A graphene composed of pentagons and octagons

We report a possible stable structure of graphene on basis of the first principle calculation. This possible two-dimensional (2D) structure consists of pentagons and octagons (PO), and likely be formed from ordinary graphene by periodically inserting specific defects. Its density is 2.78 Atom/ 2 and the cohesive energy per atom is 8.96 eV, slightly higher than that of graphene. The calculation indicates that PO-graphene behaves like a 2D anisotropic metal. The dispersion relation of electrons near the Fermi surface shows a significant flat segment along a direction and linear behavior in different regions of the Brillouin zone. If the growth of samples is successful, the PO-graphene not only be used as anisotropy conductor and other practical application, but also can be served as a good sample for experiments which need 2D anisotropic materials.