[Pw_forum] disconverge about phonon calculation

[Eyvaz Isaev]

Hi,

Try using reduced alpha_mix(1)=0.1 (in *.ph.in), default is 0.7.

>   tr2_ph=1.0d-8,
>   lnscf=.true.,

You use quite high threshold for phonons, default is 1.e-10. At least my experience tells me you do not need lnscf keyword if you use nq1,2,3 and ldisp=.true. options. It is quite useful if you choose a particular q-point.

>      ecutwfc = 40.0,
>      ecutrho = 300.0,

ecutrho looks small, more reliable one should be around 10 times of ecutwfc, you can test it.

>      conv_thr =  1.0d-11
This one is quite low. You can increase it, I think  1.d-8 is a good choice. 

Bests,
Eyvaz.


-------------------------------------------------------------------
Prof. Eyvaz Isaev, 
Theoretical Physics Department, Moscow State Institute of Steel & Alloys, Russia, 
Department of Physics, Chemistry, and Biology (IFM), Linkoping University, Sweden 
Condensed Matter Theory Group, Uppsala University, Sweden 
Eyvaz.Isaev at fysik.uu.se, isaev at ifm.liu.se, eyvaz_isaev at yahoo.com


--- On Wed, 4/1/09, 潘登 <panda.deng.pan at gmail.com> wrote:

> From: 潘登 <panda.deng.pan at gmail.com>
> Subject: [Pw_forum] disconverge about phonon calculation
> To: pw_forum at pwscf.org
> Date: Wednesday, April 1, 2009, 1:16 PM
> Dear All,
> 
>   I am doing a calculation of the LaFeAsO. And when I run
> the ph.x,
> the disconverge happens in the   Representation #  3 mode #
>   3. I am
> appraciate for any comment and suggustiong.I wonder what
> should I do
> to avoid the disconvergence like this.
> here is my inputs
> ph.in
>  LaFeAsO
> &inputph
>   amass(1)= 139.9055,
>   amass(2)= 55.845,
>   amass(3)= 74.9216,
>   amass(4)= 15.9994,
>   prefix='LaFeAsO'
>   fildyn='LaFeAsO.dyn',
>   tr2_ph=1.0d-8,
>   lnscf=.true.,
>   iverbosity=1,
>   outdir='/disk2/xgwan/tmp/',
>   ldisp=.true.,
>   nq1=4, nq2=4, nq3=4
>  /
> and scf.in
>  &control
>      calculation = 'scf'
>      restart_mode='from_scratch'
>      prefix='LaFeAsO',
>      pseudo_dir =
> '/disk2/xgwan/Quantum-Espresso/espresso-4.0.3/pseudo/',
>      outdir='/disk2/xgwan/tmp/'
>  /
>  &system
>      ibrav=6,
>      celldm(1)=7.6232,
>      celldm(3)=2.1676,
>      nat=8,
>      ntyp=4,
>      ecutwfc = 40.0,
>      ecutrho = 300.0,
>      occupations= 'smearing'
>      degauss = 0.03
>      smearing = 'marzari-vanderbilt'
>  /
>  &electrons
>      mixing_beta = 0.7
>      conv_thr =  1.0d-11
>  /
> ATOMIC_SPECIES
>  La 57.0 La.pbe-nsp-van.UPF
>  Fe 28.0 Fe.pbe-sp-van.UPF
>  As 33.0 As.pbe-n-van.UPF
>  O  16.0 O.pbe-rrkjus.UPF
> ATOMIC_POSITIONS {crystal}
> La       0.250000000   0.250000000   0.139792601
> La       0.750000000   0.750000000   0.860207399
> Fe       0.750000000   0.250000000   0.500000000
> Fe       0.250000000   0.750000000   0.500000000
> As       0.250000000   0.250000000   0.636557422
> As       0.750000000   0.750000000   0.363442578
> O        0.750000000   0.250000000   0.000000000
> O        0.250000000   0.750000000   0.000000000
> K_POINTS {automatic}
>   8 8 8 0 0 0
> 
> 
> in addition all the atiomic positions have been relaxed.
> cheers
> 
> Deng Pan
> Nanjing University
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