unwilled fixing of the scale factor parameter

[alberto martinelli]

Dear all,

I'm using PDFgui 2.0.4. In some cases, I see that at the end of the fitting the scale factor parameter results fixed, despite the fact that it was initially a free parameter. I guess that this occurs when its variation is very faint, but it is quite disturbing to me because I don't have proof.  Has anyone experienced the same thing?

[Simon Billinge]

yes this is quite common.   You need to nudge it to a different value and let the refinement engine move it to get it to move back.

On Wed, Apr 17, 2024 at 6:11 AM alberto martinelli <alberto.m....@gmail.com> wrote:

Dear all,

I'm using PDFgui 2.0.4. In some cases, I see that at the end of the fitting the scale factor parameter results fixed, despite the fact that it was initially a free parameter. I guess that this occurs when its variation is very faint, but it is quite disturbing to me because I don't have proof.  Has anyone experienced the same thing?

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Simon Billinge

Professor, 

Department of Applied Physics and Applied Mathematics

Columbia University