[GSAS-II] Pawley refinemet question

[Sergey Ushakov]

Thank you, Brian, for clarifying this!

On Wed, Apr 8, 2020 at 11:14 AM Toby, Brian H. <toby at anl.gov> 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 <
> gsas-ii at aps.anl.gov> 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
>
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>
>

-- 
--
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
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