[Wien] Seebeck coefficient_Boltztrap

[Karel Vyborny]

Hi Hannan,
as to the technical details on using Boltztrap, I cannot say anything 
since I have never really used it. Indeed, the shift (-0.15;0.15) to 
(-0.1;0.2) seems strange (given your results I saw). However, as for the 
symmetry: it may often look like that but for sure, if you look closer, 
the symmetry will most likely not be really there. There's no general 
reason why this should be so unless the bands are perfectly symmetric 
around Ef.

Karel


--- x ---
dr. Karel Vyborny
Fyzikalni ustav AV CR, v.v.i.
Cukrovarnicka 10
Praha 6, CZ-16253
tel: +420220318459


On Tue, 5 Apr 2016, Hannan.Sadek at uv.es wrote:

> Dear Gerhard; I subtracted the value of the Fermi energy that is 
> corresponding to this case(the value of the Fermi energy in the case.scf 
> file) from each values in the column of the chemical potential, and then 
> I got the zero at one of them. As I understand it should be done in that 
> way, doesn't it?
>
> But there is something that I don't understand, in the case.intrans file 
> I assigned the value of efcut=0.15(the energy range of the chemical 
> potential around efermi) even though in the case.trace file I see that 
> the calculations have been run by using chemical potential over the 
> range 0.1 lower than the Fermi energy till 0.2 higher than the Fermi 
> energy(not 0.15 in both sides)
>
> I expected that the seebeck is symmetric around zero chemical potential 
> just because in almost all the articles that I have read about the 
> boltztrap calculations, the seebeck coefficient is symmetric around zero 
> chemical; they got the p-type at the negative values of the chemical 
> potential and the n-type at the positive one. In my case, I got the n 
> and p type at the positive values of the chemical potential.
>
> Best regards
> Hannan
>
>
> why do you expect that the Seebeck is symmetric arround zero chemical potential (whatever you assume to be the Zero)
> is your density of states symmetric with respect to the middle of the band gap ?
>
> Ciao
> Gerhard
>
> DEEP THOUGHT in D. Adams; Hitchhikers Guide to the Galaxy:
> "I think the problem, to be quite honest with you,
> is that you have never actually known what the question is."
>
> ====================================
> Dr. Gerhard H. Fecher
> Institut of Inorganic and Analytical Chemistry
> Johannes Gutenberg - University
> 55099 Mainz
> and
> Max Planck Institute for Chemical Physics of Solids
> 01187 Dresden
> ________________________________________
> Von: wien-bounces at zeus.theochem.tuwien.ac.at [wien-bounces at zeus.theochem.tuwien.ac.at] im Auftrag von Hannan.Sadek at uv.es [Hannan.Sadek at uv.es]
> Gesendet: Montag, 4. April 2016 06:34
> An: A Mailing list for WIEN2k users
> Betreff: [Wien] Seebeck coefficient_Boltztrap
>
> Dear Wien2k users;
> I'm using the boltztrap code to study the thermoelectric properties of some semiconducting materials.
> I run the process and I got the results. But I have a problem; when I drew the figure that represents the Seebeck coefficient as a function of the chemical potential, I didn't get the curve symmetric around zero chemical potential. I got the curve at the right of the zero chemical potential.
> Also I tried to reproduce the examples that are given in the package like Bi2te3, to know if it is happened only with these materials, and I had the same problem.
> What could be the mistake that I did in the calculations?
> Best regards
> Hannan
>
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