[Pw_forum] problem of convergence

[Stefano de Gironcoli]

try changing mixing_mode to local-TF.
It should damp charge sloshing.

 stefano

Cyrille Barreteau wrote:

>Dear pwscf users and developpers,
>
>I am trying to do a pwscf calculation of a 100 iron surface.
>I first performed a scf calculation on a 11 layers thick
>slab without any difficulty. But to get a better description
>of the surface I have tried to perform a calculation with
>a thicker slab: 20 atomic layers. Then comes the difficulty:
>the scf cycle never converges. After 46 iterations the
>estimated scf accuracy is huge (see below).
>Any hint to improve convergency?
>  -decreasing mixing?
>  -changing occupation
>  -changing degauss...
>
>  thank you in advance
>     Cyrille
>
>====================================================
>     iteration # 46     ecut=    35.00 ryd     beta=0.30
>     Davidson diagonalization with overlap
>     ethr =  2.46E-03,  avg # of iterations =  6.7
>
>     total cpu time spent up to now is 228848.87 secs
>
>     total energy              = -1200.62214988 ryd
>     estimated scf accuracy    <  4756.34124938 ryd
>
>     total magnetization       =    10.95 Bohr mag/cell
>     absolute magnetization    =    11.56 Bohr mag/cell
>=====================================================
>
>Here is the input file:
>
>==============================================
> &control
>    calculation='scf'
>    title='Fe 001 20 layers +   vacuum'
>    restart_mode='from_scratch',
>    prefix='fe_surf_001_gga'
>    pseudo_dir = '/home/barreto/SOFTWARE/pseudo/',
>    outdir='tmp'
> /
> &system
>    ibrav = 6, celldm(1) = 5.42351511431617127800 , celldm(3)=13,
>     nat= 20, ntyp= 1,nbnd=150,nspin=2,
>    ecutwfc = 35.0, ecutrho=250.,starting_magnetization(1)=0.3,
>    occupations='smearing', smearing='methfessel-paxton', degauss=0.025
> /
> &electrons
>    conv_thr =  1.0d-8
>    mixing_beta = 0.3
> /
>ATOMIC_SPECIES
> Fe 55.847 Fe_us_gga_d2.1.8.pseudo.UPF
>ATOMIC_POSITIONS
>Fe   0.000000000000000  0.000000000000000   -5.25000000000000
>Fe   0.500000000000000  0.500000000000000   -4.75000000000000
>Fe   0.000000000000000  0.000000000000000   -4.25000000000000
>Fe   0.500000000000000  0.500000000000000   -3.75000000000000
>Fe   0.000000000000000  0.000000000000000   -3.25000000000000
>Fe   0.500000000000000  0.500000000000000   -2.75000000000000
>Fe   0.000000000000000  0.000000000000000   -2.25000000000000
>Fe   0.500000000000000  0.500000000000000   -1.75000000000000
>Fe   0.000000000000000  0.000000000000000   -1.25000000000000
>Fe   0.500000000000000  0.500000000000000   -0.75000000000000
>Fe   0.000000000000000  0.000000000000000   -0.25000000000000
>Fe   0.000000000000000  0.000000000000000    0.25000000000000
>Fe   0.500000000000000  0.500000000000000    0.75000000000000
>Fe   0.000000000000000  0.000000000000000    1.25000000000000
>Fe   0.500000000000000  0.500000000000000    1.75000000000000
>Fe   0.000000000000000  0.000000000000000    2.25000000000000
>Fe   0.500000000000000  0.500000000000000    2.75000000000000
>Fe   0.000000000000000  0.000000000000000    3.25000000000000
>Fe   0.500000000000000  0.500000000000000    3.75000000000000
>Fe   0.000000000000000  0.000000000000000    4.25000000000000
>Fe   0.500000000000000  0.500000000000000    4.75000000000000
>Fe   0.000000000000000  0.000000000000000    5.25000000000000
>K_POINTS automatic
> 14 14 1 0 0 0
>==========================================================
>
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