[QE-users] Non standard space groups usage with Qunatum Espresso

[Michal Husak]

Hi

The Quantum Espresso makes possible to enter structure, by the help 
of space group.
Namely eg:
   space_group = 19
  .....
ATOMIC_POSITIONS crystal_sg
C     0.56050   0.14143   0.60159

Unfortunately the CIF description of structures often use 
non-standard space group settings.
Typicaly:
   space_group = 14 is standardly described as P 21/c
But it can be P 21/n, P 21/b,P 21/a ... etc ... (totaly 1 standard 
and 8 non-standard setting)
The non-standard settings can be identified only through Herman-Mogen 
symbol, not by Space Group number ...

So what is the optimal solution for non -standard space group setting ?
a) transfer structure to standard space group setting
b) do not use space gropu and generate all atoms in the unit celll by 
external software
c) support symmetry input by HermanMogen symbols (not only 230 grpusp 
but cca 500 possibel descriptions) in future QE versions ?

Michal UCT Prague