[Wien] EELS of L3 Ti edge

[Peter Blaha]

I'd just like to raise a few points you need to consider when you
calculate spectra:

TM oxides are often fairly correlated materials, so you might need LDA+U
in some cases.

EELS (and X-ray absorption) spectra have a core-hole as final state. In 
most cases this should NOT be neclected!
You can simulate it with WIEN by creation of a small supercell and put
a core hole on one of your atoms, promoting this electron into valence.
/edit case.inc and reduce the core oppupation; edit case.in2 and add this
electron.
run_lapw
edit case.in2 and set the number of electrons back to "normal"
run you spectra.

L2,L3: You may take the splitting from the core eigenvalues (case.scf) and
overlay the spectra yourself (eg. in Excel) with the proper shift and
with desired intensity ratio. I know this is not perfect, but not so bad
either.

Anyway, several people have shown that WIEN can be used quite successfully
to calculate EELS spectra.

Regards
 
> I'm doing experimental and theoretical research on EELS of Ti (oxides mainly).
> I found big differences in the experimental and computed spectra (for L3 edge)
> - the computed spectra look very, very far from the experimental ones. We
> tried to include other orbitals in the computation (changing the Ar core with
> Ne and even He) but without any positive result. There are some articles in
> which is shown that the expected ratio of the L3:L2 intensities should be 2:1
> (on the basis of 2j+1 degerancy). It looks like that this can be the reason
> for these differences with the experimental results. In the same articles is
> shown that the ratio L3:L2 has to be 0.8 and in this case the spectral
> features in the computed and experimental spectra are quite similar one to
> each other. My question is it is possible to change somehow these ratios or
> how we can improve the quality of the spectra? I would like just to notice,
> that in the case of Cr we don't have such differences - the computed spectra
> look quite good.
> 
> Thanks in advance for your help
> Best regards,
> Emil Stoyanov
> 
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> Wien at zeus.theochem.tuwien.ac.at
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> 


                                      P.Blaha
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Peter BLAHA, Inst.f. Materials Chemistry, TU Vienna, A-1060 Vienna
Phone: +43-1-58801-15671             FAX: +43-1-58801-15698
Email: blaha at theochem.tuwien.ac.at    WWW: http://info.tuwien.ac.at/theochem/
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