Dear all,

This is to make the discussion done in gitlab more accessible to everyone.

If you want to use the matrix representations of the symmetry written in the 
output of QE to identify the (magnetic) space group, please refer to 
https://gitlab.com/QEF/q-e/-/issues/271

HTH,
============================================
Minkyu Park
Research Institute of Basic Sciences, University of Ulsan,
93, Daehak-ro, Nam-gu, Ulsan, 44610 Republic of Korea
[email protected]<mailto:[email protected]>
+82-52-259-1473
============================================

On 20 Jan 2021, at 10:06 AM, 박민규 
<[email protected]<mailto:[email protected]>> wrote:

Dear all,

I observed something strange in symmetry analysis.

For example, if we run any calculation with space group Pm-3m (#221), all 
symmetries are written in the output. I excerpted some of them (see below). I 
used qe-6.6.

My question is following. For simple cubic system I expect crystal and 
cartesian coordinate can be taken as same if there is no special reason to take 
them different. Then why do we have different matrix representations for 90 deg 
rotation (isym = 15, 16) and 120 deg rotation (isym = 17) depending on the 
coordinate system?

Is it intended or just a kind of bug?


      isym = 14     180 deg rotation - cart. axis [0,1,-1]

 cryst.   s(14) = (    -1          0          0      )
                  (     0          0         -1      )
                  (     0         -1          0      )

 cart.    s(14) = ( -1.0000000  0.0000000  0.0000000 )
                  (  0.0000000  0.0000000 -1.0000000 )
                  (  0.0000000 -1.0000000  0.0000000 )


      isym = 15      90 deg rotation - cart. axis [-1,0,0]

 cryst.   s(15) = (     1          0          0      )
                  (     0          0         -1      )
                  (     0          1          0      )

 cart.    s(15) = (  1.0000000  0.0000000  0.0000000 )
                  (  0.0000000  0.0000000  1.0000000 )
                  (  0.0000000 -1.0000000  0.0000000 )


      isym = 16      90 deg rotation - cart. axis [1,0,0]

 cryst.   s(16) = (     1          0          0      )
                  (     0          0          1      )
                  (     0         -1          0      )

 cart.    s(16) = (  1.0000000  0.0000000  0.0000000 )
                  (  0.0000000  0.0000000 -1.0000000 )
                  (  0.0000000  1.0000000  0.0000000 )


      isym = 17     120 deg rotation - cart. axis [-1,-1,-1]

 cryst.   s(17) = (     0          0          1      )
                  (     1          0          0      )
                  (     0          1          0      )

 cart.    s(17) = (  0.0000000  1.0000000  0.0000000 )
                  (  0.0000000  0.0000000  1.0000000 )
                  (  1.0000000  0.0000000  0.0000000 )


Best regards,
============================================
Minkyu Park
Research Institute of Basic Sciences, University of Ulsan,
93, Daehak-ro, Nam-gu, Ulsan, 44610 Republic of Korea
[email protected]<mailto:[email protected]>
+82-52-259-1473
============================================

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