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Re: [sdpd] Automatic peak position hunting
Lachlan wrote :
>What is the estimate on the percentage of synchrotron
>powder diffraction data that (had it been collected on
>a lab XRD machine) would be considered sub-standard and
>should be recollected ?
No idea. In most case those fast sub-standard patterns
are made on your worst, or less interesting samples, after
collecting good patterns of your best samples, and will
show that they should not be recollected, or are finally
sufficient.
>Is this a flaw in the synchrotron method that
>experiments and data collections are assumed to
>work flawlessly the first time?
Recording a powder pattern at room temperature
works generally flawlessly the first time.
But brillant patterns of bad samples are of little use.
Unpublished results are also of little use for the
community. You gave an interesting number of
several thousands of single crystal data collected
those last years at the 9.8 Daresbury station, and
solved. How many were published 2 years later ?
Can we expect to see a new winner soon in the CSD
list of authors http://www.cryst.chem.uu.nl/s100R ?-).
>Maybe using the latest Crysfire with the latest beta
>test of Chekcell would help go through those 300
>solutions to show it is a tricky problem in a
>relatively time effective manner - especially trying
>to match up the higher angle reflections?
Maybe. I confess that I hope that some student of
the SDPD Internet Course will succeed some day ;-).
However, that exercise does not correspond to many
points - since the teachers have not the solution...
>PS: For the laboratory version of this data - is
>the complete geometry information given anywhere for
>fundamental parameters fitting of the peak profiles?
>Goniometer radius, slit widths and heights?
>Soller acceptance angles?
Probably the fundamental parameter programs offer
also the old classical Rietveld approach, which seems
quite sufficient to me in that case. Anyway, same conditions
as the CeO2 powder patterns made here for the Size/Strain
Round Robin : http://www.cristal.org/microstruct/ssrr/
Best,
Armel Le Bail
http://www.cristal.org/course/
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