Hi,
I am trying to constrain the cell parameters of two phases (cubic and
triclinic) in GSAS. I have given the constrain of the reciprocal metric
tensor, but when I refine the cell parameters are not constrained.
how con do it correctly?
Davide
Davide Levy
Dipartimento di Scienze Mineralogiche
Hi All,
A couple of points about lattice parameter constraints:
1) Beware of using damping; it isn't needed especially for lattice parameters
in Rietveld refinements and it will mess up the intent of constraints if not
very carefully used.
2) The constraints are on the reciprocal metric tensor
Dear Davide,
As Bob said, you should constrain RM11, RM22 and RM33 of the tricilinc
phase to be equal to RM11 of the cubic one, then you MUST fix the
RM12, RM13 and RM23 to be zero (use the Hold command in EXPEDT). If
you don't fix RMij to zero then the angles will not be fixed in 90.
Also
Dear Rietvelds
My name is Shay. I am back after period time dealing other things but
XRD.
Now in my new position I focusing on structural analysis of oxidized
graphite.
If any one knows crystallographic data and CIF files of any related
polymorph derivative of such material, please let me know.
Hello,
we have a relatively new Bruker diffractometer with Cu
source and diffracted-beam graphite monochromator. When
collecting the patterns, I found it difficult to refine
them to low chi**2, even for the standard supplied by the
manufacturer. What I also found is that if I refine the
POLA
