Hydrogen Chemisorption by the Spin-Density Functional Formalism. II. Rôle of thesp-conduction Electrons of Metal Surfaces

A new derivation of an earlier published chemisorption scheme is given together with numerical estimates of its accuracy. The scheme involves solving the Kohn-Sham equations self-consistently with no adjustable parameters. Exchange and correlation are treated in the local spindensity approximation. By applying this scheme to a system consisting of a semi-infinite jellium, whose electron density is varied, plus a hydrogen adatom, the rôle of the sp-conduction electrons are investigated. Results for chemisorption energies, electron densities, dipole moments, effective potentials and densities of states are presented as a function of the conduction electron density as well as of the adatom-substrate distance. It is found that (i) the repulsive part of the interaction is strongly, while the binding energy is weakly, dependent on the conduction electron density, (ii) the adsorbate-induced electron density is almost spherical and (iii) the position of the adsorbate-induced resonance is largely determined by the location of the conduction band.