Hydrogen Raman shifts in carbon nanotubes from molecular dynamics simulation

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