[GSAS-II] Le Bail Mode

[Von Dreele, Robert B.]

Hi,
The LeBail popup handles what happens to the structure factors before beginning a LeBail fitting. It only shows up the first time a LeBail fit is done. If you respond "Yes" structure factors are set to default (1.0) and a cycle of just a LeBail refinement on them is done before doing full LeBail refinement including whatever other parameters are set for refinement. This avoids the full LeBail refinement from going haywire when starting from the default. There will be a popup show for you to check the quality of the LeBail only fit before continuing on to the full LeBail refinement. "No" just uses whatever structure factors were there from previous refinement (LeBail or otherwise). NB: a LeBail refinement can be done without knowing the atom positions - it's one way to get suitable structure factors for structure solution from powder data. See the 2 tutorials on this.
Bob
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From: GSAS-II <gsas-ii-bounces at aps.anl.gov> on behalf of Brown, Matthew via GSAS-II <gsas-ii at aps.anl.gov>
Sent: Tuesday, December 17, 2024 12:27 PM
To: gsas-ii at aps.anl.gov <gsas-ii at aps.anl.gov>
Subject: [GSAS-II] Le Bail Mode

All Apologies for writing again so quickly. I’m working through the tutorial for setting up an instrument parameter file ( https: //advancedphotonsource. github. io/GSAS-II-tutorials/CWInstDemo/FindProfParamCW. htm ) and I reach a step where things
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All



Apologies for writing again so quickly. I’m working through the tutorial for setting up an instrument parameter file ( https://urldefense.us/v3/__https://advancedphotonsource.github.io/GSAS-II-tutorials/CWInstDemo/FindProfParamCW.htm__;!!G_uCfscf7eWS!bVXlBR1Bp7GJmn-U-eukSKJ3852Le9i1BPjeMRWZWuiG5DSt3JEQ75s1nC9hwB6z028R1pZRx6O4OghbuhUmsw$ <https://urldefense.us/v3/__https://advancedphotonsource.github.io/GSAS-II-tutorials/CWInstDemo/FindProfParamCW.htm__;!!G_uCfscf7eWS!aIGzJct8Tam1doJ4NsGi36Moo0SWpwQxqyLZL61KTXNVsrMrNfN7GFmiIBwLi2obf976flpRzHruIluaWnqDVvSh2Q$> ) and I reach a step where things have changed a bit from the tutorial.



When I hit refine after starting Le Bail extraction, I get a popup asking if I want to Reset the Le Bail structure factors?  Yes will reset all structure factors to unity, and Le Bail-only fitting will be used before any least-squares cycles. No will start with the previously set structure factors.



If I’m starting a fresh refinement, what are the factors defaulting to? Ones based on the atoms I’ve entered, or is this a false choice where both answers are 1 since I’ve not refined anything before?



Later on, I imagine I’d want to keep my existing structure factors unless something has gone wrong?



Thank you all for your help!



Dr. Matthew L. Brown  (he/him, they/them)

Lab Technician V (Chemistry, Crystallography)

Office: 250-807-8365



UBC School of Engineering

1540 Innovation Dr.

Kelowna, BC

V1V 1V7


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