[Ifeffit] E0 in Co3O4

Jesús Eduardo Vega Castillo jevecas at gmail.com
Mon Oct 30 06:41:24 CDT 2017


Thank you very much Manuel,



2017-10-27 6:41 GMT-03:00 Manuel MONTE CABALLERO <manuel.monte en esrf.fr>:

> Dear Jesús,
>
> Why will you choose the maximum at 7722 eV?
> I will choose the first one (ignoring the pre-edge), around 7718 eV.
>
> The problem here, could be that in Co3O4 you have one atom of Co(II) and
> two of Co(III) so, there are absorbing at different energies.
> But the EXAFS is common so, and error will happen no matter which maximum
> you choose.
> I have a CoO spectra and the maximums of the derivative (again ignoring
> the pre-edge) appear at 7717, 7721 and 7725 eV.
> If you had a Co2O3 spectra (I don't) you can compare and decide to choose
> the E0 which is closer to that of the Co2O3 as in Co3O4 you have more
> Co(III).
>
> Also, if you make three copies of the spectra and select a different E0
> for each one you can see how it affect the x(k) and the Fourier transform
> (to R).
> The first E0 (7718 eV) make x(k) to have higher intensity (resulting in
> higher intensity of peaks in R).
> But the third one (7722) creates an extra feature below 1 in the R space
> (for k range 3-9 or 3-10).
>
> Usually I will just choose the first one or, compare some and see what
> happen.
> Probably, the different will not so high to make you worry too much.
>
>
> Regards,
>
> Manuel
>
>
>
> On 25/10/2017 17:11, Jesús Eduardo Vega Castillo wrote:
>
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> Dear list,
>
> I enclose an Athena project with a XAFS spectrum of Co3O4 with a metallic
> Co reference.
> Athena by default has chosen E0 at the absolute maximun of the derivative
> curve (at 7727.8eV) which in my opinion is too high because it is at the
> white line zone.
>
> I believe that E0 should be the previous maximun in the derivative at
> around 7722eV, which would be at the rising edge.
>
> Am I wrong?
>
> I would appreciate some help with the criterion to determine the right
> value.
>
>
> Yours,
>
> Jesús
>
>
>
>
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