On Mon, 10 Jul 2000, Brian H. Toby wrote:
> There are three polarization functions listed in the manual, but only 2
> when I try to select the function in EXPEDT. I seem to remember that the
> 1st two functions are equivalent, other than scaling, but I am not going
> to work this mystery today.
My apologies for such a public display of ignorance, I have a related
mystery to ask about. Having had a quick look at the manual, all three
corrections are for parallel geometry, I'm guessing "no monochromator",
then "incident beam mono." and then "diffracted beam mono.". OK.
The question is what about flat plate transmission (STOE) type data versus
Bragg-Brentano versus Debye-Sherrer? Doesn't a factor of cos(theta) at
least turns up in the transmission data. This is where I start to feel
rather stupid, but how can you specify these cases? It doesn't appear to
come into the instrument parameter file or the lorentz corrections
dicussed here?
Any hints or advice would be appreciated. Probably Bob has the best idea
of what GSAS is doing, and how it's doing it. I've heard rumours of
manual "corrections" being applied to data before presenting it for
refinement, which sounds ugly. Fullprof has a flag for transmission
geometry, hence my question.
Thanks in advance,
Jon Wright
PS : If someone could refer me to simple derivations of the LP
corrections for all the various geometries, I'd be very grateful.
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