Three-dimensional metallic carbon allotropes with superhardness

Abstract Three novel three-dimensional orthorhombic carbon phases are proposed based on first-principles calculations in this work. These possess dynamic stability and mechanical theoretically more favorable energy compared to most other allotropes. The hardness levels of o P-C 16 , 20 24 47.5, 49.6, 55.3 GPa, respectively, which greater than those T10, T18, O12 carbon. In addition, although metals, their ideal shear strengths also common metals such as Cu, Fe, Al. Due p y electrons crossing the Fermi level, show metallicity, charge densities band decomposition suggest that all conductive directions exhibited along a - b -axis, similar C 5 .