[Pw_forum] hybrid functional
"Valentina Dellacà C.R.F. S.C.p.A."
valentina.dellaca at tirocinanti.crf.it
Wed Apr 10 11:13:25 CEST 2013
Hi, thanks for the help!
Valentina
Il 04/10/2013 10:24 AM, mohnish pandey ha scritto:
> Hi Valentina!
>
> Yea. You described it right :)
>
>
> On Wed, Apr 10, 2013 at 9:07 AM, "Valentina Dellacà C.R.F. S.C.p.A."
> <valentina.dellaca at tirocinanti.crf.it
> <mailto:valentina.dellaca at tirocinanti.crf.it>> wrote:
>
> 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/
> <http://www.fisica.uniud.it/%7Egiannozz/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
>> -----------------------------------------------------------------
>
>
> --
>
>
>
>
> --
> Regards,
> MOHNISH,
> -----------------------------------------------------------------
> Mohnish Pandey,
> PhD Student,
> Center for Atomic Scale Materials Design,
> Department of Physics,
> Technical University of Denmark
> -----------------------------------------------------------------
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