High-pressure Single-crystal X-ray Diffraction Study on Minerals Related to the Earth's Mantle:

Pressure-induced Phase Transformation of Spinel Minerals with Jahn-Teller Effect

Abstract

High-pressure single-crystal X-ray diffraction measurement of cuprospinel CuFe₂O₄ was performed at beamline BL10A at the Photon Factory, KEK, Japan. With increasing pressure, the Cu position in the octahedral site moves toward the center of the octahedral coordination, which approaches to the regular octahedral geometry. This geometrical modification enhances the repulsion between e_g orbital from the Cu^2＋ and electrons from the ligand oxygen atoms. At 4.6 GPa, the cuprospinel with cubic structure is consequently transformed to a tetragonally distorted structure, in which the octahedral coordination is elongated along the c-axis with the Jahn-Teller effect of Cu^2＋.