At the end it is all wrong as we don’t refine individual electrons but 
restrained groups that are called “atoms” which are extrapolated with some 
average function calculated for free, unbounded atom.

Peter Zavalij

From: rietveld_l-requ...@ill.fr [mailto:rietveld_l-requ...@ill.fr] On Behalf Of 
Leonid Solovyov
Sent: Thursday, August 01, 2013 7:33 PM
To: s...@yahoogroups.com
Cc: rietveld_l@ill.fr
Subject: Re: [sdpd] Re: Are restraints as good as observations ?

>What information capacity ? The fact is that imposing
> the expected values you obtain a similar fit. This tells
> you that you cannot discuss your unrestrained "information",
> because it is unreliable.
> Information is something you may discuss reliably.
> The only possible discussion about P3-O14 = 1.72(3)A
> is to say that it is very probably strongly overestimated.

After THIS unrestrained refinement one CAN discuss RELIABLY ALL interatomic 
distances including P-O, K-O, K-P, K-K and P-P, as well as angles, orientations 
etc., WITHIN THEIR UNCERTAINTIES that are also estimated RELIABLY according to 
the EXPERIMENTALLY DETERMINED deviations of the unrestrained P-O distances. 
After the restrained refinement NOTHING can be discussed RELIABLY since neither 
the values nor their uncertainties are determined EXPERIMENTALLY.
After the unrestrained refinement one can state RELIABLY that the structure is 
DETERMINED with definite precision and, thus, discuss its features, compare it 
with other experimentally determined structures within their uncertainties, 
make more or less definite conclusions etc. After the restrained refinement one 
can only state that a hypothetical structure model is proposed and NOTHING can 
be concluded or discussed RELIABLY.
Don't you see the difference??!!
Determination = reliable experimental evaluation + reliable estimation of 
uncertainties.
Now I probably understand your "colleagues".

*******************************************************
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<mailto:x...@noos.fr>>
To: s...@yahoogroups.com<mailto:s...@yahoogroups.com>
Cc: rietveld_l@ill.fr<mailto:rietveld_l@ill.fr>
Sent: Friday, August 2, 2013 12:40 AM
Subject: Re: [sdpd] Re: Are restraints as good as observations ?


> All deviations from expected values (1.514 and 1.634) are within 3 e.s.u.s 
> that are around 0.03 A in average. Further improvements seem possible, but it 
> will require more time and efforts.
>
> So, one more example of underestimated information capacity of powder data 
> and overestimated necessity of restraints.

What information capacity ? The fact is that imposing the expected values you 
obtain a similar fit. This tells you that you cannot discuss your unrestrained 
"information", because it is unreliable.

Information is something you may discuss reliably. The only possible discussion 
about P3-O14 = 1.72(3)A is to say that it is very probably strongly 
overestimated.

Such are powder results for complex cases.

Sure, the restrained distances cannot be discussed as well. At least they are 
not completely extravagant.

Best

Armel
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