[Ifeffit] High SO2

Kaustubh Priolkar krpriolkar at yahoo.co.in
Sun Apr 12 02:32:00 CDT 2009

If I could add to the discussion and understand a bit more from it, Does Scott mean that when the structure is kind of unknown or is disordered then one follows the approach practiced by Abhijeet. Whereas when one has a crystalline system - there is no merit in fixing the parameters of the first shell and adding more paths to it. If this is the case then I would like to agree with Scott based on my experience in analyzing data on Ni2MnGa type alloys in austenitic phase and martensitic phase. 


Dr. Kaustubh R. S. Priolkar 
Department of Physics, 
Goa University 
Taleigao Plateau, 
Goa 403 206 India
Phone (O): 91-832-6519340
(R): 91-832-2412235
Fax: 91-832-2451184
email: krp at unigoa.ac.in

----- Original Message ----
From: Matt Newville <newville at cars.uchicago.edu>
To: XAFS Analysis using Ifeffit <ifeffit at millenia.cars.aps.anl.gov>
Sent: Saturday, 11 April, 2009 2:25:00 AM
Subject: Re: [Ifeffit] High SO2


I read Abhijeets's
    But what I know about fitting is that we have to first fit the
first shell and then
    keeping the first shell  parameter constant , we go for the next shell

and Jeremy's
  I typically perform the fitting as you suggest, at least in
complicated systems, one shell at a time.

to mean they fit one shell at a time, that is: when the second shell
is being fitted, the first is not and the fit R-range is changed for
the 2nd shell fit to not include (most of) the first shell.   As you
say,  there is very little value in having the R-range include the
first shell if you're not actually adjusting parameters that affect
that part of the spectrum.

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