High-Pressure Transitions of Germanium and a New High-Pressure Form of Germanium.

Some transitions in germanium and other semiconductor systems have been detected after very long exposure to high pressures followed by various quenching techniques. In the case of Ge, a new high-pressure polymorph, Ge-IV, has been synthesized above 110 kilobars with a body-centered-cubic structure. The pressure for the Ge-I right harpoon-up Ge-III (body-centered-tetragonal structure) transition has been revised from about 120 to 25 kilobars at 30 degrees C. The transition from the Ge-I (diamond structure) to the Ge-II (white tin structure) is metastable up to 140 kilobars. Thus some phase diagrams based on discontinuities observed in essentially dynamic systems may be inaccurate.