[sdpd] error measurements

[Steve Maginn <maginn...@ccdc.cam.ac.uk>]

Hi everyone,

With an increasing number of structures being determined ab initio from
powder data, the Cambridge Crystallographic Data Centre is beginning to
grapple with the problems of inclusion of these into the Cambridge
Structural Database.

There is no doubt that they should or will be included, but one problem is
that there appears to be little consistency or standard about which error
measurement is used to give a quality indicator for structures. There are a
plethora of different R-factors, chi squareds, etc. And the problem of
course is relating these to the standard R and weighted R used in
single-crystal structure determinations, with which powder structures will
be compared when they join the bulk of crystallographic data in the CSD. 

Are there any views as to which error measurement should be used ? And how
long will it be before reported powder structures are standardised using
this measurement, so database authors and more importantly users can
reliably judge the precision / quality of a structure ?

Views welcome ...

Cheers,

Steve Maginn,
CCDC, UK


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Dr. Stephen J. Maginn,
Support and Marketing Manager,
Cambridge Crystallographic Data Centre (CCDC),
12 Union Road,
Cambridge CB2 1EZ, UK

phone +44 (0)1223 762534
FAX    +44 (0)1223 331116
e-mail   maginn...@ccdc.cam.ac.uk

http://www.ccdc.cam.ac.uk

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