| EXAFS Analysis Using FEFF and FEFFIT
Analysis exercises
In the EXAFS Analysis Using FEFF and FEFFIT workshop, several analysis problems
are given as example illustrating various aspects of FEFF and FEFFIT.
Here you will find links to directories containing those analysis examples.
Included in each example is data and enough input files for ATOMS, FEFF,
AUTOBK, and FEFFIT to get started working through the examples.
These examples are not a hand-held walk through the
programs. The input file may contain typos or incomplete physical
models. However each set of files is reasonably complete and should be
made to run to some kind of conclusion without too much work. It is
intended, though, that you work through the examples carefully and
completely, making sure that you understand the issues presented by
each one.
Most of these analysis examples are discussed in the
workshop presentation and in the commentary document. However, over
time I hope to build up a large collection of interesting examples
beyond what is discussed in the course.
Each subdirectory has feffit input files and
three subdirectories. The `data/' subdirectory contains data files --
always mu(E) and sometimes chi(k). The `feff/' directory contains
ATOMS input files if the matrial is crystalline and FEFF input files
if not. The `fits/' subdirectory is usually empty, but the FEFFIT
input files are set up to write their output to those spaces.
- Copper Metal
- This is the copper metal example. It serves as the
introduction to FEFF, AUTOBK, anbd FEFFIT. It is a simple system
which allows you to explore many of the features of these programs
without getting bogged down in the details of physical modelling. In
particular, you should use this example to become familiar with the
various output files generated by FEFF and FEFFIT, you should
examine the data, fit, and individual path contributions in each of k,
R, and back-transformed k space. You should also learn how to do
additional background refinement with FEFFIT.
- GaN
- This is the hexagonal Gallium Nitride example. It
demonstrates the use of polarization dependent calculations in FEFF
and FEFFIT as well as introduces you to physical model building using
math expressions in FEFFIT.
- EuTiO3
- This is the Europium Titanate example. This example
introduces the concepts of multiple data set fitting, includes files,
phase corrections using E0 parameters, and local variables. There is
data at both the Ti K edge and the Eu L3 edge as well as data at
several temperatures, thus you can do multiple data set fits with both
edges, with many temperatures, or both.
- PbTiO3
- This is the Lead Titanate example. This introduces
complex model building using math expressions by computing bond
lengths from crystallographic parameters which are used as the
variables in the fit. This material also introduces the measurement of
bond angles using multiple scattering paths. This is a difficult and
complex analysis problem.
- AgBrCl
- This is the Silver Bromide Chloride example. This
introduces a method for handling doped meterials and other materials
with heterogeneous coordination shells.
- Ni[(CN)4]2-
- This is the Nickel Thyanocynide example. This is an example
of a small molecule in solution and so is very different from the
crystalline examples above. You will find that the analysis
techniques developped for the crystalline materials are transferable
to this system. This material has strong multiple scattering at a very
short distance and is a good example of a matrial for which the MS paths
can be used to measure bond angle.
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