[Pw_forum] hybrid functional
"Valentina Dellacà C.R.F. S.C.p.A."
valentina.dellaca at tirocinanti.crf.it
Wed Apr 10 09:07:28 CEST 2013
Dear Monhish,
thanks again for your answer. So, if I am understanding correctly I
should just perform a scf run with a dense k-point grid and then go on
with the DOS using projwfc.x or dos.x, that's right? I was performing a
nscf run after the scf one because I was following the tutorial:
http://www.fisica.uniud.it/~giannozz/QE-Tutorial/
*Post-processing and data analysis* (slides
<http://www.fisica.uniud.it/%7Egiannozz/QE-Tutorial/tutorial_postproc.pdf>,
examples
<http://www.fisica.uniud.it/%7Egiannozz/QE-Tutorial/examples_postproc.tgz>)
Regards,
Valentina
Il 04/09/2013 04:20 PM, mohnish pandey ha scritto:**
> 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
> <mailto: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
>> <mailto: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
>>> <http://www.stanford.edu/%7Ehkulik/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
>>> <mailto: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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>>
>>
>> --
>> ###---------> 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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