Re: [sdpd] Automatic peak position hunting

["L. Cranswick" <L.M.D.Cranswick...@dl.ac.uk>]

> >Thus the problem is not with the software programs 
> >but with the data collection conditions being
> >inappropriate - and then blaming the analysis software
> >as a substitute for proper recollection of the
> >data (?)
> 
> You know how recollection is not obvious at synchrotron
> places for guys not living there and even for those living
> there. 

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?

Is this a flaw in the synchrotron method that
experiments and data collections are assumed to
work flawlessly the first time?

>  >PS: Is this cell still considered to be unsolved?
> 
> Oversolved in fact : 300 different cell propositions with figures of 
> merit >200. I still don't know which one is the good one : 2 large 
> parameters highly probable, and a small one ambiguous.
> Such high figures of merit are not a usual result for non-optimal 
> data (well, two peaks pose a problem to automatic peak hunting, 
> so you may consider that a small part of the pattern is non-optimal 
> if you wish). 

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?

Lachlan.

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?


-- 
Lachlan M. D. Cranswick

Collaborative Computational Project No 14 (CCP14)
    for Single Crystal and Powder Diffraction
Daresbury Laboratory, Warrington, WA4 4AD U.K
Tel: +44-1925-603703  Fax: +44-1925-603124
E-mail: l.cranswick...@dl.ac.uk  Ext: 3703  Room C14
                           http://www.ccp14.ac.uk


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