Thanks for your response. First of all I am beginner in this issue. Because of my little experience I don't know exactly how to specify my problem but I think you write an interesting phrase in your response: "are you asking if you can distinguish random substitution from ordered substitution? I'm not sure why the Ag-Br and Ag-Cl parameters would be the same".
I don't know how to create a robust fitting model to distinguish random substitution from ordered substitution of the example found in Bruce site about AgBr(1-x)Clx. What are the parameters that I must consider to fit the spectra and to verify if exist random or ordered substitution? I am attaching a document very explicit about this. Thanks again.
> From: ifeffit-request@millenia.cars.aps.anl.gov
> Subject: Ifeffit Digest, Vol 113, Issue 11
> To: ifeffit@millenia.cars.aps.anl.gov
> Date: Sat, 14 Jul 2012 12:00:01 -0500
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> 1. problems (johnny huertas)
> 2. Re: problems (Matt Newville)
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> ----------------------------------------------------------------------
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> Message: 1
> Date: Fri, 13 Jul 2012 22:21:50 +0000
> From: johnny huertas <johnnyhf@hotmail.com>
> To: <ifeffit@millenia.cars.aps.anl.gov>
> Subject: [Ifeffit] problems
> Message-ID: <BAY167-W124DD69B56D1526E67FEC05D5D70@phx.gbl>
> Content-Type: text/plain; charset="iso-8859-1"
>
>
> Members of list:
> I have some problems to resolve a question. I have been working a lot in fit the AgBr(1-x)Clx example of FEFFIT site. My fits were good in my opinion, but I don't know how to identify the Br and Cl atomic distribution around Ag (random or specific?). I didn't find any example about this in the site. Conversely I have made some attempts to identify such distribution. I have made two fits preparing for each one feff file, a feff file puting Br and Cl atoms in face and other in medirian position around Ag knowing the CN=6 of this central atom and fiting only the first shell. Unfortunatelly I don't have found satisfactory results because the paremeter are equal in both cases. I would like you help showing a similar example. Thanks.
> Jhonny Huertas Flores
> Rio de Janeiro-Brasil
>
>
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> ------------------------------
>
> Message: 2
> Date: Fri, 13 Jul 2012 22:20:41 -0500
> From: Matt Newville <newville@cars.uchicago.edu>
> To: XAFS Analysis using Ifeffit <ifeffit@millenia.cars.aps.anl.gov>
> Subject: Re: [Ifeffit] problems
> Message-ID:
> <CA+7ESbruuJaW0KVyuE=fUP5Mzz_W63yEqc-v3OAE_KhQj6hN-A@mail.gmail.com>
> Content-Type: text/plain; charset=ISO-8859-1
>
> Hi,
>
> On Fri, Jul 13, 2012 at 5:21 PM, johnny huertas <johnnyhf@hotmail.com> wrote:
> > Members of list:
> > I have some problems to resolve a question. I have been working a lot in fit
> > the AgBr(1-x)Clx example of FEFFIT site. My fits were good in my opinion,
> > but I don't know how to identify the Br and Cl atomic distribution around Ag
> > (random or specific?). I didn't find any example about this in the site.
> > Conversely I have made some attempts to identify such distribution. I have
> > made two fits preparing for each one feff file, a feff file puting Br and Cl
> > atoms in face and other in medirian position around Ag knowing the CN=6 of
> > this central atom and fiting only the first shell. Unfortunatelly I don't
> > have found satisfactory results because the paremeter are equal in both
> > cases. I would like you help showing a similar example. Thanks.
>
> As is often requested on this list, it would be most helpful if you
> asked specific questions, and possibly post a project of what you've
> done and a clear explanation of what you are trying to do. Open ended
> questions are just too difficult to address. Are you asking how to
> include both Ag-Br and Ag-Cl in a fit, or asking if you can
> distinguish random substitution from ordered substitution? I'm not
> sure why the Ag-Br and Ag-Cl parameters would be the same, but it's
> too hard to speculate without knowing what you actually did.
>
> --Matt
>
>
> ------------------------------
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