[Pw_forum] hybrid functional

[mohnish pandey]

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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