Dear Colleagues,
I am happy to see, that the presentation of diffraction data is not just
something neglected but that there a quite a lot of people with diferent
thoughts and reasons and that is it a hot topic to find some ways to
more modern and standard presentation. Nothing is really new, nor the
Q-space of course. My initial intention for raising this topic was just
the presentation of the data, since there are many ways to work with
internal parameters, which is fully justified. I went quickly through
the list mails and like to reply generally, since there are so many. and
since it's late night, I resume from my mind, what I read during the
day, not to be understood as a full report...
Discssions were raised under the following topics:
* display of results vs working units
As I said above, it is fully justified to work in what parameter space
is best for describing the data. To my opinion, there is needs to expand
this with the new, unconventional scanning geometries.
* many different units
I was quitte surprised about the multitude of units which seems to be in
use, suuch as 10E4/d. II believed so far, Astrophisicists hold the record.
* 2Pi/d or 1/d
It has been pointed out, that there is advantage for both! Me as a
phhysicist, believe in 2Pi/d. c=1 ok, but that scales everything else,
that means, other units become functions of c. 2Pi, howeve, designs the
ratio of the circumference of a circle and its radius, and is never 1.
how long did matematicians search for this number!!! so give us at least
the options between 1 and 2Pi! As pointed out in the contibutions, much
inelastic, SANS and reflectometry data is given including the 2Pi.
* data acquisition in Q-space
Interesting thoughts! certainly works well with a point detector.
however, Q-space scans become quickly curved when using area detectors
(cylindrical, flat, inclined...)
* Cu-Kalpha problem
Haven't thought about measuring with 2 wavenumbers (2Pi/lamda ;)) only.
either used k- or angular dispersive with white or monochromatic beam so
far. There was an interesting contribution, that the deconvoluted
pattern should be presented.
* intensity axis
yes, I love sqrt(I) as well because of the statistics argument and found
it quite nice, that it is used in some programs.
* flat detector (ESRF)
now to with what I fought: we used flat detectors with High-Energy
X-Rays (doi:10.1080/07303300310001634952) which has a tangential
depedence in 2-theta. So we need rebining of the data anyway.
* cylindrical detectors
QLD machines and powder diffractometers with quasi-2d detectors use
quasi-cylindrical detectors. naturally none in in Q, 2-theta, TOF space.
* individual solutions
some colleagues brought up to read the output data from their rietveld
software and then create their own plots. I tried half way for
GSAS-output by myself.
* programming needs
In future, data spaces are much more parametric, as mentioned above in a
few examples. it would be good, if rietveld programs (and any other)
could handle parametric data and have a multitude of plotting or output
functions for individual needs.
I am sure, each point is a discussion point by itself...
Best wishes, Klaus-Dieter.
--
Dr. Klaus-Dieter Liss
Research Scientist, Bragg Institute
Australian Nuclear Science and Technology Organisation
PMB 1, Menai NSW 2234, Australia
T: +61-2-9717+9479
F: +61-2-9717+3606
M: 0419 166 978
E: [EMAIL PROTECTED]
http://www.ansto.gov.au/ansto/bragg/staff/s_liss.html
see also: http://liss.freeshell.org
