[Pw_forum] Very long time of computation

[Jun-jun Yang]

Thank you, Eyvaz.

I tried several different settings in accordence of your recommendation. Now 
ecutwfc is decreased
to 30 Ryd and ecutrho is set to 140 Ryd. But if I set KPOINTS gamma, the 
program will run into
an error:

Starting wfc are atomic
%%%%%%%%%%%%%%%%%%%%%%%
drom cdiaghg : error #    497
info =/= 0
%%%%%%%%%%%%%%%%%%%%%%%
Stopping
2

If I set
KPOINTS automatic
1 1 1 0 0 0

the program can continue to run (start SCF calculation) although I don't 
know if it can get correct
result. Each iteration costs 3-4 minutes and the estimated scf accuracy 
seems not so good (from
<160 Ryd to < 2400 Ryd, then back to 320Ryd).

Why the two KPOINTS settings result in different consequences? What does  
the error mean?

Regards,

Jun-jun


>From: Eyvaz Isaev <eyvaz_isaev at yahoo.com>
>Reply-To: pw_forum at pwscf.org
>To: pw_forum at pwscf.org
>Subject: Re: [Pw_forum] Very long time of computation
>Date: Sun, 16 Oct 2005 08:31:26 -0700 (PDT)
>
>Hi,
>
>For 56 atoms and 8x8x8 q-points it is OK. You can
>decrease ecutwfc down to 30Ry. Much more you can gain
>using just the Gamma point (1 1 1 0 0 0).
>Your calculations will be more time demanding if you
>turn to spin-polarized case.
>Even for parallel calculations it will take time.
>
>Best regards,
>Eyvaz.
>P.S. Besides, you forgot ecutrho parameter which is
>important for US pseudopotentials.
>
>
>--- Jun-jun Yang <yang_jun-jun at hotmail.com> wrote:
>
> > Hi,
> >
> > I'm a newbie user of pwscf, and working on total
> > energy calculation of
> > chromite mineral as
> > my first step for getting familiar with the program.
> > But when I run the
> > program, it looks like
> > stpping at wavefunction calculation and seems
> > endless.
> >
> > starting charge 543.97604, renormalized to 544.00000
> > Starting wfc are atomic
> >
> > The longest time it stopped (maybe still running)
> > here was over 5 hours on
> > one processor.
> > The unit cell of the mineral has 56 atoms (Z=8) and
> > crystal system is cubic.
> > I'm using USPP
> > potential. Please refer to snippet of my input file
> > below. Do I make
> > anything wrong? Is such
> > a long computation time reasonable?
> >
> > &control
> >     calculation = 'scf'
> >     restart_mode='from_scratch',
> >     prefix='fecr2o4',
> >     tstress = .true.
> >     tprnfor = .true.
> >     pseudo_dir = '../../pseudo/',
> >     outdir = $HOME/temp/
> > /
> > &system
> >     ibrav = 1, celldm(1) = 15.8321, nat = 56 , ntyp
> > = 3,
> >     ecutwfc = 40.0
> > /
> > &electrons
> >     diagonalization = cg,
> >     mixing_mode = 'plain',
> >     mixing_beta = 0.7,
> >     conv_thr =  1.0d-8
> > /
> > ATOMIC_SPECIES
> > Fe  55.847  Fe.pbe-sp-van.UPF
> > Cr  51.996  Cr.pbe-sp-van.UPF
> > O   15.999   O.pbe-van_ak.UPF
> > ATOMIC_POSITIONS angstrom
> > Fe    0.00000    0.00000    0.00000
> > Cr    5.23625    5.23625    5.23625
> > O    3.23391    3.23391    3.23391
> > ......
> > ......
> >
> > K_POINTS automatic
> > 8 8 8  0 0 0
> >
> > Please help and thanks in advance.
> >
> >
> > Jun-jun Yang
> >
> >
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