Dear All,
Firstly, it was a pleasure to return to my email and read an interesting
discussion on combined refinements. It is good to have aired some of the
problems and limitations (e.g. are neutrons and X-rays seeing the 'same'
sample?). With a simplistic view, this technique must be the way ahead as we
are adding together more independent information. A good question to raise
now, is how we should do it best. If we have an atom that is seen by one
radiation and not by the other there will be a degradation in the quality of
the parameters by combining the refinement in the current fashion. Surely, it
would be better to use a new weighting function for the atomic parameters,
that is dependent on the scattering lengths for each radiation. Ignoring the
systematic errors that differ between neutrons and X-rays , perhaps the
question that should be raised is how to best combine the information that
each dataset holds.
-Andrew
-------------------
Andrew Wills (Dr)
Centre D'�tudes Nucl�aires de Grenoble
p.s./
Tao, the easiest way to add a list of atoms to a GSAS phase is by manual
editing of the .exp file. I have a little program (DOS) that does this if you
are interested.
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