Re: Extracting Structure Factors

beers@liso.dnet.ge.com
Fri, 20 Dec 96 08:59:33 EST

The recent discussion on ab initio structure determinations
has been particularly interesting to me. My applications
involve transition metal/lanthanide oxide structures using
data from a Scintag xray unit (if I'm crazy to even try
this, someone please speak up!). This work is being done as
a 'hobby' since the results will not have an obvious effect
on this years bottom line. In general, the desired strucure
appears to be related to a known structure (based on formula
and cell parameters). However, other structural probes
(fluorescence) lead us to believe that it is a different
structure.

I have been trying to use GSAS, with limited success, by
placing a dummy atom at a non-special position for the
Le Bail extraction. The discussion has suggested that other
programs implement the Le Bail method in different, possibly
better, ways. Is FULLPROF the 'preferred' choice? I have
found that program on the Web page, but if there are other
programs, I would appreciate reference to PC versions. In
March '95, a citation list of Rietveld related programs was
distributed by Le Bail. This includes several that are
'Pawley method' based. None of these programs seem to be
listed on the Web page. Is there a reference that describes
the relative advantages of the Pawley and Le Bail methods for
extracting structure factor amplitudes?

Bill Beers

william.beers@lighting.ge.com