SPECTRAL MANIFESTATIONS OF THE DYNAMIC INTERACTIONS BETWEEN ADSORBED MOLECULES - A COMPUTER MODELING STUDY

A method for computer modelling of the IR spectra of disordered layers of molecules adsorbed on crystal surface is developed. The method inc ludes MC simulation of surface diffusion induced by intermolecular int eraction, calculating the frequency of each molecule in the local elec tric field of the surrounding molecules, and, finally, computing the s pectrum of the layer of molecules, interacting by the mechanism of dyn amic dipole coupling. Application for CO adsorbed on (<10(1)over bar 0 >) face of ZnO has shown that the computed spectra reproduce well most of the features observed in the experiment. The role of vibrational p olarizability and bandwidth of individual molecules as well as of the structure of the layer and frequency distribution of molecules in the formation of dynamic spectra was analysed in model calculations with a rbitrary chosen surface geometry and parameters. Dynamic interaction i s shown to account for the band narrowing or intensity anomalies near saturating conditions and for the elimination of the structure caused by static interaction or surface inhomogeneity. It could either affect the band contour or even produce the fine structure in the spectra of isotopic mixtures adsorbed on homogeneous surfaces.