[Wien] DOS in a single k-pointitrary

[Gerhard Fecher]

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.
>
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