[Pw_forum] Phonon branch enumeration

[Jeffrey Mullen]

Greetings

I am testing electron-phonon interaction calculations with graphene and
have encountered a problem enumerating the resulting phonon branches.
When I run the ph.x calculation at the q(0 0 0), the code calculates 4
representations:

     Representation #  1 modes #   1  2
     Representation #  2 mode #   3
     Representation #  3 mode #   4
     Representation #  4 modes #   5  6


When the values for omega are calculated, the results are:

 **************************************************************************
     omega( 1) =      -1.119851 [THz] =     -37.354451 [cm-1]
     omega( 2) =      -1.016557 [THz] =     -33.908905 [cm-1]
     omega( 3) =      -1.016557 [THz] =     -33.908905 [cm-1]
     omega( 4) =      25.882237 [THz] =     863.344237 [cm-1]
     omega( 5) =      40.051667 [THz] =    1335.988701 [cm-1]
     omega( 6) =      40.051667 [THz] =    1335.988701 [cm-1]
 **************************************************************************


with the following mode symmetries:

     Mode symmetry, D_6h(6/mmm) point group:

     omega(  1 -  1) =        -37.4  [cm-1]   --> A_2u            I
     omega(  2 -  3) =        -33.9  [cm-1]   --> E_1u            I
     omega(  4 -  4) =        863.3  [cm-1]   --> B_2g
     omega(  5 -  6) =       1336.0  [cm-1]   --> E_2g            R


My question is one of ordering. How do I extract which omega(##)
corresponds to which representation/mode?

Thanks
Jeff Mullen
North Carolina State University