Length difference effect on dynamic behaviors of double-walled carbon nanotubes

The effect of length difference on oscillation and rotation of the inner tube in a double-walled carbon nanotube (DWNT) is investigated. In the analysis, the inner tubes of the DWNTs are assumed to be of the same length but the length of the outer tubes may be different from that of inner tubes. Further, the outer tube is entirely fixed after adequate relaxation at 300 K and the inner tube is unconstrained and can move freely in the outer tube. In the simulations, each bi-tube system initially has a symmetric crosssection, and the inner tube oscillates while rotating along its own axis. The dynamic behavior studied includes oscillation and rotation of the inner tubes. The oscillation decreases along with an increase in the length difference. A greater length difference between the two tubes in a bi-tube system leads to a smaller amplitude of oscillation of mass center of the inner tube (MCIT) and a higher self-rotating speed. Moreover, the inner tube in a bi-tube with different chirality of the two tubes may have different self-rotational directions.