First-principles investigation of novel cubic allotrope C16 with original C(sp3)/C(sp1) hybridizations

Novel cubic allotrope yne-C16 with sp3/sp1 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(sp2), yne-C16 is identified with original C≡C triple bond-like units and distorted tetrahedra. The new allotrope with unknown topology resembles a pyramidal molecule as :PCl3 with three bond pairs (σ-like) forming the pyramid base and the C≡C with large π character resembling a phosphorous electron lone pair (:) at the apex of the pyramid. The resulting structure is cohesive and mechanically (positive elastic constants) and dynamically (phonon band structure) stable; C16 is characterized by weak metallic behavior.