Substantial reduction of Stone-Wales activation barrier in fullerene

Abstract

Stone-Wales (SW) transformation is a key mechanism responsible for the growth, transformation, and fusion in fullerenes, carbon nanotubes, 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 ($\ensuremath{\sim}7\phantom{\rule{0.28em}{0ex}}\mathrm{eV}$ in fullerenes). Using first-principles density functional calculations, we show that the substitutional boron doping substantially reduces the SW activation barrier (from $\ensuremath{\sim}7$ to 2.54 eV). This reduction is the largest in magnitude among all the mechanisms of barrier reduction reported to date. Analysis of bonding charge density and phonon frequencies suggests that the bond weakening at and around the active SW site in B heterofullerenes is responsible for such a reduction. Therefore, the formation of the SW defect is promoted in such heterofullerenes and is expected to affect their proposed ${\mathrm{H}}_{2}$ storage properties. Such substitutional doping also can modify the SW activation barrier in carbon nanotubes and graphene nanostructures and can catalyze isomerization, fusion, and nanowelding processes.