OK to follow up Andrew's remarks:
I use simultanous X-ray and neutron refinements almost all the time
nowadays. There are a lot of advantages when you like me work with
transition metal oxides:
1) in general the refinement is more stable.
2) the possibility the study much more complicated structures than with
only one of the techniques.
3) because you now have two really different sets of data your structural
model is more reliable.
4) you can study compounds which contain elements that are difficult to
locate precisely with one technique, think of vanadium oxides or
manganese/iron oxides.
I agree fully with the problems that Andrew indicates, and at times I
think that the refinement is rather biased to either to neutron data or
the x-ray data. It would be nice if that could be quantified in one way or
another. I am not sure whether I would like to influence it though.
I perform absorption corrections allways before i put the data into the
refinement, so there are no problems for me there. In GSAS you can refine
all the 'histogram' related parameters independently. So you can have
prefered orientation in one but not in the other, which may not be as
weird as it sounds.
One of the remaining problems is, that you have to choose which
calibration you trust most, and thus which wavelength you want to refine.
And you have to do that! However I found that in general the error is
fairly small, about the fourth or fifth decimal place orso.
I don't have a real strategy for doing those refinements. Normally i have
got a decent refinement based on X-ray data when I collect the neutron
pattern. I just read the new data into the existing experiment as a second
histogram and apply the normal strategies. Plus refining one of the
wavelengths of course, assuming I do not TOF data.
Reactions?
Best
Jaap
Jaap Vente
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