DISSOCIATION OF H-2 ON MG(0001)

First principles calculations of the potential energy surface for H-2 dissociation on the (0001) surface of Mg are presented, based on a pla ne-wave pseudopotential formalism within local density functional theo ry. It is shown that there is no molecularly chemisorbed precursor sta te, in contrast to earlier, jellium-based calculations. The lowest dis sociation barrier (0.37 eV per molecule) is found for dissociation abo ut a bridge site into neighbouring centre sites. A considerable surfac e corrugation is found, both for atomic adsorption and for the propert ies of the transition state. Charge density difference maps, showing t he charge transfer between the metal and the molecule, support the pic ture that dissociation occurs through occupation of anti-bonding state s of the molecule.