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Joint refinement with individual Rwp
DanielIrving #1
Member since Dec 2018 · 12 posts · Location: Southampton
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Subject: Joint refinement with individual Rwp
Hi everyone,

I've recently started doing joint refinements of Bragg and PDF data and noticed that the Rwp seems to be a lot lower on the read out of TOPAS (typically around 3%) but was wondering how this value was calculated?

Also is there any way in a dual refinement like this to get the Rwp of each individual refinement?

Thanks for any help
Daniel
johnsoevans (Administrator) #2
User title: John Evans
Member since Aug 2009 · 209 posts
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You can get individual rwp's by adding "r_wp 0" in each xdd section.

The Rwp calculation is just the same as for a normal Rietveld.  What's probably different is the weighting scheme.  Proper weighting will depend on your experiment and data processing.  However it's common to apply a constant weighting for the pdf data (e.g. weighting 1).  You will need to think about how you want to weight the PDF against the Bragg.  If you're comparing with other software you can see what's used there and apply a similar scheme in topas.

John
DanielIrving #3
Member since Dec 2018 · 12 posts · Location: Southampton
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Perfect! I've altered the weightings on the PDF data and the R-factors appear to be a lot more realistic.

Thanks again for the help!
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