BSE solvers overview
Work in progress (please come back after 04/04/2021)
This tutorial explores the options available in Yambo for the numerical solution of the Bethe-Salpeter equation. Before running this tutorial, you should have carried out the tutorial Calculating optical spectra including excitonic effects: a step-by-step guide. We will use the same example system (bulk hBN). The various options correspond to different numerical methods for solving (large) eigenvalue problems. The numerical methods are not covered in this tutorial and the interested user is directed to the references.
After completion of this tutorial, you are expected to recognize which solver to use depending on the system, computational load and desired output. Also, for each of the solver, you should be able to choose the values for the key input parameters.
Three main solvers are available in Yambo:
Full diagonalization solver
diagonalization of the full Hamiltonian using the standard LAPACK library (diagonalization solver) you should've already carry out the Bethe-Salpeter solver: diagonalization
Lanczos-Haydock solver
subspace iterative Lanczos algorithm which by-pass diagonalization with the Haydock approach[1] (Lanczos-Haydock solver) follow the link to Bethe-Salpeter solver: Lanczos-Haydock then return to this tutorial
SLEPc solver
(3) subspace iterative which provide the eigensolutions about a user-input-energy using the external SLEPc library[2] (SLEPC solver) follow the link to Bethe-Salpeter solver: SLEPC then return to this tutorial