Energetics and stability of vacancies in carbon nanotubes

TL;DR

This study uses ab initio calculations to analyze the formation energies and stability of vacancies in carbon nanotubes, revealing how defect reconstruction and pentagon formation influence energetics and stability.

Contribution

It introduces a model linking defect stability to dangling bonds, pentagon formation, and relaxation effects, advancing understanding of vacancy energetics in nanotubes.

Findings

Reconstruction reduces formation energy by eliminating dangling bonds.

Vacancies with even numbers of removed carbons are more stable.

A model predicts stable defect 'magic numbers' based on defect structure.

Abstract

In this work we present ab initio calculations of the formation energies and stability of different types of multi-vacancies in carbon nanotubes. We demonstrate that, as in the case of graphene, the reconstruction of the defects has drastic effects on the energetics of the tubes. In particular, the formation of pentagons eliminates the dangling bonds thus lowering the formation energy. This competition leads to vacancies having an even number of carbon atoms removed to be more stable. Finally the appearance of magic numbers indicating more stable defects can be represented by a model for the formation energies that is based on the number of dangling bonds of the unreconstructed system, the pentagons and the relaxation of the final form of the defect formed after the relaxation.