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@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/