Structural stability of CuAl$_{2}$O$_{4}$ under pressure

TL;DR

This study investigates the structural stability of CuAl₂O₄ under pressure, revealing its decomposition at around 6 GPa and linking this to its compressibility and Jahn-Teller distortions through experimental and computational methods.

Contribution

It provides new insights into the pressure-induced instability and decomposition of CuAl₂O₄, combining experimental X-ray diffraction data with DFT+U+SOC calculations.

Findings

CuAl₂O₄ decomposes into CuO and Al₂O₃ at ~6 GPa

Decomposition is driven by high compressibility of Jahn-Teller distorted CuO

Structural instability occurs at pressures around 6 GPa

Abstract

Structural properties of CuAl$_{2}$O$_{4}$, which was recently argued to show unusual suppression of the Jahn-Teller distortions by the spin-orbit coupling, are investigated under pressures up to 6 GPa. Analysis of X-ray powder diffraction experiments shows that CuAl$_{2}$O$_{4}$ gets unstable and decomposes onto CuO and Al$_{2}$O$_{3}$ at pressures $\sim$ 6 GPa and temperature $\sim$ 1000 K. This finding is complemented by the DFT+U+SOC calculations, which demonstrate that this instability is partially driven by a (relatively) large compressibility of strongly Jahn-Teller distorted CuO.