Structural determination of an adsorbate-induced surface reconstruction: P4g(2×2)N versus c(2×2)O on Ni(100)

The adsorption site of N and O on Ni(100) for a c(2×2) overlayer is determined by x-ray-absorption fine-structure measurements. The O atoms adsorb in the fourfold hollow site on the unreconstructed surface with an O-Ni distance of R1=1.97(2) and d =0.88(4) above the first Ni layer. The N atoms also occupy a fourfold hollow site with a bond length of R1=1.89(3) but the nearest Ni atoms are rotated by a tangential displacement of =0.68(10), such that d =0.11(6). The differences in the bonding of N and O are linked to the occupation of their 2p levels. © 1987 The American Physical Society.