In the GUI mode, you simply initialize a parameter by entering
its name in into the grid on the "codes" tab, without the "=" sign!
This is equivalent to changing the line of code you've sent
from
Site OH num_posns 4 x 0 y 0 z 0.315309 occ O =oh; : 0.5 min =0; max =0.5;
beq 1
to
Site OH num_posns 4 x 0 y 0 z 0.315309 occ O oh; : 0.5 min =0; max =0.5;
beq 1
i.e. delete the "=" sign before the "oh".
Thus, I think there is no need to use the "prm" command
(or the launch mode) in your case.
However, there may be cases where it could be convenient to
declare a parameter separately. For example, I have a solid solution
series where all lattice parameters are a known function of
the stoichiometry parameter "X".
If I now want to do some restrictive fitting (instead of
four independent monoclinic lattice parameters I would
like to refine just "X"), then I can use the following workaround
to emulate something like the "prm" command in the GUI:
I simply add an additional dummy site to my structure phase.
Dummy site means that I may chose the name of the site and
the element freely, but set the occupancy to zero.
Now, I can use the x, y and z coordinates and the Beq as
"containers" for my parameters, because with zero occupancy,
the dummy atom will not contribute to the calculated intensities!
I enter the starting values for my parameter(s) in the "Values" tab
of the grid and the parameter name(s) in the "Codes" tab.
If a parameter is not to be refined, a "!" needs to precede
the parameter name.
Maybe this little workaround is useful to some of you.
I should add that this trick works in Topas version 3,
I'm not sure if it does with other versions...
Best wishes,
Frank
Habib Boughzala wrote:
So,
How to initialize a variable ?
Cheers
/-------Message original-------/
/*De :*/ Kern, Arnt <mailto:arnt.k...@bruker-axs.de>
/*Date :*/ 12/03/2010 09:05:03
/*A :*/ 'ian.mad...@csiro.au' <mailto:ian.mad...@csiro.au>;
habib.boughz...@ipein.rnu.tn <mailto:habib.boughz...@ipein.rnu.tn>;
rietveld_l@ill.fr <mailto:rietveld_l@ill.fr>
/*Sujet :*/ RE: Topas prm keyword
The keyword "prm" is exclusive to so-called Launch Mode operation,
please see also the Technical Reference manual.
Cheers,
Arnt
------------------------------------------------------------------------
*From:* ian.mad...@csiro.au [mailto:ian.mad...@csiro.au]
*Sent:* Freitag, 12. März 2010 08:53
*To:* habib.boughz...@ipein.rnu.tn; rietveld_l@ill.fr
*Subject:* RE: Topas prm keyword
Try prm not Prm (ie with all lower case letters)
/Cheers/
/ /
/o----------------------------oo0oo----------------------------o/
/ Ian Madsen/
/ Team Leader - Diffraction Science/
/ CSIRO Process Science and Engineering/
/ Box 312, Clayton South 3169/
/ Victoria, AUSTRALIA/
/ Phone +61 3 9545 8785 direct/
/ +61 3 9545 8500 switch/
/ +61 (0) 417 554 935 mobile/
/ FAX +61 3 9562 8919/
/ Email //_____ian.mad...@csiro.au_/ <mailto:ian.mad...@csiro.au>/ /
/o----------------------------oo0oo----------------------------o/
------------------------------------------------------------------------
*From:* Habib Boughzala [mailto:habib.boughz...@ipein.rnu.tn]
*Sent:* Friday, 12 March 2010 6:45 PM
*To:* rietveld_l@ill.fr
*Subject:* Topas prm keyword
Hi,
My mail is intended to Topas users, especially to Dr. Alan Coelho
I am trying to determine the carbonate / hydroxide ratio in some compounds.
This is a part of 'str' block In the input file (*.inp)
__________________________________________________________________________
Str
....
Prm oh 0.5
....
Site OH num_posns 4 x 0 y 0 z 0.315309 occ O =oh; : 0.5 min =0;
max =0.5; beq 1
Site C num_posns 2 x 0 y 0 z 0 occ C =1 - 0.5 oh; : 1 min =0; max
=0.5; beq 1
Site Oc num_posns 12 x 0.040114 y 0.953411 z 0.629971 occ O =(1 -
0.5 oh) / 3; : 1 min =0; max =0.25; beq 1
__________________________________________________________________________
Topas 4.2 run failed... Error: prm command in unrecognised !!!
Any suggestion ?
P.S. This keyword is unrecognised too in all tutorials inp file examples !!!
Thanks for help
Habib
Prof. Habib Boughzala.
*L*aboratoire de *M*atériaux et *C*ristallochimie.
*A*ssociation *T*unisienne de *C*ristallographie
I.P.E.I.N. Mrezga, 8000.
Nabeul. Tunisie.
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