Re: [sdpd] error measurements

[Jaap Vente <jaap...@jade.mda.cinvestav.mx>]

The pain with background substraction CAN be that you have high values
with a further 'perfect' fit. In my experience this has often to do the
presence of a relative large amount of peaks with low intensity. You may
argue that you should measure longer under these circumstances, or reduce
the 2 theta angle you are using. Even so, the improvement is minor if you
have a low symmetry structure with atoms having very different scattering
factors (heavy metal oxides for instance). And yes your Rwp might than be
more an indication of how good the back ground has been fitted. High
background level gives a nice and low Rwp. With this in mind I think that
at the moment of writing there is no proper figure of merit for a Rietveld
refinement, and yes the diffraction pattern should be available. I am sure
that Steve Maginn is happy with this view :-).

By the way I assume that the background is never substracted in the Rwp
unless stated otherwise.

Best wishes


Jaap 


Jaap Vente
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