Structural stability of CuAl2O4under pressure.

Structural properties of CuAl2O4, which was recently argued to show unusual suppression of the Jahn-Teller distortions by the spin-orbit coupling, are investigated under pressures up to 8 GPa. Analysis of X-ray powder diffraction experiments shows that CuAl2O4gets unstable and decomposes onto CuO and Al2O3at pressures ~6 GPa and temperature ~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.