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.

14 pages; 1 Table, 4 Figures. arXiv admin note: text overlap with arXiv:2404.01813