[QE-users] pw.x Bands Calculation not Converging for Ba4Sn9Bi3

[Tamas Karpati]

1, As degauss has quite an effect on the band energies (and 0.1 is
fairly large),
    i suggest you check its effect for a smaller test system (with
similar elements).

2, When you change the no. of k points do you mean the SCF run?
    I think that convergence is better when both cut-off energy and k
grid density is higher
    (i do not know how large Ecut and kdens you can afford, though).

3, Altough your elements are main group metals, increasing nbnd by ca.
25% may help,
    especially with such great degauss (check your output file for
what no. of bands was
    actually used by default).

HTH,
  t

On Wed, Jul 22, 2020 at 9:44 PM Stephen Zhang <lolzen at berkeley.edu> wrote:
>
> Hi everyone,
>
> The compound Ba4Sn9Bi3 is rather complex, with 32 atoms in the unit cell. I've tried a couple ways to make the calculation converge, setting the mixing_beta = 0.2, decreasing the k point count to just 6 total k-points, as well as increasing the degauss value, degauss = 0.1, but to no avail. If anyone has any input on how to approach this problem, please let me know? Thank you everyone so much!
>
> Here is the input file below:
>
> &control
>     calculation = 'bands'
>     prefix = 'BaSnBi'
>     restart_mode='from_scratch'
>     outdir = './outdir'
>     pseudo_dir = '/home/stephen/qe-6.5/SSSP_precision_pseudos'
> /
> &system
>     ibrav=4, celldm(1) =13.891678598121974, celldm(3) = 3.110345010544163,
>     nat=32, ntyp=3,
>     ecutwfc= 30,
>     ecutrho = 300
>     occupations = 'smearing', degauss = 0.1, smearing = 'marzari-vanderbilt'
> /
> &electrons
>     mixing_beta = 0.2,
>     conv_thr=1e-9,
> /
> ATOMIC_SPECIES
>  Ba  137.327 Ba.pbe-spn-kjpaw_psl.1.0.0.UPF
>  Sn  118.71 Sn.pbe-dn-kjpaw_psl.1.0.0.UPF
>  Bi  208.9804 Bi.pbe-dn-kjpaw_psl.1.0.0.UPF
>
> ATOMIC_POSITIONS crystal
>  Ba 0.333333 0.666667 0.134175
>  Ba 0.666667 0.333333 0.865825
>  Ba 0.666667 0.333333 0.634175
>  Ba 0.333333 0.666667 0.365825
>  Ba 0 0 0
>  Ba 0 0 0.5
>  Ba 0 0 0.25
>  Ba 0 0 0.75
>  Sn 0.192731 0.385463 0.624898
>  Sn 0.807269 0.614537 0.375102
>  Sn 0.614537 0.807269 0.624898
>  Sn 0.807269 0.614537 0.124898
>  Sn 0.385463 0.192731 0.375102
>  Sn 0.192731 0.385463 0.875102
>  Sn 0.192731 0.807269 0.624898
>  Sn 0.385463 0.192731 0.124898
>  Sn 0.807269 0.192731 0.375102
>  Sn 0.614537 0.807269 0.875102
>  Sn 0.807269 0.192731 0.124898
>  Sn 0.192731 0.807269 0.875102
>  Sn 0.528449 0.056899 0.25
>  Sn 0.471551 0.943101 0.75
>  Sn 0.943101 0.471551 0.25
>  Sn 0.056899 0.528449 0.75
>  Sn 0.528449 0.471551 0.25
>  Sn 0.471551 0.528449 0.75
>  Bi 0.5 0.0 0.0
>  Bi 0.0 0.5 0.0
>  Bi 0.5 0.0 0.5
>  Bi 0.5 0.5 0.0
>  Bi 0.0 0.5 0.5
>  Bi 0.5 0.5 0.5
>
> K_POINTS crystal_b
> 2
>   0.0000000000 0.0000000000 0.0000000000 3 !G
>   0.5000000000 0.0000000000 0.0000000000 3 !M
>   !0.3333333333 0.3333333333 0.0000000000
>   !0.0000000000 0.0000000000 0.0000000000
>   !0.0000000000 0.0000000000 0.5000000000
>   !0.5000000000 0.0000000000 0.5000000000
>   !0.3333333333 0.3333333333 0.5000000000
>   !0.0000000000 0.0000000000 0.5000000000
>
> --
> University of California, Berkeley
> Department of Letter and Sciences
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