[Pw_forum] Convergence Problem

[AZGlobal]

Usually oscillating  SCF process is result of some flat band  (lots of 
low-dispersion bands in Pd near Ef) flipping below/above Ef from 
iteration to iteration, when you iterate. The cure is smaller admixing. 
Takes much more processor time, but you can iterate for weeks with too 
big admix and no result. Hope this helps.
> Dear All,
>
> When I do the calculation of the electronic structure of slab
> Palladium under the external electric field,
> convergence problems appear. The typical problem is that the estimated
> scf accuracy value drop down
> down and bounce back. It seems that the calculation does not know
> where the system would go for
> minimizing the total energy. The electric field that I applied is
> saw-tooth like one. I tried many things like
> increasing the mixing_ndim, decreasing the mixing_betta to 0.1, adding
> empty bands changing the mixing
> mode and even increase the degauss. But, none of them would work for
> the scf accuracy oscillating problem.
> Below is the input file. Any suggestion is highly appreciated.
>
>
>
>
> &control
>     calculation='scf'
>     restart_mode='from_scratch',
>     pseudo_dir = '$PSEUDO_DIR/',
>     outdir='$TMP_DIR/'
>     prefix='Pd'
>     tefield = .true.
>     dipfield = .true.
>     nstep = 300
>
>  /
>  &system
>     ibrav = 6
>     celldm(1) = 7.3331
>     nspin = 2
>     celldm(3) = 4.5
>     edir = 3
>     emaxpos=0.72
>     eopreg=0.28
>     eamp = -0.001944
>     starting_magnetization=0.05
>     ntyp = 1
>     nat= 14
>     ecutwfc = 25.0,
>     ecutrho = 500.0,
>     occupations='smearing',
>     degauss=0.2
>     nbnd=160
>  /
>
>  &electrons
>     conv_thr = 1.0e-4
>     mixing_mode='local-TF'
>     mixing_beta = 0.05
>     mixing_ndim = 12
>
>  /
> ATOMIC_SPECIES
>  Pd  100  Pd.pz-nd-rrkjus.UPF
> ATOMIC_POSITIONS
> Pd       0.500000000   0.000000000  -1.496126804
> Pd       0.000000000   0.500000000  -1.496126804
> Pd       0.000000000   0.000000000  -1.002542052
> Pd       0.500000000   0.500000000  -1.002542051
> Pd       0.500000000   0.000000000  -0.501470158
> Pd       0.000000000   0.500000000  -0.501470158
> Pd       0.000000000   0.000000000   0.000000000
> Pd       0.500000000   0.500000000   0.000000000
> Pd       0.500000000   0.000000000   0.501470158
> Pd       0.000000000   0.500000000   0.501470158
> Pd       0.000000000   0.000000000   1.002542052
> Pd       0.500000000   0.500000000   1.002542051
> Pd       0.500000000   0.000000000   1.496126804
> Pd       0.000000000   0.500000000   1.496126804
>
>
>
>
> K_POINTS (automatic)
>  8 8 1 0 0 0
>
>
>
>