[Pw_forum] hybrid functional

[mohnish pandey]

Dear Valentina,

You can do the calculations with the SCF run in HSE/PBE0, that shouldn't be
a problem. And why do you need nscf calculation anyway to do the DOS
calculation. 'nscf' calculation is needed when you are interested in
band-structure where you use the ground state charge density for
interpolation along certain directions. Your scf calculations will won't
have any problem in calculation the DOS. Hope it helps :)


On Tue, Apr 9, 2013 at 3:10 PM, "Valentina Dellacà C.R.F. S.C.p.A." <
valentina.dellaca at tirocinanti.crf.it> wrote:

>  Dear Arles,
> thanks for your answer. My doubts are about the employment of the
> projwfc.x, post processing tool, when using hybrid functional,  since the
> README of the hybrid functional tutorial says that one gets into troubles
> when performing non-scf calculations. At the moment I see the way to
> proceed if I wish to plot the band structure from the log file of the scf
> run, but i do not know how to get informations about the dos from such
> file, since it (as far as I understand) seems to be the only run i can
> perform when employing hybrid functionals. Do you know how to get
> informations about the dos from the .log of a scf run?
> Thank you!!!
> Valentina
>
> Il 04/09/2013 02:24 PM, Arles V. Gil Rebaza ha scritto:
>
>    Dear Valentina,
>  Yes, projwfc.x is a postprocessing tool like dos.x, whether you want to
> get only the density of state, "dos.x" is enough, whereas "projwfc.x" you
> can obtain DOS, projected DOS (PDOS) and the magnetic moment per atom too.
> http://www.quantum-espresso.org/?page_id=876
>
>  Best
>
>  PhD Arles V. Gil Rebaza
>  Instituto de Física de La Plata
>  Argentina
>
>
> 2013/4/9 "Valentina Dellacà C.R.F. S.C.p.A." <
> valentina.dellaca at tirocinanti.crf.it>
>
>>  Dear Mohnish,
>> thanks for you answer. I will follow your suggestion and try also HSE,
>> with a coarser k-point mesh, (indeed with PBE0 the computation time is
>> quiet large), and I did not know about projwfc.x.
>> I have a further question concerning the DOS. If I wish to know about the
>> DOS of my system, which uses  the hybrid functional implementation, am I
>> able to use the projwfc.x? Is'n it a postprocessing tool?
>> Thanks,
>> regards,
>> Valentina
>>
>> Il 04/09/2013 11:18 AM, mohnish pandey ha scritto:
>>
>>  Hi,
>>
>>  As far as I can understand there is no rule. It depends how fine you
>> want to represent your Fock operator. Normally calculations of the Fock
>> exchange in expensive, so its not affordable to do very fine grid
>> calculations  So I suggest you start with low nqx(1, 2, 3) and increase it
>> systematically. Increasing it will give you better results( I mean
>> converged results, not necessarily close to experiments).
>>
>> Just an advice, PBE0 needs much more high density k-point mesh for the
>> convergence of Fock exchange since it's a long range interaction. So you
>> have to do calculations with high density of k-points. But if you use HSE
>> instead of PBE0 you get away with coarser k-point mesh since it involves
>> screened exchange interaction which converges much faster than bare Coulomb
>> exchange as in PBE0. Regarding to the DOS plot you will find a nice
>> tutorial on Heither's website, I am pasting the link
>> http://www.stanford.edu/~hkulik/www/Tutorials/Entries/2012/1/24_Population_analysis_and_PDOS.html
>>
>>
>> On Tue, Apr 9, 2013 at 10:05 AM, "Valentina Dellacà C.R.F. S.C.p.A." <
>> valentina.dellaca at tirocinanti.crf.it> wrote:
>>
>>>  Hi,
>>> I am a Quantum Espresso beginner user, and I am simulating the Ta2O5
>>> structure, with the employment of the hybrid functional PBE0. I have some
>>> questions :
>>>
>>> - if I choose a k-point grid not in automatic, how should I pick the
>>> nqx1,2,3? Is there a rule?
>>> - when one wishes to have informations (ex. plot) about the density of
>>> states from the scf run, how should I proceed?
>>>
>>> Thank you,
>>> regards
>>> Valentina
>>>
>>>
>>>  --
>>>
>>>
>>>
>>> --
>>>
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>>
>>
>>
>> --
>> Regards,
>> MOHNISH,
>> -----------------------------------------------------------------
>> Mohnish Pandey,
>> PhD Student,
>> Center for Atomic Scale Materials Design,
>> Department of Physics,
>> Technical University of Denmark
>> -----------------------------------------------------------------
>>
>>
>>
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>>
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>
>
>
> --
> ###--------->   Arles V.   <---------###
>
>
>
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-- 
Regards,
MOHNISH,
-----------------------------------------------------------------
Mohnish Pandey,
PhD Student,
Center for Atomic Scale Materials Design,
Department of Physics,
Technical University of Denmark
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