Tight-binding molecular dynamics simulations of radiation-induced fragmentation ofC60

Abstract

The fragmentation of the ${\mathrm{C}}_{60}$ fullerene was investigated using tight-binding molecular dynamics simulations based on the parametrization of Papaconstantopoulos et al. [MRS Symposia Proceedings No. 491 (Materials Research Society, Pittsburgh, 1998), p. 221]. Averaged fragment size distributions over random sets of initial configurations were obtained from simulations of radiation-induced fragmentation in the $50--500\phantom{\rule{0.3em}{0ex}}\mathrm{eV}$ excitation energy range. The excitation caused by the radiation was simulated simply by ascribing suddenly random velocities to each atom of the fullerene cage. For low excitation energies, the size distributions are peaked for dimers (reflecting a preferential ${\mathrm{C}}_{2}$ emission) and a bimodal size dependence characterizes the distributions of the complementary small and large fragments. For high excitation energies, predominantly multifragmentation occurs, but a genuine power-law dependence of small fragments is not yet observable. A phase transition is found for rather low excitation energies $(100--120\phantom{\rule{0.3em}{0ex}}\mathrm{eV})$.