Adsorption-induced relaxation of Ni(001)-c(2×2)-O

Comparisons between full-potential, spin-polarized, total-energy calculations with a low-energy electron diffraction (LEED) intensity analysis for the adsorbed system Ni(001)-c(2×{}2)-O suggest the importance of bonding between oxygen and the second-layer nickel atom below it. By fixing the associated bond length, we are able to explain the results of a new multilayer LEED analysis which reduces the spacing between the oxygen and the first nickel layer below all previous determinations to 0.75±{}0.04 {} and increases the spacing of the first two nickel layers from the bulk value by 5.7% to 1.86±{}0.02 {}. Differences between LEED and surface extended x-ray-absorption fine-structure spectroscopy structure parameters are noted.