Dear all,
I am currently trying to perform a simple refinement of Corundum in the
hexagonal setting, namely the unit cell parameters (a=b=4.7589 A, c=12.991
A, alpha=beta=90 deg., gamma=120 deg): Refining the cell parameters a and c
works without problems, and putting limits to the refinement of the
parameter c also works as expected.
However, when I try to add limits to the parameter a (=b) I am running into
issues:
The original value is a=4.7589 A, and I would like to add the following
limits: Min=4.7 A, Max=4.8 A. Hence, I have added the following line in the
pcr-file:
! Limits for selected parameters :
1 4.7 4.8 0.0000 0 Cell_A_ph1_pat1
After running FullProf, I found the following section in the .out-file:
=> The following parameter limits have been read:
-> Parameter no.: 1 Limits: 4.7000 4.8000 Step for SA &
BoundaryCond: 0.0000 0
-> Modified internal limit for cell parameter no.: 1 Limits:
0.00000 0.00000
-> Modified internal limit for cell parameter no.: 1 Limits:
0.00000 0.00000
-> Modified internal limit for cell parameter no.: 1 Limits:
0.00000 0.00000
--------------------------------------------------------------
SYMBOLIC NAMES AND INITIAL VALUES OF PARAMETERS TO BE VARIED:
--------------------------------------------------------------
-> Parameter number 1 -> Symbolic Name:
Cell_A_ph1_pat1 4.7589002
As you can see, the limits "Min=4.7 A" and "Max=4.8 A" have been read from
the pcr-file, however, FullProf then seems to calculate "modified internal
limits" for this parameter, and these are zero in this case. As you can
imagine, the refinement does not work, of course.
I have also tried the same for a cubic structure (in which case you also
have "coupled" unit cell vector lengths); this worked without problems.
I have searched the FullProf documentation as well as the tutorials and
finally the web, but I could not find anything about it.
Do you have any idea why this might happen? Am I doing something wrong?
Thank you very much in advance!
Holger Putz
Crystal Impact
Dr. H. Putz & Dr. K. Brandenburg GbR
Kreuzherrenstr. 102
53227 Bonn
Germany
Tel . : +49-228-9813643
Fax : +49-228-9813644
E-mail: <mailto:i...@crystalimpact.de> i...@crystalimpact.de
Web : <https://www.crystalimpact.de> https://www.crystalimpact.de
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