▎ 摘　　要

Based on first principles, we predict a new low-energy Stone-Wales graphene SW40, which has an orthorhombic lattice with Pbam symmetry and 40 carbon atoms in its crystalline cell forming well-arranged Stone-Wales patterns. The calculated total energy of SW40 is just about 133 meV higher than that of graphene, indicating that its excellent stability exceeds all the previously proposed graphene allotropes. We find that SW40 exhibits an intrinsic type-III Dirac cone [Phys. Rev. Lett. 120, 237403 (2018)] formed by band crossing of local linear and flat bands, which can result in highly anisotropic fermions in the system. Interestingly, such an intrinsic type-III Dirac cone can be effectively tuned by inner-layer strain and it will be transferred into type-I and type-II Dirac cones under tensile and compressed strain, respectively. Finally, a general tight-binding model was constructed to understand the electronic properties near the Fermi level in SW40. The results show that type-III Dirac cone features can be well understood by the pi-electron interactions between adjacent Stone-Wales defects.