In a few words -- you probably can't do that with GSAS. This is not true
of all Rietveld codes, but in GSAS a variable parameter can only appear
in one constraint equation. One option that might help would be to put a
soft constraint on the total composition.
Brian
Donggeun Ko wrote:
>
> Could any of you point me to the good document about the method of applying
> constraints in GSAS?
> I am trying to figure out some complex cationic intermixing in a layered
> cuprate superlatttice compound.
> But I couldn't find a good documentation in the manual. Specially trouble
> with a constraint with >2 variables.
> For example, how do you make a constraint for something like x+2y+2z=1.
> Thanks for your help.
>
> /////////////////////////////////////////////////////////////////////
> Donggeun Ko, Ph.D
> The Science and Technology Center for Superconductivity
> Northwestern University
> 2145 Sheridan Road
> Evanston, IL60208-3113
> Phone : (847)491-4228/5008
> Fax : (847)491-7713
> Home Page : http://pubweb.nwu.edu/~dko901
> //////////////////////////////////////////////////////////////////////
--
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Brian H. Toby, Ph.D. Leader, Crystallography Team
[EMAIL PROTECTED] NIST Center for Neutron Research, Stop 8562
voice: 301-975-4297 National Institute of Standards & Technology
FAX: 301-921-9847 Gaithersburg, MD 20899-8562
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