A first-principles study on chromium sesquioxide, Cr2O3

Chromium sesquioxide has been investigated by the density-functional theory (GGA/PBE/PAW). This study focuses on the experimental high-pressure polymorph, which until now could not be characterized satisfactorily. The eligible structures for high-pressure Cr2O3, [Rh2O3(II)] and the orthorhombic perovskite [GdFeO3], are compared to the ambient-pressure corundum polymorph. The analysis yields the [Rh2O3(II)] structure as the most likely high-pressure phase while phonon calculations verify its dynamic stability. Additionally, the cubic [c-type Ln2O3], dubbed bixbyite, is identified as a possible ambient-pressure polymorph.