Ab initio study of relative motion of walls in carbon nanotubes

We study the interwall interaction and relative motion of walls in carbon nanotubes using density functional theory. The interwall interaction energy surface as a function of relative rotation and sliding of walls is calculated for the (5,5)@(10,10) nanotube. The barriers to relative rotation and sliding are estimated ab initio for the chiral walls of the (8,2)@(16,4) nanotube. These results are used to extract information on experimentally measurable quantities, such as threshold forces, diffusion coefficients, and mobilities of walls. Possible applications of these nanotubes in mechanical nanodevices are discussed. Two distinct regimes of the wall movement exist: athermal, forced movement (accelerating mode) and movement controlled by thermal diffusion (Fokker-Planck mode). We calculate the limits of these regimes from first principles.