Wall "thickness" effects on Raman spectrum shift, thermal conductivity, and Young's modulus of single walled nanotubes

TL;DR

This paper theoretically investigates how the effective wall thickness of single walled carbon nanotubes, including thermal vibrations, influences their Raman spectrum, Young's modulus, and thermal conductivity, revealing temperature-dependent effects.

Contribution

It introduces a model combining static and dynamic thickness to explain temperature effects on nanotube properties, supported by simulations and theoretical analysis.

Findings

Dynamic thickness increases with temperature as √T.

Dynamic thickness significantly affects Raman spectrum shifts.

Inclusion of dynamic thickness alters Young's modulus and reduces thermal conductivity estimates.

Abstract

We theoretically demonstrate that at a finite temperature, an effective wall thickness of a single walled carbon nanotube (SWNT) should be $W=W_s+W_d$, where $W_s$ is the static thickness defined as the extension of the outmost electronic orbit and $W_d$ the dynamic thickness due to thermal vibration of atoms. Both molecular simulations and a theoretical analysis show that $W_d$ is proportional to $\sqrt{T}$. We find that the increase of dynamic thickness with temperature is the main mechanism of Raman spectrum shift. The introduction of dynamic thickness changes some conclusions about the Young's modulus and reduces the values of thermal conductivity.