[Pw_forum] Allowed symmetries in GIPAW

[J. Nelson]

Dear all QE users,

I am using QE-6.1.

The user guide for GIPAW explains that 'symmetry operations that do not 
map cartesian axes are not allowed (i.e. 120 deg. rotations)'.

Does this mean that the Cartesian rotation matrices for each symmetry 
operation - e.g.:

       isym =  4     180 deg rotation - cart. axis [1,0,0]

  cryst.   s( 4) = (     0          1          0      )
                   (     1          0          0      )
                   (     0          0         -1      )

  cart.    s( 4) = (  1.0000000  0.0000000  0.0000000 )  [<--this matrix 
here]
                   (  0.0000000 -1.0000000  0.0000000 )
                   (  0.0000000  0.0000000 -1.0000000 )

need to be diagonal for the symmetry operation to be compatible with 
GIPAW? Are symmetry operations with an associated fractional translation 
allowed?


Many thanks,

Joseph Nelson
TCM Group
Cavendish Laboratory
University of Cambridge