Peculiarities of low-frequency vibrational dynamics and low-temperature heat capacity of double-walled carbon nanotubes

TL;DR

This paper develops a model for low-frequency vibrational dynamics and heat capacity of double-walled carbon nanotubes, highlighting the impact of interlayer coupling on their thermal properties at low temperatures.

Contribution

It introduces a continuous model for DWCNT low-frequency phonons and a novel method to evaluate van der Waals coupling coefficients using Raman data.

Findings

DWCNT specific heat is lower than the sum of individual SWCNTs at temperatures below 35 K.

Interlayer coupling significantly influences DWCNT vibrational and thermal properties.

The model effectively describes environmental effects on DWCNT phonon spectra.

Abstract

A continuous model of double-walled carbon nanotube (DWCNT) low-frequency dynamics was constructed. In the frame of the approach proposed formation of a DWCNT low-frequency phonon spectrum from the ones of corresponding single-walled carbon nanotubes (SWCNTs) was considered. Environmental influence on the individual DWCNT phonon spectrum was studied. A combined method of van der Waals interlayer coupling coefficients evaluation was proposed, and it is based on Raman spectroscopy data and known values of graphite elastic moduli. Also DWCNT low-temperature specific heat was calculated. In the model applicability region (at temperatures lower than 35 K) DWCNT specific heat turned out to be significantly lower than the specific heat sum of corresponding individual single-walled SWCNTs. This effect is caused mainly by the interlayer coupling instead of DWCNT interaction with environment.