[Ifeffit] Transferability of S02

[Scott Calvin]

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

P.S. I resent this to change the subject line to something more  
appropriate; this may be a thread that people will want to find in  
searches later. Sorry for the double post!

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