[Ifeffit] Question on GDS values: amp

[Bruce Ravel]

On Monday, August 01, 2011 12:36:19 am Nicholas.Tse at csiro.au wrote:
> Just wondering what could I do to make the amp guess value as a positive
> number? If I run it and let it float (i.e. guess), the amp becomes
> negative in the resulting fits, but the fit has nice delr and ss values
> (i.e. make sense). If I restrict the amp value to 1, everything else
> doesn't fit. I am only fitting the first nearest neighbour in a measured
> standard; Gadolinium oxide.

Are you sure that you ran the Feff calculation with the correct edge?
You will find that the K edge and L3 edge calculations are roughly 180
degrees out of phase.  That mistake (one I make annoyingly regularly)
could account for a negative amplitude.

B

-- 

 Bruce Ravel  ------------------------------------ bravel at bnl.gov

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