Bending Induced Rippling and Twisting of Multiwalled Carbon Nanotubes

We report that a twisting deformation mode emerges with the rippling in bent multiwalled carbon nanotubes via atomistic simulations. This mode arises from the curvature-induced lattice mismatch, and is energetically favorable. For the nanotubes with larger radii, twisting may enhance the local strain relaxation. Under the thermal fluctuation, the nucleation of defects involves bond breaking and reconstruction due to strain localization. The defective inner tubes undergo the cyclic torsion, resulting in unstable necking and even failure. Prior to fracture, a monatomic chain is formed under the combination of bending and twisting.

Figure 1

Geometrical morphologies of bent 10-walled CNTs: (a) longitudinal section; (b) three characteristic transversal sections; (c) 3D configuration of deformed MWCNT. Atoms are colored according to potential energy [see color bar in (b)].

Figure 2

Time-sequential series of snapshots for bent carbon nanotube with different shell labels: (a) thermal-activated defects are highlighted by high potential energies, and torsion causes 0-CNT to a ribbonlike flattened shape; (b) twisting mode results in necking effect and formation of monatomic chain in 1-CNT; (c) locally stored strain is released through the twisting mode, with bond breaking and reconstruction in 2-CNT; (d) rippling process of 9-CNT. Atoms are colored according to potential energy [see color bar in Fig. 1b].

Figure 3

Variations of the bending and twisting moments with deformation curvature for 10-walled CNTs. Four snapshots correspond to four typical points, respectively.