Brian wrote:
>Finally, I should mention in response to Armel that at least here at
>NIST, most requests for time are scheduled within 2-8 weeks of when we
>get them (see http://www.ncnr.nist.gov/~toby/bt1.html).
The confirmation of what I suspected : some peoples are
more equal than others !-). Looking at the two quite different
X-ray and neutron communities applying the Rietveld
method, I note that this is mainly the neutron community
that is not preoccupated by improving the positions of the
heavy atoms by using X-ray ;-). Few people are seen
simultaneously in both lists below (those who would feel
concerned by a double refinement). X-ray seems inaccessible
to many neutron experts or at least lacking of any interest, and
vice versa. The most productive neutron experts are 3x more
productive than the X-ray experts, probably because the
birth of X-ray Rietveld applications is more recent (~1981
with DBW, possibly). But it seems to me that Rietveld
adaptation to X-ray was made by X-ray experts, because
neutron experts did not care a lot about doing it.
Why X-ray users should be interested in the precision on light
atoms when neutron users don't seem to care about heavy
atoms ?
Of course this is only kidding and provocative opinion, as
usual. I love both radiations, indeed. However, I tend to think
that a simultaneous refinement could eventually degrade
the heavy atom position accuracy AND degrade the light
atoms accuracy. The former being better from the X-ray only
and the latter from the neutron only, not to speak of the various
problems that hurt me like, for instance :
- the need to refine two sets of cell parameters, inevitably
slightly different if both data are of high resolution.
- not exactly the same temperature
- bulk with neutrons, surface with X-ray
Giving the results of 2 independent refinements seems better
to me.
Armel
==============ICSD data=======================
http://pcb4122.univ-lemans.fr/icsd/icsdrndp.txt
Authors versus numbers of Neutron Rietveld-refined
structures in ICSD - release 1998/1
(REM=RVP AND REM=NDP : 3276 entries).
------------------------------------------------------
324 Fischer P
240 Jorgensen J D
189 Hewat A W
171 Hinks D G
125 Dabrowski B
115 Hitterman R L
110 Vogt T
108 Shaked H
107 Marezio M
105 Radaelli P G
103 Weller M T
101 Rodriguez-Carvajal J
http://pcb4122.univ-lemans.fr/icsd/icsdrxdp.txt
Authors versus numbers of conventional X-ray
Rietveld-refined structures in ICSD - release 1998/1
(REM=RVP AND REM=XDP : 2557 entries).
------------------------------------------------------
122 Kanno R
107 Takeda Y
104 Kawamoto Y
80 Raveau B
79 Yamamoto O
76 Takano M
67 Hawthorne F C
66 Hervieu M
59 Michel C
54 Yamamoto T
51 Sato M
