Apologies if this is in an FAQ somewhere, but I couldn't find it.
When refining unit cell parameters with a magnetic structure in GSAS or
Fullprof (or anywhere else) and using a separate magnetic phase, how does
one go about constraining the cell parameters? The specific example of
interest is triclinic with a magnetic cell of a*2b*2c.
The reciprocal cell quadratic products don't appear to lend themselves
easily to keeping the cell angles equal across the two phases. Any ideas?
On a related question - is there a really good reason for putting
quadratic products into the least squares matrix rather than the real
space unit cell parameters? I haven't picked up yet on why the derivatives
cannot be converted from w.r.t A* etc to w.r.t a etc. Is it just a time
saving?
Thanks
Jon Wright
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