Orbital ordering, ferroelasticity, and the large pressure induced volume collapse in PbCrO3

TL;DR

This study uses DFT+U calculations to reveal a new tetragonal phase of PbCrO3 with orbital ordering, explaining its large volume and pressure-induced phase transition with significant volume collapse, highlighting potential for magnetostrictive applications.

Contribution

It introduces a new tetragonal ground-state for PbCrO3 stabilized by orbital ordering and explains its large volume and phase transition behavior under pressure.

Findings

Identification of a new tetragonal phase stabilized by orbital ordering.

Observation of a large 11.5% volume collapse at the phase transition.

Discovery of strong ferroelasticity coupled with orbital degrees of freedom.

Abstract

We report a new tetragonal ground-state for perovskite-structured PbCrO3 from DFT+U calculations, and explain its anomalously large volume. The new structure is stabilized due to orbital ordering of Cr-d in the presence of a large tetragonal crystal field, mainly due to off-centering of the Pb atom. At higher pressures (smaller volumes) there is a first-order transition to a cubic phase where the Cr-d orbitals are orbitally liquid. This phase-transition is accompanied by a ~11.5% volume collapse, one of the largest known for transition-metal oxides. The large ferroelasticity and its strong coupling to the orbital degrees of freedom could be exploited to form potentially useful magnetostrictive materials