[Pw_forum] phonon calculation not converge

[Xiaolin Xu]

Dear Ari and Jiqiang,

Thank you so much for all the instructions! Yes I ran pw.x using K_POINTS
automatic // 1 1 1  0 0 0 before running ph.x. I will increase the cut-off
energy and hope it will work!

Lin

On Thu, Oct 29, 2015 at 3:34 PM, Ari P Seitsonen <Ari.P.Seitsonen at iki.fi>
wrote:

>
> Dear Xiaolin, Jiqiang et co,
>
>   Did you re-run 'pw.x' using the 'K_POINTS automatic // 1 1 1  0 0 0'
> before trying to run 'ph.x'?
>
>   On the other hand the number of k points depends on your system, the
> amount of band dispersion it etc. So indeed, if the electronic structure is
> not yet converged well with only Gamma point, it is better to apply more k
> points. This you can do by testing for the convergence.
>
>   By the way, the cut-off energy of 80 Ry is probably far too low for the
> HGH/GTH pseudo potentials that you have used: We used 125 Ry for the oxygen
> - I would guess that the one for iron, maybe also lithium - and that was in
> molecular dynamics; for phonons I would expect even higher a value
> necessary.
>
>     Greetings,
>
>        apsi
>
>
> -=*=-=*=-=*=-=*=-=*=-=*=-=*=-=*=-=*=-=*=-=*=-=*=-=*=-=*=-=*=-=*=-=*=-=*=-=*=-
>   Ari Paavo Seitsonen / Ari.P.Seitsonen at iki.fi / http://www.iki.fi/~apsi/
>   Ecole Normale Supérieure (ENS), Département de Chimie, Paris
>   Mobile (F) : +33 789 37 24 25    (CH) : +41 79 71 90 935
>
>
>
>
>> 在 2015-10-30 00:26:09，"Xiaolin Xu" <xiaolin0314 at gmail.com> 写道：
>>
>> Hi Jiqiang,
>>>
>>>
>>> Thank you very much for your help!
>>> I tried using only gamma point, but I got an error message when I
>>> calculated phonon saying "can't start from gamma tricks...". Besides, I
>>> need to calculate the raman frequencies after phonon calculation, so I
>>> think it's better if I use more k points.
>>>
>>> Have you tried Raman calculation? Could you give me more advice?
>>>
>>> Best,
>>>
>>> Xiaolin
>>>
>>>
>>> On Wed, Oct 28, 2015 at 10:21 PM, Xiaolin Xu <xxu2 at caltech.edu> wrote:
>>>
>>> Hi Jiqiang,
>>>
>>> Thank you very much for your help!
>>> I tried using only gamma point, but I got an error message when I
>>> calculated phonon saying "can't start from gamma tricks...". Besides, I
>>> need to calculate the raman frequencies after phonon calculation, so I
>>> think it's better if I use more k points.
>>>
>>> Have you tried Raman calculation? Could you give me more advice?
>>>
>>> Best,
>>>
>>> Xiaolin
>>>
>>>
>>> On Wed, Oct 28, 2015 at 6:20 PM, jqli14 <jqli14 at fudan.edu.cn> wrote:
>>> (1)employ k_points gamma instead of k_pionts automatic 1 1 1 0 0 0,
>>> although both give the same result, but the later does not call the gamma
>>> point specific algorithm to speed the calculation.
>>> (2)if it can not converge within handreds of electronic steps, reduce
>>> the value of mixing_beta or change the mixing_mode.
>>>
>>> Jiqiang Li
>>>
>>>
>>> 在 2015-10-29 07:57:58，"Xiaolin Xu" <xiaolin0314 at gmail.com> 写道：
>>>
>>> Dear all,
>>>>
>>>> I was doing phonon dispersion calculations for lithium iron phosphate.
>>>> However, the calculation speed is really slow and it does not converge. Is
>>>> this because my system is too big? There are 28 atoms in the unit cell. My
>>>> input file is like this:
>>>> (1)
>>>>
>>>>
>>>> &CONTROL
>>>> calculation = "scf",
>>>> pseudo_dir = "/home/xiaolin/pseudo",
>>>> outdir = "/home/xiaolin/test2",
>>>> tstress=.true.,
>>>> tprnfor=.true.,
>>>> nstep=100,
>>>> /
>>>>
>>>> &SYSTEM
>>>> ibrav = 8,
>>>> celldm(1) = 19.749526
>>>> celldm(2) = 0.582432,
>>>> celldm(3) = 0.454693,
>>>> nat = 28,
>>>> ntyp = 4,
>>>> ecutwfc = 80.D0,
>>>> /
>>>>
>>>> &ELECTRONS
>>>> mixing_beta = 0.7,
>>>> /
>>>>
>>>> &IONS
>>>> /
>>>>
>>>> ATOMIC_SPECIES
>>>>
>>>> Li 6.941 Li.pbe-s-hgh.UPF
>>>> Fe 55.845 Fe.pbe-sp-hgh.UPF
>>>> P 30.97376 P.pbe-hgh.UPF
>>>> O 15.9994 O.pbe-hgh.UPF
>>>> ATOMIC_POSITIONS (alat)
>>>> Li 0 0 0
>>>> ...
>>>> K_POINTS (automatic)
>>>> 1 1 1 0 0 0
>>>>
>>>> (2)
>>>>
>>>> Normal modes for lifepo4
>>>> &inputph
>>>> tr2_ph=1.5d-5,
>>>> amass(1)=6.941,
>>>> amass(2)=55.845,
>>>> amass(3)=30.97376,
>>>> amass(4)=15.9994,
>>>> outdir = '/home/xiaolin/test2',
>>>> trans=.true.,
>>>> asr=.true.,
>>>> nogg=.true.,
>>>> fildyn='dmat.lifepo4'
>>>> /
>>>> 0.0 0.0 0.0
>>>>
>>>>
>>>>
>>>> Thank you in advance!
>>>>
>>>>
>>>> Lin
>>>>
>>>
>>>
>>>
>>>
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