[Pw_forum] more about K points of the whole BZ or the irreducible part?

[W. YU]

>from the manual:
>------------------------------------------------------
>Note about k points:
>The k-point grid can be either automatically
>generated or manually provided as a list of k-points
>and a weight in the Irreducible Brillouin Zone only
>of the Bravais lattice of the crystal.The code will
>generate (unless instructed not to do so: see
>variable "nosym") all required k-points and weights
>if the symmetry of
>the system is lower than the symmetry of the Bravais
>lattice. The automatic generation of k-points follows
>the convention of Monkhorst and Pack.
------------------------------------------------------
 
>Paolo Giannozzi               

Sorry, I still don't quite understand here. What does
it mean by  "all required k-points "? Those outside
the irreducible part of the BZ? 

>if the symmetry of
>the system is lower than the symmetry of the Bravais
>lattice."

What's the meaning of "the symmetry of the system is
lower than the symmetry of the Bravais lattice"? Are
there other occasions when the code doesn't need to
generate all the other k-points?

By the way, I know there is a small tool called
kpoints which generate kpoints according to the
convention of Monkhorst and Pack. But it seems the PW
automatically generated kpoints are not always the
same as those by this program. Do they use the same
scheme?  

How did the following 10 kpoints in example2
generated? It doesn't seems to be generated either by
kpoints tool or the PW automatic generating code.
Either non-shifted or shifted.

best regards,

W. YU 
======================================================
10
   0.1250000  0.1250000  0.1250000   1.00
   0.1250000  0.1250000  0.3750000   3.00
   0.1250000  0.1250000  0.6250000   3.00
   0.1250000  0.1250000  0.8750000   3.00
   0.1250000  0.3750000  0.3750000   3.00
   0.1250000  0.3750000  0.6250000   6.00
   0.1250000  0.3750000  0.8750000   6.00
   0.1250000  0.6250000  0.6250000   3.00
   0.3750000  0.3750000  0.3750000   1.00
   0.3750000  0.3750000  0.6250000   3.00

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