[ccp4bb]: Tetragonal Twinning & Detwin

[David Briggs <d.briggs@mail.cryst.bbk.ac.uk>]

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Dear ccp4-ers...

	I have a dataset that I scales equally well in P4 and P422. In
order to resolve this ambiguity I looked at the p4 scaled data in hklview
and found mirror planes in all the right places suggesting that the laue
class was 4/m mm, therefore p422.
All the moments and intensity statistics in Scala/truncate look fine when
the data is scaled in p422, but not quite as good in p4.
Just for the hell of it, I ran the detwin program on the p4 scaled data,
and detwin reckons my data is pretty much a perfect twin.
So... if the true space group is p422, and you put p4 data through detwin,
will it appear twinned? (as 'perfectly' twinned p4 data can appear to be
p422...)

The UCLA twinning server indicates that my data is not perfectly twinned
when tested in p422...
so now I'm getting two conflicting results and I'm confused...

(basically... is my data twinned or not!!!)

Thank you all in advance for any replies and assistance...

	Cheers

		Dave

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