title: Novel superhard carbon: C-centered orthorhombic C8.
abstract: A novel carbon allotrope of C-centered orthorhombic C(8) (Cco-C(8)) is predicted by using a recently developed particle-swarm optimization method on structural search. Cco-C(8) adopts a sp(3) three-dimensional bonding network that can be viewed as interconnected (2,2) carbon nanotubes through 4- and 6-member rings and is energetically more favorable than earlier proposed carbon polymorphs (e.g., M carbon, bct-C(4), W carbon, and chiral C(6)) over a wide range of pressures studied (0-100 GPa). The simulated x-ray diffraction pattern, density, and bulk modulus of Cco-C(8) are in good accordance with the experimental data on structurally undetermined superhard carbon recovered from cold compression of carbon nanotube bundles. The simulated hardness of Cco-C(8) can reach a remarkably high value of 95.1 GPa, such that it is capable of cracking diamond.
authors.affiliation: State Key Laboratory of Metastable Materials Science and Technology, Yanshan University, Qinhuangdao, China.
authors.forename: Zhisheng
authors.initials: Z
authors.lastname: Zhao
authors.forename: Bo
authors.initials: B
authors.lastname: Xu
authors.forename: Xiang-Feng
authors.initials: XF
authors.lastname: Zhou
authors.forename: Li-Min
authors.initials: LM
authors.lastname: Wang
authors.forename: Bin
authors.initials: B
authors.lastname: Wen
authors.forename: Julong
authors.initials: J
authors.lastname: He
authors.forename: Zhongyuan
authors.initials: Z
authors.lastname: Liu
authors.forename: Hui-Tian
authors.initials: HT
authors.lastname: Wang
authors.forename: Yongjun
authors.initials: Y
authors.lastname: Tian