Ru oxidizes easily. Since you fixed CN in bulk Ru as total 12 in the fit to hcp Ru it probably gave you a small amplitude factor for the foil. Thus when you transferred that small amplitude factor to fit NP Ru it resulted in large CN. We use freshly made Ru powders as standards. What amplitude factor have you got from the foil? Anatoly Sent from my mobile phone, please forgive typos. -----Original message----- From: Anatoly I Frenkel To: Dreher Marian , "ifeffit@millenia.cars.aps.anl.gov" Sent: Tue, Sep 20, 2011 18:27:57 GMT+00:00 Subject: Re: [Ifeffit] particle size and coordination number in Ru nanoparticles on carbon You have to be careful using Ru foil. Sent from my mobile phone, please forgive typos. -----Original message----- From: Dreher Marian To: "ifeffit@millenia.cars.aps.anl.gov" Sent: Tue, Sep 20, 2011 18:00:15 GMT+00:00 Subject: [Ifeffit] particle size and coordination number in Ru nanoparticles on carbon Dear Ifeffit Community, I am currently trying to extract the particle size of Ru supported on carbon from EXAFS data. I also recorded spectra of a Ru foil as a bulk reference sample. So, my approach is to fit the first coordination shell of my bulk reference, setting CN to 12. From that I get a value for s02. I'm then using this value in the first shell fit for the Ru nanoparticles in order to get the coordination number. However, the fit suggests that CN is still pretty much 12. What is changing drastically, though, is sigma^2 which usually doubles in value compared to the bulk sample. That makes sense, I guess, since there might be higher disorder in the nanoparticles. Obviously, there is a chance that my nanoparticles are rather big, in which case CN would be close to 12. However, STEM and HRTEM pictures suggest that the Ru particles are between 1 and 2 nm in diameter. I'm just starting to get into EXAFS analysis and pretty clueless right now about how to approach this. Happy about any input, many thanks, Marian.