I thought I'd start a new thread, because the subject has diverged
(hmmmm....) from the original.
If there are 5000 conventional, fixed-wavelength powder XRD systems in
the world, they must have been manufactured within about the last 4-5
years. In 1995 I attended a workshop at Denver X-ray Conference when
the person leading the discussion talked about "resolution" (which for
purposes of this note means the ability to separate peaks). He cited
usual resolutions of about 0.08-0.12 deg. 2-theta (or thereabouts) for
sealed-tube systems, except for Scintag systems which were in a class
alone, with resolution of about 0.04-0.05 deg. 2-theta. My experience
is with a 1981-vintage Scintag system (#9 sold by Scintag) and I
routinely obtain patterns where I can monitor the anisotropic nature of
the peak breadths of the materials I'm analyzing.
Now the big question? What do I do with data with this good
resolution? I know there are differences, but is there software to do
something with it? For instance, I have a pattern with clearly
resolved, indexed peaks from about 13-33 degrees 2-theta which have
varying breadths. The variations of of the order of 0.04-0.10 degrees
2-theta. Over the years I have looked at patterns from this material
which appear to vary as a function of preparation (which causes
differences in particle shape--by SEM). Any suggestions?
I have tried Rietveld refinement on the pattern(s) (structure is known),
but the program I'm using doesn't allow me to accommodate the different
peak breadths. Any hope for Rietveld?
Frank May
