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.

From soft to superhard: Fifty years of experiments on cold-compressed graphite

“…One parameter to evaluate a material's strength is its hardness, however, M-carbon has not been recovered at ambient conditions, thus a hardness measurement is lacking. However, the hardness obtained from theoretical computations (83.1 GPa [55], 91.5 GPa [58]) suggest that this high-pressure graphite phase is a superhard material.…”

Computational prediction of body-centered cubic carbon in an all-sp3six-member ring configuration

“…3 These discoveries have stimulated great interest in search of more carbon allotropes. [4][5][6][7][8] A particularly appealing approach is to explore new carbon phases under extreme conditions, such as high pressure or shock compression, which can induce new bonding modifications. A prominent example is the recent discovery of cold-compressed graphite 9 that has led to the identification of several new carbon forms.…”

Multiporous carbon allotropes transformed from symmetry-matched carbon nanotubes

“…Besides the well-known diamond, graphite, fullerenes, 1 carbon nanotube(CNTs), 2 amorphous carbon 3 and graphene, 4,5 many other carbon allotropes have been presented in the past decade, including graphdiyne, 6 bcc-C6, 7 HOP graphene, 8 oC32, 9 net W carbon, 10 H-net, 11 GT-8 and CT-12, 12 sp 2 -diamond and cubic-graphite, 13 oP24-I, oP24-II, oP20, oP28, mP16 and mS32, 14 T-carbon, 15 OPG-L and OPG-Z, 16 hexagon-preserving carbon foams, 17 O-carbon, 18 amorphous diamond, 19 R and P carbon, 20 hP3 tI12, and tP12, 21 yne-carbon and tetrayne-carbon, 22 T graphene, 23 oC16, 24 X-carbon and Y-carbon, 25 bct C 4 , 26 carbon schwarzites, 27 K 4 -carbon, 28 T 6 and T 14 -carbon. 29 Their mechanical and electrical properties vary significantly from superhard to soft and from metallic to insulating, which enriches the real applications of carbon materials tremendously.…”

“…10,12,28,29 The hP3 and tI12 are the densest carbon crystals, 21 but carbon schwarzites, T-Carbon, T 6 and T 14 -Carbon are lightweight carbon materials. 15,27,29 Among all carbon allotropes experimentally synthesized, graphdiyne occupies an important position not only because of its many potential applications, such as lithium storage 30 and hydrogen purification, 31 but also because of its high free energy. It might be the least stable carbon allotrope experimentally synthesized until now.…”