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