[Pw_forum] IFC's and eigendisplacements in example06

[Ömer Koç]

Dear PWSCF users,

 My questions are about example06



1) Could you give me some analysis and explanations on the range of the
interatomic force constants (IFC's) for AlAs in example06.
 On the Forum, there are  some informations and explanations but i don't
understand them. I need more explanations.



alas444.fc



  2     2  2 10.5000000  0.0000000  0.0000000  0.0000000   0.0000000
0.0000000

           1   'Al '    24590.7655930491

           2   'As '    68285.4024548272

    1     1      0.0000000      0.0000000      0.0000000

    2     2      0.2500000      0.2500000      0.2500000

 T

     13.7439581       0.0000000      0.0000000

      0.0000000      13.7439581      0.0000000

      0.0000000       0.0000000     13.7439581

    1

      2.5582103       0.0000000      0.0000000

      0.0000000       2.5582103      0.0000000

      0.0000000       0.0000000      2.5582103

    2

     -2.5582103       0.0000000      0.0000000

      0.0000000      -2.5582103      0.0000000

      0.0000000       0.0000000     -2.5582103

   4    4   4

   1    1   1   1

   1    1   1   2.17004984418E-01

   2    1   1  -5.06952740903E-03

   3    1   1   9.99492789182E-05

   4    1   1  -5.06952740903E-03

   1    2   1   1.07967422105E-02

   2    2   1  -6.07584921925E-04

   3    2   1  -1.61474518909E-04

   4    2   1  -5.06952740903E-03

   1    3   1   4.18136269798E-03

   2    3   1  -6.07584921925E-04

   3    3   1   9.99492789182E-05

   4    3   1  -6.07584921925E-04

   1    4   1   1.07967422105E-02

   2    4   1  -5.06952740903E-03

   3    4   1  -1.61474518909E-04

   4    4   1  -6.07584921925E-04

   1    1   2  -5.06952740903E-03

   2    1   2  -1.61474518909E-04

   3    1   2  -6.07584921925E-04

   …………………………………………………………………………




2) Is there a meaning of ratio of displacement of the two ions (Al and As)
in the eigendisplacement pattern?
The calculated vibrational eigenvectors at X point are below. How can we
evaluate this data?



q =       0.0000       0.0000      1.0000

 **************************************************************************

     omega( 1) =        2.841119 [THz] =      94.770143 [cm-1]

 (   0.611885   0.039292    -0.353070  -0.018348     0.000000    0.000000   )
Al

 ( -0.352406   -0.018313     0.610733   0.039218     0.000000   0.000000    )
As

     omega( 2) =        2.841119 [THz] =      94.770143 [cm-1]

 (   0.353530   0.003400     0.613143  -0.001588      0.000000   0.000000
)

 (   0.611989  -0.001585     0.352865   0.003394     0.000000    0.000000
)

     omega( 3) =        6.563802 [THz] =     218.946309 [cm-1]

 (   0.000000   0.000000     0.000000   0.000000     0.000000    0.000000
)

 (   0.000000   0.000000     0.000000   0.000000     1.000000    0.000000
)

     omega( 4) =       10.442067 [THz] =     348.312171 [cm-1]

 (   0.753056   0.016289    -0.563430   0.002731     0.000000    0.000000
)

 (   0.203284  -0.000985    -0.271700  -0.005877     0.000000    0.000000
)

     omega( 5) =       10.442067 [THz] =     348.312171 [cm-1]

 ( -0.563178   -0.017050    -0.753227  -0.002855     0.000000   0.000000
)

 (   0.271762   0.001030     0.203193   0.006152     0.000000    0.000000
)

     omega( 6) =       12.209736 [THz] =     407.275646 [cm-1]

 (   0.000000   0.000000     0.000000   0.000000    -0.138259    0.990396
)

 (   0.000000   0.000000     0.000000   0.000000     0.000000    0.000000
)

 **************************************************************************

     diagonalizing the dynamical matrix ...


Many thanks in advance

Ömer.


-- 
Ömer Koç
100. Yıl University
Dept of Physics Van, Turkey
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