Peculiarities of the vibratioanl spectra of molecules adsorbed on the surface of heterogeneous catalysts: theoretical analysis

The vibrational spectra of adsorption complexes resulting from the adsorption of ammonia on the surface of heterogeneous catalysts are interpreted by computation of frequencies and forms of normal vibrations. The characteristics of normal vibrations are computed from the state of separate fragments of adsorption complexes. It is shown that an interaction of internal coordinates, associated with the adsorption bond, with internal coordinates of the adsorbed molecule leads to a decrease of characteristics of vibrations sensitive to the surface area. A correlation is established between the characteristics of such vibrations and the changes in their frequencies in comparison with the free molecule.