[Pw_forum] Regarding LA_TA modes

[Kondaiah Samudrala]

Dear all,

I'm wondering if anybody knows how to identified LA-TA modes along
high symmetry directions. I have 8 atoms system , which gives 24 modes
at Gamma point. On the other hand, at X-direction it shows 12
modes(each mode is degenerate). So how can I identified LA and TA
modes. I am sure that all transverse modes are degenerate.. That means
no LA mode along this direction???? Below, I copy the first 4 modes
along X-Direction

I am very happy to know the  Gruneisen parameter spectrum  along High
symmetry directions by QE. I haven't seen any example file or document
about above mentioned
quantities.

Hope Pssitive reply from experts

 q =       0.0000      0.5000      0.0000
 **************************************************************************
     omega( 1) =       1.598127 [THz] =      53.307789 [cm-1]
 (  0.000000   0.000000    -0.066130   0.000000    -0.125554   0.000000   )
 (  0.000000   0.000000     0.109756   0.000000     0.075649   0.000000   )
 (  0.000000   0.000000    -0.068974   0.000000    -0.432281   0.000000   )
 (  0.000000   0.000000     0.041559   0.000000     0.717454   0.000003   )
 (  0.000000   0.000000     0.078828   0.000000     0.051986   0.000000   )
 (  0.000000   0.000000    -0.047495   0.000000    -0.086281   0.000000   )
 (  0.000000   0.000000     0.180727   0.000000     0.287614   0.000001   )
 (  0.000000   0.000000    -0.299951  -0.000001    -0.173293   0.000000   )
     omega( 2) =       1.598127 [THz] =      53.307789 [cm-1]
 (  0.000000   0.000000     0.109756   0.000000    -0.075649   0.000000   )
 (  0.000000   0.000000     0.066130   0.000000    -0.125554   0.000000   )
 (  0.000000   0.000000    -0.041559   0.000000     0.717454   0.000000   )
 (  0.000000   0.000000    -0.068974   0.000000     0.432281   0.000002   )
 (  0.000000   0.000000     0.047495   0.000000    -0.086281   0.000000   )
 (  0.000000   0.000000     0.078828   0.000000    -0.051986   0.000000   )
 (  0.000000   0.000000    -0.299951   0.000000     0.173293   0.000001   )
 (  0.000000   0.000000    -0.180727  -0.000001     0.287614   0.000000   )
     omega( 3) =       2.327611 [THz] =      77.640735 [cm-1]
 (  0.100914   0.000029     0.000000   0.000000     0.000000   0.000000   )
 ( -0.023825   0.000000     0.000000   0.000000     0.000000   0.000000   )
 ( -0.174218  -0.000002     0.000000   0.000000     0.000000   0.000000   )
 (  0.737912   0.000209     0.000000   0.000000     0.000000   0.000000   )
 ( -0.019375   0.000000     0.000000   0.000000     0.000000   0.000000   )
 (  0.082062   0.000023     0.000000   0.000000     0.000000   0.000000   )
 (  0.621104   0.000176     0.000000   0.000000     0.000000   0.000000   )
 ( -0.146640  -0.000002     0.000000   0.000000     0.000000   0.000000   )
     omega( 4) =       2.327611 [THz] =      77.640735 [cm-1]
 (  0.023825   0.000006     0.000000   0.000000     0.000000   0.000000   )
 (  0.100914  -0.000001     0.000000   0.000000     0.000000   0.000000   )
 (  0.737912  -0.000008     0.000000   0.000000     0.000000   0.000000   )
 (  0.174218   0.000046     0.000000   0.000000     0.000000   0.000000   )
 (  0.082062  -0.000001     0.000000   0.000000     0.000000   0.000000   )
 (  0.019375   0.000005     0.000000   0.000000     0.000000   0.000000   )
 (  0.146640   0.000038     0.000000   0.000000     0.000000   0.000000   )
 (  0.621104  -0.000007     0.000000   0.000000     0.000000   0.000000   )


with Regards
S. Appalakondah
PhD student
University of Hyderabad
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