[Pw_forum] A question about force constants calculation output

[Zhen Huang]

Dear PWSCF users-

I am a little bit confused by the output from example06. ph.x calculation
generated files alas.dynX where X goes from 0 to 8. In the file alas.dyn0 it
gives the k points. Seems in the other dynX files for example .dyn1 it gives
force constants of q=(0.0, 0.0, 0.0)  and .dyn2 gives force constants of
q=(-0.25   0.25  -0.25), (0.25  0.25   0.25), ( 0.25  -0.25  -0.25), and
such. One of the dynmical matrix is shown below. On the other hand, matdyn.x
also give force constants file alas444.fc which is also partialy attached.
What is the T matrix  and Matrix 1 and 2 labeled below. Also, the questions
are what is 4 4 4 representing the the force constants information part
labeled below,  what does the 1 1 1 1 mean on the second line and also what
is the meaning of the index  2   1   1  -6.26636620736E-03 (for example), I
assume -6.266e-03 is the force constants but what is 2 1 1. If the forth
column is the force constants why it is different from Ph.x calcualtion's
output.

One more question, if I want to look at the force constants between a unit
cell and its closest nearest neibhor unit cell do I look at the dynX output
with k=(0, -1, 0), (-1, 0, 0) and such and second nearest unit cells will be
in dynX of k=(0, -.5, 0), (-.5, 0, 0)?

Thanks for your help. Have a merry christmas and happy new year.

$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$
Dynamical Matrix from Ph.x calcualtion of example06
$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$
     Dynamical  Matrix in cartesian axes

     q = (    0.000000000   0.000000000   0.000000000 )

  1  1
  0.21172298  0.00000000    0.00000000  0.00000000    0.00000000  0.00000000
  0.00000000  0.00000000    0.21172298  0.00000000    0.00000000  0.00000000
  0.00000000  0.00000000    0.00000000  0.00000000    0.21172298  0.00000000
  1  2
 -0.21171370  0.00000000    0.00000000  0.00000000    0.00000000  0.00000000
  0.00000000  0.00000000   -0.21171370  0.00000000    0.00000000  0.00000000
  0.00000000  0.00000000    0.00000000  0.00000000   -0.21171370  0.00000000
  2  1
 -0.21171370  0.00000000    0.00000000  0.00000000    0.00000000  0.00000000
  0.00000000  0.00000000   -0.21171370  0.00000000    0.00000000  0.00000000
  0.00000000  0.00000000    0.00000000  0.00000000   -0.21171370  0.00000000
  2  2
  0.21201035  0.00000000    0.00000000  0.00000000    0.00000000  0.00000000
  0.00000000  0.00000000    0.21201035  0.00000000    0.00000000  0.00000000
  0.00000000  0.00000000    0.00000000  0.00000000    0.21201035  0.00000000
$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$

$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$
alas444.fc
$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$
T Matrix
 T
     13.7429074      0.0000000      0.0000000
      0.0000000     13.7429074      0.0000000
      0.0000000      0.0000000     13.7429074

$$$$$$$$$$$$$$$$$$$$$
 Matrix 1 and 2
    1
      2.5582692      0.0000000      0.0000000
      0.0000000      2.5582692      0.0000000
      0.0000000      0.0000000      2.5582692
    2
     -2.5582692      0.0000000      0.0000000
      0.0000000     -2.5582692      0.0000000
      0.0000000      0.0000000     -2.5582692
$$$$$$$$$$$$$$$$$$$$$
Force Constants Infromation
   4   4   4
   1   1   1   1
   1   1   1   2.24392881916E-01
   2   1   1  -6.26636620736E-03
   3   1   1   6.76999450859E-05
   4   1   1  -6.26636620736E-03
   1   2   1   1.16718256113E-02
   2   2   1  -6.20697521626E-04
   3   2   1  -2.58577048375E-04
   4   2   1  -6.26636620736E-03
   1   3   1   4.19167726130E-03
   2   3   1  -6.20697521626E-04
   3   3   1   6.76999450859E-05
   4   3   1  -6.20697521626E-04
   1   4   1   1.16718256113E-02
   2   4   1  -6.26636620736E-03

$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$
Best Regards
-------
Zhen (Alex) Huang
Ph.D. Student
Nanoscale Transport Research Group
Laboratory for Computational Methods in Emerging Technologies
Cooling Technologies Research Center
School of Mechanical Engineering
Purdue University
Tel: 765 237 9733
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