Diffusion dynamics of the Li ion on C-60: A direct molecular orbital-molecular dynamics study

Abstract

The diffusion dynamics of the Li+ ion on fullerene (C-60) have been investigated by means of the direct molecula-orbital-molecular dynamics (MO-MD) method. The total energy and energy gradient on the full dimensional potential energy surface of the Li(+)C60 system were calculated at each time step in the trajectory calculation. The optimized structure, where the Li+ ion is located at the hexagonal Site Of C60, was used as an initial itructure at time zero. Simulation temperatures were chosen in the range of 10-300 K. The dynamics calculations showed that the Li+ ion vibrates around the initial equilibrium point below 40 K, while the ion can move above 50 K. At low temperature (below 300 K), the diffusion coefficients for the Li+ ion on the C60 surface are larger than those of the graphite surface. The diffusion coefficients on both C60 and the graphite surface were almost equivalent at medium temperatures around 300 K. At higher temperatures (T > 300 K), the coefficients for the graphite surface were significantly larger than those Of C60. On the basis of theoretical results, A e designed an ion-switching molecular device composed Of C60 and graphite sheet.