[QE-users] [PW_forum] IFC file structure

[Adrien Descamps]

Dear all,

I am trying to calculate the phonon dispersion for Silicon. Thanks to the
previous posts, I think I understand the structure of the output file and
how to extract the interatomic force constant matrices.
Since the Cartesian frame is given by the vectors (-1,0,1)a/2; (0,1,1)a/2
and (-1,1,0)a/2, where can I find the IFC for the interaction between the
two atoms in the unit cell, namely the interaction between atom at (0,0,0)
and the 4 nearest neighbors at (1/4,1/4,1/4), (1/4,-1/4,-1/4),
(-1/4,1/4,-1/4), (-1/4,-1/4,1/4)? I would expect to find it in the section
1 1 1 2 section but none of the position vector match the four first
nearest neighbor, unless I making a mistake:

1   1   1   2
   1   1   1  -6.76355682813E-02
   2   1   1   7.83560937500E-05
   3   1   1  -4.45195312500E-05
   4   1   1   7.20209843750E-04
   1   2   1  -6.76355682813E-02
   2   2   1  -4.13570781250E-04
   3   2   1  -4.13570781250E-04
   4   2   1  -6.76355682813E-02
   1   3   1  -4.63088953125E-03
   2   3   1   1.34053593750E-04
   3   3   1  -4.13570781250E-04
   4   3   1   7.20209843750E-04
   1   4   1  -4.63088953125E-03
   2   4   1  -4.13570781250E-04
   3   4   1  -4.45195312500E-05
   4   4   1   3.78551718750E-04
   1   1   2   7.83560937500E-05
   2   1   2   1.17258593750E-04
   3   1   2   3.07267343750E-04
   4   1   2   7.20209843750E-04
   1   2   2  -4.13570781250E-04
   2   2   2   1.34053593750E-04
   3   2   2  -4.63088953125E-03
   4   2   2   7.20209843750E-04
   1   3   2   1.34053593750E-04
   2   3   2   1.34053593750E-04
   3   3   2   3.07267343750E-04
   4   3   2   3.07267343750E-04
   1   4   2  -4.13570781250E-04
   2   4   2   1.17258593750E-04
   3   4   2   2.44567968750E-04
   4   4   2   3.07267343750E-04
   1   1   3  -4.45195312500E-05
   2   1   3   3.07267343750E-04
   3   1   3   3.78551718750E-04
   4   1   3   2.42503593750E-04
   1   2   3  -4.13570781250E-04
   2   2   3  -4.63088953125E-03
   3   2   3   3.78551718750E-04
   4   2   3  -4.45195312500E-05
   1   3   3  -4.13570781250E-04
   2   3   3   3.07267343750E-04
   3   3   3   2.44567968750E-04
   4   3   3   1.17258593750E-04
   1   4   3  -4.45195312500E-05
   2   4   3   2.44567968750E-04
   3   4   3   2.44567968750E-04
   4   4   3  -4.45195312500E-05
   1   1   4   7.20209843750E-04
   2   1   4   7.20209843750E-04
   3   1   4   2.42503593750E-04
   4   1   4   2.42503593750E-04
   1   2   4  -6.76355682813E-02
   2   2   4   7.20209843750E-04
   3   2   4  -4.45195312500E-05
   4   2   4   7.83560937500E-05
   1   3   4   7.20209843750E-04
   2   3   4   3.07267343750E-04
   3   3   4   1.17258593750E-04
   4   3   4   7.83560937500E-05
   1   4   4   3.78551718750E-04
   2   4   4   3.07267343750E-04
   3   4   4  -4.45195312500E-05
   4   4   4   2.42503593750E-04

Thank you very much,

Best regards,
Adrien Descamps

Stanford Unversity, Aeronautics and Aerospace Engineering
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