title: A new carbon allotrope with six-fold helical chains in all-sp2 bonding networks.
abstract: Using a recently developed approach to constructing covalent network structures from linear carbyne, we identify by ab initio calculations a new carbon allotrope in R3m (D(3d)(5) symmetry that comprises six-fold helical chains with alternating sp(2)-type single and double bonds along the chains that are connected via zigzag benzene rings. This 6-fold carbene is characterized as a three-dimensional three-connected chiral crystalline modification of graphite. Phonon and electronic band calculations indicate that this new structure is dynamically stable and is a semiconductor with a band gap of 0.47 eV, in contrast to the semimetallic nature of graphite. Simulated x-ray diffraction patterns of the 6-fold carbene provide an excellent match to the previously unexplained distinct diffraction peak of a new carbon allotrope found in recent detonation experiments. These results establish a new carbon phase and offer insights into its outstanding structural and electronic properties.
authors.affiliation: Beijing National Laboratory for Condensed Matter Physics, Institute of Physics, Chinese Academy of Sciences, Beijing 100190, China.
authors.forename: Jian-Tao
authors.initials: JT
authors.lastname: Wang
authors.affiliation: Department of Physics and High Pressure Science and Engineering Center, University of Nevada, Las Vegas, Nevada 89154, USA.
authors.forename: Changfeng
authors.initials: C
authors.lastname: Chen
authors.affiliation: International Center for Quantum Materials, School of Physics, Peking University, and Collaboration Innovation Center of Quantum Matter, Beijing 100871, China.
authors.forename: Enge
authors.initials: E
authors.lastname: Wang
authors.affiliation: 1] New Industry Creation Hatchery Center, Tohoku University, Sendai 980-8579, Japan [2] Institute of Thermophysics, Siberian Branch of Russian Academy of Sciences, Novosibirsk 630090, Russia.
authors.forename: Yoshiyuki
authors.initials: Y
authors.lastname: Kawazoe