Length dependent stability of single-walled carbon nanotubes and how it affects their growth

Daniel Hedman,J Andreas Larsson

doi:10.1016/j.carbon.2017.02.007

Daniel Hedman, J Andreas Larsson

Open Access

https://doi.org/10.1016/j.carbon.2017.02.007

Copy DOI

Journal: Carbon	Publication Date: Feb 6, 2017
Citations: 14	License type: cc-by

Affiliation: Luleå University of Technology

Abstract

Using density-functional theory the stability of armchair and zigzag single-walled carbon nanotubes and graphene nanoribbons was investigated. We found that the stability of armchair and zigzag nanotubes has different linear dependence with regard to their length, with switches in the most stable chirality occurring at specific lengths for each nanotube series. We explain these dependencies by competing edge and curvature effects. We have found that within each series armchair nanotubes are the most stable at short lengths, while zigzag nanotubes are the most stable at long lengths. These results shed new insights into why (near) armchair nanotubes are the dominant product from catalytic chemical vapor deposition growth, if templating is not used. Paradoxically, the stability of armchair nanotubes at short lengths favors their growth although zigzag nanotubes are more stable at long lengths, resulting in the production of the least stable nanotubes.

Highlights

Since the discovery of single-walled carbon nanotubes (SWCNTs) [1e3] and their remarkable properties [4,5], huge amount of time and effort from both experimental and theoretical researchers has been spent in order to unravel their growth process [6]
We present new results connecting the relative energy of armchair and zigzag SWCNT-fragments to their length, expanding on the results of our previous paper [11], and answering the question of why products from catalytic chemical vapor deposition (CVD) growth shows a strong preference towards armchair and near-armchair chirality
A diameter selectivity narrower than 0.34 Å is required in order to single out zigzag SWCNTs, which is currently not experimentally feasible

Summary

Introduction

Since the discovery of single-walled carbon nanotubes (SWCNTs) [1e3] and their remarkable properties [4,5], huge amount of time and effort from both experimental and theoretical researchers has been spent in order to unravel their growth process [6]. 11 (diameter above $ 8Å), the relative energy switches towards armchair (n 1⁄4 m) and near-armchair (nzm) short SWCNTfragments being the most stable. This correlation with experiment is rather insensitive to other growth parameters, such as feed-stock, pressure, and catalytic particle composition, as long as the temperature is optimized for SWCNT growth and the metals catalytic ability is satisfied [12,13]. We present new results connecting the relative energy of armchair and zigzag SWCNT-fragments to their length, expanding on the results of our previous paper [11], and answering the question of why products from catalytic CVD growth shows a strong preference towards armchair and near-armchair chirality

Computational model

Results and discussion

Conclusions