[Ifeffit] Quick first shell (QFS) theory in Artemis

Bruce Ravel bravel at bnl.gov
Tue Oct 2 13:40:27 CDT 2012

Hi all,

One of the bugs reported last week involved a project file which made
extensive use of the "quick first shell" -- or QFS -- feature of
Artemis.  The bug involved a problem importing such paths from a saved
project file.  That bug has been fixed in the 0.9.13 release that I
announce a short while ago.

This project file that triggered the bug reminded me of an issue that
has come up at several recent XAS training courses that I have
participated in.

In situations where rather little is known about the structure of a
material, there is a thought that the QFS tool could provide a
model-independent way of generating scattering amplitudes and phase
shifts for atoms suspected of being in the material.

While the QFS tool is a reasonable thing for atoms in the first
coordination shell (hence the name!), this is a dangerous practice for
atoms at longer distances.  Artemis does not police its misuse in this
way beyond simply issuing a warning sugesting that you may be doing
something inappropriate.

A full discussion of this topic is rather lengthy, so I will refer you
to a wiki page that I wrote:


If you have considered using the QFS tool for atoms beyond the first
coordination shell, please read that wiki page all the way to the



 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

 Homepage:    http://xafs.org/BruceRavel
 Software:    https://github.com/bruceravel

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