[Pw_forum] phonon calculations do not converge

[Iyad AL-QASIR]

Hello Matt,

Can I introduce some broadening,  keeping in mind this structure is
semiconductor no metallic?

Thanks
IYAD

On Wed, Aug 15, 2012 at 1:38 PM, Matthijs Mentink <mgtmentink at lbl.gov>wrote:

> Hi Iyad,
>
> Have you considered introducing some broadening in the pwscf calculation?
> It helps. Be careful not to go overboard though. You could try introducing
> some broadening (like 1e-3 Ry or so) and see if it converges. If that works
> than you can see how far you can reduce broadening while still having the
> phonon calculations converge.
>
> cheers,
>
> Matthijs
>
>
> On Wed, Aug 15, 2012 at 10:27 AM, Iyad AL-QASIR <iyad.ne at gmail.com> wrote:
>
>> 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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>>
>
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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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