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 dependence of the dielectric constants in a low symmetry crystal on the polarization energy E_pol, induced by electron holes in the bulk and on the surface of the molecular solids, is investigated. The analytical expressions are obtained and evaluated for SF₆, SO₂, CS₂ and seven aromatic organic compounds. The theory is in good agreement with the experimental data. The deviation of the molecular cavity shape from a sphere has a marked influence on the calculated extra-atomic relaxation energy in large molecules. The E_pol value depends on the hole position. In SF₆ this value is larger for F atom photoionization than for S atom photoionization. The angular dependence of the dielectric constants has a smaller effect on the E_pol value than does that of the cavity shape. The E_pol value on the surface of a single crystal depends on the crystallographic plane. The polarization energy for CO molecules on the top of Xe layers on Al(111) is calculated in dependence on the number of Xe layers. The calculated extra-atomic relaxation energy is in good agreement with experiment.