Electromechanical characterization of carbon nanotubes in torsion via symmetry adapted tight-binding objective molecular dynamics

Abstract

The nonlinear elastic response of carbon nanotubes ͑CNTs͒ in torsion is derived with objective molecular dynamics and a density-functional-based tight-binding model. The critical strain beyond which CNTs behave nonlinearly, the most favorable rippling morphology, and the twist-and morphology-related changes in fundamental band gap are identified from a rigorous atomistic description. There is a sharply contrasting behavior in the electronic response: while in single-walled CNTs the band-gap variations are dominated by rippling, multiwalled CNTs with small cores exhibit an unexpected insensitivity. Results are assistive for experiments performed on CNT-pedal devices.

Buckling of single-walled carbon nanotubes using two criteria

“…This implies that the tube buckled in the (2,1) mode at c ¼ 4.6%. Using objective MD, Zhang et al 26 found a similar bifurcation in the potential energy for infinitely long (12,12) SWCNT deformed in torsion. Their critical value of the shear strain, 6.2%, is about 30% higher than the present value of 4.6%.…”

“…23 . The exponent 1.23 is between 1.5 obtained by Yakobson et al 2 and 0.99 by Zhang et al 26 which could be due to the consideration of finite length SWCNTs with clamped ends. From Fig.…”

“…They also found that at / ¼ 4 /nm the morphology of the SWCNT changed from cylindrical to that of a twisted shell with two circumferential waves. Using symmetry arguments, they 26 identified the sequence of bifurcation points corresponding to different morphologies and also determined mode shapes corresponding to the lowest energy. For a three-walled CNT, they deduced similar results.…”

“…Zhang et al 26 studied nonlinear elastic response of infinitely long armchair SWCNTs in torsion using objective MD. In the objective MD, 48 the potential is simplified by considering the helical symmetry rather than invariance with respect to translations only.…”

Thin-shell theory based analysis of radially pressurized multiwall carbon nanotubes

“…The salient feature of carbon nanotubes is their mechanical robustness and resilience [6]: Due to the extremely large stiffness, for instance, their thermal conductivity becomes higher than even that of diamond [7]. Besides, their flexibility in bending [8,9], twisting [9,10,11,12], radial compression [13,14,15,16,17], and the associated variations in the physical properties hold promise for developing nanoelectromechanical devices [18,19]. Towards successful implementations of such ideas, computational studies have been playing a vital role in complementing experimental observations, often difficult and incomplete for nanomaterials [20].…”