The adsorption of atomic nitrogen on Ru(0001): geometry and energetics

The local adsoprtion geometries of the (2 × 2)-N and (✓3 × ✓3)R30°-N phases on the Ru(0001) surface are determined by analyzing low-energy electron diffraction intensity data. For both phases, nitrogen occupies the threefold hcp site. The nitrogen sinks deeply into the top Ru layer resulting in a N-Ru interlayer distance of 1.05 and 1.10 Å in the (2 × 2) and the (✓3 × ✓3)R30° unit cell, respectively. This result is attributed to a strong N binding to the Ru surface (Ru-N bond length = 1.93 Å) in both phases as also evidenced by an initio calculations which revealed binding energies of 5.82 and 5.59 eV, respectively.