On Sun, 9 Mar 2008, Alan Hewat wrote:
Precision of CW neutron machines is
frequently not so high as X-ray diffractometers, but this problem is
masked in Rietveld by extremely (artficialy) low e.s.d.'s of lattice
parameters.
Hmm?? With CW neutron machines, the wavelength is sometimes not well
Hi,
To what has already been said I think the two round-robin articles are a
must-read about this issue, as they compare refinement of neutron and X-ray
data for a given (simple) compound. They are a bit old, especially by today's
synchrotron standards, but are still very interesting
o with the
accuracy with which the atom coordinates are determined.
Of course, if you can collect both neutron and x-ray data, especially
synchrotron data, on similar samples at the same temperature, you may
improve accuracy by performing a combined refinement, but that is often
not possible. And again
xray/
From: Davide Levy [mailto:[EMAIL PROTECTED]
Sent: Sunday, March 09, 2008 5:53 AM
To: rietveld_l@ill.fr
Subject: Neutron or X-ray?
Dear All,
I have a ”philosophic” question for you: the structure obtained by NPD are
better than the ones found by XRPD?
I explain a little bit mor
Davide,
Did you check for extinction and preferred orientation? Otherwise what
does a combined fit give? The difference of about 10 sigma suggests a
remaining systematic error. What is the impact of refining anisotropically?
Good luck,
Jon
Davide Levy wrote:
Dear All,
I have a ”philosoph
Hello,
do not mind statistical precision (your error at the oxygen coordinate)
and look at the errors (e.s.d.) of the interatomic distances, especially
of those between bonded atoms. Precision of CW neutron machines is
frequently not so high as X-ray diffractometers, but this problem is
masked
The advantage of neutron powder diffraction is that the scattering power
of light atoms like oxygen is as great as for heavy atoms; for X-rays, the
heavy atoms dominate, so errors for the light atoms will be greater. A
second advantage is that with neutrons you have a larger sample, so a
better pow
Dear All,
I have a philosophic question for you: the structure obtained by NPD are
better than the ones found by XRPD?
I explain a little bit more my question, I studied a MgAlFeO4 spinel both by
NDP and XRPD from RT to 1000°C. The O coordinate it is different for two
data set (0.2581 vs.0.25
