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Dayane:
Someone may propose an elegant rigid-body solution, but I would just switch from a rigid-body to bond and angle restraints, using a fairly large overall restraint weight to keep the molecule semi-rigid. This isn't a large molecule, so it's pretty easy to implement. It's not as elegant as a rigid-body, but it should work just as well. Sincerely, Joel -----Original Message----- From: GSAS-II <[email protected]> On Behalf Of [email protected] Sent: June 20, 2026 11:00 AM To: [email protected] Subject: External: GSAS-II Digest, Vol 436, Issue 1 Send GSAS-II mailing list submissions to [email protected] To subscribe or unsubscribe via the World Wide Web, visit https://mailman.aps.anl.gov/mailman/listinfo/gsas-ii or, via email, send a message with subject or body 'help' to [email protected] You can reach the person managing the list at [email protected] When replying, please edit your Subject line so it is more specific than "Re: Contents of GSAS-II digest..." Today's Topics: 1. GSAS-II Rigid Body Refinement with Partial Disorder in a CF3COO Group (Dayane Vieira Nascimento dos Santos) ---------------------------------------------------------------------- Message: 1 Date: Fri, 19 Jun 2026 18:17:30 +0000 From: Dayane Vieira Nascimento dos Santos <[email protected]> To: "[email protected]" <[email protected]> Subject: [GSAS-II] GSAS-II Rigid Body Refinement with Partial Disorder in a CF3COO Group Message-ID: <co1pr11mb502759d61d062d452d262401e8...@co1pr11mb5027.namprd11.prod.outlook.com> Content-Type: text/plain; charset="utf-8" Hi, I am trying to refine a CF3COO group as a rigid body in a crystal with space group P-1. The atoms in the group occupy sites with 1 symmetry. The CF3 moiety is disordered over two positions with a 70:30 occupancy ratio. When I define the entire CF3COO group as a rigid body and keep the occupancy fixed, the refinement quality deteriorates significantly: the Rw increases from about 5% to 20%, and the fit becomes much worse. However, if I allow the occupancy to refine, the refinement converges well and the fit remains good (Rw ? 5%). The problem is that the resulting structure assigns fractional occupancies (0.5 or lower) not only to the disordered CF? moiety but also to the COO group, which was not disordered in the original model. My question is: how can I refine a rigid body in which only part of the group has fractional occupancy? More specifically, is there a way in GSAS-II to model a rigid body where the CF3 atoms are disordered, but the COO atoms remain fully occupied? I am a little puzzled because GSAS-I/EXPGUI handled this situation without any apparent difficulty, so I suspect there must be a way to do it in GSAS-II as well. Any suggestions or guidance would be greatly appreciated. Thank you, Dayane V. N. Dos Santos Graduate Teaching Assistant Department of Chemistry Wayne State University Detroit, MI 48202 Email: [email protected] -------------- next part -------------- An HTML attachment was scrubbed... URL: <http://mailman.aps.anl.gov/pipermail/gsas-ii/attachments/20260619/391eda7c/attachment-0001.html > ------------------------------ Subject: Digest Footer _______________________________________________ GSAS-II mailing list [email protected] https://mailman.aps.anl.gov/mailman/listinfo/gsas-ii ------------------------------ End of GSAS-II Digest, Vol 436, Issue 1 ***************************************
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