o-C12: A novel orthorhombic metallic superhard carbon phase

Based on the RG2 structure search and DFT calculations, we propose a novel orthorhombic metallic carbon phase, o-C12 with high stability and hardness. Its stability is confirmed by phonon spectrum, molecular dynamics simulation and elastic constants. Its hardness is 48.4 GPa and its failure mode is mainly tensile. The energy band structure and DOS show that the proposed carbon phase has metallic characteristics, and the electron localization function shows that there is a conductive channel along the b direction. Its simulated X-ray diffraction matches well with some peaks in the experimental XRD spectrum of detonation soot. This novel metallic superhard carbon phase is expected to be applied to practical electronic and mechanical devices.