Octagraphene as a versatile carbon atomic sheet for novel nanotubes, unconventional fullerenes, and hydrogen storage

摘要

We study a versatile structurally favorable periodic $sp^2$-bonded carbonatomic planar sheet with $C_{4v}$ symmetry by means of the first-principlescalculations. This carbon allotrope is composed of carbon octagons and squareswith two bond lengths and is thus dubbed as octagraphene. It is a semimetalwith the Fermi surface consisting of one hole and one electron pocket, whoselow-energy physics can be well described by a tight-binding model of$pi$-electrons. Its Young's modulus, breaking strength and Poisson's ratio areobtained to be 306 $N/m$, 34.4 $N/m$ and 0.13, respectively, which are close tothose of graphene. The novel sawtooth and armchair carbon nanotubes as well asunconventional fullerenes can also be constructed from octagraphene. It isfound that the Ti-absorbed octagraphene can be allowed for hydrogen storagewith capacity around 7.76 wt%.