I sympathise with Luca. There is no generally accepted name for this kind of profile refinement, as there is for Pawley or Le Bail refinement, terms that are well understood. I would simply call it *Profile Refinement*, as Rietveld did, specifying *Quantitative Phase Analysis* where that is appropriate. It's true that you can refine the atomic coordinates for the different phases (to reduce the R-factor :-) but it would be better "conduct" to fix atomic coordinates as determined from well prepared mono-phase samples, refining only particle size, preferred orientation etc for each phase. So "Rietveld Refinement" would be restricted to cases where the atomic coordinates were refined to fit the profile. I don't think this was the case here.
On Sat, 13 Jan 2024 at 09:39, Luca Lutterotti <luca.luttero...@unitn.it> wrote: > You are both true in a certain sense. It is true that this is not the core > of the Rietveld refinement per se, but we don’t have an “official” term to > call a refinement of a powder pattern using crystallographic parameters. > Hence I tried to call it Rietveld-like or extended Rietveld. > The alternatives are full pattern fitting, but this is usually referring > to an unconstrained refinement, Pawley like. In XRF they use the term > Fundamental Parameters approach, but I am afraid in diffraction was already > used (first Cohere, am I remembering right?) for fitting profiles using > physical models for the instrumental broadening. > The Rietveld community never defined a generally accepted term for this > kind of refinement, so people outside it what can they use? > > I am amused how Armel can spot such articles and especially notice the > trick they did. I would not call the worse Rietveld refinement but for sure > a bad misconduct case. Were they removing some peaks they could not explain > or put down an amorphous halo at low angle? I am sad they used Maud in the > first place and then manipulate the image. I notice that they report the > intensity as (linear) counts, but it is not, they replaced also the labels > as from the noise, residual and peaks intensity I am sure it was in square > root of the intensity. Background was removed too. But I think there was no > review at all, as the figure caption contains errors even for the chemical > formula (Fe -> F). > > Best regards, > <http://www.unitn.it/> > [image: logo_unitrento_firma.png] > > > *Luca Lutterotti* > Dipartimento di Ingegneria Industriale > Università di Trento > via Sommarive, 9 - 38123 Trento (Italy) > tel. +39 0461 2824-14 (Office), -34 (X-Ray lab) > > [image: ico_fb_32x32.png][image: ico_twitter_32x32.png][image: > ico_insta_32x32.png][image: ico_linkedin_32x32.png][image: > ico_youtube_32x32.png] > > Maud: http://maud.radiographema.com <http://maud.radiographema> > > > > On 13 Jan 2024, at 07:39, Alan W Hewat <alan.he...@neutronoptics.com> > wrote: > > The core of Rietveld refinement is REFINING the crystallographic > parameters to fit the pattern. That was the great innovation. Is that done > here ? To calculate various patterns to refine phase composition you > necessarily need models of the crystal structures. But all refinements of > powder patterns are not Rietveld Refinement. Quantitative analysis of > powder samples is an important technique, and to attribute that to Rietveld > is wrong. Same goes for Pair Distribution Function analysis. Calling > everything "Rietveld Refinement" is not helpful, and actually hides the > fundamental contribution of this technique to crystallography. > > ________________________________ > Dr Alan Hewat, NeutronOptics > Grenoble, FRANCE (from phone) > alan.he...@neutronoptics.com > +33.476984168 VAT:FR79499450856 > http://NeutronOptics.com/hewat <http://neutronoptics.com/hewat> > _______________________________ > > > On Sat, 13 Jan 2024, 07:00 Matthew Rowles, <rowle...@gmail.com> wrote: > >> Hard disagree here. >> >> You're using crystallographic parameters to calculate the (intensities >> and positions of the) pattern. >> >> To me, that's the core of Rietveld refinement. >> >> You need to apply a peak shape model. Why not apply a model from which >> you can extract crystallite parameters? >> >> QPA can then be done on the output of a refinement, eg application of the >> internal standard method using the Hill /Howard algorithm. >> >> Its still a Rietveld refinement, I'm not just fitting peaks willy nilly; >> they're constrained by a crystal model. >> >> >> Matthew >> >> On Sat, 13 Jan 2024, 01:48 Alan W Hewat, <alan.he...@neutronoptics.com> >> wrote: >> >>> Apart from the record number of atoms, phases, parameters, citations etc >>> used to describe just 3 broad peaks, I object to this kind of refinement >>> being called "Rietveld refinement". Luca called it "Rietveld-like" in MAUD, >>> which was used here, but even that is wrong. The term "Rietveld refinement" >>> should be restricted to the refinement of crystallographic parameters - >>> cell dimensions, atom coordinates etc. and not applied to quantitative >>> analysis of phases, particle size etc. Fitting peaks in powder patterns was >>> done before Rietveld, who must be turning in his grave to see his name >>> associated with this kind of thing. >>> >>> ________________________________ >>> Dr Alan Hewat, NeutronOptics >>> Grenoble, FRANCE (from phone) >>> alan.he...@neutronoptics.com >>> +33.476984168 VAT:FR79499450856 >>> http://NeutronOptics.com/hewat <http://neutronoptics.com/hewat> >>> _______________________________ >>> >>> >>> On Fri, 12 Jan 2024, 12:57 Le Bail Armel, <le-bail.ar...@orange.fr> >>> wrote: >>> >>>> Hi, >>>> >>>> A good candidate for the "worst Rietveld refinement of the year" award : >>>> >>>> https://pubpeer.com/publications/12069A6AD9D5D34F26031F34705D06 >>>> >>>> Even the difference pattern is totally fabricated. >>>> >>>> Best >>>> >>>> Armel >>>> ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++ >>>> Please do NOT attach files to the whole list >>>> <alan.he...@neutronoptics.com> >>>> Send commands to <lists...@ill.fr> eg: HELP as the subject with no >>>> body text >>>> The Rietveld_L list archive is on >>>> http://www.mail-archive.com/rietveld_l@ill.fr/ >>>> ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++ >>>> >>>> ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++ >>> Please do NOT attach files to the whole list >>> <alan.he...@neutronoptics.com> >>> Send commands to <lists...@ill.fr> eg: HELP as the subject with no body >>> text >>> The Rietveld_L list archive is on >>> http://www.mail-archive.com/rietveld_l@ill.fr/ >>> ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++ >>> >>> ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++ > Please do NOT attach files to the whole list <alan.he...@neutronoptics.com > > > Send commands to <lists...@ill.fr> eg: HELP as the subject with no body > text > The Rietveld_L list archive is on > http://www.mail-archive.com/rietveld_l@ill.fr/ > ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++ > > > -- ______________________________________________ Dr Alan Hewat, NeutronOptics, Grenoble, FRANCE <alan.he...@neutronoptics.com> +33.476.98.41.68 http://www.NeutronOptics.com/hewat <http://www.neutronoptics.com/hewat> ______________________________________________
++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++ Please do NOT attach files to the whole list <alan.he...@neutronoptics.com> Send commands to <lists...@ill.fr> eg: HELP as the subject with no body text The Rietveld_L list archive is on http://www.mail-archive.com/rietveld_l@ill.fr/ ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
