[Pw_forum] ph.x cannot reach convergence within 100 steps

[Eyvaz Isaev]

> I was not sure whether this problem caused by empty-band number, so I increase nbnd.
 
You should increase nbnd if you see "too few bands" message  in *.ph.out file. 

Bests,
Eyvaz. 
 

 


________________________________
From: GAO Zhe <flux_ray12 at 163.com>
To: Eyvaz Isaev <eyvaz_isaev at yahoo.com>; PWSCF Forum <pw_forum at pwscf.org>
Sent: Sunday, July 17, 2011 11:33 AM
Subject: Re: [Pw_forum] ph.x cannot reach convergence within 100 steps


Thank you very much, Prof. Isaev.
I tried all of 'scf', 'relax' and 'vc-relax' before ph.x, but got the same problem in each case~
I was not sure whether this problem caused by empty-band number, so I increase nbnd. It may too large for my model~ Now, I am trying to change the values of alpha_mix(1) and nmix_ph for a better convergent.
Thank you, again ^_^

--
GAO Zhe
CMC Lab, MSE, SNU, Seoul, S.Korea

At 2011-07-16 16:39:40，"Eyvaz Isaev" <eyvaz_isaev at yahoo.com> wrote:

Hi, 
>
>
>
>>Recently, I am trying to calculate phonon dispersion via ph.x. However, 
in some cases, ph.x cannot reach convergence within 100 steps and stop 
>automaticly.
> 
>1. You should  perform 'scf', not 'vc-relax' before phonon calculations.
>2. You have a rather large system (nbnd=100), but used alpha_mix(1) by default (0.7). Try it around 0.1.
>3. Try changing nmix_ph (by default 4).
>4. If this does not help change 'maxter=100' in phcom.f90 and recompile.
>
>Bests,
>Eyvaz.
>
>
>-------------------------------------------------------------------
>Prof. Eyvaz Isaev, 
>Department of Physics, Chemistry, and Biology (IFM), Linkoping University, Sweden 
>Theoretical Physics Department, Moscow State Institute of Steel & Alloys, Russia, 
>isaev at ifm.liu.se, eyvaz_isaev at yahoo.com
>
>
>________________________________
>From: GAO Zhe <flux_ray12 at 163.com>
>To: PWSCF Forum <pw_forum at pwscf.org>
>Sent: Saturday, July 16, 2011 7:40 AM
>Subject: [Pw_forum] ph.x cannot reach convergence within 100 steps
>
>
>Dear QE developer and users:
>Recently, I am trying to calculate phonon dispersion via ph.x. However, in some cases, ph.x cannot reach convergence within 100 steps and stop automaticly.
>I have tested the convergent lattice parameter, cut-off energy and k-points (M-P grid), and the thresholds of force and stress were also very low. Even if I increase the tr2_ph from 1.0d-12 (default) to 1.0d-10, the |ddv_scf|^2  values was around 10^(-6) or 10^(-7) magnitude. The problem usually occurred at the second q-point, but sometimes, even if lucky enough, it would definitely occur at
 the third q-point (4 q-points in 3x3x3 case).
>Are there any methods to solve this problem? Any suggestion will be welcome.
>Calculations were used GGA-PBE USPP.
>This is my input file:
>cat >W25.relax.in <<EOF
>&control
>     calculation = 'vc-relax' ,
>     disk_io = 'low' ,
>     prefix = 'W' ,
>     outdir = '$TempDIR/' ,
>     pseudo_dir = '$PseudoDIR/' ,
>     etot_conv_thr = 1.0d-12 ,
>     forc_conv_thr = 1.0d-4 ,
>/
>&system
>     ibrav = 1 ,
>     celldm(1) = ******* ,
>     nat = ** ,
>     ntyp = 3 ,
>     nbnd = 100 ,
>     ecutwfc = 47.5 ,
>     ecutrho = 450 ,
>     occupations =
 'smearing' ,
>     smearing = 'mp' ,
>     degauss = 0.003 ,
>/
>&electrons
>     conv_thr = 1.0d-12 ,
>     startingpot = 'atomic' ,
>     startingwfc = 'atomic+random' ,
>     diagonalization = 'cg' ,
>     electron_maxstep = 150 ,
>/
>&ions
>     ion_dynamics = 'bfgs' ,
>/
>&cell
>     cell_dynamics = 'bfgs' ,
>     press_conv_thr = 0.01 ,
>/
>ATOMIC_SPECIES
>  V   50.9415   V.pbe-n-van.UPF
>  W   183.800   W.pbe-nsp-van.UPF
>  C   12.0110   C.pbe-van_ak.UPF
>ATOMIC_POSITIONS crystal
>  V   0.50  0.50  0.00
>...........
>  C   0.50  0.50  0.50
>K_POINTS
 automatic
>13  13  13   0  0  0
>EOF
>echo -e "  Relaxing Structure...\c"
>$MPIBIN/mpirun -n 6 pw.x -npool 2 <W.relax.in >W.relax.out
>echo -e " DONE"
>
>cat >W.ph.in <<EOF
>Phonon Calculation
>&inputph
>     outdir = '$TempDIR/' ,
>     prefix = 'W' ,
>     ldisp = .true. ,
>     nq1 = 3 ,
>     nq2 = 3 ,
>     nq3 = 3 ,
>     tr2_ph = 1.0d-10 ,
>     fildyn = 'W.dyn' ,
>/
>EOF
>echo -e "  Calculating Dynamic Matrix...\c"
>$MPIBIN/mpirun -n 6 ph.x -npool 2 <W.ph.in >W.ph.out
>echo -e " DONE"
>
>
>
>--
>GAO Zhe
>CMC Lab, MSE, SNU, Seoul, S.Korea
>
>
>
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>Pw_forum at pwscf.org
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>
>


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