[Pw_forum] About the Frozen Phonon Method

[mohaddeseh abbasnejad]

Dear users,

I have plotted the harmonic frequency (obtained within the frozen phonon
approach) of Diamond as a function of atomic displacements (small
displacements in the [1 1 1] direction, u(1)=±(u,u,u) and
u(2)=±(-u,-u,-u) are the displacements of two atoms in the basis). I expect
to see a range of displacements that tend to the similar frequency, but
there is no convergence in the plot. Also, the displacements with the same
amplitude but different in sign, do not tend to the same frequency, which is
not what I expect, too. The plot is attached.
I was wondering if anyone could help me to find the source of error. I
should expect the mentioned symmetry, right? Why there is no convergence?

Thanks in advance.

Yours,
Mohaddeseh
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Mohaddeseh Abbasnejad,
Room No. 323, Department of Physics,
University of Tehran, North Karegar Ave.,
Tehran, P.O. Box: 14395-547- IRAN
E-Mail:     m.abbasnejad at gmail.com
Website:  http://physics.ut.ac.ir

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