Re: [Ifeffit] Ifeffit Digest, Vol 88, Issue 12

Dear Darek, Sorry for the late response. To fit the "first shell" the No.of independent points and No.of variables which i use are as follows: I use deltaK=11, deltaR = 1.1 so No.of independent points are 8 and No.of variables are 4 (i.e. N, e0, delr, and ss2) I set s02=0.9. Best regards, Rana On 14.06.2010 19:00, ifeffit-request@millenia.cars.aps.anl.gov wrote:

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Today's Topics:

1. XAFS fitting with multiple atomic sites of absorbing atom (Jatinkumar Rana) 2. ODP: XAFS fitting with multiple atomic sites of absorbing atom (Zajac, Dariusz A.)

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Message: 1 Date: Mon, 14 Jun 2010 12:00:27 +0200 From: Jatinkumar Rana To: Ifeffit users Subject: [Ifeffit] XAFS fitting with multiple atomic sites of absorbing atom Message-ID:<4C15FDBB.1050203@helmholtz-berlin.de> Content-Type: text/plain; charset=ISO-8859-1; format=flowed

Dear users,

I have measured XAFS spectra on Mn and Fe edge on my material. The material contains 3 different atomic positions for Mn and 4 different atomic positions for Fe.

Initially, I tried fitting Fe-edge/Mn-edge spectra using indiviual Fe/Mn atomic position one-by-one (i.e. first take one Fe/Mn position, calculate Feff paths, consider certain paths to fit specific R-range, then take another Fe/Mn position and do the same) but the fit was not good visually and in terms of goodness of fit parameters.

Then, i tried fitting Fe-edge/Mn-edge spectra, taking into account all Fe/Mn atomic position together i.e. I separately calulated Feff paths for each Fe/Mn atomic position and summed up related paths from each Feff calculation for fitting a specific R-range. (The assumption being, the experimental Fe-edge/Mn-edge XAFS spectra has varying contribution from all Fe/Mn atomic position in crystal structure).

Anybody in the group could comment about my approach to fit such problem ?

Is there any specific strategy to fit such problem ?

I would be thankful if you could suggest some literature available on such problems.

Thanks in advance.

Best regards, Rana

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Message: 2 Date: Mon, 14 Jun 2010 13:34:18 +0200 From: "Zajac, Dariusz A." To: "XAFS Analysis using Ifeffit" Subject: [Ifeffit] ODP: XAFS fitting with multiple atomic sites of absorbing atom Message-ID: <35E004AD6290A7438FCA34BBF325F41601206741@ADXV2.win.desy.de> Content-Type: text/plain; charset="iso-8859-2"

Dear Rana, could you specify how many independent data points and variables you have and you use for fitting? thnx darek

-----Wiadomo?? oryginalna----- Od: ifeffit-bounces@millenia.cars.aps.anl.gov w imieniu Jatinkumar Rana Wys?ano: Pn 2010-06-14 12:00 Do: Ifeffit users Temat: [Ifeffit] XAFS fitting with multiple atomic sites of absorbing atom

Dear users,

I have measured XAFS spectra on Mn and Fe edge on my material. The material contains 3 different atomic positions for Mn and 4 different atomic positions for Fe.

Initially, I tried fitting Fe-edge/Mn-edge spectra using indiviual Fe/Mn atomic position one-by-one (i.e. first take one Fe/Mn position, calculate Feff paths, consider certain paths to fit specific R-range, then take another Fe/Mn position and do the same) but the fit was not good visually and in terms of goodness of fit parameters.

Then, i tried fitting Fe-edge/Mn-edge spectra, taking into account all Fe/Mn atomic position together i.e. I separately calulated Feff paths for each Fe/Mn atomic position and summed up related paths from each Feff calculation for fitting a specific R-range. (The assumption being, the experimental Fe-edge/Mn-edge XAFS spectra has varying contribution from all Fe/Mn atomic position in crystal structure).

Anybody in the group could comment about my approach to fit such problem ?

Is there any specific strategy to fit such problem ?

I would be thankful if you could suggest some literature available on such problems.

Thanks in advance.

Best regards, Rana _______________________________________________ Ifeffit mailing list Ifeffit@millenia.cars.aps.anl.gov http://millenia.cars.aps.anl.gov/mailman/listinfo/ifeffit

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End of Ifeffit Digest, Vol 88, Issue 12 ***************************************