Novel metastable metallic and semiconducting germaniums

TL;DR

This study uses ab initio metadynamics to discover new metastable germanium phases, revealing a monoclinic structure and a metallic bct-5 phase with potential superconductivity, expanding understanding of germanium's phase diagram.

Contribution

It introduces previously unknown metastable germanium phases, including a monoclinic structure and a metallic bct-5 phase, using ab initio metadynamics simulations.

Findings

Discovered a monoclinic germanium phase with four-membered rings.

Identified a metallic bct-5 phase stable at low pressures.

Bct-5 phase may be superconducting.

Abstract

By means of ab initio metadynamics runs we explored the lower-pressure region of the phase diagram of germanium. A monoclinic germanium phase with four-membered rings, less dense than diamond and compressible into \beta-tin phase (tI4) was found. A metallic bct-5 phase, mechanically stable down to room conditions appeared between diamond and tI4. mC16 is a narrow-gap semiconductor, while bct-5 is metallic and potentially still superconducting in the very low pressure range. This finding may help resolving outstanding experimental issues.