Hi B. Have you had any lessons on XAFS? i. e. attended an XAFS course offered by many synchrotrons and related institutions. Do you know the difference between pre-edge features and absorption edge? In the plot you provided, the edge positions
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Hi B.

Have you had any lessons on XAFS? i.e. attended an XAFS course offered by many synchrotrons and related
institutions.

Do you know the difference between pre-edge features and absorption edge?
In the plot you provided, the edge positions are clearly different.

Formal oxidation state is a convenient way to count electrons.

Edge position is governed by how the screening of the nucleus of the absorber is affected
by the type and arrangement of near neighbours - orbitals involved in bonding and extent of
charge transfer between absorber and ligands...hence the usefulness of XAFS as a technique
for characterising local environments.

Still confused? Start here: https://xafs.xrayabsorption.org/tutorials.html

-R.



On 2025-02-26 11:31 p.m., Benito Melas via Ifeffit wrote:
Hi all, I was following this article about Li2TiS3 https: //pubs. acs. org/doi/full/10. 1021/acs. inorgchem. 4c03864 and found this Ti edge XANES figure The authors claim The peak position for LTS-213 is approximately 4970 eV, which agrees well with
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Hi all,
I was following this article about Li2TiS3

https://pubs.acs.org/doi/full/10.1021/acs.inorgchem.4c03864

and found this Ti edge XANES figure

image.png
The authors claim

The peak position for LTS-213 is approximately 4970 eV, which agrees well with that for rutile TiO2 with a valence of titanium species in the 4+ oxidation state.

Should we use the pre-edge to determine the oxidation state? Is it reliable, or should we use E₀ and compare it with references of well-known oxidation states?
 
In addition, TiS2, in which titanium is also in the 4+ oxidation state, shows pre-edge peaks at 4968–4971 eV. (21) Considering the titanium oxidation state in the raw materials, the stability of the titanium species, and the XANES results, the oxidation state of the titanium species in LTS-213 is likely to be 4+.

The second conclusion is even more unclear.

Would you help me see if I am missing something in my understanding of oxidation states using XANES?


Best, B.

 

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