ADSORPTION POTENTIALS AND SPECTRAL SHIFTS OF CO ADSORBED ON C-60

Adsorption potentials and IR spectral shifts of CO physically adsorbed on high surface area C-60 films were calculated and compared with res ults obtained with other carbon allotropes, graphite and diamond. The potentials were calculated as a sum of dispersion and repulsion intera ctions of the adsorbed molecule with each atom of the adsorbent using the Buckingham-Corner and Lennard-Jones potentials. The calculations w ere performed for different sites on the (100) and (111) surface plane s of two C-60 structures, fcc and hcp. The lowest potentials were obta ined for CO adsorbed in voids between the C-60 molecules. Spectral shi fts (Delta nu) from the CO gas frequency were calculated by means of t he perturbation method. The Delta nu values calculated for sites betwe en four and two C-60 molecules were in good agreement with previously reported FTIR spectra of CO adsorbed on C-60 where two absorption band s shifted by -15 and -8 cm(-1) were obtained. The two bands were assig ned to CO adsorbed on sites differing in energy.