Vibrational and elastic properties of 2D carbon allotropes: A first principles study

The present paper reports the calculated vibrational and elastic properties of some two dimensional carbon allotropes such as graphene, α-, β- and γ-graphynes using first principles density functional theory. The phonon modes of graphynes show quite distinct behavior than graphene and have real frequency throughout the Brillouin zone thus indicating dynamically stable structures. The out of plane, ZA mode is more dispersive in the case of graphynes. We have discussed the implications of phonon modes to the thermal conductance in graphynes and graphene. We have also calculated the elastic constants for graphene and graphynes. Calculated elastic constants of graphynes show more anisotropic conformer nature than graphene.