Nanoscale high friction in double- and triple-wall carbon nanotubes: a molecular dynamics study

Understanding friction in carbon nanotube (CNT) assemblies is
essential for the development of nanoscale mechanical systems and CNT-
based tribological interfaces. In this work, non-equilibrium molecular dynamics
simulations are employed to investigate frictional sliding in layered CNT systems,
focusing on double-wall (DWCNT) and triple-wall (TWCNT) configurations.
Armchair nanotubes with diameters corresponding to different chiralities were
considered, while the overlap ratio and nanotube length were systematically varied
to explore their influence on friction. The results reveal pronounced stick-slip
dynamics and demonstrate that the effective friction coefficient depends strongly
on nanotube diameter, overlap ratio, and wall multiplicity. For DWCNTs, the
friction coefficient varies in the range μ ≈ 2.0-5.2, whereas TWCNTs exhibit
slightly lower values in the range μ ≈ 1.5-4.5 due to the presence of an
additional sliding interface and increased radial stiffness. Thin nanotubes display
a compliance-dominated regime in which bending-mediated relaxation can reduce
friction at large overlap ratios, while larger diameters exhibit a corrugation-
dominated regime characterized by a monotonic increase in friction with contact
area. Temperature elevation induces a moderate friction reduction while high
temperatures lead to structural deformation in thin nanotubes. These findings
provide atomistic insight into friction regulation in CNT assemblies and offer
design guidelines for tunable nanoscale tribological interfaces.