modes and phase transition behaviors in perovskites.

Contribution

It provides a detailed first-principles analysis of phonon dispersions in three perovskites and explores the transferability of force constants for predicting lattice dynamics.

Findings

Significant differences in unstable phonon modes due to compositional changes.

Most interatomic force constants are similar across compounds.

Key interactions cause the observed differences in phonon dispersions.

Abstract

The full phonon dispersion relations of lead titanate and lead zirconate in the cubic perovskite structure are computed using first-principles variational density-functional perturbation theory, with ab initio pseudopotentials and a plane-wave basis set. Comparison with the results previously obtained for barium titanate shows that the change of a single constituent (Ba to Pb, Ti to Zr) has profound effects on the character and dispersion of unstable modes, with significant implications for the nature of the phase transitions and the dielectric and piezoelectric responses of the compounds. Examination of the interatomic force constants in real space, obtained by a transformation which correctly treats the long-range dipolar contribution, shows that most are strikingly similar, while it is the differences in a few key interactions which produce the observed changes in the phonon dispersions. These trends suggest the possibility of the transferability of force constants to predict the lattice dynamics of perovskite solid solutions.