Adsorption potentials and spectral shifts of CO adsorbed on C60

Abstract

Adsorption potentials and IR spectral shifts of CO physically adsorbed on high surface area C60 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 C60 structures, fcc and hcp. The lowest potentials were obtained for CO adsorbed in voids between the C60 molecules. Spectral shifts (Δν) from the CO gas frequency were calculated by means of the perturbation method. The Δν values calculated for sites between four and two C60 molecules were in good agreement with previously reported FTIR spectra of CO adsorbed on C60 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.