The two most likely possibilities are:
1. Beam position changed somewhat after the repair and the site file was
not updated with the new position. This could result in misindexing of the
diffraction pattern with poor positional agreement (Chi2) as a
consequence. The diagnosis of misindexing is very simple, as it will not
produce acceptable merging statistics even in P1 space group. The
correction is also simple: by updating the site file with the correct beam
position.
2. A non-ideal crystal with a complex spot shape in its diffraction
pattern. This could result, for example, from uneven cooling rates and
variability in the crystal lattice. Merging statistics should be
acceptable, however they may not be perfect. Better cryo-cooling is likely
to help.
Zbyszek Otwinowski
> Dear Colleagues,
>
> I'm collecting a dataset on our recently repaired Rigaku home source.
Crystal diffracts to 2.2A. Indexing seems to be all fine. However,
during integration, I realize Y-Chi2 is increasing constantly (from 2 to
4.5, almost linear) within 60 degree collection, whereas X-Chi2 stays
the same. An image is attached. There are still another 60 degree to go.
Although the
> prediction fits the images well so far, I'm afraid the Y-Chi2 will
eventually run out of the chart.
> My question is could it be related to any hardware malfunctioning, i.e.,
goniometer, image plates, etc, which may be a side effect of the recent
major repair? Or what else it can be?
>
> Thanks,
> Bing
>
Zbyszek Otwinowski
UT Southwestern Medical Center at Dallas
5323 Harry Hines Blvd.
Dallas, TX 75390-8816
Tel. 214-645-6385
Fax. 214-645-6353
Zbyszek Otwinowski
UT Southwestern Medical Center at Dallas
5323 Harry Hines Blvd.
Dallas, TX 75390-8816
Tel. 214-645-6385
Fax. 214-645-6353
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