[Pw_forum] Interferences between symmetry generation and "ecutrho" value

[Stefano de Gironcoli]

this issue has been discussed several times in this forum.
please check the archive looking for "fractional translation"
best regards,
Stefano de Gironcoli  - SISSA and DEMOCRITOS

Sylvian Cadars wrote:
> Hi,
>
> Playing with test files of the GIPAW_example, and more specifically the 
> basic SCF "quartz.scf.in" calculation, I found the symmetry generation 
> would fail for certain values of "ecutrho" (see list of the tests 
> conducted below). Importantly, problems can occur even though one sticks 
> to the default value (=4*ecutwfc).  These errors seem to be independent 
> of the ecutwfc value, at least this is what my tests suggest.
> Is this a known issue?  Where does it come from? Is it predictable and 
> avoidable?
> Thanks.
> All the best.
>
> Sylvian.
>
> ---------------------------
> ecutwfc ecutrho result
> ---------------------------
> 70      140     failed
> 70      210     OK
> 70      280     OK (=default)
> 70      300     OK
> 70      420     OK
> 70      600     failed
> 150     600     failed (=default)
> 150     -       failed (ecutrho=600)
> 105     -       OK (ecutrho=420)
> 200     800     OK
> 200     1200    OK
> --------------------------
>
> The error messages that occur are the following:
>      Max angular momentum in pseudopotentials (lmaxx) =  3
>      warning: symmetry operation #  7 not allowed.   fractional translation:
>        0.0000000  0.0000000 -0.3333333  in crystal coordinates
>      warning: symmetry operation #  8 not allowed.   fractional translation:
>        0.0000000  0.0000000  0.3333333  in crystal coordinates
>      warning: symmetry operation # 11 not allowed.   fractional translation:
>        0.0000000  0.0000000  0.3333333  in crystal coordinates
>      warning: symmetry operation # 12 not allowed.   fractional translation:
>        0.0000000  0.0000000 -0.3333333  in crystal coordinates
>
> And 2 symmetry operations are found instead of 6 when everything works 
> properly.
>       2 Sym.Ops. (no inversion)
>
>
> For convenience, here is a typical input file that fails:
>
> &CONTROL
>         calculation = 'scf' ,
>         restart_mode = 'from_scratch' ,
>         outdir = '/home/sc/espresso_tmp' ,
>         pseudo_dir = '/home/sc/PWscf/PseudoPotentials/PBE_090707/' ,
>  /
> &system
>         ibrav = 0
>         celldm(1) = 1.
>         nat = 9
>         ntyp = 2
>         ecutwfc = 150
>         ecutrho = 600
>  /
> &ELECTRONS
>         electron_maxstep = 100
>         conv_thr = 5.0e-8
>         startingpot = 'atomic'
>         startingwfc = 'atomic'
>         mixing_mode = 'plain'
>         mixing_beta = 0.7
>         diagonalization = 'david'
>         diago_thr_init = 1.e-2
>  /
> ATOMIC_SPECIES
>    Si   28.0855000  SiPBE_nc.UPF
>     O   15.9994000  OPBE_nc.UPF
>
> ATOMIC_POSITIONS crystal
> Si    0.4701     0.0000      0.3333333333
> Si    0.0000     0.4701      0.6666666667
> Si   -0.4701    -0.4701      0.0000000000
> O     0.4139     0.2674      0.2144
> O     -0.2674    0.1465      0.5477333333
> O     -0.1465   -0.4139      0.8810666667
> O      0.2674    0.4139     -0.2144
> O      0.1465   -0.2674      0.4522666667
> O     -0.4139   -0.1465      0.1189333333
>
> CELL_PARAMETERS hexagonal
> 4.642775480     -8.041523019    0.000000000
> 4.642775480     8.041523019     0.000000000
> 0.000000000     0.000000000     10.213406856
>
> K_POINTS automatic
> 2 2 2   1 1 1
>
>
> *Dr. Sylvian CADARS*
> CEMHTI-CNRS
> 1D, Av. de la Recherche Scientifique
> 45071 Orléans Cedex 2, France
>
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