[Pw_forum] PHonon calculation in amorphous cell

[Louis Fry-Bouriaux]

Hi all,


    I am experimenting with a large 120 atom amorphous Al2O3 cell. I wish to calculate the electronic and ionic contributions to the dielectric constant, I am currently running the ground state calculations, however I am not sure what to expect with the phonon calculations. According to an experimental paper (http://aip.scitation.org/doi/abs/10.1063/1.341367), one should expect two broad modes, and an LO/TO splitting, I then would use the Lyddane-Sachs-Teller relation to estimate the ionic contribution using these two modes. What can I expect in terms of the mode analysis (how many modes will the code find)? The paper I am basing my study on as a starting point is (http://journals.aps.org/prb/abstract/10.1103/PhysRevB.73.054108) which suggests this is entirely possible.


Kindest regards,

Louis Fry,

PhD student, University of Leeds, IMP
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