[Pw_forum] problem with final scf calculation with vc-relax

[Ilya Ryabinkin]

Hi Leonid:
you error is typical for the variable-cell optimization: the problem
is in the size of PW basis for the fixed energy cutoff. If the size of
a cell is changing, there are more/fewer basis plane waves (G
vectors)for the same energy cutoff. Just ignore this error and re-run
SCF calculations with new cell parameters. Alternatively, to make sure
that everything is fine, restart vc-relaxation with new cell
parameters, it should converge very quickly with no errors.

--
Ilya

On Sat, Oct 14, 2017 at 3:04 AM, Leonid Kahle <leonid.kahle at epfl.ch> wrote:
> Dear developers,
>
> There are frequent problems with the "final scf" after the convergence of a
> vc-relaxation with the recalculated G-vectors.
> In this case, the volume grows during the vc-relax by 3.5%, and G-vectors
> are assigned from
>
> sticks:   dense  smooth     PW     G-vecs:    dense   smooth      PW
>      Min          77      38     11                 1889      668     114
>      Max          78      39     12                 1891      671     118
>      Sum        1393     685    211                34015    12039    2085
>
> to:
>
>      sticks:   dense  smooth     PW     G-vecs:    dense   smooth      PW
>      Min          78      38     11                 1973      689     115
>      Max          79      39     12                 1977      693     120
>      Sum        1417     701    211                35557    12429    2109
>
>
> for the final scf. The final scf-calculation crashes with the following
> error:
>
>      Error in routine ggen (78):
>      smooth g-vectors missing !
>
> Before I get told about strange input:
>
>  - The input is 2 atoms (LiI) in a reasonable cell (and the vc-relax goes
> fine)
>  - 10x10x10 kpoints, dense enough for an insulator
>
> Furthermore, this is QE6.0 compiled with Intel. I run on 18 cores on a Cray
> XC40, with no command line switches.
>
> If I'm doing something wrong, please let me know.
> But regardless, I would be happy to see the final scf in a vc-relax being
> optional. As said,  this is happening frequently for all kinds of systems.
> I've attached input, submission script,  and a (shortened for size
> limitations) output file for this mentioned case.
>
> Thanks a lot and best regards,
>
>     Leonid Kahle
>
> --
>
> Doctoral Assistant
> EPFL STI IMX THEOS
> ME-D2 1019 (Bâtiment ME)
> Station 9
> CH-1015 Lausanne (Switzerland)
>
>
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-- 
*******************************************************
                    Ilya Ryabinkin
                 Postdoctoral Scholar
          Physical and Environmental Sciences
           University of Toronto Scarborough
  http://www.utsc.utoronto.ca/~aizmaylov/Members.html
*******************************************************