RE: One GSAS question.

[Radaelli, PG (Paolo)]

Dear Xiangyun Qiu,

the easiest thing is to create a new purely magnetic phase containing only
Mn and with P1 symmetry.  Since Mn is in a special position, you don't need
to refine the coordinates.  You'll have to constrain the reciprocal lattice
tensor parameters and the phase fraction between the two phases.  The latter
are inversely proportional to the cell volume.  Tricky but a good
exercise...

Paolo Radaelli