[Ifeffit] k range in ARTEMIS fitting

[Bruce Ravel]

On Friday 20 July 2007, Yuan Ping wrote:
> Hello Bruce,
>
> Thank you for sharing your software. I found IFEFFIT in google and
> installed it recently in my MAC OSX computer. Trying to learn how to
> use it, I took a sample chi_k data (Al, k-edge) and played with the
> fitting in Artemis. One problem I can't solve by myself is that no
> matter how I chose the k range, r range, dr, dk, the fitting always
> stops at k~ 3 even though the data covers k= 1-8. So in the plot, the
> fit curve is much shorter than the data. Is this a plotting problem
> or a fitting problem? I've saved and attached the project to this
> email.
>
> Thank you very much for your attention.
> Yuan


Hi Yuan,

First off, I want to apologize for the tardy response.  Your message
to the mailing list arrived at a time when I was very busy.
Fortunately, I noticed the email this afternoon while reading other
email.

The problem you are seeing is due to the unfortunate confluence of two
things: (1) the chi(k) data that you imported into Artemis does not
start at k=0, and (2) you are using a very old -- version 0.8.002 --
version of Artemis.

Versions of Artemis from 0.8.007 on will recognize when the chi(k)
data you import is not on Ifeffit's standard k grid and interpolate.
So, if you were using a more up-to-date version of Artemis, you would
not have seen this problem.

You have two choices to fix this problem:

  1. Update the Ifeffit package on your machine and rebuild your
     project file.
       http://cars9.uchicago.edu/iffwiki/Downloads

  2. If you must, for some reason, continue using the old version of
     Artemis, you will have to do the interpolation yourself.  Artemis
     expects the data to be on a k-grid that starts at 0 and goes in
     steps of 0.05 invAng until the end of the data.

The most direct method of putting chi(k) data into Artemis is to read
it directly from the Athena project file.  That is, using the Open
file dialog in Artemis, select the Athena project file and use the
Athena project dialog in Artemis to select your chi(k) data.

Regards,
B



-- 
 Bruce Ravel  ---------------------------------------------- bravel at anl.gov

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