Pressure-induced structural phase transition in Li4Ge

Abstract

The structural, dynamic, elastic, and electronic properties of Li₄Ge were investigated by means of evolutionary crystal structure prediction in conjunction with first-principles calculations. We find that the ground-state Li₄Ge under ambient conditions has a cubic symmetry. Li₄Ge undergoes a structural phase transition at about 2 GPa from the cubic P2₁3 phase to the Rm phase. The dynamic and mechanical stabilities of P2₁3 and Rm were confirmed by phonon and elastic constant calculations. From the calculated elastic constants, we obtained the elastic moduli and discussed their elastic anisotropy effect. Our calculation shows that the P2₁3 structure is brittle while the Rm structure is ductile. The anisotropic properties of Rm are more pronounced than those of P2₁3 at ambient pressure. P2₁3-Li₄Ge is a narrow band gap semiconductor while the Rm phase is a poor metal.