fredmarlton
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
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
Ok, thanks Alan, good to know :)
Fred