Semimetallic 2D Alkynyl Carbon Materials with Distorted Type I Dirac Cones
Wei Zhang, Changchun Chai, Qingyang Fan, Yanxing Song, Yuqian Liu, Yintang Yang, Minglei Sun, Udo Schwingenschlögl
Abstract
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.