I also dislike the phrase "Debye-Waller factor" for the exafs disorder term. In crystallography, the Debye-Waller factor refers to disorder of atoms about their lattice positions. In exafs, the disorder is about the path length of the N-body configuration -- clearly not the same thing. I am, apparently, in the minority on this topic -- "Debye-Waller factor" is in wide use in the exafs literature. But, as everyone here knows, I often like to stand up on my soapbox and yell into the crowd. ;-)

Bruce, While you're on your soapbox, if we drop "Debye-Waller factor" to describe the EXAFS disorder term, would you suggest using only "disorder" or do you have a better phrase to use? Rich -- Richard Mayes Barnes Group 450/452 Buehler Hall Department of Chemistry University of Tennessee Knoxville, TN 37996

I'd like to add my 2cents worth about the mean square displacement term. I wrote it up on the EXAFS wiki, since I like to say it over and over. see http://www.xafs.org/Common_Mistakes Shelly ________________________________ From: ifeffit-bounces@millenia.cars.aps.anl.gov on behalf of Scott Calvin Sent: Wed 7/16/2008 3:54 PM To: XAFS Analysis using Ifeffit Subject: Re: [Ifeffit] quotation of figures Hi Rich, "Mean-square radial disorder" (MSRD) is one good alternative. I'll also point out another bit of ambiguity with "Debye-Waller factor" aside from the confusion with the XRD term. Some EXAFS practitioners use Debye-Waller factor to indicate all disorder-type modifications to the EXAFS equation, including higher cumulants. Most use it only for the Gaussian part; i.e. the second cumulant. Another good reason to avoid the term. --Scott Calvin Sarah Lawrence College On Jul 16, 2008, at 4:41 PM, Richard Mayes wrote:

...

I also dislike the phrase "Debye-Waller factor" for the exafs disorder term. In crystallography, the Debye-Waller factor refers to disorder of atoms about their lattice positions. In exafs, the disorder is about the path length of the N-body configuration -- clearly not the same thing. I am, apparently, in the minority on this topic -- "Debye-Waller factor" is in wide use in the exafs literature. But, as everyone here knows, I often like to stand up on my soapbox and yell into the crowd. ;-)

Bruce,

While you're on your soapbox, if we drop "Debye-Waller factor" to describe the EXAFS disorder term, would you suggest using only "disorder" or do you have a better phrase to use?

Rich

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On Wednesday 16 July 2008 15:27:27 Scott Calvin wrote:

Bruce--I'm not following your critique of the third panel. Where's the   confusion? I see the disorder term, and I see the mean-free path term,   but I don't see them inappropriately labeled or confused with each   other (aside from the common use of "Debye-Waller factor"). Unless   perhaps it's just that the spacing and arrows in the label "From ab- initio calculations or from reference compounds"  is confusing? (i.e.   it kind of looks at first like the slide claims that the mean-free   path comes from a reference compound)

Unless you redefine sigma^2 such that it has units of 1/angstrom^2 and it subsumes the 2 we usually put in that exponential, the expression exp( -k^2 / sigma^2 ) is incorrect. I concur that one is always free to define ones terms. But redefining what sigma means in the exafs equation can only lead to confusion. (BTW, When you analyze your data by comparison to an empirical standard, I would presume that the mean free path is considered to be chemically transferable.) 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/

Yah know,,,I'm wrong.... The last one is a triple scattering path with just two scattering atoms. the leg part is right... oops SK ________________________________ From: ifeffit-bounces@millenia.cars.aps.anl.gov on behalf of Kelly, Shelly D. Sent: Wed 7/16/2008 11:45 PM To: XAFS Analysis using Ifeffit Subject: Re: [Ifeffit] quotation of figures Hi Eckhard, The first slide also has problems. The first path is a single scattering path. All the others are double scattering paths. The word "single", "double" and "triple" are used to describe the number of atoms that scatter. The number of legs is used to tell the difference between the different kinds of double scattering. So the first (A-B-A) single scattering path has 2 legs (nlegs=2). The next one (A-C-B-A) is a double triangle scattering path with 3 legs. The next one (A-B-C-A) is equivalent to the previous one so that the CN for that path is twice the number of atoms for that path. The last one (A-C-B-C-A) is a double scattering path with 4 legs. HTH Shelly ________________________________ From: ifeffit-bounces@millenia.cars.aps.anl.gov on behalf of s440697@stud.uni-goettingen.de Sent: Wed 7/16/2008 11:04 AM To: ifeffit@millenia.cars.aps.anl.gov Subject: [Ifeffit] quotation of figures Hi, i have a print out of a talk (about XANES, XAFS and multiple scattering...) and i want to cite some figures (attached). Can anybody tell me the author etc...? I searched everywhere on the web (on several sites of XAFS-Summer Schools...). Unfortunately i do not have the talk as pdf-file only the print out. Maybe the talk is from Matt Newville? Maybe anybody recalls on this talk/slides or recognizes them? Thanks for your help. Have a nice day, Eckhard --------------------------------- Eckhard Bosman e.bosman@stud.uni-goettingen.de +49 (0)551-39-14441 Raum: E0.104 Institut für Röntgenphysik Friedrich-Hund-Platz 1 37077 Göttingen Germany _______________________________________________ Ifeffit mailing list Ifeffit@millenia.cars.aps.anl.gov http://millenia.cars.aps.anl.gov/mailman/listinfo/ifeffit