Ab-initio structural, elastic, and vibrational properties of carbon nanotubes

TL;DR

This paper uses ab initio calculations to analyze the structural, elastic, and vibrational properties of single-wall carbon nanotubes, examining how these properties vary with radius and chirality, and comparing phonon spectra with zone-folding predictions.

Contribution

It provides detailed ab initio insights into how curvature affects properties of carbon nanotubes and evaluates the accuracy of zone-folding approximation for vibrational spectra.

Findings

Bond distances and elastic moduli vary with tube radius.

Zone-folding approximation is accurate except at low frequencies.

Curvature effects cause deviations from graphite-based expectations.

Abstract

A study based on ab initio calculations is presented on the estructural, elastic, and vibrational properties of single-wall carbon nanotubes with different radii and chiralities. We use SIESTA, an implementation of pseudopotential-density-functional theory which allows calculations on systems with a large number of atoms per cell. Different quantities like bond distances, Young moduli, Poisson ratio and the frequencies of different phonon branches are monitored versus tube radius. The validity of expectations based on graphite is explored down to small radii, where some deviations appear related to the curvature effects. For the phonon spectra, the results are compared with the predictions of the simple zone-folding approximation. Except for the known defficiencies of this approximation in the low-frequency vibrational regions, it offers quite accurate results, even for relatively small radii.