Can Barrier to Relative Sliding of Carbon Nanotube Walls Be Measured?

TL;DR

This paper calculates interwall interaction energies and sliding barriers for carbon nanotubes, showing they are nearly independent of radius beyond 5 nm, and discusses how to measure these barriers experimentally.

Contribution

It provides the first detailed calculations of sliding barriers for various nanotube pairs and estimates measurable physical quantities related to these barriers.

Findings

Barriers are nearly radius-independent for radii > 5 nm

Shear strengths and diffusion coefficients are estimated as functions of radius

Maximum overlap for static friction exceeds capillary forces in nonreversible extension

Abstract

Interwall interaction energies, as well as barriers to relative sliding of the walls along the nanotube axis, are first calculated for pairs of both armchair or both zigzag adjacent walls of carbon nanotubes with a wide range of radiuses. It is found that for the pairs with the radius of the outer wall greater than 5 nm both the interwall interaction energy and barriers to the relative sliding per one atom of the outer wall only slightly depends on the wall radius. A wide set of the measurable physical quantities determined by these barriers are estimated as a function of the wall radius: shear strengths and diffusion coefficients for relative sliding of the walls along the axis, as well as frequencies of relative axial oscillations of the walls. For nonreversible telescopic extension of the walls, maximum overlap of the walls for which threshold static friction forces are greater than capillary forces is estimated. Possibility of experimental verification of the calculated barriers by measurements of the estimated physical quantities is discussed.