  Using systematic evolutionary structure searching we propose a new carbon
allotrope, phagraphene, standing for penta-hexa-hepta-graphene, because the
structure is composed of 5-6-7 carbon rings. This two-dimensional (2D) carbon
structure is lower in energy than most of the predicted 2D carbon allotropes
due to its sp2-hybridization and density of atomic packing comparable to
graphene. More interestingly, the electronic structure of phagraphene has
distorted Dirac cones. The direction-dependent cones are further proved to be
robust against external strain with tunable Fermi velocities.
