[Pw_forum] Symmetry-finding problems in pw.x

[Steven Kirk]

Hello,

I am trying to simulate a multiwalled carbon nanotube in pw.x using the
input file:

   &CONTROL
    title='MWNT calculation',
    calculation='scf',
    restart_mode='from_scratch',
    prefix='MWNT',
  /
  &SYSTEM
    ibrav = 6,
    A = 17.0, B = 17.0, C = 4.26, cosAB = 0, cosAC = 0, cosBC = 0,
    nat = 24,
    ntyp = 1,
    ecutwfc = 73.4986,
  /
  &ELECTRONS
  /
ATOMIC_SPECIES
C 12.0107 C.pbe-rrkjus.UPF
ATOMIC_POSITIONS {crystal}
C     0.18067    0.03594    0.47051
C     0.18067    0.03594    0.80385
C     0.15316    0.10234    0.97051
C     0.15316    0.10234    0.30385
C     0.10234    0.15316    0.47051
C     0.10234    0.15316    0.80385
C     0.03594    0.18067    0.97051
C     0.03594    0.18067    0.30385
C    -0.35480   -0.09923    0.18505
C    -0.32863   -0.16654    0.35171
C    -0.35480   -0.09923    0.85171
C    -0.28982   -0.22745    0.18505
C    -0.23988   -0.27962    0.35171
C    -0.32863   -0.16654    0.68505
C    -0.28982   -0.22745    0.85171
C    -0.18072   -0.32105    0.18505
C    -0.11461   -0.35014    0.35171
C    -0.23988   -0.27962    0.68505
C    -0.18072   -0.32105    0.85171
C    -0.04410   -0.36577    0.18505
C     0.02810   -0.36734    0.35171
C    -0.11461   -0.35014    0.68505
C    -0.04410   -0.36577    0.85171
C     0.02810   -0.36734    0.68505
K_POINTS gamma

I am trying to make maximum use of symmetry, because the wavefunction
file gets too big when I don't use it.

Unfortunately it seems that pw.x says 'No symmetry !' with the input
data above. How can I make sure that pw.x detects the 4-fold symmetry
and simulates the structure correctly with the minimum number of atoms ?

Many thanks in advance,
Steve Kirk
-- 
Dr. Steven R. Kirk           <Steven.Kirk at hv.se, S.R.Kirk at physics.org>
Dept. of Technology, Mathematics & Computer Science  (P)+46 520 223215
University West                                      (F)+46 520 223299
P.O. Box 957 Trollhattan 461 29 SWEDEN       http://taconet.webhop.org