Alberto Martinelli schrieb:
Thank you for you suggestion, but I'd need a further explanation, if you
are experienced with Fullprof.
The manual states:
- at pg 53 (Debye-Scherrer geometry): "Monochromator polarisation
correction (Cthm and K in LINE 4)" and then "For synchrotron radiation, K
must be given (K=0.1)"
- at pg. 76: "Cthm - coefficient for monochromator polarisation correction"
and then "Rpolarz - polarisation factor"
It is not clear to me if the value that you suggest to me (~ 1) is Rpolarz
and if Cthm correspond to K and must setted equal to 0.1, since an input
referred to as K is not present in the input PCR file.
For the primary beam polarisation factor to be nearly 1 or nearly 0
is just a matter of definition (unless you use an exotic instrument
geometry). For Fullprof K should be close to 0 for synchrotron data.
Make sure you have set Ilo=3, otherwise K will not be used at all! CTHM
depends on your instrument's monochromator setup. It is
cos^2(2*ThetaMonochromator) for a single crystal monochromator. Your
local contact should know the correct value.
At 18.02 24/11/2004 +0100, you wrote:
Alberto,
Check you have the right polarisation correction. Synchrotron ~ 1,
laboratory typically 0.5 with no mono...
HTH,
Jon
Alberto Martinelli wrote:
Dear all,
I've got a problem with the Rietveld refinements of synchrotron data.
I'm using Fullprof and the problem is that the overall B, and then also
some of the isotropic displacement parameters, fall down to negative
values. I'm not very experienced in the treatment of synchrotron data and
may be I put some errouneous input in the PCR file, but I cannot understand
what.
Thanks in advance for your helpful suggestions, best regards
Alberto Martinelli
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