[Ifeffit] larch xray plugin - incorrect chantler data at edges

Dr. Johannes Zellner johannes at zellner.org
Wed Oct 14 01:11:05 CDT 2015


 

Hi, 

the larch xraydb plugin doesn't provide correct numbers for chantler f1
data around edges. 
Apparently this is due to incorrect interpolation in xray/xraydb.py in
line 274. 
Below is a plot of "delta" from xraydb_plugin.xray_delta_beta() for
Silicon which is terrribly wrong. 

The more correct "delta" as from chantler is shown in the following
plot: 

--> I'd recommend to replace (line 274 in plugin xray/xraydb.py): 

out = UnivariateSpline(te, ty, s=smoothing)(energy) 

by a simple linear interpolation 

out = np.interp(energy, te, ty) 

The latter yields linear segments between chantler's data, but this is
still better than the totally unphysical spline interpolation. 

Best regards, 

-- 
Johannes 
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