Mg adsorption on Si„001... surface from first principles

First-principles calculations using density functional theory based on norm-conserving pseudopotentials have been performed to investigate the Mg adsorption on the Si~001! surface for 1/4, 1/2, and 1 monolayer ~ML! coverages. For both 1/4 and 1/2 ML coverages it has been found that the most favorable site for the Mg adsorption is the cave site between two dimer rows consistent with the recent experiments. For the 1 ML coverage we have found that the most preferable configuration is when both Mg atoms on 231 reconstruction occupy the two shallow sites. We have found that the minimum energy configurations for 1/4 ML coverage is a 232 reconstruction while for the 1/2 and 1 ML coverages they are 231.