Temperature and pressure effects on phase stabilities in the Ca-Ge system from first-principles calculations and Debye-Gruneisen model

► Finite temperature thermodynamics in the Ca−Ge system. ► Two new polymorphs of the CaGe2 compound are predicted. ► A new compound Ca3Ge4 is stabilized with pressure and temperature. ► The P-T phase diagram of the CaGe2 polymorphism is calculated.