Spectroscopic determination of surface geometry: Ti(0001)-H(1×1)

The electronic structure of a Ti(0001) film covered by a monolayer of H is shown to depend strongly on the location of the H atom in the surface unit cell. Best agreement with experiment is found with the H's in three-fold sites, 0.8 a.u. outside the outer Ti layer. In this geometry the H atoms "heal" the surface—the clean Ti(0001) surface state near the Fermi level is removed and the outer layer $d$-like local density of states (LDOS) is quite similar to that of the interior. Additionally, the calculated work function is 4.0 eV and an H-derived peak in the calculated LDOS appears 5 eV below $E_F$, in agreement with photoemission measurements.