Symmetry-Adapted Tight-Binding Electronic Structure Analysis of Carbon Nanotubes with Defects, Kinks, Twist, and Stretch

TL;DR

This paper introduces a symmetry-adapted computational method to analyze how various deformations and defects affect the electronic and band structures of carbon nanotubes, providing accurate insights into defect-induced localized states.

Contribution

The paper develops a symmetry-adapted approach combined with perfectly-matched layers to efficiently study electronic structures of deformed and defective nanotubes, including localized defect modes.

Findings

Stretch and twist influence band structure in nanotubes.

Vacancy defects interact with mechanical deformations.

Localized defect modes are identified within the bandgap.

Abstract

This paper applies a symmetry-adapted method to examine the influence of deformation and defects on the electronic structure and band structure in carbon nanotubes. First, the symmetry-adapted approach is used to develop the analog of Bloch waves. Building on this, the technique of perfectly-matched layers is applied to develop a method to truncate the computational domain of electronic structure calculations without spurious size effects. This provides an efficient and accurate numerical approach to compute the electronic structure and electromechanics of defects in nanotubes. The computational method is applied to study the effect of twist, stretch, and bending, with and without various types of defects, on the band structure of nanotubes. Specifically, the effect of stretch and twist on band structure in defect-free conducting and semiconducting nanotubes is examined, and the interaction with vacancy defects is elucidated. Next, the effect of localized bending or kinking on the electronic structure is studied. Finally, the paper examines the effect of 5-8-5 Stone-Wales defects. In all of these settings, the perfectly-matched layer method enables the calculation of localized non-propagating defect modes with energies in the bandgap of the defect-free nanotube.