A SEXAFS STUDY OF THE P(2 X 2)-O/NI(111) SYSTEM

Oxygen K-edge SEXAFS studies on the p(2 x 2)-O/Ni(111) system show that the O atoms are located in threefold coordinated fcc sites with a nearest-neighbour O-Ni bond length of 1.85 +/- 0.03 angstrom. The SEXAFS data are compatible with outward shifts of the three nearest-neighbour Ni atoms by up to 0.2 angstrom. It is shown that a possible outward shift of the three nearest-neighbour Ni atoms must be coupled with an inward shift of the next nearest-neighbour Ni atoms by roughly the same amount.