[Wien] About spin-resolved optical analysis

[Laurence Marks]

Answering my own question, for the case when up & dn are the same,

eps_2_Full = eps_2_up + eps_2_dn
eps_1_Full = eps_1_up + eps_1_dn - 1 = 1 + (eps_1_up -1) + (eps_1_dn -1)

The "-1" is because otherwise the vacuum contribution is being double
counted. This does not occur in the other case as there is no energy loss
in vacuum.

On Thu, Apr 30, 2026 at 2:13 PM Laurence Marks <laurence.marks at gmail.com>
wrote:

> A minor question: if spin-up & dn are the same (runsp_c) is it also
> necessary to add (double) the spin-resolved?
>
> On Thu, Apr 30, 2026 at 9:06 AM Peter Blaha <peter.blaha at tuwien.ac.at>
> wrote:
>
>> Just to make this clear:
>>
>> You still get epsilon-2 (imaginary part of epsilon) for spin-up and dn
>> separately (eps-2 is related to optical absorption).
>>
>> However, the Kramers-Kronig transformation is not additive, i.e. in
>> order to get epsilon-1 (real part, i.e. refraction index), you need to
>> add the spin-up and dn part of eps-2 and then continue with kram.
>>
>> Thus, any optical quantity which is derived (partly) from eps-1 is not
>> spin-dependent, quantities derived only from eps-2 are spin-dependent.
>>
>> PS: With spin-orbit coupling and spin-polarization, you can also
>> calculate the cross terms and off-diagonal terms of the dielectric tensor.
>>
>>
>> Am 29.04.2026 um 10:07 schrieb evren görkem özdemir:
>> > Dear Wien2k users,
>> >
>> > How is spin-resolved optical analysis performed on half-metallic
>> materials?
>> >
>> > The results obtained after performing spin-up and spin-down steps
>> > individually in optical properties are spin-averaged optical
>> coefficients.
>> >
>> > I would be grateful if you could help me with this.
>> >
>> > Sincerely,
>> >
>> > Evren G. Özdemir
>> >
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>>
>> --
>> -----------------------------------------------------------------------
>> Peter Blaha,  Inst. f. Materials Chemistry, TU Vienna, A-1060 Vienna
>> Email: peter.blaha at tuwien.ac.at
>> WWW:   http://www.imc.tuwien.ac.at      WIEN2k: http://www.wien2k.at
>> -------------------------------------------------------------------------
>>
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>
>
> --
> Emeritus Professor Laurence Marks (Laurie)
> Northwestern University
> Webpage <http://www.numis.northwestern.edu> and Google Scholar link
> <http://scholar.google.com/citations?user=zmHhI9gAAAAJ&hl=en>
> "Research is to see what everybody else has seen, and to think what nobody
> else has thought", Albert Szent-Györgyi
>


-- 
Emeritus Professor Laurence Marks (Laurie)
Northwestern University
Webpage <http://www.numis.northwestern.edu> and Google Scholar link
<http://scholar.google.com/citations?user=zmHhI9gAAAAJ&hl=en>
"Research is to see what everybody else has seen, and to think what nobody
else has thought", Albert Szent-Györgyi
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