A Fermi level is *only* well defined for metallic systems where there are
no band-gabs. When determining the Fermi level for gabbed materials it may
be arbitrarily chosen in the gabbed region.

Often one chooses the fermi level to lie *exactly* in the middle of the
gab. However you have to manually shift the energies in the band-structure.

Note that the important thing is that the number of electrons at the Fermi
level corresponds to the valence charge. With this in mind it should be
clear why the fermi level cannot be uniquely determined for gabbed
materials.

2018-02-01 9:12 GMT+01:00 Sunetra Das <sunetra.das...@gmail.com>:

> Dear all Siesta users,
>
> I am trying to calculate and reproduce the band structure for a certain 2D
> system. The band structure of the system has already been calculated using
> a different software and published. Even though the band structure remains
> the same when calculated using Siesta, the bands are forming at lower
> energy values with respect to the Fermi level.
> How to correct this mismatch and get the bands at their correct energies?
> In my calculation the Fermi level lies near the conduction band whereas in
> the already published data the Fermi level lies very close to the valence
> band. Is there any way to correct for this discrepancy?
> The calculations have been performaned in GGA-PBE exchange correlation
> functional as was done in published data.
> Any suggestion is humbly appreciated.
>
> Thankfully,
> Sunetra Das.
>



-- 
Kind regards Nick

Responder a