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 results obtained with other carbon allotropes, graphite and diamond. The potentials were calculated as a sum of dispersion and repulsion interactions of the adsorbed molecule with each atom of the adsorbent using the Buckingham-Corner and Lennard-Jones potentials. The calculations were performed for different sites on the (100) and (111) surface planes of two C-60 structures, fcc and hcp. The lowest potentials were obtained for CO adsorbed in voids between the C-60 molecules. Spectral shifts (Delta nu) from the CO gas frequency were calculated by means of the perturbation method. The Delta nu values calculated for sites between four and two C-60 molecules were in good agreement with previously reported FTIR spectra of CO adsorbed on C-60 where two absorption bands shifted by -15 and -8 cm(-1) were obtained. The two bands were assigned to CO adsorbed on sites differing in energy.