As Darek said, your issue is that you have crystal data which has sites of mixed occupancy. Read the Ifeffit FAQ entry on this topic at http://cars9.uchicago.edu/ifeffit/FAQ/FeffitModeling Question #15 on that page is the one you are looking for. B ________________________________________ From: ifeffit-bounces@millenia.cars.aps.anl.gov [ifeffit-bounces@millenia.cars.aps.anl.gov] on behalf of Wei Li [weili@udel.edu] Sent: Friday, May 04, 2012 10:50 PM To: XAFS Analysis using Ifeffit Subject: [Ifeffit] How to use ATOM on this file? Hello, Bruce, I have a *.cif, in which structure contains Zn and Al in the same site but diferent ratio. I cannot use ATOM to build a cluster for Feff. I am wonder if you could figure this out. Thanks in advance! best wishes yours Wei Li -- Wei Li Postdoc researcher Environmental Soil Chemistry Group Delaware Environmental Institute University of Delaware, Newark,19713 Tel:631-949-0663 http://ag.udel.edu/soilchem/li.htmlhttp://ag.udel.edu/soilchem/