Role of inter-tube corrugation in the dynamic sliding friction of concentric carbon nanotubes: Implications for nanomechanical oscillator devices

Based upon the experimental realization of low-friction nanoscale bearings, carbon nanotubes (CNTs) attracted interest for designing GHz nested CNT nanomechanical oscillators. A key issue in designing such devices is the energy dissipation during the oscillatory sliding of the inner CNT. In this work, dynamical sliding of concentric double-walled CNTs of nanometer lengths and different commensurations is investigated with molecular dynamics (MD) simulations and a model potential that accounts for inter-tube corrugation. We find that the small variations in energy under inter-tube shifts and rotations, usually not accounted for in classical MD, give rise to a rich dependence of the frictional forces not only on velocity and edge, but also on the contact area and commensuration. Coupled to sliding, there is an unusual self-excited spinning motion, which is also connected to commensuration. These results advance our understanding of dynamical friction and suggest that considerations on interfacial corrugation should not be overlooked when designing CNT oscillators even when their intra-tube gap is around 3.4 Å.