Marco, On Mon, Sep 7, 2015 at 9:53 PM, M.F.Bertuzzo <mb...@kent.ac.uk> wrote:
> Dear all, > > I am facing this error when I try to run a fit. The file in question > required a larger than normal Rbkg value of 3.0. > > In what sense did this **require** Rbkg > 3.0? Normally (and for your data as well), Rbkg around 1.0 is sufficient. Well, if you want to analyze the first shell, that is. Your example nicely demonstrates how Rbkg > first shell distance can remove the first shell from the EXAFS... if that's what you want. > I have attatched the Athena file & the subsequent Artemis project file > that I tried to fit so you can see the error I am facing. > > >From what I can understand, I need to reduce the Rbkg value in the Athena > file to a lower number. But whenever I try to do this it causes the > background function to mess up which then also causes problems for the fit > in 'R' space. > > Well, it needs to be a lower number if you want to analyze the first shell, because with Rbkg=3, you've mostly removed the first shell from your data. > Is this problem because I have badly modeled the data badly in Athena to > begin? > > I'm not really sure how to solve the problem so your help and advice is > much appreciated! > > For your data, I'd recommend trying kweight=2 in the background subtraction, and perhaps moving e0 up a little bit. You could try a "clamp" on the **high k** side, too. Be aware that you're not going to analyze the data below 2 Ang^-1 anyway, so that if the background looks like it's way to high at very low k, this is not actually a problem. Hope that helps, --Matt
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