Abstract
Carbon nanotubes (CNTs) with homogeneous diameters have been proven to transform into new carbon allotropes under pressure but no studies on the compression of inhomogeneous CNTs have been reported. In this study, we propose to build new carbon allotropes from the bottom-up by applying pressure on symmetry-matched inhomogeneous CNTs. We find that the (3,0) CNT with point group C3v and the (6,0) CNT with point group C6v form an all sp3 hybridized hexagonal 3060-Carbon crystal, but the (4,0) CNT with point group D4h and the (8,0) CNT with point group D8h polymerize into a sp2+sp3 hybridized tetragonal 4080-Carbon structure. Their thermodynamic, mechanical and dynamic stabilities show that they are potential carbon allotropes to be experimentally synthesized. The multiporous structures, excellently mechanical properties and special electronic structures (semiconductive 3060-Carbon and semimetallic 4080-Carbon) imply their many potential applications, such as gases purification, hydrogen storage and lightweight semiconductor devices. In addition, we simulate their feature XRD patterns which are helpful for identifying the two carbon crystals in future experimental studies.
Highlights
Carbon with sp, sp[2], and sp[3] hybridization states can form numerous polymorphs
We find that the (3,0) Carbon nanotubes (CNTs) with point group C3v and the (6,0) CNT with point group C6v form an all sp[3] hybridized hexagonal 3060-Carbon crystal, but the (4,0) CNT with point group D4h and the (8,0) CNT with point group D8h polymerize into a sp2+sp[3] hybridized tetragonal 4080-Carbon structure
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 sp2diamond 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 C4,26 carbon schwarzites,[27] K4-carbon,[28] T6 and T14-carbon.[29]
Summary
Sp[2], and sp[3] hybridization states can form numerous polymorphs. 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 sp2diamond 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 C4,26 carbon schwarzites,[27] K4-carbon,[28] T6 and T14-carbon.[29]. Graphene is a soft semimetal[4,5] and the net W carbon, K4 crystal carbon, T6-carbon, T14-carbon, GT-8 and CT-12 are reported to be metallic carbon.[10,12,28,29] The hP3 and tI12 are the densest carbon crystals,[21] but carbon schwarzites, T-Carbon, T6 and T14-Carbon are lightweight carbon materials.[15,27,29] Among all carbon allotropes experimentally synthesized, graphdiyne occupies an important position because of its many potential applications, such as lithium storage[30] and hydrogen purification,[31] and because of its high free energy. Any new carbon allotrope which stability is between graphdiyne and graphite is thermodynamic stable and might be synthesized in future experimental study
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