[gpaw-users] Wavefunction convergence problem

[Ask Hjorth Larsen]

Hi Gaël

What is the smearing temperature?

Best regards
Ask
El 16/07/2014 10:37, "Gaël Donval" <gael.donval at cnrs-imn.fr> escribió:

> Hi,
>
> I have generated a quite a big slab (80 atoms, time reversal symmetry
> only) with ASE and try to perform structure optimization on it.
>
>         Unit Cell:
>                    Periodic     X           Y           Z      Points
>  Spacing
>
> --------------------------------------------------------------------
>           1. axis:    no    23.278154    0.000000    0.000000   128
> 0.1819
>           2. axis:    yes    0.000000    7.679180    0.000000    40
> 0.1920
>           3. axis:    yes    0.000000    0.000000    8.145000    48
> 0.1697
>
>
> I use only one k-point (gamma).
>
> When I first tried to get SCF convergence, I couldn't even converge to
> anything, even with very low mixing parameters. I had to remove bands
> (from nelectron to 25 unoccupied bands) to get the convergence that you
> will see bellow.
>
> At the first relaxation step, in the SCF calculation, everything
> converges smoothly down to some point then hits a limit: the error on
> the density stays around 10^-4 and the error on the wavefunction is
> switching between two values. For instance:
>
>         iter:  47  10:02:07  -3.19  -4.20    -356.939274  2      2
>         iter:  48  10:02:09  -3.11  -4.13    -356.938830  2      3
>         iter:  49  10:02:12  -3.19  -4.43    -356.938031  2      2
>         iter:  50  10:02:14  -3.11  -4.49    -356.937563  2      2
>         iter:  51  10:02:17  -3.19  -4.60    -356.937381  1      1
>         iter:  52  10:02:20  -3.11  -4.57    -356.937543  1      1
>         iter:  53  10:02:22  -3.19  -4.59    -356.938149  1      1
>         iter:  54  10:02:25  -3.11  -4.56    -356.937988  1      1
>         iter:  55  10:02:27  -3.19  -4.53    -356.938700  2      2
>         ...
>         iter: 283  10:12:19  -3.15  -3.84    -356.893178  2      2
>         iter: 284  10:12:22  -3.08  -4.34    -356.882750  1      1
>         iter: 285  10:12:24  -3.15  -4.55    -356.858456  2      2
>         iter: 286  10:12:27  -3.08  -4.24    -356.864220  2      1
>
>
> If I consider that this is enough and stop there, then I got the same
> behavior in the second step with the error on the density converging to
> ~10^-4 *but* the error on the wavefunctions stays at ~10^-1.4 (same
> behavior, switches between two values).
>
> I followed the recommandations on the "Convergence issues" web page,
> without success. I also tried different mixers and eigensolvers.
>
> Does anyone has an idea about that?
>
>
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