Issue with Imaginary Dielectric Function (BSE Calculation) for 4x4 MoS₂

[shishir1]

I am encountering an issue with obtaining the desired optical absorption spectrum (imaginary part of the dielectric function) from my BSE calculation for a 4x4 MoS₂ system. Despite the standard procedures, the output does not match expected results.

Details:
System: 4x4 monolayer MoS₂
Calculations performed: SCF, EXACT, GW then BSE
Fermi energy:
1. SCF E-fermi : -0.7494
2. Exact : E-fermi : -0.7499
3. GW : E-fermi : 0.0264
4. BSE : E-fermi : 1.2681

Files attached: INCAR, POSCAR, KPOINTS, OUTCAR, vasprun.xml and Graph for Im(ε) for GW and BSE.

Problem:
The obtained Im(ε) spectrum does not exhibit the expected graph for BSE calculation.

[fabien_tran1]

Hi,

What are the expected results? Are you referring to other published theoretical results? Have you checked the convergence of the results with respect to the parameters, like the number of bands or number of k-points?

[shishir1]

Here I have attached the Graph for Imag. part of Dielectric function (parallel and perpendicular components).

[fabien_tran1]

These are the spectra that you have already sent in your first post. Formulated differently, my first question is: What is wrong with your results? Are you trying to reproduce some published results?

[shishir1]

My concern is, in the parallel component of Imag part of dielectric function, the amplitude for the BSE is very less as compared to GW, Is there anything wrong I did with the calculations ?