[Pw_forum] PBE0 Hybrid functional SCF doesn't complete

[stefano de gironcoli]

the Hybrid calculations are VERY expensive.
in solids the expensive Fock step has an inner summation on k-point that 
makes it QUADRATIC in the grid dimension used (20*20*20)^2, in your case.
No wonder it does not complete

Things I would do:
- reduce the cutoff to the minimum.
- consider using a NC pseudopential.
- please no gaussian smearing. use 'mv' or 'mp'.
- use larger smearing => smaller k-points set
- read, understand and test the nqx1,nqx2,nqx3 input options
- look for a big machine and use band parallelization to distribute work 
load.

HTH

stefano

On 22/06/2016 12:22, Thierry Clette wrote:
>
> Hello,
>
>
> I'm a student at the University of Brussels. I use QE 5.2.1.
>
> I'm trying to do a SCF calculation of bulk black Phosphorus, a 
> semiconductor with a small gap. PBE0 seems to be the right method for 
> this, so I use a normcon PBE pseudopotential from the QE site with the 
> option "input-DFT=PBE0". The inputs and outputs are attached.
>
> As you can see in the output, the calculation in itself seems to work, 
> but the process doesn't seem to finish. It seems it can't write to the 
> save. Usually the process never finishes and is killed by time out. In 
> some cases, it is killed for using too much RAM (after the calculation 
> is complete, very strange). Anyway, as it doesn't finish, I can't do 
> band calculations.
>
> Are some of my parameters wrong ?
>
>
> Thanks in advance
>
>
> Thierry Clette
>
>
>
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