Theoretical prediction of the Cmca phase in Ge under high pressure

Abstract

We have performed first-principles self-consistent total-energy calculations within the local-density approximation using the full-potential linear-muffin-tin-orbital method to investigate crystal structures at high pressure in Ge. We predict a crystallographic phase transition from the simple hexagonal structure to the Cmca phase, which is similar to the Si–VI phase which has recently been observed by Hanfland et al. [Phys. Rev. Lett. 82, 1197 (1999)]. Our calculated pressure for this phase transition is around 94 GPa in Ge. Further, at the very high pressure of about 150 GPa, the Cmca phase is predicted to transform into the hexagonal-close-packed phase.