Hydrogen chemisorption on Al,Mg and Na surfaces — calculation of adsorption sites and binding energies

Chemisorption properties for H on Al, Mg and Na surfaces have been computed. Starting with the results from a self-consistent, Kohn-Sham calculation for a H-jellium system, the effects of the substrate pseudopotential lattice have been included by first order perturbation theory. An improved method, namely inclusion of part of the pseudopotentials in a self-consistent way and only the remainder in perturbation theory, has also been used. Binding energies, bond lengths, vibrational frequencies and activation energies have been calculated. It is found that the three substrates behave qualitatively different, as Al is a segregator, Na is an absorber and Mg is in between. Calculated bond lengths agree in general well with the ones for the corresponding molecules. The binding energy is predicted to be below or close to the dissociation energy of H₂ for Al and Na, while it is slightly larger for Mg.