Re: [Ifeffit] Ifeffit Digest, Vol 114, Issue 7

Dear all, Thank you so much for all your valuable input. I attached the fitting result using ATHENA as pdf file. Seems that the fitting is not bad. Like Dominik and Maria pointed out, it takes some caution to do the fitting. My experience is, do not fit all parameters at the same time first. Approach by a try-and-error method, manually adjusting the parameters based on observation of difference between fitted data and experimental data. When you think it's about the time, free all parameters (no including centroid) for the final try. Good luck with that. Here's another question, how do I compute the centroid of the fitted peaks? ATHENA gives the centroid for each peak, do I just average them? thanks! Enyuan On Thu, Aug 9, 2012 at 11:26 AM, wrote:

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Today's Topics:

1. Re: Ifeffit Digest, Vol 114, Issue 5 (Mar?a Elena Montero Cabrera) 2. Re: Ifeffit Digest, Vol 114, Issue 6 (Enyuan Hu)

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Message: 1 Date: Thu, 9 Aug 2012 09:19:13 -0600 From: Mar?a Elena Montero Cabrera To: XAFS Analysis using Ifeffit Subject: Re: [Ifeffit] Ifeffit Digest, Vol 114, Issue 5 Message-ID: Content-Type: text/plain; charset="iso-8859-1"

Hello all, I have done pre-edge fitting of Ti in multiferroic ceramics with Athena. I have selected error function for the "background" and alternatively Lorenztian or Gaussian function for *several* peaks, and Athena has worked quite well. The point is to do it with some systematic procedure, and fixing some parameters, instead of letting them being free in each step. Certainly, Athena doesn't have the pseudo-Voigt function. Try to do this way, Enyuan. I think Bruce has commented something about this way sometime ago, but I am not sure. Regards Maria Elena

2012/8/9 Enyuan Hu

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Hi Dominik,

Thank you so much for your quick response. Indeed, it's really nice fitting according to your result. But my situation seems a little bit different as I'm dealing with the Mn XANES data and there're doublets and sometimes triplets in the pre-edge. Actually, I might as well explain my interest of doing such fitting. I read in the paper *(F Farges, PHYSICAL REVIEW B 71, 155109 (2005))* that the centroid of pre-edge peak is a more accurate measurement of the oxidation state of the element of interest, compared to the more conventional inflection point or half-way method. So I was trying to follow the paper and see if it also works for my samples. Anyway, thanks again for your help!

Enyuan

On Thu, Aug 9, 2012 at 9:11 AM, < ifeffit-request@millenia.cars.aps.anl.gov

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Today's Topics:

1. Re: question for ifeffit mailing list - ATHENA NORMALIZATION (Marie Zwetsloot) 2. Re: question for ifeffit mailing list - ATHENA NORMALIZATION (Scott Calvin) 3. pre-edge centroid (Enyuan Hu) 4. Re: pre-edge centroid (Dominik Samuelis)

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Message: 1 Date: Wed, 8 Aug 2012 13:17:59 -0400 From: Marie Zwetsloot To: ifeffit@millenia.cars.aps.anl.gov Subject: Re: [Ifeffit] question for ifeffit mailing list - ATHENA NORMALIZATION Message-ID: Content-Type: text/plain; charset="iso-8859-1"

Hi Scott Calvin,

Thanks for your help. Yes, this is as far as my pre- and post-edge range go. I realized I should have made them longer; it was my first time doing this and wasnt aware that i should lengthen my pre and post-edge for later on analysis. This will be good lesson for the future.

So you would not recommend doing linear combination fitting? I was planning on trying it out.. But I wouldnt want to do it if with my pre- and post-edge range, I am bound to derive wrong conclusions from the data.

Best, Marie