[Wien] Reference point of Fermi energy

[Peter Blaha]

I think this was answered many times before. You should search the 
mailing list before asking questions.

In a "infinite bulk" calculation there is no vacuum a meaningful 
reference point cannot be set and EF has no other meaning than being the 
energy of the highest occupied state. EF is with respect to the average 
coulomb potential in the interstitial region, which is set to zero 
(therefore positive EF values are possible).

E-tot does not depend on any reference energy and is thus an "absolute" 
quantity.

In surface slab calculations you can define an "approximate" reference 
point in the middle of the vacuum region. The potential there is given 
in the scf file (:VZERO) and can be used as reference and for the 
calculation of a work function (provided your vacuum is large enough).


On 03/30/2015 01:51 PM, Mohammed Abujafar wrote:
> Dear Wien2k developers and users,
> Hi!
> I am concerning about the reference point of the Fermi energy in the
> calculations.For an example,
>
> :FER  : F E R M I - ENERGY(TETRAH.M.)=   0.2689240706 Ry
> :ENE  : ********** TOTAL ENERGY IN Ry =        -1634.03683409
>
> The value  of the Fermi energy 0.2689240706 Ry is relative to what point? ?Is the reference point for the Fermi energy and the total energy the same ? Thanks a lot in advance.
> With best regards
> Mohammed
>
>
>
>
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-- 

                                       P.Blaha
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Peter BLAHA, Inst.f. Materials Chemistry, TU Vienna, A-1060 Vienna
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