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/Nit1111 systzm show that the 0 atoms are located in threefold coordinated fee sites with a nearest-neighbour 0-Ni bond leagth of 1.85 + 0.03 A. The SEXAFS data are compatible with outward shifts of the three nearest-neighbour Ni atoms by up to 0.2 A. 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.