[Ifeffit] Why different installations of Atoms generate different results?

[Matt Newville]

Dear Ku-Ding,

On Sat, Sep 22, 2012 at 8:13 AM, Tsuei, Ku-Ding <tsuei at nsrrc.org.tw> wrote:
> Hi Bruce,
>
> Thanks a lot for your reply and comments particularly on how to change
> k-weight in (D)Artemis-Atoms. Sorry for not being able to provide clear
> results stating exactly where my confusion came from. I was not sure if an
> attachment could be readable to this email list but let me try this time.
> Certainly I do not know how to retrieve data values from these plots yet.
>
> The attached pdf file compares the output plots of k^n*chi(k) with n=0, 1, 2
> and 3 of the Au L3 EXAFS of the shortest path calculated from Artemis-Atoms
> in Demeter and old Artemis. I suppose to read identical plots of k^n*chi(k)
> from different programs but they are not. That is why I feel confused.
>
> Your help on clearing my confusion is appreciated. Then I can move on to do
> model fit on real data.
>
> Ku-Ding


The two results you show are quite different, but you don't tell us
how you got them, expect to say the they were calculated by
Artemis-Atom and D(Artemis)-Atoms.   This is an incomplete
description, allowing many possible differences.   To be clear, Atoms
only generates the feff.inp file.  These should be the same between
the two versions, especially for as simple a case as fcc Au.  Next,
Feff has to be run.   This will be the same, assuming the input files
are the same.    Next, Artemis reads in the output files from Feff
(you say you're using the first shell only, but I encourage you to
verify that),  applies Path Parameters to these, and generates chi(k).
 Are the number of Paths used, and the Path Parameters (N*S02, sigma2,
e0, deltaR) the same in these two calculations?     I'd guess that
they are not.

Providing plots of outputs is helpful, but as is said many times here,
providing the project file is much more helpful as it shows not only
the final result, but how you got there.

Cheers,

--Matt