Problem with imaginary modes and anharmonic contribution

[chandan.singh]

Hi everyone

I am doing el-ph coupling calculation for Bi-based layered material using EPW. In phonon-dispersion, there are four imaginary frequencies around M point (pi,pi,0) that is related to charge density wave instability of material. For these modes, I am getting high el-ph coupling.

My questions are

1. How to calculate el-ph coupling without taking imaginary phonon contribution?

2. Is it possible to calculate el-ph interaction using frozen phonon method in EPW?

3. How to calculate the anharmonic contribution to el-ph coupling in EPW?


Thank you all
Chandan .

[sponce]

Dear Chandan,

1) This is the default behaviour or EPW. Modes with negative phonons will be neglected.

2) Not really. At least not without hacking the code

3) You will need to hack the code to do that. Not implemented by default.

Best,
Samuel