Hi Steven, If I understand correctly what you're describing, I would certainly recommend against trying to use the first Co-Co peak as any indication of the size of the metal particles. As Anatoly indicates in his post, there's a bunch of interacting factors that control the size of that peak, making it very dicey to use it as any indication of size. If the oxide really doesn't contribute much beyond the first peak, it might be possible to look at the relative sizes of the Co-Co peaks as a function of R (i.e. go well beyond the first shell; say, out to 5 Angstroms if the data supports it) and compare to a Co metal standard (or a FEFF calculation). At least this has the benefit of making use of redundant data (the amplitude of more than one Co-Co peak). --Scott Calvin Sarah Lawrence College At 03:12 PM 5/5/2005 -0400, you wrote:
<fontfamily><param>Arial</param>Dear all, </fontfamily> <fontfamily><param>Arial</param>I have a question to ask all of you as follows. </fontfamily> <fontfamily><param>Arial</param>We have been investigating the EXAFS of some partially reduced Co materials (by Co EXFAS) and would wish to obtain some qualitative information on the Co metal particles. If, in fact, the Co had some average coordination environment because we have a distribution of Co particle sizes with oxygen adsorption, analyzing the windowed Co-O and Co-Co peaks together as a linear combination and assessing the average oxygen and Co coordination from the Co edge absorption (what we do with Athena) would appear to give a useful answer. However, if what we have is closer to a physical mixture of small Co metal particles and Co oxide particles, it would seem that it would be more appropriate to analyze separately the windowed Co-O and Co-Co peaks in R-space, to somehow normalize the Co-Co to the fraction of metal in the sample and use this as a qualitative measure of metal particle size. Is there a way to do this with Athena or other method? Or do you know of a reference where this has been discussed? Of course, we can (and will) make experimental mixtures as references but wonder if there is a different way of doing the analysis or if there is some literature on this problem (which we have not been able to locate). </fontfamily> <fontfamily><param>Arial</param>Thank you. </fontfamily> <fontfamily><param>Arial</param>Steven </fontfamily>_______________________________________________ Ifeffit mailing list Ifeffit@millenia.cars.aps.anl.gov http://millenia.cars.aps.anl.gov/mailman/listinfo/ifeffit <<<<<<<<