XRD measures interplanar spacing, and XAFS - interatomic distances, and they are not the same if disorder is present. Look for articles by Boyce and Mikkelsen, Jr., in Phys Rev B in 1980's who were the first discussing these concepts in GaAs-InAs semiconductors and also KBr-RbBr ionic salts. They showed that the average structure ascertained by diffraction differs from the local structure measured by EXAFS. Modern day high energy XRD/PDF measures interatomic distances more accurately than Bragg peak analysis can do but how accurately it agrees with EXAFS is still subject of debates. Anatoly ________________________________ From: ifeffit-bounces@millenia.cars.aps.anl.gov on behalf of Joseph Washington Sent: Fri 11/27/2009 2:08 PM To: XAFS Analysis using Ifeffit Subject: [Ifeffit] Bond length determination EXAFS vs XRD Happy Thanksgiving All! Can someone, send me some references which explains some of the reasons why the bond lengths fitted in EXAFS would be different from that fitted in XRD (assuming that we implemented the crystal model predicted by XRD correctly in Artemis)? I would really appreciate this! Sincerely -- Joseph Washington Research Assistant Department of Physics North Carolina State University 431 Riddick Hall Raleigh, NC 27695-8202 email: jswashin@ncsu.edu _______________________________________________ Ifeffit mailing list Ifeffit@millenia.cars.aps.anl.gov http://millenia.cars.aps.anl.gov/mailman/listinfo/ifeffit