Effects of Bending on Raman-active Vibration Modes of Carbon Nanotubes

TL;DR

This study explores how bending affects the vibrational modes and Raman activity of single-walled carbon nanotubes, revealing that bending can induce Raman activity and significantly alter spectral features.

Contribution

The paper introduces novel boundary conditions in density-functional tight-binding calculations to analyze bending effects on Raman-active modes in carbon nanotubes.

Findings

Raman activity can be induced by bending nanotubes.

High-energy Raman peaks shift and change intensity with bending.

Node migration explains spectral changes.

Abstract

We investigate vibration modes and their Raman activity of single-walled carbon nanotubes that are bent within their intrinsic elastic limits. By implementing novel boundary conditions for density-functional based tight-binding, and using non-resonant bond polarization theory, we discover that Raman activity can be induced by bending. Depending on the degree of bending, high-energy Raman peaks change their positions and intensities significantly. These effects can be explained by migration of nodes and antinodes along tube circumference. We discuss the challenge of associating the predicted spectral changes with experimental observations.