John and Bruce, Thank you for your kind help. I'm still a little perplexed... Basically I'm taking SEXAFS on a Ni(110) single crystal substrate (with a fraction of a monolayer of Au which substitutes into the first layer... SEXAFS spectra were obtained at the AuL3 edge). I've taken data in four different posistions: "grazing incidence" with the E vector of the x-rays parallel to the surface normal 1) with x-rays along the (001) direction 2) with x-rays along the (-110) direction and "normal incidence" with the E vector of the x-rays perpendicular to the surface normal (E parallel to the surface plane) 3) with x-rays along the (001) direction 4) with x-rays along the (-110) direction After receiving both Bruce and John's emails I tried three different feff.inp files, using my original hemisphere cluster, each using one of the following: POLARIZATION 1 1 0 or POLARIZATION 0 0 1 or POLARIZATION -1 1 0 but upon ploting out chi(k) vs. k from the chi.dat's for each of these they looked identical... did I miss something? Thanks, Kristine Witkowski Northwestern University

Hi Kristine, I basically agree with what Bruce Ravel wrote. We've occasionally done FEFF calculations on surfaces (e.g. with K. Baberschke and students), and the key to the calculation is to use appropriate Polarization cards (and Ellipticity cards) in the calculation as described in the doc. Please let me know if you have problems doing this. Cheers, John