Numerous new carbon allotropes have been uncovered by compressing carbon nanotubes based on our computational investigation. The volume compression calculations suggest that these new phases have a very high anti-compressibility with a large bulk modulus （B0）. The predicted B0 of new phases is larger than that of c-BN （373 GPa） and smaller than that of diamond （453 GPa）. All of the predicted structures are superhard transparent materials with a larger band gap and possess the covalent characteristics with sp3-hybridized electronic states. The simulated results will help us better understand the structural phase transition of cold-compressed carbon nanotubes.
In order to explore the transport properties of nonsymmetric three-terminal T-shaped graphene nanoribbons (GNRs) devices,the nonequilibrium Green's function method and Landauer-Buttiker formula were adopted. It shows that the transport properties of T-shaped GNRs are highly sensitive to the details of the leads. The T-shaped GNRs show metallic characteristics when electrons transmit from the metallic GNRs lead to the metallic GNRs lead, while the T-shaped GNRs show semiconducting characteristics when electrons transmit from the metallic GNRs lead to the semiconducting GNRs lead. The conductance between the random two leads can be adjusted by varying the size of the leads.
A new family of superhard carbon allotropes C48（2i ＋ 1 ） is constructed by alternating even 4 and 8 membered rings. These new carbon allotropes are of a spatially antisymmetrical structure, compared with the symmetrical structures of bet- C4, Z-carbon, and P-carbon. Our calculations show that bulk moduli of C48（2i ＋ 1 ） are larger than that of c-BN and smaller than that of cubic-diamond. C48（2i ＋ 1 ） are transparent superhard materials possessing large Vicker hardness comparable to diamoud. This work can help us understand the structural phase transformations of cold-compression graphite and carbon nanotubes.
