>All Rietvelders (included me) are certainly trying
> a completely free refinement before to decide or
> not to use selected restraints.
About "All" I certainly doubt.
>Am I especially scrutinized? I feel more and more
>uncomfortable about such verifications of everything I do:
I believe that one should be happy about such an interest to his works ;-)
>Leonid, I suggest you to try K4P2O7 - synchrotron data...
If you send me the data I may try.
Regarding the fears, the colleagues etc.: geometric and other parameters can
not be regarded as wrong or right irrespectively of their uncertainties. If
distances deviate from their expectations or DFTized values within 3 e.s.u.
they are not wrong - they are REAL (if e.s.u. are real).
*******************************************************
Leonid A. Solovyov
Institute of Chemistry and Chemical Technology
660049, K. Marx 42, Krasnoyarsk, Russia
http://sites.google.com/site/solovyovleonid
*******************************************************
________________________________
From: Armel Le Bail <x...@noos.fr>
To: rietveld_l@ill.fr
Cc: s...@yahoogroups.com
Sent: Wednesday, July 31, 2013 11:48 PM
Subject: Re: [sdpd] Re: Are restraints as good as observations ?
>The problem of having jammed
the wrong molecule
>> into a unit cell can be identified by restraints which
>> are violated. With rigid bodies it is more difficult to
>> find out what the data are trying to tell you. Is this
>>wrong molecule issue the problem you fear?
>
>I prefer resolving such problems by unrestrained refinement with minimal
rigid constraints on unambiguous parts which can't be
refined.
All Rietvelders (included me) are certainly trying a completely free
refinement before to decide or not to use selected restraints. I tried,
and finally preferred to use some soft restraints (the fear of being
DFTized because of some interatomic distances obviously out of their
usual range). Some of my old SDPDs without restraints were DFTized, the
DFTizers were claiming that powder results are good for some dustbin...
Now I am guilty according to Leonid (guilty to not use DDM working so
much better than Fullprof in such cases; dur to the so clever background
treatment)... But the paper was accepted ;-). A few days after I received
a DFTization... Am I especially scrutinized ? I feel more and more
uncomfortable about such verifications of everything I do (Leonid, I
suggest you to try K4P2O7 - synchrotron data, space group P61 - for which
I had to put distance restraints on the three P2O7 independent groups -
Powder Diffraction, 28, 2-12, 2013) !
Are all my results so bad ? Below is the COMPSTRU Bilbao software output
of the comparison of the calcium glycinate trihydrate as published in
Acta C and as from the Leonid DDMization with contraints "only"
on H atoms (a lot of constraints BTW, there are 14 independent H
atoms...). The measure of similarity is 0.027. We will have to wait for
the single crystal results (if any some day) before to conclude to the
best way to proceed in that case. Anyway, if the molecule is wrong, it is
wrong in both powder refinements.
Armel
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