[Pw_forum] Phonon freqencies

[Uttam Paliwal]

Dear QE users
I am computing phonon frequencies for BeS. I am attaching here the output
file part



     q = (    0.000000000   0.000000000   0.000000000 )

 **************************************************************************
     freq (    1) =       0.105756 [THz] =       3.527650 [cm-1]
     freq (    2) =       0.105756 [THz] =       3.527650 [cm-1]
     freq (    3) =       0.105756 [THz] =       3.527650 [cm-1]
     freq (    4) =      16.460235 [THz] =     549.054328 [cm-1]
     freq (    5) =      16.460235 [THz] =     549.054328 [cm-1]
     freq (    6) =      16.460235 [THz] =     549.054328 [cm-1]
 **************************************************************************

     Mode symmetry, T_d (-43m)  point group:

     freq (  1 -  3) =          3.5  [cm-1]   --> T_2  G_15 P_4   I+R
     freq (  4 -  6) =        549.1  [cm-1]   --> T_2  G_15 P_4   I+R


******************************************************************************
these are TO (Transverse Optical) or LO (Longitudinal Optical), how to
know. please suggest
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