Hi Armel, A more extreme example was in Acta D56, 1549-1533 (2000) where a protein structure (a new insulin phase) was solved by rigid body Rietveld refinement from a synchrotron powder data set & subsequently confirmed by a single crystal analysis (see Acta Cryst. (2001). D57, 1091-1100). NB: this kind of thing has also happened more recently (see papers by Margiolaki, et al). Bob Von Dreele
-----Original Message----- From: rietveld_l-requ...@ill.fr <rietveld_l-requ...@ill.fr> On Behalf Of Larry Finger Sent: Wednesday, August 29, 2018 11:10 AM To: Le Bail Armel <le-bail.ar...@orange.fr>; Rietveld_L@ill.fr Subject: 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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