[Ifeffit] Ifeffit Digest, Vol 114, Issue 5
Enyuan Hu
bearcharge at gmail.com
Thu Aug 9 09:53:32 CDT 2012
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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