[Wien] DOS in a single k-pointitrary
Gerhard Fecher
fecher at uni-mainz.de
Thu Dec 18 13:13:45 CET 2008
One answer was just given by Peter replying to another question:
otherwise you
get a very "spiky" DOS (or no DOS for a single k-point, because the tetrahedron
integration does not capture the set of delta-functions coming from a single k-point)
So what do you mean with the DOS of a single k-point ?
It is just a single delta function (not respecting degeneracies) so
plot the bandstructure in any direction you like and the spaghettis tell you at which energy the delta functions appear.
Ciao
Gerhard
====================================
Dr. Gerhard H. Fecher
Institut of Inorganic and Analytical Chemistry
Johannes Gutenberg - University
55099 Mainz
________________________________________
Von: wien-bounces at zeus.theochem.tuwien.ac.at [wien-bounces at zeus.theochem.tuwien.ac.at] im Auftrag von Oleg Artamonov [arto at mail.nnz.ru]
Gesendet: Donnerstag, 18. Dezember 2008 11:51
An: A Mailing list for WIEN2k users
Betreff: Re: [Wien] DOS in a single k-pointitrary
Dear Wien2k users,
I need to get the spin-asymmetry distribution of the valence
electrons in the energy interval about 1 eV near the Fermi level
along the specified direction in the surface BZ of W(110).
I have performed a runsp_lapw -orb -so.
I would like to use the Wien2k to calculate the DOS in the specified point
of the BZ and compose then the DOS distribution along a line in the
SBZ.
Can anyone guide me how to calculate the DOS for one specified point?
Thanks in advance,
Oleg Artamonov.
----- Original Message -----
From: "Oleg Artamonov" <arto at mail.nnz.ru>
To: "A Mailing list for WIEN2k users" <wien at zeus.theochem.tuwien.ac.at>
Sent: Friday, December 12, 2008 2:20 PM
Subject: Re: [Wien] DOS in a single k-pointitrary
> Dear Gerhard,
>
> Thank you for detailed reply. I'll try to explain my position.
> I would like to service my angle resolved e,2e experiment with
> the inelastic scattering of polarized electrons from W(110).
> We assume that the experimental spin-asymmetry is related to
> the spin-asymmetry of the valence states. For this reason
> I need to get the spin-asymmetry distribution of the valence
> electrons in the energy interval about 1 eV near the Fermi level
> along the specified direction in the surface BZ.
> I am running now the spin-resolved calculations with the orbital
> potential as advised by P. Novak to resolve spin-states.
> I can compose a script to describe the line in the surface BZ,
> but I need to get an idea how to calculate the DOS for the arbitrary
> k-point.
>
> Thank you in advance,
> Oleg Artamonov.
>
> ----- Original Message -----
> From: "Gerhard Fecher" <fecher at uni-mainz.de>
> To: "A Mailing list for WIEN2k users" <wien at zeus.theochem.tuwien.ac.at>
> Sent: Friday, December 12, 2008 11:42 AM
> Subject: Re: [Wien] DOS in a single k-pointitrary
>
>
>> What you are looking for is most probably the Bloch spectral function.
>> Usually this is calculated easily from the Greens function, but Wien2k is
>> not a Green's function method as for example KKR, LMTO, or ASW are
>> therfore I have no idea how to calculate the Bloch spectral function in
>> Wien2k.
>>
>> In an ordered lattice, however, the Bloch spectral function is simply a
>> sum of delta-functions (equation in my last mail) and just
>> reveals the bandstructure. That means, the spaghetti plot of Wien2k tells
>> you already where the Bloch spectral function is non-zero.
>> If you like to have any other point or line, you simply need to change
>> the
>> input file case.klist_band. This you may do either by hand or by using
>> XCrysden to be sure where you are in the Brillouin zone.
