Reduction of Activation Energy Barrier of Stone-Wales Transformation in Endohedral Metallofullerenes

TL;DR

This study uses ab initio calculations to show that encapsulating metal atoms inside C60 molecules lowers the activation energy for Stone-Wales transformations, facilitating isomerization of metallofullerenes.

Contribution

It demonstrates that encapsulated metal atoms significantly reduce the activation energy barrier for Stone-Wales transformations in C60, a novel insight into fullerene chemistry.

Findings

Encapsulated K, Ca, La reduce activation barriers by 0.30, 0.55, 0.80 eV respectively.

Lower barriers increase likelihood of isomerization and coalescence.

Charge transfer from metal atoms influences transformation ease.

Abstract

We examine effects of encapsulated metal atoms inside a C$_{60}$ molecule on the activation energy barrier to the Stone-Wales transformation using {\it ab initio} calculations. The encapsulated metal atoms we study are K, Ca and La which nominally donate one, two and three electrons to the C$_{60}$ cage, respectively. We find that isomerization of the endohedral metallofullerene via the Stone-Wales transformation can occur more easily than that of the empty fullerene owing to the charge transfer. When K, Ca and La atoms are encapsulated inside the fullerene, the activation energy barriers are lowered by 0.30, 0.55 and 0.80 eV, respectively compared with that of the empty C$_{60}$ (7.16 eV). The lower activation energy barrier of the Stone-Wales transformation implies the higher probability of isomerization and coalescence of metallofullerenes, which require a series of Stone-Wales transformations.