[Ifeffit] Ifeffit Digest, Vol 114, Issue 5
María Elena Montero Cabrera
elena.montero at cimav.edu.mx
Thu Aug 9 10:19:13 CDT 2012
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 <bearcharge at gmail.com>
> 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 at millenia.cars.aps.anl.gov
> > wrote:
>
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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)
>>
>>
>> ----------------------------------------------------------------------
>>
>> Message: 1
>> Date: Wed, 8 Aug 2012 13:17:59 -0400
>> From: Marie Zwetsloot <mjz56 at cornell.edu>
>> To: ifeffit at millenia.cars.aps.anl.gov
>> Subject: Re: [Ifeffit] question for ifeffit mailing list - ATHENA
>> NORMALIZATION
>> Message-ID:
>> <CALtZdD54=
>> 1-w4U3vk7DdNU_CUkGpK-1vJ3ioOR_CSvkj4UeCXw at mail.gmail.com>
>> 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
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>> ------------------------------
>>
>> Message: 2
>> Date: Wed, 8 Aug 2012 15:10:16 -0400
>> From: Scott Calvin <scalvin at sarahlawrence.edu>
>> To: XAFS Analysis using Ifeffit <ifeffit at millenia.cars.aps.anl.gov>
>> Subject: Re: [Ifeffit] question for ifeffit mailing list - ATHENA
>> NORMALIZATION
>> Message-ID: <B36E3403-35BC-48BE-8E4D-AE2CB8556769 at slc.edu>
>> Content-Type: text/plain; charset="iso-8859-1"
>>
>> Hi Marie,
>>
>> I think you can try linear combination fitting, but you'll have to build
>> in the uncertainty in normalization in to your own estimates of uncertainty.
>>
>> If you don't check the box that says "force weights to sum to 1," then
>> you can allow for normalization errors in your sample.
>>
>> If your standards also have only short energy ranges, then there's
>> nothing you can do about that, though. As I said, you'll just have to build
>> them in to your uncertainty. If you are unsure of the edge jump of a
>> standard to 20%, then the contribution of that standard to the linear
>> combination fit is uncertain by 20%.
>>
>> Uncertainty in normalization is one of the leading contributions to the
>> uncertainty that should be associated with linear combination fitting, even
>> when the energy ranges are sufficient. In a case like yours, they're bigger
>> than they could have been, but it doesn't mean you can't use linear
>> combination analysis at all.
>>
>> --Scott Calvin
>> Sarah Lawrence College
>>
>> On Aug 8, 2012, at 1:17 PM, Marie Zwetsloot wrote:
>>
>> > 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
>> > _______________________________________________
>> > Ifeffit mailing list
>> > Ifeffit at millenia.cars.aps.anl.gov
>> > http://millenia.cars.aps.anl.gov/mailman/listinfo/ifeffit
>>
>>
>>
>>
>> ------------------------------
>>
>> Message: 3
>> Date: Thu, 9 Aug 2012 00:21:14 -0400
>> From: Enyuan Hu <bearcharge at gmail.com>
>> To: ifeffit <ifeffit at millenia.cars.aps.anl.gov>
>> Subject: [Ifeffit] pre-edge centroid
>> Message-ID:
>> <CAJud35NRYb67J7xLATPHPJGjEyvOK_gUKZur+dL9T30x8k=
>> UHA at mail.gmail.com>
>> Content-Type: text/plain; charset="iso-8859-1"
>>
>> Dear all,
>>
>> I was wondering if anyone could comment on how to get the centroid of
>> pre-edge by fitting the pre-edge peak by pseudo-Voigt functions. I tried
>> to
>> do that in Athena, but it seemed that peaking fitting part is the
>> relatively less developed function in the software. Any comment would be
>> appreciated.
>>
>> Enyuan
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>> ------------------------------
>>
>> Message: 4
>> Date: Thu, 09 Aug 2012 15:11:31 +0200
>> From: Dominik Samuelis <d.samuelis at fkf.mpg.de>
>> To: XAFS Analysis using Ifeffit <ifeffit at millenia.cars.aps.anl.gov>
>> Subject: Re: [Ifeffit] pre-edge centroid
>> Message-ID: <5023B703.6020609 at fkf.mpg.de>
>> Content-Type: text/plain; charset="iso-8859-1"; Format="flowed"
>>
>> Dear Enyuan,
>>
>> in my experience, peak fitting works very well with Athena. Try not to
>> fit only the prepeak, but maybe include an arctan describing the edge
>> (see attached pdf, the fit was made using athena). This makes isolating
>> the prepeak much more reliable.
>>
>> Best regards,
>> Dominik
>>
>> On 09.08.2012 06:21, Enyuan Hu wrote:
>> > Dear all,
>> >
>> > I was wondering if anyone could comment on how to get the centroid of
>> > pre-edge by fitting the pre-edge peak by pseudo-Voigt functions. I tried
>> > to do that in Athena, but it seemed that peaking fitting part is the
>> > relatively less developed function in the software. Any comment would be
>> > appreciated.
>> >
>> > Enyuan
>> >
>> >
>> > _______________________________________________
>> > Ifeffit mailing list
>> > Ifeffit at millenia.cars.aps.anl.gov
>> > http://millenia.cars.aps.anl.gov/mailman/listinfo/ifeffit
>> >
>>
>>
>> --
>> Dr. Dominik Samuelis
>> d.samuelis at fkf.mpg.de
>> Max-Planck-Institut f?r Festk?rperforschung
>> Max Planck Institute for Solid State Research
>> Heisenbergstr. 1
>> 70569 Stuttgart
>> Germany
>> Phone +49-711-689-1769
>> Fax +49-711-689-1722
>> Web http://www.fkf.mpg.de/maier/
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>>
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>> End of Ifeffit Digest, Vol 114, Issue 5
>> ***************************************
>>
>
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--
María Elena
Dra. María Elena Montero Cabrera
Centro de Investigación en Materiales Avanzados (CIMAV)
Miguel de Cervantes 120, Compl. Ind. Chihuahua
Chihuahua CP 31109, Chih. México
Tel (614) 4391123
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