DFT investigation of novel cubic carbon allotrope, yne-C$_{16}$

Abstract

Novel cubic allotrope yne-C$_{16}$ with sp$^3$/sp$^1$ carbon hybridizations is devised based on crystal chemistry and computations of the ground structure and the energy-dependent quantities within the quantum density functional theory DFT. With respect to srs-C8 characterized by trigonal C(sp$^2$), yne-C$_{16}$ is identified with original C -- C triple bond-like units and distorted tetrahedra. The new allotrope is qualified with unknown topology. At the elementary building unit, C$_{16}$ looks like a pyramidal molecule such as :PCl3, with ":" symbolizing the phosphorous lone pair. With this conceptualization C$_{16}$ has three bond pairs (SIGMA-like) making the pyramid base and the C(triple-bond)C with large PI character resembling phosphorous electron lone pair (:) at the apex of the pyramid. The new allotrope was found cohesive and stable both mechanically (positive elastic constants) as well as dynamically (phonons band structure). C$_{16}$ is characterized with a weakly metallic character.