QPHT-graphene: A new two-dimensional metallic carbon allotrope

A new two-dimensional metallic carbon allotrope (QPHT-graphene) composed by quadrangular, pentagonal, hexagonal rings, and large tetradecagonal pores, has been predicted based on the first-principles calculations. The total energy, phonon spectra, and elastic constants calculations as well as MD simulations prove that QPHT-graphene is a metastable carbon phase and can exist at room temperature. The calculations on the mechanical properties show that QPHT-graphene possesses an anisotropic mechanical behavior, and is much softer than graphene. Both GGA-PBE and HSE06 calculations confirm that QPHT-graphene is a metallic carbon allotrope with a much higher electronic density of states of ∼0.15 eV/states per atom at the Fermi level due to the emergence of flat bands. The current prediction further broadens the list of planar metastable carbon allotropes.