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[sdpd] Dubious structure

Hi,

The question today is : shall we use systematically
either soft constraints on interatomic distances or rigid
body refinements or ab initio quantum chemistry
calculations (or etc) when dealing with Rietveld refinements.

The simple presentation of the raw result may generate
the comment "dubious structure" from the "usual monster
referee,"  even saying that "this is powder, low resolution
data (or intrinsic strong line broadening), no accuracy can
be expected on the atomic coordinates and interatomic
distances and angles, so, be indulgent."

You cannot find in the journal recommendations to authors
any obligation to force the distances to "be" what you think
they should be. If we did so, never more we would be able to
find something different from the range of expected values
when publishing results based on powder diffraction data.

Of course, when high resolution synchrotron data is available
for a structure not too complex, the standard of quality may
be higher than when using laboratory X-rays or neutron data.
Anyway, they are almost no case known where powder data
produces better results than single crystal data - when
available.

On the other hand, letting publish raw refinements, even
producing clearly wrong interatomic distances, provide
a job for the experts in redressing bad structures, and you
get citations ;-).

Maybe we should present 2 tables : one as obtained without
massaging, the other with....

Comments ?

Best regards,

Armel

  



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