Hi All,
I'm trying to use EXAFS data I have of Cu nanoparticles dispersed on SiO2 and ZnO to calculate their particle size.
Searching the archives, i've come by these topics and papers, which have helped immensely, but I'm still a little bit in the dark about the specifics of the fits:
So these discussions and papers make it clear that CNs for the 2nd or 3rd coordination shells will give a more accurate picture of the particle size (and even shape). Also, just comparing SO2s between a foil and the sample isnt the most accurate.
My initial thought was to get a good fitting model on Cu foil, obtain coordination numbers which are very close to 1, then apply that same fitting model to the Cu nanoparticles (for the Cu-SiO2 species we have TEM data I can again calibrate myself with)
However, my specific problem is getting reasonable coordination numbers for the Cu foil.
- I can set the SO2 to 1 and get a very good fit for the data, but this is not useful for the nanoparticles
- I can give all paths the same SO2 variable, and get a fitted value close to 1, but this isnt useful for comparing first and second shell CNs, as the ratio will always be the same.
- And finally, when I try to give each scattering shell its own independent CN, I again get a good fit, but while the first shell SO2 is close to 1, the 2nd shell value is closer to 1.5
I've been playing with which variables are the same between paths, etc, and I can get more reasonable numbers, but the problem then becomes that I cant easily justify my fitting model.
Attached is my Artemis file for Cu foil.
Any help or suggestions with how to proceed (specifically with how to group variables) would be much appreciated. I apologize in advance if i'm asking about a topic that's been covered extensively.
thanks,
Georges Siddiqui