Hi all,
Thought I'd take the opportunity to introduce myself and at the same
contribute something back to the list after "absorbing" for about a
year. (Yes, I agree with Lachlan, even the trivial may be gold for
some like myself.)
I am mineralogist at the Geoscience Labs in Sudbury Ontario (part of
Ministry of Northern Development and Mines - for now) and I am new to
both diffraction and Rietveld so I get a lot of info from this list and
the recent resurgence of activity is refreshing and inspiring. My
interest in Rietveld is for quantitative applications on geological
materials.
I wanted to reply to a question by Scott Meilicke on theta compensating
slits.
** snip **
As an aside,
Does anybody know if Rietan94 or any other code can take into account
theta compensating slits? I can't disable them on our Philips
machine...
** snip **
We also have theta compensating slits (ADS) on our Philips and before
using the data for any refinement (I use SIROQUANT) I use an Excel
spreadsheet to convert the ADS data to fixed divergence slits FDS using
a simple formula supplied in the Philips documentation for the ADS.
SIROQUANT also has a bundled calibration for converting (or
calibrating) the ADS to FDS. I have not done a rigorous comparison but
I think they are similar.
There is a caveat here I believe that I'm sure others are more
knowledgeable about than myself so I'll only stir the pot. This is the
problem of penetration depth. Although you can convert ADS intensities
to FDS intensities based on iluminated _area_, you cannot acurately
compensate for the increased _volume_ of illumination when using ADS vs
FDS at low angles. There was a paper in Powder Diffraction some time
ago by Matulus and others that discussed this exact problem (sorry I
can't find the reference right now). Any other opinions on this?
Regards.
Stu
P.S. Scott (and others) I have also written a program in Visual Basic
to convert the Philips .RAW files from our VMS system (and the raw data
files from our Rigaku as well) to the .CPI format used by SIROQUANT.
The output file format from my program is easily modified and if there
is interest, it can be modified to output ascii files in other formats
for a particular application. Let me know if you are interested. It's
free!
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/ \._ _|_ _.._ o _ Stu Miller - Mineralogist
\_/| | |_(_|| |(_) internet: millers@gov.on.ca
____ _____ ___ e-mail: miller_s@torv05.ndm.gov.on.ca
/ ___| ____/ _ \ voice: (705)670-5635 FAX:(705)670-3047
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| |_| | |__| |_| | _ _ ._ o _ _ _ / _ ._ _|_ ._ _
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Geoscience Laboratories
Ministry of Northern Development & Mines
933 Ramsey Lake Road, Sudbury, Ontario, CANADA P3E 6B5
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