Electronic and optical trends in carbon nanotubes under pure bending

TL;DR

This paper presents a cost-effective modeling approach to study how small bending affects the electronic and optical properties of carbon nanotubes, revealing chirality-dependent trends crucial for their application.

Contribution

It introduces a revised periodic boundary condition method combined with density-functional tight-binding to accurately model bent nanotubes under small deformations.

Findings

Bending induces chirality-dependent changes in electronic properties.

Optical properties are similarly affected by small bending.

Full structural relaxation is necessary for precise trend prediction.

Abstract

The high aspect ratio of carbon nanotubes makes them prone to bending. To know how bending affects the tubes is therefore crucial for tube identification and for electrical component design. Very few studies, however, have investigated tubes under small bending well below the buckling limit, because of technical problems due to broken translational symmetry. In this Letter a cost-effective and exact modeling of singe-walled nanotubes under such small bending is enabled by revised periodic boundary conditions, combined with density-functional tight-binding. The resulting, bending-induced changes in electronic and optical properties fall in clear chirality-dependent trend families. While the correct trends require full structural relaxation, they can be understood by one general argument. To know these trends fills a fundamental gap in our understanding of the properties of carbon nanotubes.