[Ifeffit] FEFF6L.02 - missing path?

Matt Newville newville at cars.uchicago.edu
Fri Jul 29 10:28:15 CDT 2011

Hi Pawel,

On Fri, Jul 29, 2011 at 7:13 AM, Pawel Zajdel <pawel.zajdel at us.edu.pl> wrote:
> Matt,
> Thanks for the explanation.
> In this case, next two questions.
> 1. Is there a way to say it was rejected other than re-running feff with
> CRITERIA 0 0? I expected it to show in Feff.run file with "neglected" flag.
> My "default" Feff.run file says
> "     Curved wave chi amplitude ratio   4.00%
>    Discard feff.dat for paths with cw ratio <   2.67%"
> and the "neglected" flag is present for those with <2.67%.

Well, you don't need to run all the Feff modules, but it would
probably take more time to edit the input file than to run the program
to select the modules.

> 2. Also there is still one path left (all paths No# 10 Se-Zn-Se) with cw
> ratio 2.83, which passes the <2.67 criterion but is weaker than the two
> paths that are rejected before it with amps 3.952 and  3.999.
> In other words - when using "default" generated feff.inp, which paths  in
> Feff.run are reported as neglected and which are not reported at all?

As you've probably read in the Feff documentation, Feff has a couple
of filters that it uses: one fast and less accurate to eliminate
really unimportant scattering paths to make the path-finding mechanism
more efficient, and one slightly more accurate one to decide later
which paths to calculate the EXAFS for.  At this point, both of these
optimizations seems less-than-critical, and just turning them off
completely (CRITERIA 0 0) is not so bad, especially for moderately
ordered systems like your crystal structure.


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