Dear all, I have the same problem with Hashem. My sample is nanocrystal Wurtzite InN (XRD and AFM results). I do the absorption experiment at In L3-edge at room temperature. After an data processing process, I get 2 broad peaks in FT. When i try to fitting a Wurtzite InN model to the EXAFS spectra for the first and second shells, I always get unacceptable parameters. First of all, I try to change my WZ InN model (changing lattice constant a and c, u-parameter) but it is inefficiently. How could I do? This figure 1 shown a FT of In-L3 EXAFS spectra, the Blue line is my 2 broad peaks and red line is calculate with my WZ InN model which set all parameter to initial value (not guess any thing). figure 1 >> http://nanotech.sytes.net/kaswat/01.emf After I have read Bruce's mail ("If your sigma^2 parameter is negative, perhaps you have too much structural disorder in your model and the fit is compensating by inflating those paths with a negative sigma^2."). How do I construct a WZ InN model which have too many structural disorder. P.S. I have read some papers, they have use model of nanocrystalline alloy which containing amorphous model. How to construct an amorphous model like they. -- Mr. Kittiphong Amnuyswat [kaswat] Post Graduate student College of KMITL Nanotechnology Contact : kaswat@gmail.com, nakz_zz@hotmail.com [MSN Available]