[Pw_forum] d3.x: Symmetry operation in third-order anharmonic force tensor of Si

[Haru Deku]

Dear all


I want to examine the lifetime of phonon at Gamma-point via the calculations
of phonon-phonon interaction with use of d3.x.

Recently I encountered one problem rerating on the symmetry operation of the
third-order anharmonic force tensor of Si.



------------------------


(1) I calculated the tensor at q=(0,0,1) (X-point) following the strategy
shown in example 14, with PWSCF ver4.1. Then, I obtained the anharmonic
tensor ( see please, "si.anh_X" attached with this mail), and I confirmed it
is completely the same as the one seen in reference in example 14.


(2) Next, I calculated the tensor at q=(0,1,0) which point is equivalent to
X-point, and anharmonic force tensor at q=(0,0,1) is obtained by symmetry
operation.



I expected that the tensor obtained in (1) SHOULD be equivalent to that in
(2) after symmetry operation due to the equivalence in q-points.



However, contrary to the expectation, a different result is observed in the
anharmonic tensor at q=(0,0,1) obtained by the symmetry operation ( from
q(0,1,0) to q(0,0,1)), see please, "si. anh_X_2"); actually, some components
are same but considerable difference are observed.


I'd like to know what is wrong in my calculation/input-files/strategy on the
computation.


--------------------------

I am a really beginner for use of d3.x, and may be this problem comes from a
lack of my attentiveness to the calculation.

I'm so sorry for disturbing your time, but If you could give me some helps,
I really appreciate for your kindness.


I attached some files; the input and output files that are in
"files.tar.gz".



I'd like to say thank you very much, in advance.


Haruhiko Dekura







========================================

Haruhiko Dekura


Postdoctoral Fellow

Senior Research Fellow Center, Ehime University, 2–5 Bunkyo-cho, Matsuyama,
Ehime 790-8577, Japan

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