Surface diffusion and desorption of exohedral Li⁺ from the surface of a fullerene

Surface diffusion and desorption of Li⁺ from the outer surface of C₆₀ are explored by quasiclassical trajectory calculations. The dynamics of exohedral Li⁺, initially at the center of a ring on the outer cage of C₆₀, is followed as a function of time. Ring hopping between adjacent rings is the major diffusion mechanism but 12–20 % of the ions, depending on the temperature, leave the ring, orbit the molecule, and fall back on a nonadjacent ring. There can be a sequence of hopping and orbiting before total desorption takes place. The average lifetime of an orbit is independent of the temperature, while the exohedral complex lifetime decreases with temperature. Rate coefficients for ring hopping and desorption are reported as a function of temperature. The average kinetic energy removed from the C₆₀ by the desorbing ion increases with temperature and it is independent of the lifetime of the complex. Kinetic-energy release distributions at various temperatures are reported.