Dear Quantum Espresso users,
I just finished the phonon calculation at Gamma point of a material with T_h
symmetry. But it seems that the code could not determine the mode symmetry as
shown in the output file:
###############################################################
Mode symmetry, T_h (m-3) point group:
freq ( 1 - 3) = 9.1 [cm-1] --> T_u I
freq ( 4 - 6) = 14.5 [cm-1] --> T_u I
freq ( 7 - 9) = 48.9 [cm-1] --> T_g R
freq ( 10 - 12) = 81.9 [cm-1] --> T_g R
freq ( 13 - 15) = 100.1 [cm-1] --> T_u I
freq ( 16 - 16) = 254.2 [cm-1] --> ?
freq ( 17 - 17) = 254.2 [cm-1] --> ?
freq ( 18 - 20) = 265.1 [cm-1] --> T_g R
freq ( 21 - 23) = 347.7 [cm-1] --> T_u I
freq ( 24 - 26) = 349.8 [cm-1] --> T_u I
freq ( 27 - 27) = 350.5 [cm-1] --> A_u
freq ( 28 - 28) = 394.8 [cm-1] --> ?
freq ( 29 - 29) = 394.8 [cm-1] --> ?
freq ( 30 - 32) = 395.2 [cm-1] --> T_u I
freq ( 33 - 35) = 396.8 [cm-1] --> T_g R
freq ( 36 - 36) = 398.8 [cm-1] --> ?
freq ( 37 - 37) = 398.8 [cm-1] --> ?
freq ( 38 - 40) = 479.4 [cm-1] --> T_g R
…….
…….
###############################################################
As from above, the code could notice the point group is T_h. However, for the
two-fold modes (16 and 17, 28 and 29, 36 and 37, actually, all the two-fold
modes have the same problem), which seem to be E_g (or E_u) mode, there is no
symmetry information. In stead, there is only two “?” marks.
Any hint for this problem could be very welcome.
Best regards
Zhishuo Huang
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