[Pw_forum] band gap from hybrid pseudopotentials

[Lorenzo Paulatto]

The Fermi energy is only defined for metals, for insulators and
semiconductors you can put it anywhere between the highest occupied and the
lowest unoccupied level. The latter is only computed if you increase nbnd
to compute at least one empty band.

HTH

-- 
Lorenzo Paulatto
Written on a virtual keyboard with real fingers

On 6 Aug 2016 2:34 p.m., "MSaqlain" <saqlain at bilkent.edu.tr> wrote:

> Dear Pulatto
>
> Thanks for your correction. Yes, it is true that the code performs nsf in
> DFT mode. However, my concern was that neither scf (with hybrid scheme) nor
> the nscf (DFT only) of my system has any information about the Fermi energy.
>
> Can you please trough some light on this issue? If the the system is
> relaxed with paw/us peusodos, Is it fair enough to use NC pseudos with
> hybrid scheme for obtaining band gap?
>
> On 08/06/2016 04:56 PM, Lorenzo Paulatto wrote:
>
> Hello Saqlain,
> it is the functional, not the psuedopotentials, that is hybrid. And, as
> far as I know, you cannot do a non-scf calculation with hybrid functional
> (the code should raise an error, there are some deep technical reason for
> this). If I were you I would recheck the input and output files to be sure
> you're actually doing what you think you are doing.
>
> hth
>
> On 4 August 2016 at 19:34, saqlain <saqlain at bilkent.edu.tr> wrote:
>
>> Dear QE users
>>
>> I would like to use QE for calculating band gap with hybrid
>> pseusopotentials approach.
>>
>> after going from the discussions available at different sites, I have
>> done the calculation in this way: vc-relax the system, did scf and then
>> nscf followed by band structure calculation. My questions are,
>>
>> 1. How can I now extract the band gap from the file generated by bands.x?
>>
>> 2. in the scf and nscf output files, I can't see Fermi energy. How can I
>> know about the Fermi energy?
>>
>> 3. The scf and nscf files contain, highest occupied and lowest occupied
>> levels? what is meaning of this? does the highest occupied level mean
>> Fermi energy?
>>
>> 4. does the difference of highest occupied and lowest occupied level
>> correspond to band gap?
>>
>> your response would be highly appreciated
>>
>> Msaqlain
>>
>> Bilknet, Ankara. Turkey
>>
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>
>
>
> --
> Dr. Lorenzo Paulatto
> IdR @ IMPMC -- CNRS & Université Paris 6
> phone: +33 (0)1 44275 084 / skype: paulatz
> www:   http://www-int.impmc.upmc.fr/~paulatto/
> mail:  23-24/4é16 Boîte courrier 115, 4 place Jussieu 75252 Paris Cédex 05
>
>
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