Hi everyone, Below is an email I received this morning. I thought I would pass it along to the mailing list. I know that some of you work on projects very close to this fellow's question and thought he would benefit by the wisdom of the masses. Hi Sumit, A few pointers: * There is a wealth of information about Feff and XAFS analysis at http://xafs.org * I strongly encourage you to join and follow this mailing list. I explain the many benefits of the mailing list and offer some advice on using it effectively at this page: http://cars9.uchicago.edu/ifeffit/BruceRavel/FormLetters/HelpRequest As for your question -- there are a number of approaches to the problem of sorbed species that have been adopted by folks working both catalysis, in environmental science, and elsewhere. Obviously, sorbed species are a very important topic in many fields and XAS is very attractive for learning something about them. You would be very well served by examining the very large body of published literature on this topic. Much of that work has been done by people who read this mailing list -- I am hoping some of them will speak up. As I said, there are a number of ways to approach the problem. One fairly simple way is to run atoms on the substrate crystal and then "cut" the resulting cluster to "expose" the surface. What does this mean? The simplest case is to "expose" a (001) surface by simply deleting all atoms from the Feff input file with a positive value for the Z coordinate (assuming, of course, that the crystal is of an orthogonal type -- this "cutting" trick is a bit trickier for other cystal types). Then simply decorate the atoms list with the absorber by placing at coordinates relative to the "exposed" surface that is a plausible place to find that atom. Be sure you set the POTENTIALS list on the Feff input file correctly to account for the newly introduced absorber. This is explained in the Feff documentation and ion several places at xafs.org. Hope that helps, B --------------------------------------------------------------------------------- On Tuesday 12 January 2010, 08:21:04 am, sumitk@barc.gov.in wrote: Dear Sir, This is in regrad to the problem in making the FEFF input file for the Eu species sorbed on the the alumina surface. I am Sumit Kumar, Working as Reseach Scholar In Indian Nuclear Establishment. Recenrly I have carried out Eu-L3 EXAFs experiemnt at Elettra Synchrotron EXAFS beamline for delineating Eu species sorbed on alumina and other clay surfaces under different experiemntal/environmental conditions. As I understand for FeFf input file ATOMS SOFTWARE can be used, but as my species are just sorbed/chemical bonded on the surface, I can not take Eu as part of the bulk and then using ATOMS will be not be correct. I need your suggestion in this regard. Pl. suggest how to make the FEFF input file in this case. My problem is similar to one of yours paper sumitted to Geochimica Cosmochimica acta(Zn on Rutile).If you could send FEFF input file file for that work or similar other FEFF input file, it will be of much help to me. With Regards, Sumit Kumar Radiochemistry Division Bhabha Atomic Research Centre, Mumbai, India -------------------------------------------------