Lattice dynamical analogies and differences between SrTiO3 and EuTiO3 revealed by phonon-dispersion relations and double-well potentials

TL;DR

This study compares the lattice dynamics and phase transition mechanisms of EuTiO3 and SrTiO3 using phonon dispersion and density functional calculations, revealing similarities in soft mode behavior but differences in elastic properties due to double-well potential variations.

Contribution

It provides a detailed comparative analysis of the phonon-dispersion relations and double-well potentials in EuTiO3 and SrTiO3, highlighting their similarities and differences in structural phase transitions.

Findings

Both compounds exhibit phase transitions driven by softening of transverse acoustic modes.

EuTiO3 and SrTiO3 have similar temperature-dependent soft mode behavior.

Their elastic properties differ significantly due to variations in double-well potentials.

Abstract

A comparative analysis of the structural phase transitions of EuTiO3 and SrTiO3 (at TS = 282 and 105 K, respectively) is made on the basis of phonon-dispersion and density functional calculations. The phase transition of EuTiO3 is predicted to arise from the softening of a transverse acoustic zone-boundary mode caused by the rotations of the TiO6 octahedra, as also found for the phase transition of SrTiO3. While the temperature dependence of the soft mode is similar in both compounds, their elastic properties differ drastically due to a large difference in the double-well potentials associated with the soft zone boundary-acoustic mode.