The Pawley refinement is superior to LeBail refinement in that it provides the esd's. The problem of negative intensities may be mitigated by the negative weight factor Brian implemented in GSAS-II.
Hooman On Wed, Apr 8, 2020 at 1:22 PM <[email protected]> wrote: > 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. Pawley refinemet question (Sergey Ushakov) > 2. Re: Pawley refinemet question (Toby, Brian H.) > 3. Re: Pawley refinemet question (Sergey Ushakov) > > > ---------------------------------------------------------------------- > > Message: 1 > Date: Wed, 8 Apr 2020 10:58:15 -0700 > From: Sergey Ushakov <[email protected]> > To: [email protected] > Subject: [GSAS-II] Pawley refinemet question > Message-ID: > < > cag1yaupgkqpv-hkdrbmudofczjeslkd6ykvpaxryek+15bu...@mail.gmail.com> > Content-Type: text/plain; charset="utf-8" > > Greetings! I have a question maybe not specific to GSAS-II but more about > Pawley vs Le Bail fitting of powder XRD data. > I work on high temperature data from laser-heated solid spheroids which > rotate in a gas flow in aerodynamic levitator. > The data are collected in transmission geometry at 6-ID-D at APS. > The rotation is not well controlled since it depends on the shape of each > bead formed by melt solidification, i.e., on surface tension, volume change > on melting, etc. > So, sometimes data are very much powder-like and amenable to Rietveld > refinement of the structure, but sometimes they are not, and in this case, > I do Pawley fit for cell parameters. > I used to do Le Bail fitting for that in GSAS-I, but I understand that it > was replaced by Pawley refinement (although there is an option for Le Bail > extraction of intensities?). > > To my surprise, Pawley fit in GSAS-II yield phase/weight fraction if one > turns it on for refinement. > I thought phase fraction could be correctly refined only from Rietveld? > > I would appreciate any comments on this! > > Sergey > > -- > Sergey Ushakov PhD > > Staff Research Associate > > Peter A Rock Thermochemistry Laboratory and NEAT ORU > Rm 4415, Chemistry Annex > University of California, Davis > Davis, CA 95616 > -------------- next part -------------- > An HTML attachment was scrubbed... > URL: < > http://mailman.aps.anl.gov/pipermail/gsas-ii/attachments/20200408/36fe4e9c/attachment-0001.html > > > > ------------------------------ > > Message: 2 > Date: Wed, 8 Apr 2020 18:14:35 +0000 > From: "Toby, Brian H." <[email protected]> > To: "Ushakov, Sergey V." <[email protected]> > Cc: "Von Dreele, Robert B. via GSAS-II" <[email protected]> > Subject: Re: [GSAS-II] Pawley refinemet question > Message-ID: <[email protected]> > Content-Type: text/plain; charset="us-ascii" > > Hi Sergey, > > Both LeBail and Pawley fits are not able to determine phase fractions > because the scale factors are all arbitrary and thus the phase fractions > cannot be refined. However, the reported mass/weight fractions are > determined from the unrefined phase fractions and they are displayed even > though meaningless. > > Brian > > On Apr 8, 2020, at 12:58 PM, Sergey Ushakov via GSAS-II < > [email protected]<mailto:[email protected]>> wrote: > > Greetings! I have a question maybe not specific to GSAS-II but more about > Pawley vs Le Bail fitting of powder XRD data. > I work on high temperature data from laser-heated solid spheroids which > rotate in a gas flow in aerodynamic levitator. > The data are collected in transmission geometry at 6-ID-D at APS. > The rotation is not well controlled since it depends on the shape of each > bead formed by melt solidification, i.e., on surface tension, volume change > on melting, etc. > So, sometimes data are very much powder-like and amenable to Rietveld > refinement of the structure, but sometimes they are not, and in this case, > I do Pawley fit for cell parameters. > I used to do Le Bail fitting for that in GSAS-I, but I understand that it > was replaced by Pawley refinement (although there is an option for Le Bail > extraction of