Bending Deformation of Single-Walled Carbon Nanotubes Caused by 5–7 Pair Couple Defect

Abstract

The characteristics of 5 -7 pair couple defects formed in single-walled carbon nanotubes were investigated. For armchair nanotubes with diameters from 6.8 to 13.6 A ˚, such defects were formed by removing atoms. Structural optimization, which was carried out using tight-binding molecular dynamics, resulted in the bending deformation of the nanotubes due to the defects. The resulting stable structure was found to change with the number of atoms removed, showing a bending angle of 16.6 for a diameter of 10.7 A ˚. The dependence of bending angle on the diameter of nanotubes was analysed using a simple model. As results, several sets of 5 -7 pair couple defects were found to be necessary in order to induce plastic deformation that was experimentally observed in nanotubes.

Ab initio study on the electronic transport properties of carbon nanotube intramolecular junctions

“…The microscopic details about the connections between carbon nanotubes are very clear 38, 39. Namely, just like in pristine CNTs, in carbon nanotube junctions, all carbon atoms including connecting atoms tend to be sp 2 hybridized and thus 5–7 pair defects are formed at the interface which breaks the topological hexagonal geometry.…”

Effects of a bent structure on the linear viscoelastic response of diluted carbon nanotube suspensions

“…For example, it has been demonstrated that a bent structure is thermodynamically more stable than a straight one once a localized topological defect appears in the SWNT growth (Xue et al 2009). Additionally, it has been shown that a single pentagonheptagon pair can bend the SWNT tubular structure forming a localized junction (Ajayan et al 1998) with angles varying from 0 • to 34 • (Han et al 1998;Wako et al 2008) depending on the distance between the pentagon and heptagon pair defect (Lambin and Meunier 1999).…”

Shear‐strain step response in linear regime of dilute suspensions of naturally bent carbon nanotubes

“…Persistence length of SWNTs approaches its physical length L ( L p ∼ L ) in absence of external forces and/or under the action of an external flow field51, 52 and, hence, can be represented by semiflexible filaments. In addition, we are tackling with slender systems exhibiting a bent structure in absence of external forces due to the existence of structural defects (e.g., topological defects on the honeycomb‐like lattices of CNTs) 39–45. Previous physical model can also be extended for representing the structure of stiff macromolecules with sterical‐hindered dihedral angles as short DNA, collagen fibrils, rod‐like viruses and some synthetic polymers 32…”

“…In addition, considering the probable existence of topological bent defects on the CNT structure, BD simulations of small‐amplitude oscillatory deformation tests on dilute suspensions of SWNTs (mimicked by semiflexible chain models with a natural bent configuration) demonstrated that nonnegligible differences exist with respect to the dynamic response of dilute suspensions of semiflexible chains with naturally straight configurations 38. The assumption of the natural existence of bent junctions in the CNT structure is justified by two facts: The common apparition of topological defects (for instance, pentagon/heptagon pair defect) during the CNT synthesis39 that can induce several kinds of curvatures on the CNT structure according to the specific morphology of the localized defect 40–45 The experimental evidence obtained by Fresnel projection microscopy,46 scanning tunnelling microscopy (STM),47, 48 voltage‐contrast scanning electron microscopy (VC‐SEM),49 and atomic force microscopy (AFM)50 revealing both the presence of localized junctions on CNT structures and a generalized tortuosity in CNT samples. …”

“…The common apparition of topological defects (for instance, pentagon/heptagon pair defect) during the CNT synthesis39 that can induce several kinds of curvatures on the CNT structure according to the specific morphology of the localized defect 40–45…”