[Pw_forum] hybrid functional

["Valentina Dellacà C.R.F. S.C.p.A."]

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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