[Pw_forum] Slow convergence of Fe-111 surface by QE

[Ari P Seitsonen]

Dear Naren,

   In addition to the (much) too low cut-off energy you wrote that you 
tried several parametres, but it is difficult to us to guess for what you 
tried: Clearly now there is no spin polarisation, the mixing parametre is 
probably much too large, the 'degauss' too small (personally I prefer the 
Fermi-Dirac broadening), is the system ferromagnetic, why 'nosym = 
.true.'...? Please try a systematic approach, starting from most 
"physical" values for the parametres and then try to switch to something 
simpler, trying to understand for what goes wrong.

     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


On Fri, 5 May 2017, Narendranath Ghosh wrote:

> Dear all!
> 
> I am currently trying to optimize a Fe-111 surface.But I find very slow convergence even after 229
> iteration it didn't get converged.I have changed some parameters like smearing , degauss
> ,nspin, K_POINTS but nothing happened. 
> Input
>  &CONTROL
>   calculation='relax',
>   outdir='/share_home/hpc/BONS_QE/Fe-111/OUTPUT',
>   prefix='Fe-111',
>   pseudo_dir='/share_home/hpc/BONS_QE/pseudo',
>   verbosity='low',
>   nstep=500,
> /
> 
> &SYSTEM
>   ibrav=0,
>   celldm(1)=22.9819600668d0,
>   nat=81,
>   ntyp=1,
>   ecutwfc=30.0d0,
>   input_dft='PBE',
>   nosym = .true.,
>   occupations='smearing',
>   smearing='mv',
>   degauss=0.005000d0,
>   starting_magnetization(1)=0.5
>   
> 
> /
> 
> &ELECTRONS
>   mixing_mode='local-TF',
>   mixing_beta=0.700d0,
>   electron_maxstep=500,
> /
> 
> &IONS
> /
> 
> ATOMIC_SPECIES
>   Fe 55.845000d0 Fe.pbe-mt_fhi.UPF
> 
> ATOMIC_POSITIONS {alat}
> Fe       0.166666360   0.096224929   1.432718760
> Fe       0.499999991   0.096224958   1.432718812
> Fe       0.833333491   0.096224719   1.432718553
> ....................................................................
> 
> K_POINTS {automatic}
> 3 3 1 0 0 0
> CELL_PARAMETERS {alat}
>   1.000000000000d0  0.000000000000d0  0.000000000000d0
>   -0.500000000000d0  0.866025403784d0  0.000000000000d0
>   0.000000000000d0  0.000000000000d0  3.339792528637d0
> 
> 
> ...
>  
> 
> Any comment to help me getting started is very much appreciated!
> 
>  
> 
> Best regards,
> 
> Naren
> 
>  
> 
>  
> 
> Dr. Narendra Nath Ghosh
> Research Associate
> University of Gour Banga
> Department of Chemistry
> Malda-732102
> India
> Phone: +919126667601
>