>> Anyway, I do not see a real reason what the knowledge about states in
>> points or on lines with arbitrary symmetry should tell,
>> at least if you do not do an angular resolved photoemission experiment,
>> and even there the knowledge about the states itself does not tell you
>> about the matrix elements between initial and final states. As physics
>> does not jump, the states on a line close to a high symmetry line
>> should be close, and inspecting the band structure in the high symmetry
>> directions gives you the idea how the spaghettis should look like
>> if you are slightly off a certain direction. If you find singular points
>> then something is completely wrong, anyway.
>>
>> The Bloch spectral function is much more interesting for statistically
>> disordered systems.
>> In that case you do not have a band structure anymore as the (infinite)
>> periodicity of youre lattice is lost.
>> Roughly spoken, in such systems the spaghettis will be smeared about each
>> point in k and E.
>> For Wien2k, there is no need to think further about that situation, as it
>> does not allow to calculate for statistically disordered systems.
>>
>> Indeed, one should remark that the use of supercells to model
>> statistically disordered systems is very dangerous,
>> as the artificially brought in symmetry may result in band gaps that are
>> not existent in real live as they become completely
>> smeared over by the statistical disorder.
>>
>> Ciao
>> Gerhard
>>
>> ====================================
>> Dr. Gerhard H. Fecher
>> Institut of Inorganic and Analytical Chemistry
>> Johannes Gutenberg - University
>> 55099 Mainz
>> ________________________________________
>> Von: wien-bounces at zeus.theochem.tuwien.ac.at
>> [wien-bounces at zeus.theochem.tuwien.ac.at] im Auftrag von Oleg Artamonov
>> [arto at mail.nnz.ru]
>> Gesendet: Donnerstag, 11. Dezember 2008 19:27
>> An: A Mailing list for WIEN2k users
>> Betreff: Re: [Wien] DOS in a single k-pointitrary
>>
>> Dear Gerhard,
>>
>> Yes, You are right and a lot of states should be empty.
>> I consider the DOS in the arbitrary k-point as a number of occupied
>> states in a selected energy range and in the chosen volume of the
>> k-space around the k-point. This value depends on the dispersion of
>> states. Please, give me a hint how it is possible to calculate this
>> value in Wien2k.
>> Thanks,
>> Oleg Artamonov.
>>
>>
>> On Thu, 2008-12-11 at 18:04 +0100, Gerhard Fecher wrote:
>>> rho(E) = 1/N_k sum delta( epsilon_i,k - E)
>>> delta( epsilon_i,k - E) is 1 if you hit the state on the spaghetti and 0
>>> if you do not hit it with youre k-point
>>> that means for most of the arbitrary k-points at arbitrary energies the
>>> density of states is zero.
>>>
>>> Ciao
>>> Gerhard
>>>
>>> ====================================
>>> Dr. Gerhard H. Fecher
>>> Institut of Inorganic and Analytical Chemistry
>>> Johannes Gutenberg - University
>>> 55099 Mainz
>>> ________________________________________
>>> Von: wien-bounces at zeus.theochem.tuwien.ac.at
>>> [wien-bounces at zeus.theochem.tuwien.ac.at] im Auftrag von Oleg Artamonov
>>> [arto at mail.nnz.ru]
>>> Gesendet: Donnerstag, 11. Dezember 2008 17:34
>>> An: A Mailing list for WIEN2k users
>>> Betreff: [Wien] DOS in a single k-pointitrary
>>>
>>> Dear Wien2k users,
>>>
>>> Perhaps, somebody has calculated the DOS in an arbitrary single
>>> k-point or the DOS distribution along a line in the BZ.
>>> How is it possible to do that in Wien2k?
>>>
>>> Thanks in advance,
>>> Oleg Artamononov.
>>>
>>> _______________________________________________
>>> Wien mailing list
>>> Wien at zeus.theochem.tuwien.ac.at
>>> http://zeus.theochem.tuwien.ac.at/mailman/listinfo/wien
>>> _______________________________________________
>>> Wien mailing list
>>> Wien at zeus.theochem.tuwien.ac.at
>>> http://zeus.theochem.tuwien.ac.at/mailman/listinfo/wien
>>
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>
>
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