Oxide/metal interface distance and epitaxial strain in the NiO/Ag(001) system

Geometric parameters of NiO films epitaxially grown on Ag(001) were determined using two independent experimental techniques and ab initio simulations. Primary beam diffraction modulated electron emission experiments determined that the NiO films grow with O on top of Ag and that the oxide/metal interface distance is d=2.3+/-0.1 Angstrom. Polarization-dependent x-ray absorption, at the Ni-K edge, determined the tetragonal strain (r(parallel to)=2.046+/-0.009 Angstrom, r(perpendicular to)=2.12+/-0.02 Angstrom) and d=2.37+/-0.05 Angstrom. Periodic slab model results agree with the experiments (d=2.40, r(parallel to)=2.07, r(perpendicular to)=2.10 Angstrom; the O-on-top configuration is the most stable).