[Pw_forum] phonon calculations do not converge

[Iyad AL-QASIR]

Hi Wiliam,

I used tr2_ph = 1.0d-10, it did not converge either after 100 steps. The
|ddv_scf|^ values are about ~ E-07.

However, when I used tr2_ph = 1.0d-14, the |ddv_scf|^ values are diverging
strongly ~E+20 and even more.

Kindest Regards,



On Fri, Aug 10, 2012 at 5:16 PM, William Parker <wparker at anl.gov> wrote:

> Hi Iyad,
>
> How strong is the failure to converge at (0, 1/6, 1/6)?  Perhaps a less
> tight tr2_ph value of, say, 1.0d-10 would get you where you need to be.
>
> --William
>
> On Aug 10, 2012, at 12:29 PM, Iyad AL-QASIR wrote:
>
> > Dear PW_Forum,
> >
> > I am running phonon calculations for FeSi (a narrow band gap
> semiconductor) using QE-5.0. I am using a 6x6x6 q-vectors mesh. The first 4
> q-points ran successfully and got good phonon values. However when I reach
> the 5th point(0 1/6 1/6). The self-consistent calculations do not converge.
> I tried to reduce alpha_mix(1) to 0.3 but still have the same problem.
> >
> > Below are my input files:
> >
> > &control
> >  calculation='scf',
> >  restart_mode='from_scratch',
> >  title='FeSi',
> >  outdir='./',
> >  prefix='FeSi',
> >  pseudo_dir='./',
> > /
> > &system
> >  ibrav=1,
> >  celldm(1)=8.4165,
> >  nat=8, ntyp=2,
> >  ecutwfc=60.0,
> >  ecutrho= 720.0,
> > /
> > &electrons
> >  conv_thr=1.0d-9,
> >  mixing_mode='plain',
> >  mixing_beta=0.7,
> >  diagonalization='david',
> > /
> > ATOMIC_SPECIES
> > Fe 55.847 Fe.pw91-sp-van_ak.UPF
> > Si 28.086 Si.pw91-n_van.UPF
> > ATOMIC_POSITIONS
> > Fe 0.134855265   0.134855265   0.134855265
> > Fe 0.634855265   0.365144735   0.865144735
> > Fe 0.865144735   0.634855265   0.365144735
> > Fe 0.365144735   0.865144735   0.634855265
> > Si 0.839976366   0.839976366   0.839976366
> > Si 0.339976366   0.660023634   0.160023634
> > Si 0.160023634   0.339976366   0.660023634
> > Si 0.660023634   0.160023634   0.339976366
> > K_POINTS {automatic}
> > 10 10 10  0 0 0
> > ***********************************
> > phonons of FeSi
> >  &inputph
> >   tr2_ph=1.0d-14,
> >   prefix='FeSi',
> >   amass(1)=55.847,
> >   amass(2)=28.086,
> >   outdir='./'
> >   fildyn='FeSi.dyn',
> >   trans=.true.,
> >   ldisp=.true.,
> >   nq1=6, nq2=6, nq3=6
> >   recover=.true.,
> >   alpha_mix(1)=0.30
> >
> > Any comments and suggestions are welcomed.
> >
> > Thanks
> > IYAD
> >
> >
> > _______________________________________________
> > Pw_forum mailing list
> > Pw_forum at pwscf.org
> > http://www.democritos.it/mailman/listinfo/pw_forum
>
> *********************************************************
>   William D. Parker                 phone: (630) 252-4834
>   Computational Postdoctoral Fellow   fax: (630) 252-4798
>   MSD-212, Rm. C-215
>   Argonne National Laboratory
>   9700 S. Cass Ave.
>   Argonne, IL 60439
> *********************************************************
>
>
>
>
>
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-- 
___________________________
IYAD I. AL-QASIR, PhD
Postdoc Research Associate

X-Ray and Neutron Scattering and Spectroscopy Group
Materials Science and Technology Division
Oak Ridge National Lab
Oak Ridge, TN
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