Hi About my question, after getting Bob's remark to avoid singular matrix, I used a constraint on the sum of s.o.f parameter for Ti and Sc (say 0.9), and refined s.o.f of each, later repeating that up to 1.0. Then I took the best fit to be the proper answer.
VIC בתאריך יום ב׳, 8 ביוני 2020 ב-20:00 מאת <[email protected]>: > 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. Parameters that won't refined (Victor Zenou) > > > ---------------------------------------------------------------------- > > Message: 1 > Date: Mon, 8 Jun 2020 09:29:32 +0300 > From: Victor Zenou <[email protected]> > To: [email protected] > Subject: [GSAS-II] Parameters that won't refined > Message-ID: > <CAOFFwJ43WRN=F4_psG6_JpPE=Y7znJDz5mPfD0= > [email protected]> > Content-Type: text/plain; charset="utf-8" > > Hi > > I'm working on Sc-doped TiO2 nano-crystallites. As Sc and Ti have close > atomic number, and therefore atomic scattering factor, XRD cannot be used > to differentiate between Sc and Ti, sitting on the same Wyckoff atomic > position. On the other hand, the neutron scattering length of Sc is > different from Ti. > > Therefore, I'm using neutron diffraction (ND) data and X-ray diffraction > (XRD) data of a few Sc-doped TiO2 samples in a joint refinement using > GSAS-II. Among the usual lattice parameters and sample displacement (bragg > brentano geometry; XRD) or zero shift (*Debye**-*Scherrer ; ND) the > refinement includes Ti and Sc site occupancy parameters (s.o.f) in addition > to the crystallite size. These site occupancy parameters are refined at the > end, however they won't be "refined" (refinement ends without changing the > s.o.f. parameters). > > Changing these Ti/ Sc s.o.f manually can give better results. It is more > complicated as there are some vacancies at the same position. > > Does anybody have an idea how to refine these s.o.f of Ti and Sc? > > Best regards, > > Victor Zenou > -------------- next part -------------- > An HTML attachment was scrubbed... > URL: < > http://mailman.aps.anl.gov/pipermail/gsas-ii/attachments/20200608/e11ab9f4/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 267, Issue 1 > *************************************** >
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