[Ifeffit] Third cumulant in DWF

[Bruce Ravel]

On Friday, April 01, 2011 05:03:17 pm Ping, Yuan wrote:
> Dear IFEFFIT experts:
> 
> Is it possible to add a k^3 term in the phase for fitting to take into
> account anharmonic effect? The fitted coefficient will be proportional to
> the 3rd cumulant of Debye-Waller factor. I work with high-temperature
> high-pressure systems where anharmonic effect is not negligible.
> 
> Thanks.
> Yuan Ping


Hi Yuan,

Here is the relevant page from the Ifeffit reference manual:

   http://cars9.uchicago.edu/~ifeffit/refman/node51.html

You want to use the "3rd" path parameter, which adds a term
proportional to C3*k^3 to the sine function in the exafs equation.

See the attached figure for the place in Artemis where this parameter
is introduced.

HTH,
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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