In situ X-ray observation of phase transitions in Mg2Si under high pressure

The structural behavior of magnesium silicide (Mg2Si) was investigated in a diamond anvil cell (DAC) by energy dispersive synchrotron X-ray diffraction up to 41.3 GPa at room temperature. Two pressure-induced structural phase transitions for Mg2Si have been identified, at around 7.5 GPa and 21.3 GPa, respectively. The new structures of Mg2Si are in turn determined as orthorhombic phase with anti-cotunnite (Pnma,Z=4)(Pnma,Z=4) structure and hexagonal phase with Ni2In-type (P63/mmc,Z=2)(P63/mmc,Z=2) structure. Both the structural phase transitions are of first-order nature and are reversible.