[Wien] EELS of L3 Ti edge

[Emil Stoyanov]

Dear All,
thanks a lot for the help. I'll post a message when I have some results.
Cheers,
Emil

Peter Blaha wrote:

>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
>--------------------------------------------------------------------------
>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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>