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

[Sylvian Cadars]

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