Substantial reduction of Stone-Wales activation barrier in fullerene

TL;DR

This study demonstrates that substitutional boron doping in fullerenes drastically lowers the Stone-Wales activation barrier, facilitating defect formation and potentially impacting the properties and transformations of carbon nanostructures.

Contribution

First-principles calculations reveal that boron doping reduces the Stone-Wales barrier in fullerenes more than other known mechanisms, enabling new pathways for nanostructure modification.

Findings

Boron doping reduces the activation barrier from ~7 eV to 2.54 eV.

Bond weakening at the active site causes the barrier reduction.

Doping influences defect formation and properties of carbon nanostructures.

Abstract

Stone-Wales transformation is a key mechanism responsible for growth, transformation, and fusion in fullerene, carbon nanotube and other carbon nanostructures. These topological defects also substantially alter the physical and chemical properties of the carbon nanostructures. However, this transformation is thermodynamically limited by very high activation energy (\sim 7 eV in fullerene), which can get reduced due to the presence of hydrogen, extra carbon atom, or due to endohedral metal doping. Using first-principles density functional calculations, we show that the substitutional boron doping substantially reduces the Stone-Wales activation barrier (from \sim 7 eV to 2.54 eV). This reduction is the largest in magnitude among all the mechanisms of barrier reduction reported till date. Analysis of bonding charge density and phonon frequencies suggests that the bond weakening at and around the active Stone-Wales site in B-heterofullerene is responsible for such reduction. The formation of Stone-Wales defect is, therefore, promoted in such heterofullerenes, and is expected to affect their proposed H2 storage properties. Such substitutional doping can also modify the Stone-Wales activation barrier in carbon nanotube and graphene naonostructures, and catalyze isomerization, fusion, and nanowelding processes.