Figure 1

(Color online) Microscopic mechanism of fullerene fusion in peapods. (a) Optimum pathway for the $2{\mathrm{C}}_{60}\to C_{120}$ fusion reaction, involving the smallest number of generalized Stone-Wales bond rotations, determined by a graphical search of all possible bond rotation sequences (Ref. 24). Polygons other than hexagons are emphasized by color and shading. (b) Snapshots of the optimized initial and final structures, and the metastable structures “2” and “3,” depicted in (a). Also shown are two intermediate structures along the optimum fusion pathway between “2” and “3,” resulting from the phase space search by the “string method.” The bond involved in the $2\to 3$ Stone-Wales transformation is emphasized by dark color.Reuse & Permissions

Figure 2

Energetics of the fullerene fusion in peapods. (a) Energy change along the optimum reaction path, given by the solid line (Ref. 38). Energy results for the 25 intermediate structures, shown in Fig. 1, based on our total energy functional (●), are compared to ab initio density functional results (+). The contiguous minimum energy path in configurational space was identified using a “string” technique. (b) Details of the energy change along the optimum path between structures “12” and “13” of Fig. 1, showing several local minima and implying a multistep nature of this Stone-Wales transformation. The activation barrier limiting the reaction rate is denoted by $\Delta E_l$. (c) Energetics of the $(2+2)$ cycloaddition reaction, corresponding to the $0\to 1$ transition in Fig. 1a, which is a necessary prerequisite for the fusion process.Reuse & Permissions