Lubomir Smrcok wrote the following on 17/12/2015 16:48:
Sorry,
Arie, genetic algorithm (or its relatives) does not shuffle electron
density, just atom coordinates.
And with the atom coordinates the electron density is shuffled, not?
The unit cell electron density is just the convolution of the atomic
coordinates with spherical or non-spherical electron densities centered
on each atom (3D) coordinate.
Arie
Taking them the procedure (not GA
itself) calculates structure factors and compares them to the "observed"
structure factors (their squares, or intensities). Decision making
process of GA is not based on the differences in electron density, but
on |Fo|^2-|Fc|^2.
Lubo
On Thu, 17 Dec 2015, A. van der Lee wrote:
I agree with Yaroslav Filinchuk's thoughts:
"However, the "structure solution in direct space" does not attempt to
work in the reciprocal space - all the manipulations are done in the
direct space."
RMC, normal MC, genetic algorithms, they all shuffle electron density
in some or another way in real space. So 'real space structure
solution' sounds the best, and 'real space' is better than 'direct
space' as to avoid confusion with 'direct methods'.
Arie
ps: we should propose a new possible data value for
_atom_sites_solution_primary
By the way the data value vecmap (real-space vector search) is, I
suppose, equivalent to a real-space Patterson search, which is indeed
not the same as RMC, normal MC, genetic algorithms or other shuffle
methods.
Mike Glazer wrote the following on 17/12/2015 12:50:
But the original question was:
What's the right nickname for the method of structure solution from
powders, which instead of analyzing electron (nuclear) density
shuffles atoms or molecules around a cell and compares experimental
and calculated patterns ?
That's what we do with RMC in practice. We use RMC to create models
and then compare with experimental patterns.
Mike
Professor A M Glazer
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-----Original Message-----
From: Radovan Cerny [mailto:radovan.ce...@unige.ch]
Sent: 17 December 2015 11:03
To: Mike Glazer <mike.gla...@physics.ox.ac.uk>; Lubomir Smrcok
<uachs...@savba.sk>; Leonid Solovyov <l_solov...@yahoo.com>
Cc: rietveld_l@ill.fr
Subject: RE: structure solution terminology
RMC covers only a part of the "Direct space methods", not for example
methods using evolution algorithms.
Radovan Cerny
Laboratoire de Cristallographie, DQMP
Universit? de Gen?ve
24, quai Ernest-Ansermet
CH-1211 Geneva 4, Switzerland
Phone : [+[41] 22] 37 964 50, FAX : [+[41] 22] 37 961 08 mailto :
radovan.ce...@unige.ch
URL : http://www.unige.ch/sciences/crystal/cerny/rcerny.htm
-----Message d'origine-----
De : rietveld_l-requ...@ill.fr [mailto:rietveld_l-requ...@ill.fr] De
la part de Mike Glazer Envoy? : jeudi 17 d?cembre 2015 11:49 ? :
Lubomir Smrcok; Leonid Solovyov Cc : rietveld_l@ill.fr Objet : RE:
structure solution terminology
This all sounds like Reverse MonteCarlo (RMC) modelling. We have used
this with PDF analysis.
Mike Glazer
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A. van der Lee
Institut Européen des Membranes
CNRS - UMR 5635
Université de Montpellier II - Case Courrier 047
Place E. Bataillon
34095 MONTPELLIER Cedex 5 - FRANCE
Tel : 33 (0) 4 67 14 91 35
Fax : 33 (0) 4 67 14 91 19
**********************************************************************
member of RECIPROCS - Réseau des Enseignants, Chercheurs et ITA
Professionnels de la Cristallographie Structurale (French professional
crystallographer network):
http://metiersit.dsi.cnrs.fr/index.php?page=ReseauMetiers&codeBap=B
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Please do NOT attach files to the whole list <alan.he...@neutronoptics.com>
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