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 _______________________________ 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 >> _______________________________ >> >> >> 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/ ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
