Twist-direction-dependent buckling behaviors of single-walled carbon nanotubes

The twist-induced buckling behaviors of single-walled carbon nanotubes (SWCNTs) are studied by a nonlinear structural-mechanics finite element method proposed in this paper, which is essentially an efficient molecular mechanics method. For chiral carbon nanotubes, it is found that the critical torsion angle of buckling for two opposite twisting directions may be significantly different, e.g., up to 50% amplitude difference can be observed in (6,3) CNT. More interestingly, we noted that by taking the wall thickness h as 0.1 nm, the shell theory is able to accurately predict the critical torsion angles of armchair, zigzag and chiral SWCNTS under positive torsion (see the definition in the text), but fails to predict those of the chiral SWCNTs under negative torsion.