Dear Paolo ( others)At 01:56 PM 9/15/00 +0100, you wrote:
You wrote:
>Finally, here is a question for Bob and Juan. To me, it would be much more
>natural to remove Vo from the scale factor, that is to redefine a new S' so
>that
>
>
>Y=S'*L*A*E*|F|^2/Vo^2 and S'=K*Ltot*f
>
>This way, the scale factor will only depend on the sample effective density
>and not its crystal structure. This is very useful in phase transitions
>involving a change in the size of the unit cell, as you can imagine. Is
>there any rationale in doing it the way it's currently done?
To me it made more sense for the scale factors to be proportional to the
"mole fraction unit cells"; so that's what was chosen for GSAS. Considering
that there is frequently a change of density associated with many phase
changes, tying the scales to density makes construction of constraints
between the scales more difficult than having the scales tied to the number
of unit cells.
Bob Von Dreele
