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Parameter refinement, dual space
FredMarlton #1
Member since Jul 2018 · 17 posts
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Subject: Parameter refinement, dual space
Hi all,

In a dual space refinement (PDF and Bragg) is it possible to assign refinement of a parameter to a particular dataset? In the case of doing a dual space refinement, can I set the lattice parameters to be determined against the Bragg data only?

Is it a simple case of doing something like:

xdd Bragg_data
   ....
      str
         ...
         a a_lat = 4;
         ...

xdd PDF_data
   ....
      str
         ...
         a = a_lat;
         ...

Thanks,
Fred
AlanCoelho #2
Member since Aug 2011 · 288 posts
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Hi Fred

Your INP snippet will use both data sets to determine a_lat. I don't think there is a way to do what you want.

If the derivative of Ycalc with respect to a_lat was set to zero for the PDF data set then that would do what you want. However, the refinement will probably be unstable. You are probably better off refining a_lat on the Bragg data  and then fixing it what refining on both data sets.

I will however keep in mind ignoring a derivative with respect to a particular; there could be a simple way to implement this  and to investigate the effects.

cheers
alan
FredMarlton #3
Member since Jul 2018 · 17 posts
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Ok, thanks Alan, good to know :)

Fred
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