There aren't a very precise description of constraints in the manual.
Soft constraints are usersupplied values for expected interatomic
distances.
The F factor defines the weight with which they enter the refinement,
compared to the observed data. This is an *extremely* useful feature,
when refining atomic coordinates. It helps alot in keeping the
refinement stable. Set F high to begin with, and as the refinement
converges, lower it to allow more freedom for the atomic coordinates.
Rigid body constraints, allows you to group together atoms in "rigid
bodys" say a SiO4 tetrahedron. I haven't used them myself, so I don't
know much about implementation.
Do try to get your hands on the very useful book: "The Rietveld
Method" from IUCr, edited by Young (1993?). A lot of this is
explained in that fine book.
Greetings
> I try to find the explanation for "Soft constraint" and "Rigid body
> constraints" function of GSAS but I can't find in manual. Does
> anybody know where the explanation or document for these functions?
> Thanks.
>
Jens Wenzel Andreasen "If only those geologists would let me
Dept. of Mineralogy alone, I could do very well, but those
Institute of Geology dreadful hammers! I hear the clink of
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Phone: +45 33 25 20 60 Bible verses." - John Ruskin, 1851