[Ifeffit] Ifeffit Digest, Vol 113, Issue 11

johnny huertas johnnyhf at hotmail.com
Sat Jul 14 12:51:20 CDT 2012


Hi Matt: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.  

Jhonny Huertas Flores
Rio de Janeiro-Brasil


 > From: ifeffit-request at millenia.cars.aps.anl.gov
> Subject: Ifeffit Digest, Vol 113, Issue 11
> To: ifeffit at millenia.cars.aps.anl.gov
> Date: Sat, 14 Jul 2012 12:00:01 -0500
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> Today's Topics:
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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 at hotmail.com>
> To: <ifeffit at millenia.cars.aps.anl.gov>
> Subject: [Ifeffit] problems
> Message-ID: <BAY167-W124DD69B56D1526E67FEC05D5D70 at 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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> ------------------------------
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> Message: 2
> Date: Fri, 13 Jul 2012 22:20:41 -0500
> From: Matt Newville <newville at cars.uchicago.edu>
> To: XAFS Analysis using Ifeffit <ifeffit at millenia.cars.aps.anl.gov>
> Subject: Re: [Ifeffit] problems
> Message-ID:
> 	<CA+7ESbruuJaW0KVyuE=fUP5Mzz_W63yEqc-v3OAE_KhQj6hN-A at mail.gmail.com>
> Content-Type: text/plain; charset=ISO-8859-1
> 
> Hi,
> 
> On Fri, Jul 13, 2012 at 5:21 PM, johnny huertas <johnnyhf at 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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> End of Ifeffit Digest, Vol 113, Issue 11
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