Hydrogen in subsurface sites of Pd(111): Self-consistent electronic structure

The electronic structures of monolayer atomic hydrogen in subsurface sites of the Pd(111) surface are studied with self-consistent pseudopotential calculations. Results of the present calculations include the density of states, electronic character of the Pd--H bond, and analyses of surface states and surface density of states. It is shown that H in subsurface tetrahedral sites have electronic properties very similar to those of H in the surface threefold sites. On the other hand, near the zone center, the electronic properties for H in subsurface octahedral sites are similar to the clean surface. This is a consequence of the symmetry of the (111) surface. The H-induced features for this geometry would then be difficult to detect by normal-emission spectroscopy, which samples states near the zone center, but should be observable at the zone boundaries by angle-resolved photoemission spectroscopy. The subsurface chemisorption model for the high-temperature phase of H/Pd(111) is discussed in light of the present calculation