I would like to know whether GSAS is able to constraint the Uiso value
so that it will be always bigger than zero.
As others have indicated - GSAS does not do that (topas gives you the
option, doubtless amongst others). Shelx does do that (with single
crystal data) and you can't turn it off
Dear colleagues:
The Los Alamos Neutron Science Center
(LANSCE) ( http://lansce.lanl.gov ) is
extending the
deadline for
submitting proposals to 8:00 a.m. Mountain Standard Time on
Thursday July 6.
Proposals must be submitted on-line at
:
http://lmisgreen.lanl.gov:8080
Available instrumen
Alan Hewat wrote:
Should one first refine lattice parameters and then "fix" them before
proceeding with structure
refinement?
In the early stages of a Rietveld refinement you might want to fix some
parameters, for example
you might want to refine just zero point, cell constants, scale factor
>Should one first refine lattice parameters and then "fix" them before
>proceeding with structure refinement?
In the early stages of a Rietveld refinement you might want to fix some
parameters, for example you might want to refine just zero point, cell
constants, scale factor etc to get them
of course, we could all start refining corrected S(Q) instead of raw
data. This is less convenient, but not outrageously so with modern
computing. A bit of work on the software side would also make it more
convenient if there is interest in the community.
Simon
Brian H. Toby wrote:
I wo
With regard to "constrained" refinement: Should one first refine lattice
parameters and then "fix" them before proceeding with structure refinement? As
I see it, lattice parameters are directly observable in the xrd pattern; if one
allows lattice parameters to change during structure refinemen
>A common, but minor reason why negative displacement values occur is due to
>ambiguity in the placement of the background at high Q (angle).
Another common reason why Uiso is low is because of the neglect of absorption.
(We have been through this many times - see the Rietveld archive eg
http:
I would like to know whether GSAS is able to constraint the Uiso value so that it will be always bigger than zero.GSAS does not have the ability to do that. Personally, I would prefer that people not use constraints or restraints to prevent negative displacement parameters (or even worse, have the
Dear all,
I would like to know whether GSAS is able to
constraint the Uiso value so that it will be always bigger than zero.
Thank you very much,
ana
Dr. Ana Isabel Becerro
Departamento Química Inorgánica
Instituto de Ciencia de Materiales de Sevilla
Universidad de Sevil
I will be out of the office starting 07/03/2006 and will not return until
07/10/2006.
I am out of town and will respond to your message upon my return. Please
contact Cheryl Vinson (ext. 14526) or Glenn van Gaalen (ext. 14597) with
any X-ray diffraction needs.
Hi Lachlan
Good to hear from you. Sorry I havn't been in touch for a while, but
I've hit one of those personal crises life throws up. The new job has basically
made me realise that I want out of London. I'm thinking of doing a bit of
travelling first and then maybe trying to settle down in
Dear Srebri and Yaroslav,
Thanks a lot for your input. However, my question does not concern a
specific compound I'm working with myself, but rather the ranking of the
solutions in Armel Le Bail's benchmark tests with bethanechol chloride
(http://sdpd.univ-lemans.fr/uppw/benchmarks/).
In case A(1
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