[GSAS-II] Single peak fits

[Von Dreele, Robert B. via GSAS-II]

Dear Davide,
Actually what happened is that if sig & gam are not refined, they revert to 
what would be calculated from U, V, W X & Y. Usually one refines X & Y during 
single peak fits & not sig or gam. This assumes that U, V & W have been 
established for the diffractometer so sig is fixed by them, and that the sample 
broadening (almost always Lorentzian) is isotropic and thus given by X (related 
to size broadening) and Y (related to mustrain broadening). If the broadening 
isn't isotropic, the usual approach is to refine X & Y and any individual peak 
gam that seem to be anomalous (usually a handful). NB: this usually has little 
or no effect on peak positions needed for e.g. indexing.
Bob
Hi,
When I refine the peaks with the peak fitting routine I found a problem: if I 
refine the sigma and gamma peak parameters and then I fix the gamma parameters 
these parameters become 0 after the fitting.
I think it is a bug in the code.
bests
Davide

--- Begin Message ---

Hi,
When I refine the peaks with the peak fitting routine I found a problem: if I 
refine the sigma and gamma peak parameters and then I fix the gamma parameters 
these parameters become 0 after the fitting.
I think it is a bug in the code.
bests
Davide
Dr. Davide Levy, Ph.D.
Head of XRD laboratory
Wolfson Applied Materials Research Center
Tel Aviv University
Phone: +972-3-6407815<tel:+972%203-640-7815>
Fax:   +972-3-6407819<tel:+972%203-640-7819>
http://www3.tau.ac.il/wamrc/
[http://www3.tau.ac.il/wamrc/templates/labs_3/images/new-tau-logo.png][WAMRC-LOGO_new]

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