I analyzed EXAFS spectra of trace of Fe in lithium tantalate crystals. At first, I created the feff.inp file of LiTaO3. Then I changed central Li atom to Fe atom and added Fe atom at the Ta site. So that, the fitted results is good except amp(amp results is 0.3). I think that the model structure is good, but I can not understand why amp is too low. How do you think about this results? And, I tried to fitting treatment using GDS parameters. But, I do not know that the general method how to use the GDS parameters. Please tell me the general way of GDS manipulation. My PC runs under Win XP, and My Artemis runs under feff8 conditions. Thank you.