Igor Djerdj schrieb:
The following question is addressed more to FULLPROF users. I want to
refine atomic occupancies of Fe-doped TiO2 for instance. Assuming that
Ti is substituted with Fe at some sites, how can I provide that the
sum of occupancies of Fe and Ti is 1 or 100%?
There are two options I'm aware of:
1) has been mentioned by Alexandre already: Using the same parameter
code number for both occupancies, setting the starting values to the
correct chemistry and coupling the damping factors to keep the chemistry
fixed. This look like this:
Mn1 MN 0.12500 0.12500 0.12500 0.38224 5.00252 0 0 0 0
0.00 0.00 0.00 261.00 -271.00
Cr1 CR 0.12500 0.12500 0.12500 0.38224 2.99748 0 0 0 0
0.00 0.00 0.00 261.00 271.00
Mn2 MN 0.50000 0.50000 0.50000 0.38923 2.99748 0 0 0
0
0.00 0.00 0.00 411.00 271.00
Cr2 CR 0.50000 0.50000 0.50000 0.38923 13.00253 0 0 0
0
0.00 0.00 0.00 411.00 -271.00
2) If the distribution is over more than two positions, you can use
linear restraints. You can set them in the pcr-Editor. In the .pcr-file
it looks like this:
a) NLI is the number of restraints.
b) The linear restraints themselfs are given behind the distance and
angular restraints:
Chemcomp 3 28.000000 0.000010 -> Current
calculated value: 28.001480
1.0000 5 2.0000 6 1.0000 7
This example couples the 3 parameters with the code numbers 5, 6, 7 to a
total sum of 28. The value of
parameter 6 is multiplied by a factor 2 in this summation (to keep a
constant charge in a distribution of Na+1 and Ca+2).
--
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Daniel M. Többens Tel.: +43 512 507-5532
Institut für Mineralogie und Petrographie Fax : +43 512 507-2926
Universität Innsbruck
Innrain 52, Bruno-Sander-Haus
A-6020 Innsbruck, Österreich
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