[Pw_forum] convergence for CaMg2

[adwait mevada]

Dear Giovanni,
Thanks for the prompt response, I will do as you suggested.
The above data was obtained without fixing ecutrho to480 (it was commented)
. I felt that may be a lower kpoint grid or wrong smearing might be the
source.
I will do as you suggested and get back to you.
Thanks again.
Adwait
Ph.D. Student,
Gujarat University,
Gujarat, India.
On 23-Oct-2015 8:56 pm, "Giovanni Cantele" <giovanni.cantele at spin.cnr.it>
wrote:

> one of the problems that you might be running across is that you keep
> ecutrho fixed. That means that with ecutwfc=30, ecutrho/ecutwfc=16, whereas
> with ecutwfc=120, the same ratio is 4. The latter is definitely too small
> for ultrasoft pseudo potentials, that you are including in your
> calculation. In other words, you might be comparing values of the total
> energies with different convergence levels with respect to ecutrho, which
> can be the origin (or a partial explanation) of the oscillations you find.
>
> I would try (maybe this will not solve your problem!) to retry the test as
> a function of ecutwfc, as you did, but keeping the ecutrho/ecutwfc ratio
> (rather than the ecutrho variable) constant, to a more or less safe value
> (e.g. 8).
>
> Giovanni
>
> > On 23 Oct 2015, at 17:05, adwait mevada <adwait.mevada at gmail.com> wrote:
> >
> > Dear All,
> > I am trying to find optimal ecutwfc for CaMg2.
> > As a first step i varied ecutwfc from 30-150 but i found that
> > energy was fluctuating
> > I cannot decide what to set for ecutrho if my ecutwfc is fluctuating
> > , what can be the reason for this? any help in this regard is
> appreciated.
> >
> > note : i am not finding ecutwfc for equilibrium volume.
> >
> > I am attaching png output of gnuplot for it.
> >
> > data for various ecutwfc
> > ecut    energy                 vol              kpoints  stress  time.
> > 30     -932.78387473      1314.9516     40   459.00   7m 4.75s
> > 40     -932.78292968      1314.9516     40   458.52  10m35.69s
> > 50     -932.78368793      1314.9516     40   458.74  14m22.97s
> > 60     -932.78388413      1314.9516     40   458.90  17m48.05s
> > 70     -932.78547210      1314.9516     40   457.91  25m37.98s
> > 80     -932.78563717      1314.9516     40   459.77  29m17.84s
> > 90     -932.78419457      1314.9516     40   459.42  35m28.98s
> > 100     -932.78387315      1314.9516     40   458.78  37m40.76s
> > 110     -932.78425940      1314.9516     40   458.38  41m34.44s
> > 120     -932.78459959      1314.9516     40   458.94  52m35.88s
> > 130     -932.78422725      1314.9516     72   459.24      2h 0m
> > 140     -932.78394222      1314.9516     72   458.91      2h 3m
> > 150     -932.78396419      1314.9516     72   458.69      2h30m
> > my input file is:
> > C=9
> > A=5
> > for ECUT in 30 40 50 60 70 80 90 100 ; do
> > cat > camg2e$ECUT.in << EOF
> >  &control
> >     calculation = 'scf'
> >     prefix='camg2e$ECUT',
> >     tstress = .true.
> >     tprnfor = .true.
> >  /
> >  &system
> >     ibrav=4, a=$A ,c=$C ,nat=12, ntyp=2,
> >     ecutwfc=$ECUT ! ,ecutrho=480,
> >     occupations='smearing',smearing="mv",degauss=0.02,
> >  /
> >  &electrons
> >     diagonalization='david'
> >     mixing_mode = 'plain'
> >     mixing_beta = 0.7
> >     conv_thr =  1.0d-8
> >  /
> > ATOMIC_SPECIES
> >  Mg  24.305  Mg.pw91-np-van.UPF
> >  Ca  40.078  Ca.pw91-nsp-van.UPF
> > ATOMIC_POSITIONS crystal
> > Ca      0.3333333   0.6666667   0.0668052
> > Ca      0.3333333   0.6666667   0.4331948
> > Ca      0.6666667   0.3333333   0.5668053
> > Ca      0.6666667   0.3333333   0.9331947
> > Mg      0.0000000   0.0000000   0.0000000
> > Mg      0.0000000   0.0000000   0.5000000
> > Mg      0.3397683   0.1698842   0.2500000
> > Mg      0.8301158   0.6602317   0.2500000
> > Mg      0.1698842   0.8301158   0.7500000
> > Mg      0.8301158   0.1698842   0.2500000
> > Mg      0.1698842   0.3397683   0.7500000
> > Mg      0.6602317   0.8301158   0.7500000
> > K_POINTS automatic
> > 8 8 4 1 1 1
> > EOF
> > mpirun -np 4   pw.x -in camg2e$ECUT.in > camg2e$ECUT.out
> >    ENERGY=`grep ! camg2e$ECUT.out | cut -b 33-49`
> >    VOL=`grep volume camg2e$ECUT.out | cut -b 33-45 `
> >    KP=`grep points= camg2e$ECUT.out | cut -b 25-31`
> >    TIME=`grep "PWSCF  " camg2e$ECUT.out | cut -b 37-47`
> >    STRESS=`grep "total   stress" camg2e$ECUT.out | cut -b 72-78`
> >    FOR=`grep "Total force  " camg2e$ECUT.out`
> >    echo "$ECUT $ENERGY $ALAT $VOL $KP $STRESS $TIME $FOR"
> > sleep 60
> >    echo "$ECUT $ENERGY $ALAT $VOL $KP $STRESS $TIME $FOR" >>
> camg2r480.dat
> > done
> >
> > Thank you for your help in advance
> >
> > --
> > -Adwait
> > Ph.D. Student,
> > Gujarat University,
> > Gujarat, India.
> > <camg2ecut.png>_______________________________________________
> > Pw_forum mailing list
> > Pw_forum at pwscf.org
> > http://pwscf.org/mailman/listinfo/pw_forum
>
> --
>
> Giovanni Cantele, PhD
> CNR-SPIN
> c/o Dipartimento di Fisica
> Universita' di Napoli "Federico II"
> Complesso Universitario M. S. Angelo - Ed. 6
> Via Cintia, I-80126, Napoli, Italy
> e-mail: giovanni.cantele at spin.cnr.it
> Phone: +39 081 676910
> Skype contact: giocan74
>
> ResearcherID: http://www.researcherid.com/rid/A-1951-2009
> Web page: http://people.na.infn.it/~cantele
>
>
>
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