Structural behavior and electrical transport properties of Mg2Ge under high pressure

Abstract

The structural and electrical transport properties are investigated from ambient pressure to 40 GPa for Mg2Ge using first-principles calculations and in situ high-pressure electrical experiments. Mg2Ge undergoes reversible phase transitions from anti-fluorite structure to anti-cotunnite structure and then to Ni2In-type structure by enthalpy calculations, both reflected in the cell volume collapse and discontinuous axial ratios of lattice constants. The inter- and intra-layer sliding of Mg and Ge atomic pairs is revealed induced by phase transitions. The metallization transition is determined by the energy-band closure, in good agreement with the enhancing metallic behavior experimentally evidenced above approximately 7 GPa according to the temperature-dependent resistivity measurement. The structural phase transitions are determined at around 9.6 GPa and 35.8 GPa based on discontinuous electrical parameters. The paper tends to shed light on the structural behaviors and electrical transport properties of intermetallic compounds Mg2X-type (X = IVA group elements) family under extreme conditions.