[Ifeffit] Lattice distortion
Scott Calvin
SCalvin at slc.edu
Sat Mar 21 11:09:55 CDT 2009
Hi all,
One of the most universally accepted facts used in EXAFS analysis is
that the amplitude reduction factor S02 is chemically transferable.
I've been trying to find a good reference for this--either a key study
establishing it, or a review article asserting it. I know there has
been plenty of good work in recent years trying to make theoretical
calculations of S02, and that they are gradually becoming more
accurate. But these recent advances can't be the reason we treat S02
as transferable, because we've been doing it for decades.
How was this established? It seems devilishly difficult to do
experimentally with good accuracy, because S02 will correlate to some
extent with other parameters. Those correlations can be broken to
some extent by using k dependence, but it seems the uncertainties
would still be somewhat high. On the other hand, were there compelling
theoretical reasons back in the 80's for believing transferability to
hold?
Currently, how good do we think the assumption of transferability
really is? Good to 5% for any compound at that edge? Good to 1% for
compounds with similar local environments at that edge? Better than
that? (I'm asking about the EXAFS region; say, more than two inverse
angstroms above the edge.)
I eagerly await your collective wisdom, knowledge, and humorous
anecdotes.
--Scott Calvin
Sarah Lawrence College
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