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Hi,
It might be using isomorphous Cullis R factor for the anomalous dispersion
change (using a difference between wavelengths instead of between F+ and
F-). Otherwise, it wouldn't be very meaningful (R factors that are always
infinite probably aren't useful to assess data quality).
The defination I've got for isomorphous Cullis is ( \sum_{hkl}{ ( |F_{PH}
(+/) F_{P}| - | F_{H,calc} | } ) / ( \sum_{hkl}{ | F_{PH} (+/-) F_{P} | }
) ; where the (+/-) is + if the signs of F_{PH} and F_{P} are opposite,
and - if the signs are the same (from Dreth 2nd edition...I'm unclear on
how the signs could be opposite, as that would imply a negative amplitude
for either F_{PH} or F_{P}); substitute inflection/remote/peak as
necessary for F_{PH} and F_{P}.
Pete
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>
>
> Hi everyone:
>
> How is an anomalous Cullis R defined for centric reflections? (If it is
the F+ - F-, how can that be meaningful?)
>
> Thanks.
>
> Bill Scott
>
>
>
Pete Meyer
Fu Lab
BMCB grad student
Cornell University
