  Based on first-principles method 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 its excellent stability exceeds all the previously
proposed graphene allotropes. We find that SW40 processes intrinsic Type-III
Dirac-cone (Phys. Rev. Lett., 120, 237403, 2018) formed by band-crossing of a
local linear-band and a local flat-band, which can result in highly anisotropic
Fermions in the system. Interestingly, such intrinsic type-III Dirac-cone can
be effectively tuned by inner-layer strains and it will be transferred into
Type-II and Type-I Dirac-cones under tensile and compressed strains,
respectively. Finally, a general tight-binding model was constructed to
understand the electronic properties nearby the Fermi-level in SW40. The
results show that type-III Dirac-cone feature can be well understood by the
$\pi$-electron interactions between adjacent Stone-Wales defects.
