Hydrogen Raman shifts in carbon nanotubes from molecular dynamics simulation

Shifts in Raman peak position relative to the gas-phase vibrational frequen cy have been calculated for molecular hydrogen in individual single-shell c arbon nanotubes and nanotube ropes using a semiclassical model. The calcula tions predict that isolated hydrogen molecules inside of nanotubes have a R amon frequency that increases with nanotube size for radii less than about 2 nm, while intercalated hydrogen frequencies are independent of nanotube s ize. The model indicates that shifts in Raman frequencies could be used exp erimentally to distinguish between hydrogen inside and intercalated between nanotubes. (C) 2001 Elsevier Science B.V. All rights reserved.