First-principles study of electronic structure and metallization of Mg2Pb under high pressure

The high-pressure electronic structure and electrical properties of Mg2Pb are investigated from ambient pressure to 42 GPa by first-principles calculation. Mg2Pb undergoes reversible structural transitions from Fm3m structure to Pnma structure and then to P63/mmc structure. The structural phase transitions are determined respectively at around 6 GPa and 28 GPa using pressure-dependent enthalpy calculations, which are also reflected from the cell volume collapse and discontinuous axial ratios of lattice constants. The sliding of Mg and Pb atomic layers is revealed via the Mg1-Pb-Mg2 atom pair during structural phase transitions, corresponding to abrupt decrease of c/b and a/b. The semimetal-to-metal transition is also observed at approximately 28 GPa owing to energy-band closure, whilst metallic character is strengthened with increasing pressure. The paper is prone to theoretically explore the structural phase transition and metallization of Mg2Pb-type family under extreme conditions.