<p dir="ltr">Dear Giovanni,<br>
Thanks for the prompt response, I will do as you suggested.<br>
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.<br>
I will do as you suggested and get back to you.<br>
Thanks again.<br>
Adwait<br>
Ph.D. Student,<br>
Gujarat University,<br>
Gujarat, India.</p>
<div class="gmail_quote">On 23-Oct-2015 8:56 pm, "Giovanni Cantele" <<a href="mailto:giovanni.cantele@spin.cnr.it">giovanni.cantele@spin.cnr.it</a>> wrote:<br type="attribution"><blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex">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.<br>
<br>
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).<br>
<br>
Giovanni<br>
<br>
> On 23 Oct 2015, at 17:05, adwait mevada <<a href="mailto:adwait.mevada@gmail.com">adwait.mevada@gmail.com</a>> wrote:<br>
><br>
> Dear All,<br>
> I am trying to find optimal ecutwfc for CaMg2.<br>
> As a first step i varied ecutwfc from 30-150 but i found that<br>
> energy was fluctuating<br>
> I cannot decide what to set for ecutrho if my ecutwfc is fluctuating<br>
> , what can be the reason for this? any help in this regard is appreciated.<br>
><br>
> note : i am not finding ecutwfc for equilibrium volume.<br>
><br>
> I am attaching png output of gnuplot for it.<br>
><br>
> data for various ecutwfc<br>
> ecut energy vol kpoints stress time.<br>
> 30 -932.78387473 1314.9516 40 459.00 7m 4.75s<br>
> 40 -932.78292968 1314.9516 40 458.52 10m35.69s<br>
> 50 -932.78368793 1314.9516 40 458.74 14m22.97s<br>
> 60 -932.78388413 1314.9516 40 458.90 17m48.05s<br>
> 70 -932.78547210 1314.9516 40 457.91 25m37.98s<br>
> 80 -932.78563717 1314.9516 40 459.77 29m17.84s<br>
> 90 -932.78419457 1314.9516 40 459.42 35m28.98s<br>
> 100 -932.78387315 1314.9516 40 458.78 37m40.76s<br>
> 110 -932.78425940 1314.9516 40 458.38 41m34.44s<br>
> 120 -932.78459959 1314.9516 40 458.94 52m35.88s<br>
> 130 -932.78422725 1314.9516 72 459.24 2h 0m<br>
> 140 -932.78394222 1314.9516 72 458.91 2h 3m<br>
> 150 -932.78396419 1314.9516 72 458.69 2h30m<br>
> my input file is:<br>
> C=9<br>
> A=5<br>
> for ECUT in 30 40 50 60 70 80 90 100 ; do<br>
> cat > camg2e$ECUT.in << EOF<br>
> &control<br>
> calculation = 'scf'<br>
> prefix='camg2e$ECUT',<br>
> tstress = .true.<br>
> tprnfor = .true.<br>
> /<br>
> &system<br>
> ibrav=4, a=$A ,c=$C ,nat=12, ntyp=2,<br>
> ecutwfc=$ECUT ! ,ecutrho=480,<br>
> occupations='smearing',smearing="mv",degauss=0.02,<br>
> /<br>
> &electrons<br>
> diagonalization='david'<br>
> mixing_mode = 'plain'<br>
> mixing_beta = 0.7<br>
> conv_thr = 1.0d-8<br>
> /<br>
> ATOMIC_SPECIES<br>
> Mg 24.305 Mg.pw91-np-van.UPF<br>
> Ca 40.078 Ca.pw91-nsp-van.UPF<br>
> ATOMIC_POSITIONS crystal<br>
> Ca 0.3333333 0.6666667 0.0668052<br>
> Ca 0.3333333 0.6666667 0.4331948<br>
> Ca 0.6666667 0.3333333 0.5668053<br>
> Ca 0.6666667 0.3333333 0.9331947<br>
> Mg 0.0000000 0.0000000 0.0000000<br>
> Mg 0.0000000 0.0000000 0.5000000<br>
> Mg 0.3397683 0.1698842 0.2500000<br>
> Mg 0.8301158 0.6602317 0.2500000<br>
> Mg 0.1698842 0.8301158 0.7500000<br>
> Mg 0.8301158 0.1698842 0.2500000<br>
> Mg 0.1698842 0.3397683 0.7500000<br>
> Mg 0.6602317 0.8301158 0.7500000<br>
> K_POINTS automatic<br>
> 8 8 4 1 1 1<br>
> EOF<br>
> mpirun -np 4 pw.x -in camg2e$ECUT.in > camg2e$ECUT.out<br>
> ENERGY=`grep ! camg2e$ECUT.out | cut -b 33-49`<br>
> VOL=`grep volume camg2e$ECUT.out | cut -b 33-45 `<br>
> KP=`grep points= camg2e$ECUT.out | cut -b 25-31`<br>
> TIME=`grep "PWSCF " camg2e$ECUT.out | cut -b 37-47`<br>
> STRESS=`grep "total stress" camg2e$ECUT.out | cut -b 72-78`<br>
> FOR=`grep "Total force " camg2e$ECUT.out`<br>
> echo "$ECUT $ENERGY $ALAT $VOL $KP $STRESS $TIME $FOR"<br>
> sleep 60<br>
> echo "$ECUT $ENERGY $ALAT $VOL $KP $STRESS $TIME $FOR" >> camg2r480.dat<br>
> done<br>
><br>
> Thank you for your help in advance<br>
><br>
> --<br>
> -Adwait<br>
> Ph.D. Student,<br>
> Gujarat University,<br>
> Gujarat, India.<br>
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<br>
--<br>
<br>
Giovanni Cantele, PhD<br>
CNR-SPIN<br>
c/o Dipartimento di Fisica<br>
Universita' di Napoli "Federico II"<br>
Complesso Universitario M. S. Angelo - Ed. 6<br>
Via Cintia, I-80126, Napoli, Italy<br>
e-mail: <a href="mailto:giovanni.cantele@spin.cnr.it">giovanni.cantele@spin.cnr.it</a><br>
Phone: +39 081 676910<br>
Skype contact: giocan74<br>
<br>
ResearcherID: <a href="http://www.researcherid.com/rid/A-1951-2009" rel="noreferrer" target="_blank">http://www.researcherid.com/rid/A-1951-2009</a><br>
Web page: <a href="http://people.na.infn.it/~cantele" rel="noreferrer" target="_blank">http://people.na.infn.it/~cantele</a><br>
<br>
<br>
<br>
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</blockquote></div>