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Re: [sdpd] refinement of the occupation in FULLPROF
Dear Zhen-Hua Liang,
this problem has already been discussed several times on the list (or was
it on the Rietveld mailing list ?).
A description of the solution to this problem can be found in J.-M.
Joubert, R. Cerný, M. Latroche, A. Percheron-Guégan and K. Yvon, J. Appl.
Crystallogr., 31 (1998) 327-332.
If using Fullprof you should work on the real number of atoms and not SOF
as described in your message (ie occupancy numbers on site 4e should be
twice those on site 2a).
If using variables numbers 1 and 2 (you have two unknows in your case since
the total number of atoms is known), you get the following with the trick
of introducing a supplementary fictive atom on the third site:
Ta1 1.766
11.00
Nb1 0.234
-11.00
Ta2 3.304
21.00
Nb2 0.696
-21.00
Ta3 1.482
-11.00
Nb3 2.498
11.00
Ta3 0.01
-21.00
Nb3 0.01
21.00
With best regards
/Jean-Marc Joubert
23:17 28/03/2005 +0800, Zhen-Hua Liang a écrit :
>Dear all,
> I have a problem about refinement of the occupation in the Rietveld
>Refinement by FULLPROF. For example, Nb1.72Ta3.28S2(ICSD #71171):
>Atom # OX SITE x y z SOF
> Ta 1 +0 2 a 0 0 0 0.883
> Nb 1 +0 2 a 0 0 0 0.117
> Ta 2 +0 4 e 0 0 0.4248(1) 0.826
> Nb 2 +0 4 e 0 0 0.4248(1) 0.174
> Ta 3 +0 4 e 0 0 0.1560(1) 0.373
> Nb 3 +0 4 e 0 0 0.1560(1) 0.627
> S 1 +0 4 e 0 0 0.3024(4) 1.
>How to set the Codewords of the occupation of Ta and Nb atom in the Rietveld
>Refinement by FULLPROF? For example, Ta1+Nb1=1.000 and Ta1+Ta2+Ta3=3.28.
----------------------
Jean-Marc Joubert
Laboratoire de Chimie Métallurgique des Terres Rares
UPR 209 - Institut des Sciences Chimiques Seine-Amont - CNRS
2-8 rue Henri Dunant 94320 Thiais
phone/fax: 33 1 49 78 12 11/12 03
email/web : jean-marc.joubert...@glvt-cnrs.fr/http://www.glvt-cnrs.fr/lcmtr
[Non-text portions of this message have been removed]
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