OK, seems that the SDPD book preface looks unclear to some.
Western movies adepts well know that sentence :
"You see, in this world there's two kinds of people, my friend: those with
loaded guns, and those who dig. You dig. .."
Similarly, there are two kinds of people, those believing that the sense of the
words "structure determination" and
"structure refinement" are the same, and the others. You dig.
Best
Armel
> Message du 29/08/18 18:09
> De : "Larry Finger"
> A : "Le Bail Armel" , Rietveld_L@ill.fr
> Copie à :
> Objet : Re: Rietveld website cancelled ?
>
> On 08/29/2018 04:15 AM, Le Bail Armel wrote:
> > Hi,
> >
> > After the IUCr Monograph on Crystallography 13 (2002)
> >
> > entitled "Stucture Determination from Powder Diffraction Data"
> >
> > you may find in the preface :
> >
> > "Although the Rietveld method of structure refinement from powder
> >
> > diffraction data is often loosely considered to be synonymous with structure
> >
> > determination, it is not. The Rietveld method only comes into play in the
> >
> > final stage of the structure solution process when an approximate structural
> >
> > model has been found."
> >
> > WIF David, K Shankland, LB McCusker, C Baerlocher
> >
> > A clear distinction having my complete agreement.
> >
> > Armel
>
> Armel,
>
> Although the above statement may be generally true, I can provide a counter
> example. In Max W. Schmidt, Larry W. Finger, Ross J. Angel, and Robert E.
> Dinnabier, "Synthesis, crystal structure, and phase relations of AlSiO2OH, a
> high pressure hydrous phase", American Mineralogist, V. 83, 881-888, 1998, we
> only had a powder - no single crystals. From data measured at ESRF, we used
> GSAS
> to isolate the peaks of interest for the unknown phase, and used program
> TREOR
> to autoindex the unknown and identify the impurity phases. We then extracted
> intensities using the LeBail method, and determined the structure using
> direct
> methods with program SIRPOW. The structure was then refined with GSAS. We
> were
> even able to locate the H atom from Fourier maps!
>
> Even 20 years ago, it was possible to determine the structure from X-ray
> powder
> patterns.
>
> Larry
>
>
>
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