Semimetallic 2D Alkynyl Carbon Materials with Distorted Type I Dirac Cones

Motivated by progress in the mechanochemical synthesis of alkynyl carbon materials, we propose two-dimensional carbon materials (QC-graphyne, P-graphyne, and D-graphyne) that are accessible to bottom-up synthesis using P-quinodimethane, pyren, coronene, and dibenzo[bc,kl]coronene as molecular precursors. First-principles calculations demonstrate high stability in comparison to experimentally existing two-dimensional alkynyl carbon materials (naphyne, γ-graphyne, graphdiyne, and graphtetrayne). Importantly, QC-graphyne, P-graphyne, and D-graphyne turn out to be semimetals with distorted type I Dirac cones. Their direction-dependent high Fermi velocities in excess of 105 m/s can compete with those of most known carbon Dirac materials. A Slater–Koster tight-binding model is adopted to verify the formation of a π-conjugated framework due to coupling between carbon pz orbitals. The Dirac cones survive under uniaxial and biaxial in-plane strain with only minor modifications.