[ccp4bb] Commensurate superlattice discussion; summing up and thankyou

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CCP4bb <-- 2007 <-- March 2007 <-- 29 March 2007

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Subject: Re: Merohedral twinning
From: Christopher Colbert Christopher {- dot -} Colbert {- at -} UTSOUTHWESTERN {- dot -} EDU
Date: 2007-03-29

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From: Jobichen Chacko jobichenc {- at -} NUS {- dot -} EDU {- dot -} SG
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Subject: Commensurate superlattice discussion; summing up and thankyou
From: John R Helliwell jrhelliwell {- at -} GMAIL {- dot -} COM
Date: 2007-03-29

Re a commensurate superlattice case

Dear CCP4bb Colleagues,

Thanks to the varied interest and especially even as far as browsing and
processing of diffraction images kindly undertaken by Kay Diederichs,
Gloria Borgstahl and Jeff Lovelace, I went back to one-by-one scrutiny of
images including another native that I had not done that for so far. I
finally found a zone axis which autoindexed in P2 (now with the problem axis
labelled as 'c', just a labelling effect of course). With this now known to
me I found that in the main native data set and a Pb data set that I could
just about see the same zone axis ie much more misset but capable of
indexing in the same P2 cell but with quite strong non-isomorphism (~3%).
Anyway I have provided details to Gloria Borgstahl for a grant proposal
(update) she is making imminently. So, whilst oddity 1, defined in my first
email ie 'triclinic but with alpha approx = 90 degrees', I regard as solved
oddity 2, 'the commensurate cell doubling effect', is still insurmountable
at present. Nb there can be favourable commensurate cases such as pointed
out to me by Ethan Merritt but where non-isomorphism did not strike too.
Apologies to those colleagues that I have not highlighted here, but who were
all helpful either with ingenious suggestions or with good
strategic/tactical advice.

Best wishes,

John Helliwell

--
John R Helliwell
Professor of Structural Chemistry, The University of Manchester;

CCP4bb navigation

CCP4bb <-- 2007 <-- March 2007 <-- 29 March 2007

Previous message:
Subject: Re: Merohedral twinning
From: Christopher Colbert Christopher {- dot -} Colbert {- at -} UTSOUTHWESTERN {- dot -} EDU
Date: 2007-03-29

Next message:
Subject: Multiple nucleation
From: Jobichen Chacko jobichenc {- at -} NUS {- dot -} EDU {- dot -} SG
Date: 2007-03-29