β-Tin→imma→sh phase transitions of germanium

New paths were designed for the investigations of the beta-tin -> Imma -> sh phase transitions in nanocrystalline Ge under conditions of hydrostatic stress. A second-order transition between the beta-tin and Imma phases was identified at 66 GPa, and a first-order transition between the Imma and sh phases was determined at 90 GPa. Superconductivity was obtained up to 190 GPa using the acquired structural data in first-principles calculations. This provides evidence that the standard electron-phonon coupling mechanism is responsible for superconductivity in Ge, as evidenced by the good agreement between the calculations and existing experiments.