Peter is correct, you should use very small step sizes for this material,
and it is important NOT to strip anything when attempting to determine U,
V, and W. You should also collect data over a very wide angular range,
ideally up as high as you can go. Incident- and diffracted-beam Soller
slits are a must with a conventional diffractometer.
When I determined "instrument parameters" using LaB6, I was able to refine
GU, V, and W (to fairly small values, on the order of 2-8). I then use
these values with refinements for any other materials, initially refining
only LX and LY (but never again GU, V, and W). I found that this approach
worked well and gives what appear to be realistic values for strain and
crystallite size.
Dave
At 10:52 AM 11/5/2009 -0500, David Weston wrote:
Hi
I have been trying to investigate my instrumental line broadening, as
advised by too many people to thank individually. Thankyou all.
I have aquired some LaB6 and obtained a pattern from my D8 Advance using
an Si wafer.
When I put it into EXPGUI it falls over at the U, V, and W stage.
So I tried putting it into CMPR to get the U, V and W, but again this
tripped up.
I then stripped the Kalpha2 out of my data and went back to CMPR but yet
again the program tripped up.
My peaks look very assymetric. Can anyone advise on my next step
please?
Kind regards
Dave Weston
Research Fellow
Department of M3
Wolfson Building
University of Nottingham
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