[Ifeffit] Linear Combination Fitting using ATHENA

Teck Kwang Choo teck.kwang.choo at monash.edu
Fri Aug 9 07:40:28 CDT 2013

Thanks for your reply Edmund.

I agree with you that I might have not chosen the right standards for my
sample. In fact, XRD analysis have confirmed that Ferrite is the main form
of Fe in my sample but I did not have any ferrite standards during XANES
analysis. Was wondering if you happen to have any Ferrite XANES spectra by
any chance?

Thanks and kind regards.

Teck Kwang

On 9 August 2013 16:53, Edmund Welter <edmund.welter at desy.de> wrote:

>  Dear Teck Kwang Choo,
> it is the ratio of the number of (in your case) iron atoms. This ratio has
> no unit. You will therefore get the same number if you calculate molar %
> ratio or weight % (Except you consider the weight of the missing electron
> in Fe3+... :-). Now, if you weigh your standards and want to calculate the
> "number of Fe atoms" you have to consider the weight of the oxygen. That
> means, the ratio you get from LCF fitting of your XAS spectra is NOT the
> ratio between mol of FeO and Fe2O3, but mol FeII+ to mol FeIII+! However,
> if necessary or usefull you can always calculate the latter from the
> FeII/FeIII ratio using the molar weights.
> So, as a chemist I would say, stay consequently with the molar ratio and
> you are on the safe side. You can always multiply the number of mol with
> the molar weight, but you would only make things more complicated and end
> up with the same ratio or, after multiplying with 100, percentage.
> Concerning the deviation between your result and your expectation: I would
> be more nervous about the choice of reference substances. If you only use
> FeO and Fe2O3 your result is only "correct" if your sample contains no
> other Fe component than these two. If it contains significant amounts of
> any other Fe component (even other oxides) you would better not draw any
> important conclusions from the result of your analysis.
> Best regards
> Edmund Welter
> On 09.08.2013 05:37, Teck Kwang Choo wrote:
> Hello,
> I have been using ATHENA to perform Linear Combination Fitting (LCF) on my
> XANES spectrum to quantify the amounts of Fe (II) and Fe (III) in my
> samples using only FeO and Fe2O3 as standards. The results showed a
> majority of Fe (II), which is contrary to what was expected.
> This made me wonder if the LCF results from XANES is a molar percentage
> (mol %) or weight percentage (wt%).
>  Could anyone enlighten me on this matter?
>  Thanks!
> --
> Teck Kwang Choo
> PhD Student
> Department of Chemical Engineering
> Room 225, Building 36
> Monash University
> Mobile No.: 04-11489904
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Teck Kwang Choo
PhD Student
Department of Chemical Engineering
Room 225, Building 36
Monash University
Mobile No.: 04-11489904
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