[Pw_forum] testing HSE for BCC Fe

[Daniel Stoeffler]

Hello Dario, 

This is what I guessed also and this is why I was
surprised by the computation time of QE ;). 

I am trying tqr=.true.


Because BCC Fe is metallic and magnetic, I did not modify the NKRED
and PRECFOCK default values as suggested into the VASP manual. So, it is
nearly the most computation time case for VASP (the time would be larger
only by changing PRECFOCK to Accurate). 

Best wishes, 

Daniel 

Le
2016-09-09 11:37, dario rocca a écrit : 

> Dear Daniel 
> 
>> I said
"surprisingly" huge because I compared to the VASP code with the same
parameters (Ecutoff, NKpoints, Nq) and with the HSE functional. Indeed,
with the VASP code during one night on my computer I got a few tens of
iterations compared to one with QE :(.
> 
> With exactly the same
parameters the computational time (on one processor) should be
comparable. There are two important points you should consider to make a
comparison: 
> -Different type of methodology: Using EXX with Ultrasoft
pseudopotentials a very large number of augmentation charges are
computed. As already suggested setting tqr=.true. should solve this
problem. 
> -If you changed the default values of some variables such as
Precfock or Nkred in Vasp the computational parameters are not anymore
the same in Vasp and QE. 
> Best, 
> Dario 
> 
>> From my point of view,
I compare 2 pseudopotential-based methods for the same parameters which
I can control via the input file : my question would then more
preferably be "which default parameter should I modify to make the QE
calculation time similar to the VASP one ?" 
>> 
>> Best wishes, 
>> 
>>
Daniel 
>> 
>> Le 2016-09-09 09:47, Stefano de Gironcoli a écrit : 
>>

>>> Please read the literature about hybrid functionals in plane waves;
understand why the computational time is, not unexpectedly, huge and
start think about it. 
>>> If you come up with some smart idea on how to
reduce the computational time without compromising accuracy (as for the
ACE transformation recently proposed by Lin Lin and implemented in the
latest QE version) let us know
>>> Best,
>>> stefano 
>>> (sent from my
phone) 
>>> 
>>> On 09 Sep 2016, at 09:30, Daniel Stoeffler
<daniel.stoeffler at ipcms.unistra.fr> wrote:
>>> 
>>>> Hello, 
>>>> 
>>>>
As a new QE user, I do some tests with the HSE Functional for BCC
ferromagnetic Fe with a cell containing 2 atoms (because a want to go to
CoFe after that). 
>>>> 
>>>> My input file is : 
>>>> 
>>>>
&control
>>>> title='Fe CC HSE',
>>>> calculation = 'scf',
>>>> prefix =
'Fe_CC_HSE',
>>>> pseudo_dir='./',
>>>> verbosity = 'high'
>>>> /
>>>>
&system
>>>> ibrav = 6, 
>>>> celldm(1) = 5.45, 
>>>> celldm(3) =
1.0,
>>>> nat = 2, 
>>>> ntyp = 1,
>>>> nspin = 2,
>>>>
occupations='smearing', smearing='gauss', degauss=0.01,
>>>>
starting_magnetization(1) = 1.0,
>>>> ecutwfc = 33,
>>>>
input_dft='HSE', 
>>>> report = 5
>>>> /
>>>> &electrons
>>>>
mixing_beta = 0.7
>>>> /
>>>> 
>>>> ATOMIC_SPECIES
>>>> Fe 55.845
Fe.pbe-sp-van.UPF
>>>> 
>>>> ATOMIC_POSITIONS (crystal)
>>>> Fe 0.000
0.000 0.000
>>>> Fe 0.500 0.500 0.500
>>>> 
>>>> K_POINTS
(automatic)
>>>> 7 7 7 0 0 0
>>>> 
>>>> Surprisingly, the computation
time is huge as writen into the output file : 
>>>> 
>>>>
=============================== 
>>>> 
>>>> iteration # 9 ecut= 33.00 Ry
beta=0.70
>>>> Davidson diagonalization with overlap
>>>> ethr =
5.49E-08, avg # of iterations = 2.3
>>>> 
>>>> Magnetic moment per
site:
>>>> atom: 1 charge: 14.4350 magn: 2.6346 constr: 0.0000
>>>>
atom: 2 charge: 14.4351 magn: 2.6343 constr: 0.0000
>>>> 
>>>> total cpu
time spent up to now is 7.2 secs
>>>> 
>>>> End of self-consistent
calculation
>>>> 
>>>> convergence has been achieved in 9
iterations
>>>> 
>>>> EXX: now go back to refine exchange
calculation
>>>> 
>>>> total cpu time spent up to now is 4239.4
secs
>>>> 
>>>> Self-consistent Calculation
>>>> 
>>>> iteration # 1
ecut= 33.00 Ry beta=0.70
>>>> Davidson diagonalization with overlap
>>>>
ethr = 5.49E-08, avg # of iterations = 4.9
>>>> 
>>>> total cpu time
spent up to now is 52490.2 secs
>>>> 
>>>> iteration # 2 ecut= 33.00 Ry
beta=0.70
>>>> Davidson diagonalization with overlap
>>>> 
>>>>
=============================== 
>>>> 
>>>> So, the calculation takes 7
seconds for converging with PBE, 1h10min for calculating the EXX term
and 14h35min for the first HSE iteration. Is this correct ? And if so,
please, could you try to explain me how to reduce the computation time.
Thanks in advance. 
>>>> 
>>>> Best wishes, 
>>>> 
>>>> Daniel
>>> 
>>>>
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list
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>>>
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