intensities?). > > To my surprise, Pawley fit in GSAS-II yield phase/weight fraction if one > turns it on for refinement. > I thought phase fraction could be correctly refined only from Rietveld? > > I would appreciate any comments on this! > > Sergey > > -- > Sergey Ushakov PhD > > Staff Research Associate > > Peter A Rock Thermochemistry Laboratory and NEAT ORU > Rm 4415, Chemistry Annex > University of California, Davis > Davis, CA 95616 > > _______________________________________________ > GSAS-II mailing list > [email protected]<mailto:[email protected]> > https://mailman.aps.anl.gov/mailman/listinfo/gsas-ii > > -------------- next part -------------- > An HTML attachment was scrubbed... > URL: < > http://mailman.aps.anl.gov/pipermail/gsas-ii/attachments/20200408/c2b7906d/attachment-0001.html > > > > ------------------------------ > > Message: 3 > Date: Wed, 8 Apr 2020 11:21:07 -0700 > From: Sergey Ushakov <[email protected]> > To: [email protected] > Subject: Re: [GSAS-II] Pawley refinemet question > Message-ID: > <CAG1YaUOpCYzVGfa11Y6FoW4p+9dUfgah4a9C=27H= > [email protected]> > Content-Type: text/plain; charset="utf-8" > > Thank you, Brian, for clarifying this! > > On Wed, Apr 8, 2020 at 11:14 AM Toby, Brian H. <[email protected]> wrote: > > > Hi Sergey, > > > > Both LeBail and Pawley fits are not able to determine phase fractions > > because the scale factors are all arbitrary and thus the phase fractions > > cannot be refined. However, the reported mass/weight fractions are > > determined from the unrefined phase fractions and they are displayed even > > though meaningless. > > > > Brian > > > > On Apr 8, 2020, at 12:58 PM, Sergey Ushakov via GSAS-II < > > [email protected]> wrote: > > > > Greetings! I have a question maybe not specific to GSAS-II but more about > > Pawley vs Le Bail fitting of powder XRD data. > > I work on high temperature data from laser-heated solid spheroids which > > rotate in a gas flow in aerodynamic levitator. > > The data are collected in transmission geometry at 6-ID-D at APS. > > The rotation is not well controlled since it depends on the shape of each > > bead formed by melt solidification, i.e., on surface tension, volume > change > > on melting, etc. > > So, sometimes data are very much powder-like and amenable to Rietveld > > refinement of the structure, but sometimes they are not, and in this > case, > > I do Pawley fit for cell parameters. > > I used to do Le Bail fitting for that in GSAS-I, but I understand that it > > was replaced by Pawley refinement (although there is an option for Le > Bail > > extraction of intensities?). > > > > To my surprise, Pawley fit in GSAS-II yield phase/weight fraction if one > > turns it on for refinement. > > I thought phase fraction could be correctly refined only from Rietveld? > > > > I would appreciate any comments on this! > > > > Sergey > > > > -- > > Sergey Ushakov PhD > > > > Staff Research Associate > > > > Peter A Rock Thermochemistry Laboratory and NEAT ORU > > Rm 4415, Chemistry Annex > > University of California, Davis > > Davis, CA 95616 > > > > _______________________________________________ > > GSAS-II mailing list > > [email protected] > > https://mailman.aps.anl.gov/mailman/listinfo/gsas-ii > > > > > > > > -- > -- > Sergey Ushakov PhD > > Staff Research Associate > > Peter A Rock Thermochemistry Laboratory and NEAT ORU > Rm 4415, Chemistry Annex > University of California, Davis > Davis, CA 95616 > phone (530) 902-8185 > -------------- next part -------------- > An HTML attachment was scrubbed... > URL: < > http://mailman.aps.anl.gov/pipermail/gsas-ii/attachments/20200408/878ce5e8/attachment.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 253, Issue 1 > *************************************** > -- *Hooman Yaghoobnejad AslPostdoctoral FellowTexas Materials Institute, Cockrell School of [email protected] <[email protected]>* *204 E. Dean Keeton Street, C2200Austin, Texas 78712, USA* *Office: ETC 8.112*
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