[ccp4bb] Friedel vs Bijvoet

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CCP4bb <-- 1999 <-- November 1999 <-- 30 November 1999

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Subject: Re: Restraints in Refmac5
From: Partha Chakrabarti ppchak {- at -} GMAIL {- dot -} COM
Date: 2008-06-26

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From: Christian Biertuempfel biertumpfelc {- at -} NIDDK {- dot -} NIH {- dot -} GOV
Date: 2008-06-27

Subject: Friedel vs Bijvoet
From: Bernhard Rupp bernhardrupp {- at -} SBCGLOBAL {- dot -} NET
Date: 2008-06-27

Dear All,

I wonder about the conventions using Friedel vs Bijvoet pair.

a) there are no differences. As long as h = -h, it's a Friedel
or a Bijvoet pair. They are the same.

b) A Friedel pair is any reflection h = -h including hR = -h, i.e.
including centric reflections.
A Bijvoet pair is an acentric Friedel pair, it can carry
anomalous amplitude differences, whereas centric Friedel
pairs invariably cannot. Actually, Bijvoet pairs (acentric
Friedel pairs) invariably do carry anomalous amplitude differences.
There is no such thing as no anomalous scattering.
We may elect to ignore it, only.

c) of course, this all assumes absence of anisotropic AS.

def b) seems to be helpful in discussions and make sense given that absolute

configuration that needs AS signal is somehow associated with Bijvoet's
work.

Are any authoritative answers/conventions/opinions available on that ?

Thx, BR

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CCP4bb navigation

CCP4bb <-- 1999 <-- November 1999 <-- 30 November 1999

Previous message:
Subject: Re: Restraints in Refmac5
From: Partha Chakrabarti ppchak {- at -} GMAIL {- dot -} COM
Date: 2008-06-26

Next message:
Subject: Re: TMAO for crystallization
From: Christian Biertuempfel biertumpfelc {- at -} NIDDK {- dot -} NIH {- dot -} GOV
Date: 2008-06-27