Microscopic mechanism of fullerene fusion

Combining total energy calculations with a search of phase space, we investigate the microscopic fusion mechanism of C₆₀ fullerenes. We find that the $(2+2)$ cycloaddition reaction, a necessary precursor for fullerene fusion, may be accelerated inside a nanotube. Fusion occurs along the minimum energy path as a finite sequence of Stone-Wales transformations, determined by a graphical search program. Search of the phase space using the ``string method'' indicates that Stone-Wales transformations are multistep processes, and provides detailed information about the transition states and activation barriers associated with fusion.