POLARIZATION AND EXTRA-ATOMIC RELAXATION ON THE SURFACE AND IN THE BULK OF SOLIDS - INFLUENCE OF THE MOLECULAR SHAPE, POLARIZABILITY AND COMPLEX NATURE OF THE ADSORBATE

The influence of the molecular cavity shape and of the angular depende nce of the dielectric constants in a low symmetry crystal on the polar ization energy E(pol), induced by electron holes in the bulk and on th e surface of the molecular solids, is investigated. The analytical exp ressions are obtained and evaluated for SF6, SO2, CS2 and seven aromat ic organic compounds. The theory is in good agreement with the experim ental data. The deviation of the molecular cavity shape from a sphere has a marked influence on the calculated extra-atomic relaxation energ y in large molecules. The E(pol) value depends on the hole position. I n SF6 this value is larger for F atom photoionization than for S atom photoionization. The angular dependence of the dielectric constants ha s a smaller effect on the E(pol) value than does that of the cavity sh ape. The E(pol) value on the surface of a single crystal depends on th e crystallographic plane. The polarization energy for CO molecules on the top of Xe layers on Al(111) is calculated in dependence on the num ber of Xe layers. The calculated extra-atomic relaxation energy is in good agreement with experiment.