[Pw_forum] Regarding LA_TA modes

[Lorenzo Paulatto]

On 07/30/2014 04:43 PM, Kondaiah Samudrala wrote:
> Respected Dr. Lorenzo Paulatto,
> Thank you for Quick reply..May be it is basic and crude to ask like this.can you please explain me the*"**displacement pattern of the atoms"*  in pwscf output.. I am not clear..Otherwise please give me some path for understand the output..
They are not written on output, but they are at the end of the dynamical 
matrix file. I

For every phonon band at this q point you have the energy (frequency) of 
the mode than the displacement. The displacement is a 3-component 
(x,y,z) complex vector for each atom., i.e. three complex numbers that 
describe the displacement of each atom along x, y and z.


Here is an example from some random file I had on my PC, this system 
includes 2 atoms:

[...]
      Diagonalizing the dynamical matrix

      q = (    0.000000000   0.500000000   0.000000000 )

  **************************************************************************
      freq (    1) =     -13.073222 [THz] =    -436.075739 [cm-1]
  ( -0.000000  0.000149 -0.000000  0.000000 -0.000000  0.000000 )
  ( -1.000000 -0.000000 -0.000000 -0.000000 -0.000441  0.000000 )
      freq (    2) =     -13.073222 [THz] =    -436.075739 [cm-1]
  ( -0.000000  0.000000 -0.000000  0.000000  0.000000 -0.000149 )
  ( -0.000441 -0.000000 -0.000000 -0.000000  1.000000  0.000000 )
      freq (    3) =      25.614758 [THz] =     854.416345 [cm-1]
  ( -0.000000  0.996054 -0.000000 -0.000000 -0.000000  0.087343 )
  (  0.015692 -0.000000 -0.000000  0.000000  0.001376  0.000000 )
      freq (    4) =      25.614758 [THz] =     854.416345 [cm-1]
  ( -0.000000  0.087343 -0.000000  0.000000  0.000000 -0.996054 )
  (  0.001376 -0.000000 -0.000000  0.000000 -0.015692  0.000000 )
      freq (    5) =      30.812798 [THz] =    1027.804323 [cm-1]
  ( -0.000000  0.000000  0.000001  0.437588  0.000000  0.000000 )
  (  0.000000 -0.000000  0.899176 -0.000002  0.000000 -0.000000 )
      freq (    6) =      37.682257 [THz] =    1256.944790 [cm-1]
  (  0.000000 -0.000000  0.000000  0.019458  0.000000  0.000000 )
  ( -0.000000  0.000000 -0.999811  0.000000  0.000000  0.000000 )
  **************************************************************************

You can see that bands 1, 2, 3 and 4 are transverse, band 5 and 6 are 
longitudinal.

HTH


-- 
Dr. Lorenzo Paulatto
IdR @ IMPMC -- CNRS & Université Paris 6
+33 (0)1 44 275 084 / skype: paulatz
http://www.impmc.upmc.fr/~paulatto/
23-24/4é16 Boîte courrier 115, 4 place Jussieu 75252 Paris Cédex 05

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