[QE-users] Can anybody explain, how does QE work with space group symmetry ?

[Husak Michal]

Hi

Can anybody explain, how does QE work with space group symmetry ?
I am a crystallographer - no need to explain theory ...

Let speak e.g. about e,g, P212121

I expect:

A) When space_group = 19, QE generate the 3 more molecules from 1, check the lattice is P (eventually transforms to P from A,B,C,I,F) and use restriction generated by the Sg P212121.
It use symmetry of the system as given on the input (auto symmetry check is skipped)...

B) When ibraw=0. I must generate all the atoms (1+3 molecules) myself. QE check for symmetry  and automatically apply it  to the
calculation (because default nosym = .false.)

Is this correct ?
Should A and B generate the same result (when rest of param is set identically) ?

Related question:
Can I use:
ibrav = 14
  A = 6.025
  B = 12.324
  C = 5.783
  cosBC = 0
  cosAC = 0
  cosAB = 0

To get the same as B) ?
Is the primitive triclinic ibrav used only for cell parameters interpretation ?
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