>
> I have prepared one sample which is showing some impurities. When I had
> put one impurity phase and started refining it was showing NaN for chi.
> What does that mean? and how to know for sure that the added phase is
> present.
You should send your query to the email address Rietveld_L@ill.fr - just
reply to this email.
NaN means "Not-a Number" which probably means that your refinement has
diverged. This usually happens when you try to refine too many parameters,
and/or your model is far from the observed pattern, You might first refine
without impurity phases with a minimum of parameters, look at the
difference between the calculated and experimental patterns, and try to
identify extra peaks with a specific impurity phase, by separately
calculating the pattern for that impurity phase. Then you might add the
impurity phase to your refinement and refine only the scale factor (amount)
for it. Repeat for other possible impurity phases, and be careful not to
introduce too many parameters until you have a good starting model.
If you can, also try to prepare a sample with fewer impurities :-)
Regards, Alan.
______________________________________________
* Dr Alan Hewat, NeutronOptics, Grenoble, FRANCE *
<alan.he...@neutronoptics.com> +33.476.98.41.68
http://www.NeutronOptics.com/hewat
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