THEORY OF ADSORPTION AND DESORPTION IN HIGH ELECTRIC-FIELDS

A new method is proposed which allows the inclusion of strong electric fields into Car-Parrinello-like total-energy calculations. As a first application we calculated for the adsorption of Na on Al(111) the changes in atomic geometry, binding energies and diffusion barriers due to the influence of electrostatic fields. For high fields below the evaporation field strength a strong outward relaxation of the adsorbate is found which clearly reduces the energy differences between different adsorption sites and the diffusion barriers. This results in a degeneracy of the on-top and fcc hollow positions whereas in the field free case the fcc site is preferred by 0.1 eV.