Calculating optical spectra including excitonic effects: a step-by-step guide
This tutorial guides you through the workflow of a calculation of the optical spectrum of a given material by solving the Bethe-Salpeter equation. Specifically we will use bulk h-BN as an example.
Before starting, you need to obtain the tarballs for hBN. See instructions on the main tutorials page.
The target quantity in a Bethe-Salpeter calculation is the macroscopic dielectric matrix εM. The following quantities/steps are needed to obtain εM:
The optical absorption spectrum corresponds to ImεM(ω). Following this scheme we go through the flow of a calculation:
Step 1: Static screening
Use the SAVE folders that are already provided. For the CECAM tutorial, do:
$ cd YAMBO_TUTORIALS/hBN/YAMBO/BSE_KickOff/
Follow the Static screening module and then return to this tutorial
Step 2: Bethe-Salpeter kernel
Follow the module on Bethe-Salpeter kernel and return to this tutorial
Step 3: Bethe-Salpeter solver
This is the final step in which you finally obtained the spectra. Mathematically this implies to solve a large eigenvalue problem. Two main solvers are available in yambo
(1) diagonalization of the full Hamiltonian (diagonalization solver)
- R. Haydock, in Solid State Phys., 35 215 (1980) edited by H. Ehrenfest, F. Seitz, and D. Turnbull, Academic Press