[Ifeffit] Interatomic distances from feff paths
dr.sdkelly at gmail.com
Thu Sep 30 20:35:10 CDT 2010
You can open the cif file with a text editor and check the parameters in the atoms page against what you find in the cif file.
Sometimes a shift vector is needed. Check the messages in artemis for the possible values to try.
If none of these work. Try sending us the cif file.
On Sep 30, 2010 5:01 PM, Elsa E. Sileo <sileo at qi.fcen.uba.ar> wrote:
I am trying to use the following CIF files to
generate the feff path at the As edge:
1- 'Iron(III) arsenate(V) dihydrate', Scorodite,
H4 As Fe O6'; space group P c a b; number 61; orthorhombic
2. Iron(III) tris(dihydrogenarsenate) pentahydrate
Kaatialaite, Fe (H2 As O4)3 (H2 O)5, P 1 21/n 1, number 14; monoclinic
and in both cases, after running Feff, I obtain
distances Fe-As that are not real.
For instance in scorodite I find a distance As-Fe = 1,71 A.
How can I overcome this problem?
At 14:00 30/09/2010, you wrote:
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> 1. Re: Ifeffit Digest, Vol 91, Issue 28 (Matt Newville)
>Date: Thu, 30 Sep 2010 11:28:28 -0500
>From: Matt Newville <newville at cars.uchicago.edu>
>To: XAFS Analysis using Ifeffit <ifeffit at millenia.cars.aps.anl.gov>
>Subject: Re: [Ifeffit] Ifeffit Digest, Vol 91, Issue 28
> <AANLkTinRMxoi2ANd=H=a+Bir5FRG0rruw_UPYy53sfCE at mail.gmail.com>
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>On Thu, Sep 30, 2010 at 10:33 AM, Elsa Sileo <e_sileo at yahoo.es> wrote:
> > Dear Matt,
> > I have to perform EXAFS analysis, and when I tried to fit the first
> > shell, I found deltaE0 values of about 8 eV. Following the paper of
> > Kelly et al (Analysis of soils and minerals using X-ray absorption
> > spectroscopy. In Methods of soil analysis, Part 5: Mineralogical
> > methods; 2008; pp 446) I fitted the first shell obtaining values for
> > deltaE0, sigma^2; delta R and amplitude. Then, using the obtained
> > values, and making deltaE0=0, I got the theoretical signal.
>Why is important to have a theoretical spectra with deltaE0=0?
> > When I compare the experimental and theoretical spectrum I see a mismatch
> > between the position of the nodes at low wavenumbers.
>Yes, that is what E0 does.
> > Having done this, how I have to proceed to correct the experimental
> > data in order to obtain smalller delta E0 values?
>I think what you are trying to do (though I don't understand why) is
>to adjust E0 for the experimental data so that the fit to a particular
>theoretical standard gives deltaE0 close to zero. If so, you want to
>adjust E0 in the background subtraction. If you change E0 by 8eV
>there, you should end up with a deltaE0 in the fit that is close to
>Hope that helps,
>Ifeffit mailing list
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>- Release Date: 09/30/10 06:34:00
Dra. Elsa E. Sileo
INQUIMAE - Dto. Qca. Inorganica, Analitica y Qca. Fisica; FCEN, UBA
Int. Güiraldes 2160, Pabellón 2, Piso 3, Ciudad Universitaria - C1428EHA
CABA - Argentina
Tel: (54 11) 4576 3380 ext. 113
Fax: (54 11) 4576 3341
e-mail: sileo at qi.fcen.uba.ar
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