Influence of electron quantum confinement on the strength of carbon nanotube bundles

Radial confinement and specific boundary conditions lead to inhomogeneous spatial distributions for conduction electrons in metallic carbon nanotubes.Such uneven spread of negative charge on the surface of a carbon nanotube can induce Coulomb-type interactions between parallel tubes, contributing to the relative friction. Thus, the axial conduction electron density on a single idealized carbon nanotube closed at both ends was obtained in the framework of the two-dimensional quasi-free electron approximation. A Coulomb potential energy between two parallel nanotubes was calculated as a function of the longitudinal offset between them. The study provides a simple method for estimating the friction force related to Coulomb inter-tube interactions appearing during a parallel sliding motion, with implications in the stretching resistance of various carbon nanotube bundles and in designing various nano-electromechanical devices.