EPW Forum

Dear All,

could you explain how in the EPW program to determine the type of phonon mode, which is given by the parameter ν, represented in the simulation results by an integer value. For example, in Tutorial Tue. 5, March 19-23, 2018, "Electron-phonon coupling using Quantum Espresso," in Exercise 2, on page 9, for SiC material it is stated that the value of parameter ν = 6 corresponds to LO mode (I assume this is a longitudinal optical mode, that is, it is an optical mode along the x coordinate). And how to determine the type of mode at other values of parameter ν from 1 to 5. In other words, what values of parameter ν correspond to phonon modes like TO, ZO, LA, TA, ZA. And how to determine phonon mode type for more complex structures, when value of this parameter, for example, varies in simulation results from 1 to 12.
Thanks in advance for the answer.

Best regards,

Mishchenkа Valery

Associate Professor, BSUIR

Hi Prof. Valery,

To determine the type of mode, we need to examine the phonon vibration properties (patterns) with respect to q near the Γ point. EPW does not sort these modes with respect to the mu index.

You can visualize the vibration patters (you can see the displacements given in your .dyn1 file in the phonon calculation) of each phonon mode at Γ point using VESTA (or any other) visualization program OR you can use an online tool https://interactivephonon.materialscloud.io/.

I think. this reference is helpful too; https://doi.org/10.1088/2515-7639/ab2b7c

Happy EPWing,
Hari

Dear Hari,

thank you for responding to the letter, which contains useful and valuable information for me.


Best regards,

Valery