Structural stability of CuAl 2 O 4 under pressure.

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 ∼6 GPa and temperature ∼1000 K. This finding is complemented by the density-functional theory + U + spin-orbit coupling calculations, which demonstrate that this instability is partially driven by a (relatively) large compressibility of strongly Jahn-Teller distorted CuO.
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