Ultrahigh frequency longitudinal oscillators from single-walled carbon nanotubes

The promising application of single-walled carbon nanotubes as ultrahigh frequency longitudinal oscillators is presented in this paper. A short (3, 3) carbon nanotube is considered as an example and its axial oscillation is investigated by the ab initio molecular dynamics simulations. The effect of the electromechanical coupling on the frequency-domain characteristic is studied. The variation of the electronic structure induced by the geometry deformation produces the anharmonic behavior of the oscillation, while a strong axial electric field hardly affects the eigenfrequencies. A discrete model is also demonstrated to be efficient to describe this oscillation, though the electromechanical coupling effect can not be taken into account, it can predict the fundamental frequency with an error of 0.8% compared with the result of the ab initio molecular dynamics simulation. Additionally, both the discrete model and a continuum hollow rod model are used to predict the fundamental frequencies of the single-walled carbon nanotubes with different lengths and diameters. For a tube shorter than 5 nm, the fundamental frequency is over 1 terahertz.