First-principles investigation on pressure-induced phase transitions and electronic properties in GeTe

GeTe is a crucial phase change material, and its phase transition under pressure remains incompletely understood. In this work, we employed the density functional theory calculations to establish the variations in GeTe induced by pressure. Three phases are identified from the bandgap, the enthalpy-pressure (H−P) profile, and the unit cell volume: the low-pressure rhombohedral phase (R3m), the intermediate-pressure cubic phase (Fm3¯m), and the high-pressure orthorhombic phase (Pnma). The R3m to Fm3¯m phase occurs at 4 GPa, and that from the Fm3¯m to Pnma phase occurs at 15 GPa. Analyzing electron localization functions and Born effective charges between Ge and Te atoms jointly revealed the bonding characteristics: The R3m and Fm3¯m phases are dominated by covalent bonds, and the Pnma phase is contributed by ionic bonds. This provides a theoretical basis at the electronic and bonding levels, supporting the device applications of GeTe in high-pressure environments.