[Ifeffit] Trouble with fitting with Arthemis

[Carlo Segre]

Hi Kleper:

There is a single Pt-Pt path in your fit.  This is effectively a fcc Pt 
distance of 2.77.  I see several problems:

This spectrum has distances which are much shorter than 2.77 and so I 
would expect that this single path would not be a very good fit.  I am not 
sure if the peak around 1.1A is real, but it could be given the hydrogen 
that you indicate is present in the file name.  What is clear is that the 
bigger peaks are not Pt-Pt peaks at all.  The Pt-Pt peak will usually 
appear around 2.5A in Chi(R).

The second thing that I noticed, is that you must have a problem with your 
installation of the software because I just took your file and executed 
the fit and did not get the strange values for Chi^2 and reduced Chi^2 
that you have posted.  The value for amp is negative, indicating that the 
path is not a good model, but the Chi^2 I got was around 1000.

I can't tell much form the name of your file but I suspect that you have 
Pt-Al and possibly Pt-H distances in your sample.  Do you have any other 
information about this sample?

Carlo


-- 
Carlo U. Segre -- Professor of Physics
Associate Dean for Special Projects, Graduate College
Illinois Institute of Technology
Voice: 312.567.3498            Fax: 312.567.3494
segre at iit.edu   http://www.iit.edu/~segre   segre at debian.org