[ccp4bb] Can't choose full H-M symbol for conventional cell ?

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CCP4bb <-- 2007 <-- March 2007 <-- 16 March 2007

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Subject: Re: refmac refinement and multiple conformations
From: Dirk Kostrewa dirk {- dot -} kostrewa {- at -} PSI {- dot -} CH
Date: 2007-03-16

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From: "Arti S {- dot -} Pandey" artis {- at -} CHEMISTRY {- dot -} MONTANA {- dot -} EDU
Date: 2007-03-16

Subject: Can't choose full H-M symbol for conventional cell ?
From: Ian Tickle I {- dot -} Tickle {- at -} ASTEX-THERAPEUTICS {- dot -} COM
Date: 2007-03-16

We're having some problems essentially because AFAICS Mosflm (and also
D*Trek) don't recognise the 'full' Hermann-Mauguin symbols for space
groups.

For example for space group no 18 with the 'short' H-M symbol 'P 2/1 2/1
2' in the setting with 'full' H-M symbol 'P 2 2/1 2/1' the programs
choose the correct conventional cell as say a=60, b=70, c=90 (according
to the convention a<=b<=c). But then unless I've missed something
obvious, they only seem to give the option to assign the short H-M
symbol; however the problem is that this doesn't uniquely define the
full H-M symbol (which in turn uniquely defines the general equivalent
positions), and of course in this case there are 3 possibilities (i.e.
with the 2-fold rotation axis along a, b or c resp.). Then the user,
seeing that there is only one option for SG 18, assumes that the program
knows what it's doing and naturally selects that, whereas in fact it
doesn't: it incorrectly equates the full H-M symbol to the short one,
and of course havoc breaks loose from there on!

Is there any reason why the programs don't allow the complete set of
full H-M symbols to be assigned (they are of course all defined in
syminfo.lib)?

Cheers

-- Ian

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CCP4bb <-- 2007 <-- March 2007 <-- 16 March 2007

Previous message:
Subject: Re: refmac refinement and multiple conformations
From: Dirk Kostrewa dirk {- dot -} kostrewa {- at -} PSI {- dot -} CH
Date: 2007-03-16

Next message:
Subject: Re: B-factors in Shelxl
From: "Arti S {- dot -} Pandey" artis {- at -} CHEMISTRY {- dot -} MONTANA {- dot -} EDU
Date: 2007-03-16