First-principles calculation of Mg(0 0 0 1) thin films: Quantum size effect and adsorption of atomic hydrogen

We have carried out first-principles calculation of Mg(0 0 0 1) free-standing thin films to study the oscillatory quantum size effect exhibited in the surface energy, work function, interlayer relaxation, and adsorption energy of the atomic hydrogen adsorbate. The quantum well states have been shown. The calculated energetics and interlayer relaxation of clean and H-adsorbed Mg films are clearly featured by quantum oscillations as a function of the thickness of the film, with oscillation period of about eight monolayers, consistent with recent experiments. The calculated quantum size effect in H adsorption can be verified by observing the dependence of H coverage on the thickness of Mg(0 0 0 1) thin films gown on Si(1 1 1) or W(1 1 0) substrate which has been experimentally accessible.