Structural stability of CuAl${}_2$O${}_4$ under pressure

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.

6 pages, 6 figures, 2 tables