I have fitted the first coordination shell of an EXAFS data but I am unaware of how to extract any information regarding the same. Can anyone please help me and which parameters should I check to ensure that my fitting is fine?
Dear Sauraf,
first of all your model is important - which kind of absorber atom and scattering atom did you use for the fit. You may fit anything to your data - the software is just doing what you asked it to do. And if you have a wrong underlying model, of course your fit results will be nonsense. Just a very simple example. Think that you have measured a simple Ni foil, but use a wrong fit model such as a body-centered cubic (instead of face centered cubic) - so probably your resulting coordination number may be correct, but the bond distances will be wrong, because of the self-consistent potential calculus included in the fitting software (such as e.g. Demeter (see homepage of Bruce Ravel and Matt Newville)).
Then there are further checks that should be done: Is the disorder (i.e. sigma - squared) positive and has a reasonable value? Negative values are always indications for a wrong fit. And also if the values are too small or very large are indications for a wrong model structure.
Next the bond distance: If the deviation to your model is too large (say larger than 0.1 Å) you should correct the fit model.
The correction of the edge energy is also idicative of a wrong fit model (especially for a wrong pair of absorber and scatterer): Usually, Delta E should be in the range of some few eV only, values of large than 10 eV can be though of as wrong.
And last not least - considering only the first shell may be a bit simple - try to include additional shells if the data have sufficient quality.
Hope this helps, have a nice week-end, Dirk
Hi, Saurav!
Which data treatment package are you using?
regards,
Daniel
Thanks all of you for your reply. I am using Artemis software.
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