[Wien] Wavefunctions out of IBZ

[Chiung-Yuan Lin]

Dear all,
  I have a basic question here:
How can I obain a wavefunction if its k lies out of IBZ (still in BZ)?
I know how to get wavefunctions in IBZ. The k points out of IBZ are
generated by symmetry operations. I think a non-IBZ wavefuntion is
related to its corresponding IBZ wavefuntion in some way.

Thank you
P.S. I am working on a hexagonal lattice (P-6m2).