[Wien] why hexagonal goes to monoclinic C-base or triclinic within initialization?

[Martin Gmitra]

Dear Wien2k users,

I am wondering why sgroup transfers input hexagonal system (see attachment
or below a part of the slab that reduces symmetry in Wien2k) within
initialization process to monoclinic B-base centered one while symmetry
finds 6 symmetry operations for the original hexagonal system. If I reduce
multiplicity of the atoms (to 27) the initialization goes with triclinic (P
90 90 120) and one operation symmetry. I have transferred the structure
from plane wave calculations using Quantum Espresso code where the system
is treated as hexagonal with 6 symmetry operations.

Do you have an idea why Wien2k does not treat the system as hexagonal?

Best regards,
Martin Gmitra, Uni Regensburg

H   LATTICE,NONEQUIV. ATOMS  9
MODE OF CALC=RELA unit=
 18.064563 18.064563 37.794523 90.000000 90.000000120.000000
ATOM   1: X=0.11107924 Y=0.22215827 Z=0.24924470
          MULT= 3          ISPLIT= 8
ATOM   1: X=0.11107924 Y=0.88892053 Z=0.24924470
ATOM   1: X=0.77784149 Y=0.88892053 Z=0.24924470
Mo         NPT=  781  R0=0.00001000 RMT=    2.4161   Z: 42.0
LOCAL ROT MATRIX:    1.0000000 0.0000000 0.0000000
                     0.0000000 1.0000000 0.0000000
                     0.0000000 0.0000000 1.0000000
ATOM   2: X=0.22214961 Y=0.11107481 Z=0.32975565
          MULT= 3          ISPLIT= 8
ATOM   2: X=0.88892486 Y=0.11107481 Z=0.32975565
ATOM   2: X=0.88892486 Y=0.77785005 Z=0.32975565
S          NPT=  781  R0=0.00010000 RMT=    2.0975   Z: 16.0
LOCAL ROT MATRIX:    1.0000000 0.0000000 0.0000000
                     0.0000000 1.0000000 0.0000000
                     0.0000000 0.0000000 1.0000000
ATOM   3: X=0.22234728 Y=0.11117364 Z=0.16891605
          MULT= 3          ISPLIT= 8
ATOM   3: X=0.88882603 Y=0.11117364 Z=0.16891605
ATOM   3: X=0.88882603 Y=0.77765239 Z=0.16891605
S          NPT=  781  R0=0.00010000 RMT=    2.0969   Z: 16.0
LOCAL ROT MATRIX:    1.0000000 0.0000000 0.0000000
                     0.0000000 1.0000000 0.0000000
                     0.0000000 0.0000000 1.0000000
ATOM   4: X=0.44443301 Y=0.22221629 Z=0.24939272
          MULT= 3          ISPLIT= 8
ATOM   4: X=0.77778348 Y=0.22221629 Z=0.24939272
ATOM   4: X=0.77778348 Y=0.55556676 Z=0.24939272
Mo         NPT=  781  R0=0.00001000 RMT=    2.4196   Z: 42.0
LOCAL ROT MATRIX:    1.0000000 0.0000000 0.0000000
                     0.0000000 1.0000000 0.0000000
                     0.0000000 0.0000000 1.0000000
ATOM   5: X=0.55534152 Y=0.11068338 Z=0.32969156
          MULT= 3          ISPLIT= 8
ATOM   5: X=0.55534152 Y=0.44465814 Z=0.32969156
ATOM   5: X=0.88931628 Y=0.44465814 Z=0.32969156
S          NPT=  781  R0=0.00010000 RMT=    2.0976   Z: 16.0
LOCAL ROT MATRIX:    1.0000000 0.0000000 0.0000000
                     0.0000000 1.0000000 0.0000000
                     0.0000000 0.0000000 1.0000000
ATOM   6: X=0.55573535 Y=0.11147104 Z=0.16887573
          MULT= 3          ISPLIT= 8
ATOM   6: X=0.55573535 Y=0.44426431 Z=0.16887573
ATOM   6: X=0.88852863 Y=0.44426431 Z=0.16887573
S          NPT=  781  R0=0.00010000 RMT=    2.0962   Z: 16.0
LOCAL ROT MATRIX:    1.0000000 0.0000000 0.0000000
                     0.0000000 1.0000000 0.0000000
                     0.0000000 0.0000000 1.0000000
ATOM   7: X=0.11106993 Y=0.55553475 Z=0.24900148
          MULT= 3          ISPLIT= 8
ATOM   7: X=0.44446502 Y=0.55553475 Z=0.24900148
ATOM   7: X=0.44446502 Y=0.88892983 Z=0.24900148
Mo         NPT=  781  R0=0.00001000 RMT=    2.4161   Z: 42.0
LOCAL ROT MATRIX:    1.0000000 0.0000000 0.0000000
                     0.0000000 1.0000000 0.0000000
                     0.0000000 0.0000000 1.0000000
ATOM   8: X=0.22237477 Y=0.44474987 Z=0.32919385
          MULT= 3          ISPLIT= 8
ATOM   8: X=0.22237477 Y=0.77762490 Z=0.32919385
ATOM   8: X=0.55524980 Y=0.77762490 Z=0.32919385
S          NPT=  781  R0=0.00010000 RMT=    2.0944   Z: 16.0
LOCAL ROT MATRIX:    1.0000000 0.0000000 0.0000000
                     0.0000000 1.0000000 0.0000000
                     0.0000000 0.0000000 1.0000000
ATOM   9: X=0.22210430 Y=0.44420894 Z=0.16867867
          MULT= 3          ISPLIT= 8
ATOM   9: X=0.22210430 Y=0.77789536 Z=0.16867867
ATOM   9: X=0.55579073 Y=0.77789536 Z=0.16867867
S          NPT=  781  R0=0.00010000 RMT=    2.0975   Z: 16.0
LOCAL ROT MATRIX:    1.0000000 0.0000000 0.0000000
                     0.0000000 1.0000000 0.0000000
                     0.0000000 0.0000000 1.0000000
   0      NUMBER OF SYMMETRY OPERATIONS
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