The 4th International Conference on Matter and Radiation at Extremes (ICMRE 2019)

517 / 2019-03-19 15:59:10

Germanium allotropes decompressed from high-pressure β-tin phase

New metastable Ge; Metallic; Decompressing

Plenary track > High Pressure Physics and Materials Science

The irreversible phase transition from cubic-diamond to the β-tin phase in germanium occurs at elevated hydrostatic pressures。The metastable ST12 or BC8 Ge phase can thus be produced when decompressing from the β-tin phase rather than the thermodynamically most stable cubic-diamond structure due to some kinetic factors. Here four new metastable Ge phases (i.e., tP8, oP10, hP12, and oI12 phase) are predicted in the present work through a particle swarm optimization (PSO) structural search method to explore the low-pressure phase diagram of Ge in the process of decompression, They are energetically more superior to the recently reported bct-5 phase. Electronic band structure calculations reveal that the tP8 and oP10 phases both have small band gaps, whereas hP12 and oI12 phases exhibit metallic features. These phases are promising to be retained upon decompression, particularly the oI12 phase that could give a proper interpretation of the ‘‘metallic’’ metastable phases survived through decompressing. This study provides a new idea for predicting stable or metastable phases having distinctive structure and electronic properties and thereby highlights the important role of decompression in the high pressure synthesis of unprecedented materials.