Novel Carbon Nanotubes Rolled From 6,6,12-Graphyne

The versatile exibility of carbon hybridization states(sp,sp2 and sp3)between carbon atoms results in a wide variety of allotropic structures in nature.Such as carbon nanotubes,graphene,graphyne,et.Graphyne is another another interesting 2D carbon allotrope,composing of one atom-thick sheets with both sp in addition to sp2 hybridized carbon atoms.Several different structures of graphyne(?-??-??-and 6,6,12-graphynes)can be obtained by inserting acetylenic linkages into honeycomb structure of the pristine graphene.The single and triple bonds between the carbon atoms in the honeycomb structure endow graphyne systems with a lot of excellent properties,including remarkable chemical stabilities,extremely large surface and uniformly located pores,as well as superior electronic properties.With the development of society,some of them have been carefully studied with different experimental and theoretical methods.Two kinds of carbon nanotubes,namely(N,0)and(0,N)6,6,12-Gy NTs,are constructed by rolling up the rectangular 6,6,12-graphyne sheets along two different sides into cylinders.The mechanic and electronic properties of 6,6,12-Gy NTs with varied N from 3 to 20 are investigated by using density functional theory(DFT).Unlike the single wall carbon nanotubes(SWCNTs),the Young's moduli of 6,6,12-Gy NTs are not remained constant in case of(N,0),but the(0,N)tubes possess almost the same one around 0.32 TPa.The band structures and density of states are also exhibited in this work.When the tube sizes N are bigger than four,Dirac points appear at the Fermi level in the band maps of(N,0)type 6,6,12-Gy NTs,while the(0,N)tubes are narrow gap semiconductors with tiny band gaps between 5.5 and 247.3 me V.