[Pw_forum] Which Fermi level is right?

[lan haiping]

Dear  George,
I am not familiar with all these smearing scheme, and just try to explain as
far as i know.
When we do calculation with "smearing",  fractional occupations are allowed.
For different smearing scheme, the occupation functions are defined
differently.
So, it should be nonsense to discuss the absolute  values of fermi energy
obtained from different smearing schemes.

hope  help !

H.P


On 7/17/07, Nkrumah-Buandoh George_Kofi <gnkrumah at ictp.it> wrote:
>
> I am calculating the band structure and density of states for YVO4. First
> I relaxed the atomic positions, and then used the relaxed positions of the
> atoms for doing scf calculation, and then used the same relaxed atomic
> positions for nscf calculation of the density of states. For the scf
> calculation I used occupation='smearing', the fermi energy is 7.5440 eV.
> For the density of states I used occupation='tetrahedra', and the Fermi
> energy is 6.4196 eV
>
> Why do the two different methods give two different results? Which of
> these is the correct Fermi energy level?
>
> George K Nkrumah-Buandoh
> International Centre for Theoretical Physics, Trieste Italy & Department
> of Physics, University of Ghana, Accra Ghana
>
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-- 
Hai-Ping Lan
Department of Electronics ,
Peking University , Bejing, 100871
lanhaiping at gmail.com, hplan at pku.edu.cn
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