title: T-carbon: a novel carbon allotrope.
abstract: A structurally stable crystalline carbon allotrope is predicted by means of the first-principles calculations. This allotrope can be derived by substituting each atom in diamond with a carbon tetrahedron, and possesses the same space group Fd3m as diamond, which is thus coined as T-carbon. The calculations on geometrical, vibrational, and electronic properties reveal that T-carbon, with a considerable structural stability and a much lower density 1.50  g/cm3, is a semiconductor with a direct band gap about 3.0 eV, and has a Vickers hardness 61.1 GPa lower than diamond but comparable with cubic boron nitride. Such a form of carbon, once obtained, would have wide applications in photocatalysis, adsorption, hydrogen storage, and aerospace materials.
authors.affiliation: College of Physical Sciences, Graduate University of Chinese Academy of Sciences, P.O. Box 4588, Beijing 100049, China.
authors.forename: Xian-Lei
authors.initials: XL
authors.lastname: Sheng
authors.forename: Qing-Bo
authors.initials: QB
authors.lastname: Yan
authors.forename: Fei
authors.initials: F
authors.lastname: Ye
authors.forename: Qing-Rong
authors.initials: QR
authors.lastname: Zheng
authors.forename: Gang
authors.initials: G
authors.lastname: Su
mesh_terms: D000327:Adsorption; D001896:Boron Compounds / Q000737:chemistry; D002244:Carbon / Q000737:chemistry*; D003460:Crystallization / Q000379:methods*; D018130:Diamond / Q000737:chemistry*; D004581:Electronics; D006244:Hardness; D006859:Hydrogen; D008420:Manufactured Materials; D008956:Models, Chemical; D014732:Vibration
chemical_list: D001896:Boron Compounds; C017282:boron nitride; D002244:Carbon; D018130:Diamond; D006859:Hydrogen