Phase Transitions of MnO Under Static Compression.

Abstract

Three phase transitions in MnO are newly found through in situ X-ray observation up to about 140 GPa using diamond anvil cell combined with synchrotron radiation. The rhombohedral distortion from B1 structure at 30 GPa continues to the next phase transition at 90 GPa. A change of the X-ray pattern is also observed at about 120 GPa and its crystal structure is successfully explained by B8 (NiAs) structure. The phase above 90 GPa is expected to be metallic from the highly reflective nature.