[sdpd] Chronicle from EPDIC-10

[Armel Le Bail <alb...@cristal.org>]

Hi,

Back from EPDIC-10, Geneva, September 1-4, 2006,
and from the "Under the Bonnet" workshop, with the
impression that powder diffraction software are more
powerful than ever.

Most demonstrations and explanations have shown that
the latest versions (for instance EXPO2006, DICVOL06,
etc, etc) could resolved now problems that were not
resolved (or not as well) by the previous versions. No
unsolved problem was discussed, this looked like the end
of any evolution.

But I am sure that the next meetings will show new versions
for which similar demonstrations will be made so that
the 2005/6 not shown unsolved problems will be discussed in
2007/8 ;-).

Remarkable enough is the new "charge flipping" approach
as applied to powder diffraction.

Extraordinary enough is the new indexing facility inside
of MAUD when calling the XGrid (parallel computing on the
Internet).

Good-enough is the L. Smrcok advice to "make DFT
calculations, not Rietveld" when your ratio (effective
number of peak / parameters) is too small for organic
and organometallic compounds.

Interesting enough is to see what software are using the
selected speakers of the SDPD sessions :
P. Stephens loves TOPAS and DASH
F. Costantino loves EXPO and FOX
J. Kaduk loves ENDEAVOUR and Reflex Powder Solve
Ch. Baerlocher's new toy is charge flipping (see SUPERFLIP)
P. Juhas prefers the PDF approach.

The recipient of the EPDIC Award, I. Margiolaki, prefers
clearly TOPAS.

Most Rietveld final refinements were done by either GSAS
or Fullprof.

Etc, etc

Solving a problem by a given software or a new technique may
give the false impression that no other software would have
been able to propose a solution as well. This is why SDPD
Round Robins are interesting times to times. The latest Round
Robins I and II are dated 1998 and 2002, suggesting that 2006
would be a good year for SDPD-RR-III. Just one problem,
an organizer is lacking...

Finally, paraphrasing A. Kern's sentence during the indexing
microsymposium "no d-value required for indexing", which
belongs to a category close to the "no intensity extraction
required for solving in direct space", I would say that even
not a powder pattern is required for a structure full prediction
;-).

Discussing with A. Meden close to his poster "Inorganic
crystal structure prediction - A dream coming true ?", we
agreed that it would be fine if the ICSD or the COD would
provide tools allowing for easy comparison/identification of a
real new or of n virtual inorganic structures, independently of
cell parameters, space group and chemical formula (finding all
related known structure types at a click of a mouse, entering
one real or 1000 predicted CIFs, searching the whole databases
ICSD or COD, just like it is possible with molecules or fragments
inside of the CSD). Well, there is the CMPZ software, but...

Best wishes,

Armel

PS - At the end of the "Under the Bonnet" workshop, the
future of software was discussed. Not sure of what has
to be done, but it seemed that one thing has not to be
done which is to give a developing task to a one-year
post-doc (because many software produced that way
are quickly abandoned, apparently). The example for the
need of stability is certainly DICVOL starting in the1970s
and still alive with DICVOL91, 04 and now 06 versions, the
latest being presented by D. Louër himself at EPDIC-10
the day of his 64th birthday. The indexing
microsymposium was in honour of Robin Shirley,
1941-2005, his CRYSFIRE suite being still not yet
maintained... About the lack of maintenance of old
software, it was also said (C. Giacovazzo) that we should
be confident in the replacement of obsolete programs by
more efficient and even completely new approaches. On that
side, we may wonder how many time it will be necessary to
EXPO in order to assimilate the charge flipping algorithm ?
;-).




 
Yahoo! Groups Links

<*> To visit your group on the web, go to:
    http://groups.yahoo.com/group/sdpd/

<*> To unsubscribe from this group, send an email to:
    sdpd-unsubscribe...@yahoogroups.com

<*> Your use of Yahoo! Groups is subject to:
    http://docs.yahoo.com/info/terms/