What Armel is describing is precisely the way we started. We used it when
required, discussed over a few pints whether it was a good idea or not,
and came to the conclusion that it was. Later we tried it also on
refinements where the need was not so clear, and now it is routine. I have
not read any real arguments against it. But may be I am blind to that.
Further, my remarks related the oxides were more directed at the
precision/esd of the oxide position. Of course I do know where the oxides
are within say 0.05A but i want it an order of magnitude better. Remember
that most structural distortions in metal oxides are due to displacements
of the oxide sublattice and often you fail to observe that with X-rays.
With regard to the "brown envelope" technique. I am not such a fan of
that. It is very hard for a beam line scientist the know whether the data
collected are as desired, have a good enough s/r ratio etc, which details
to look for. In addition, the last few years when we went we had more
samples that we good run sensibly. For that reason I use 'on the fly'
refinements to check whether things are going OK. With respect to the
additional costs, what are the daily running costs of say D2b or HRPD,
10,000-15,000 dollar orso? The travel costs are than a relative small part
of the total cost involved.
> refinement was really fruitful (speaking of V atoms comes certainly to
> mind, but why not prepare an isomorphous sample without V ?-).
Because you want to study the V containing sample of course!
Now I will go to the beach and dive into that glorious caribean sea and
wash my soul of all my recent sins.
Best
Jaap
Jaap Vente
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