[Ifeffit] Athena (linear combination fitting)
Bruce Ravel
bravel at bnl.gov
Thu May 12 10:12:22 CDT 2011
On Thursday, May 12, 2011 10:11:20 am Matt Newville wrote:
> Linear combinations fits are more challenging for EXAFS
> than for XANES, as EXAFS are complicated by disorder terms that do not
> strongly effect XANES, and this disorder is a "component" of the data.
> Unless you understand the set of possible atomic environments very
> well and are only interested in the fractions of known phases, I'd
> recommend against using simple linear combinations of EXAFS for
> anything except exploratory analysis.
I certanly didn't make this point strongly enough. I too am wary of
chi(k) LCF fits in most situations.
A common example of the disorder problem is a system that forms metal
nanoparticles. Using bulk metal as a standard in the XANES LCF is
much less wrong than using bulk metal as a standard in chi(k) LCF.
B
--
Bruce Ravel ------------------------------------ bravel at bnl.gov
National Institute of Standards and Technology
Synchrotron Methods Group at NSLS --- Beamlines U7A, X24A, X23A2
Building 535A
Upton NY, 11973
My homepage: http://xafs.org/BruceRavel
EXAFS software: http://cars9.uchicago.edu/~ravel/software/exafs/
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