First-principles study of the lattice dynamical properties of strontium ruthenate

TL;DR

This study uses first-principles calculations to analyze the lattice dynamical properties of SrRuO3, revealing strong antiferrodistortive instabilities and explaining its ground state and related perovskite behaviors.

Contribution

It provides detailed phonon dispersion curves and insights into phase stability, offering benchmark data and a reinterpretation of experimental phonon modes for SrRuO3.

Findings

Strong antiferrodistortive instabilities in cubic phase

Coupling of oxygen-rotation modes stabilizes Pnma phase

Benchmark phonon dispersion curves for future studies

Abstract

By means of first-principles calculations, various properties of SrRuO3 are investigated, focusing on its lattice dynamical properties. Despite having a Goldschmidt tolerance factor very close to 1, the phonon dispersion curves of the high-temperature cubic phase of SrRuO3 show strong antiferrodistortive instabilities. The energetics of metastable phases with different tilt patterns are discussed, concluding that the coupling of oxygen-rotation modes with anti-polar Sr motion plays a key role in stabilizing the Pnma phase with respect to alternative rotation patterns. This not only explains the ground state of SrRuO3 but also contributes to rationalize why most ABO3 perovskites exhibit an orthorhombic ground state. The zone-center phonon modes of the Pnma phase have been computed, from which we propose partial reassignment of available experimental data. The full dispersion curves have also been obtained, constituting benchmark results for the interpretation of future measurements and providing access to thermodynamical properties.