Thermal vibrations of Li+ ion and Li atom at the circumference of graphitecluster model: a direct molecular dynamics calculation

For simulation on thermal behavior of the migrating species, Li+ ion and Li atom, at the circumference of graphite in lithium battery, direct molecula r orbital (MO) dynamics calculation was carried out at AM I level, using th e hydrogen terminated planar cluster model C54H18. According to the static MO calculation, both species stabilize above the segment joining two termin ating hydrogen atoms, H1 and H2, which are bonded by the corner edge and th e side edge carbon atoms, respectively. Although Li+ ion is located 1.8425 Angstrom above the middle point of the segment, Li atom 1.620 Angstrom abov e the point shifted to H2 on the same segment. As results of the dynamics c alculation at 300 K for these stabilized species, Li+ ion shows the ellipti c movement under the equilibrium coulombic potential energy ascribed to bot h the side edge and corner edge carbon atoms, however, Li atom circulates a round the side carbon atom keeping the covalent bond composed of sp(3) hybr id orbitals. Migration trajectories of the species are reflected by the ele ctronic density maps. (C) 2001 Elsevier Science BN. All rights reserved.