Dynamics of Fullerene Coalescence

Fullerene coalescence experimentally found in fullerene-embedded single-wall nanotubes under electron-beam irradiation or heat treatment is simulated by minimizing the classical action for many atom systems. The dynamical trajectory for forming a (5,5) ${\mathrm{C}}_{\mathrm{120}}$ nanocapsule from two ${\mathrm{C}}_{\mathrm{60}}$ fullerene molecules consists of thermal motions around potential basins and ten successive Stone-Wales–type bond rotations after the initial cage-opening process for which energy cost is about 8 eV. Dynamical paths for forming large-diameter nanocapsules with (10,0), (6,6), and (12,0) chiral indexes have more bond rotations than 25 with the transition barriers in a range of 10–12 eV.

Figure 1

Initial and final states for forming various ${\mathrm{C}}_{\mathrm{120}}$ nanocapsules as precursors for fullerene-based nanotube growth.

Figure 2

Potential energy variation along the obtained dynamical trajectories of fullerene coalescence for forming various ${\mathrm{C}}_{\mathrm{120}}$ nanocapsules. In (a) and (b), the solid (dotted) lines indicate the potential (total) energy of the (5,5) and (10,0) capsules, respectively, along the time step. We divide the trajectories into three parts as reactant, activation, and product regions in series. In (a), ten small arrows correspond to ten Stone-Wales-type bond rotations. In (b), the single arrow indicates when the intermediate (5,5) capsule arises. In (c), we depict the potential energy variation in the case of the (6,6) and (12,0) ${\mathrm{C}}_{\mathrm{120}}$ capsules. Also, the small arrow indicates the forming of the intermediate (6,6) capsule in the trajectory of the (12,0) capsule.