The Effect of Symmetry Lowering on the Dielectric Response of $BaZrO_3$

TL;DR

This study uses first-principles calculations to show that symmetry lowering in BaZrO$_3$ due to octahedral tilting explains the experimentally observed dielectric response, resolving previous discrepancies.

Contribution

It demonstrates that including octahedral tilting in structural models aligns theoretical dielectric constants with experimental data.

Findings

Relaxed structure exhibits octahedral tilting.

Dielectric constant matches experimental values.

Symmetry lowering affects phonon frequencies and mode charges.

Abstract

We use first-principles density functional theory calculations to investigate the dielectric response of BaZrO$_3$ perovskite. A previous study [Arkbarzadeh {\em et al.} Phys. Rev. B {\bf 72}, 205104 (2005)] reported a disagreement between experimental and theoretical low temperature dielectric constant $\epsilon$ for the high symmetry BaZrO$_3$ structure. We show that a fully relaxed 40-atom BaZrO$_3$ structure exhibits O$_6$ octahedral tilting, and $\epsilon$ that agrees with experiment. The change in $\epsilon$ from high-symmetry to low-symmetry structure is due to increased phonon frequencies as well as decreased mode effective charges.