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. (C) 2017 Elsevier B.V. All rights reserved.