Dear Disha, In principle, yes, there can be a change of bond length without a notable change of the XANES. But it also depends on how large the bond length changes are that you observe. I have studied a lot of semiconductor alloys, for example (In,Ga)P or Cu(In,Ga)Se2 where the Ga and In atoms share the same lattice site. They are always coordinated to four P or Se atoms, respectively, but the bond lengths change by 0.02 to 0.03 A because the size of the unit cell changes with In/Ga ratio. At the same time, the Ga and In XANES is completely unaffected by a change of the In/Ga ratio. If you are interested in this, you may have a look at Phys. Rev. B 85, 245204 (2012), J. Appl. Phys. 116, 093703 (2014), or Appl. Phys. Rev. 2, 031304 (2015). This is just to say that, yes, in some special cases you can have a change of bond length without a change of XANES. There can be lot's of other things going on, too :) Cheers, Claudia ----- Nachricht von Disha Gupta --------- Datum: Mon, 11 Jun 2018 18:29:49 +0800 Von: Disha Gupta Antwort an: XAFS Analysis using Ifeffit Betreff: Re: [Ifeffit] No shift in XANES absorption peak An: ifeffit@millenia.cars.aps.anl.gov

Dear Dr Carlo

The edges are almost identical. The pre-edge intensity change isn't that significant I feel. I did the Artemis fittings with the coordination numbers fixed. Maybe I can try varying the coordination numbers and see if it gives a different result. I have attached the images of the pre-edge and main peak.

Thanks and Regards Disha

From: Carlo Segre Date: Mon, Jun 11, 2018, 12:34 Subject: Re: [Ifeffit] No shift in XANES absorption peak To: XAFS Analysis using Ifeffit

Hi Disha:

it would be good to see the XANES you are referring to. Are the edges identical or do they change but not shift significantly? Is the coordination number also constant? Generally, the bond distance will change with oxidation state if the coordination number is constant but if the coordination number changes, then there could be a change in bond length too.

Cheers,

Carlo

On Mon, 11 Jun 2018, Disha Gupta wrote:

...

Dear All

Firstly, I would like to say sorry if I have missed out on this discussion before but it would be great if you could help me out. I have been analyzing some Mn K-edge XAS data for some battery materials. While the XANES data shows no shift in the main absorption peak which means that there is no oxidation change happening, however, when I am fitting the data in Artemis, I can see a shift in the bond lengths suggesting an oxidation change. Is it possible that bond lengths change even though XANES spectra show no change?

Thank you and Kind Regards Disha

-- Carlo U. Segre -- Duchossois Leadership Professor of Physics Interim Chair, Department of Chemistry Director, Center for Synchrotron Radiation Research and Instrumentation Illinois Institute of Technology Voice: 312.567.3498 Fax: 312.567.3494 segre@iit.edu http://phys.iit.edu/~segre segre@debian.org _______________________________________________ Ifeffit mailing list Ifeffit@millenia.cars.aps.anl.gov http://millenia.cars.aps.anl.gov/mailman/listinfo/ifeffit Unsubscribe: http://millenia.cars.aps.anl.gov/mailman/options/ifeffit

Disha Gupta Graduate Student School of Materials Science and Engineering Nanyang Technological University (NTU), Singapore +65 84087404 DISHA001@e.ntu.edu.sg

On Mon, Jun 11, 2018 at 11:34 AM, Disha Gupta wrote:

...

Dear All

Firstly, I would like to say sorry if I have missed out on this discussion before but it would be great if you could help me out. I have been analyzing some Mn K-edge XAS data for some battery materials. While the XANES data shows no shift in the main absorption peak which means that there is no oxidation change happening, however, when I am fitting the data in Artemis, I can see a shift in the bond lengths suggesting an oxidation change. Is it possible that bond lengths change even though XANES spectra show no change?

Thank you and Kind Regards Disha

----- Ende der Nachricht von Disha Gupta ----- -- PD Dr. Claudia S. Schnohr Institut für Festkörperphysik Friedrich-Schiller-Universität Jena Max-Wien-Platz 1 D-07743 Jena Germany Tel: +49 3641 947333 Fax: +49 3641 947302

yes, the coordination number needs to be varied. The edges certainly do not show a significant change. Carlo On Mon, 11 Jun 2018, Disha Gupta wrote:

Dear Dr Carlo

The edges are almost identical. The pre-edge intensity change isn't that significant I feel. I did the Artemis fittings with the coordination numbers fixed. Maybe I can try varying the coordination numbers and see if it gives a different result. I have attached the images of the pre-edge and main peak.

Thanks and Regards Disha

From: Carlo Segre Date: Mon, Jun 11, 2018, 12:34 Subject: Re: [Ifeffit] No shift in XANES absorption peak To: XAFS Analysis using Ifeffit

Hi Disha:

it would be good to see the XANES you are referring to. Are the edges identical or do they change but not shift significantly? Is the coordination number also constant? Generally, the bond distance will change with oxidation state if the coordination number is constant but if the coordination number changes, then there could be a change in bond length too.

Cheers,

Carlo

On Mon, 11 Jun 2018, Disha Gupta wrote:

...

Dear All

Firstly, I would like to say sorry if I have missed out on this discussion before but it would be great if you could help me out. I have been analyzing some Mn K-edge XAS data for some battery materials. While the XANES data shows no shift in the main absorption peak which means that there is no oxidation change happening, however, when I am fitting the data in Artemis, I can see a shift in the bond lengths suggesting an oxidation change. Is it possible that bond lengths change even though XANES spectra show no change?

Thank you and Kind Regards Disha

-- Carlo U. Segre -- Duchossois Leadership Professor of Physics Interim Chair, Department of Chemistry Director, Center for Synchrotron Radiation Research and Instrumentation Illinois Institute of Technology Voice: 312.567.3498 Fax: 312.567.3494 segre@iit.edu http://phys.iit.edu/~segre segre@debian.org