Programme

L.9.2 -- Lecture, ANSWCCMS-2023

Date: Thursday, 9 November 2023

Time: 14:15 - 15:15

Using Density Functional Theory to Construct Tight-Binding-Based Modeling

Muhammad Aziz Majidi

Universitas Indonesia

In condensed-matter physics theoretical research, one may be interested in modeling a particular solid material using a few realistic bands and incorporating some interaction terms in the model Hamiltonian. Density Functional Theory (DFT) may provide realistic, non-interacting band structures. However, we may need to limit the number of bands around the Fermi energy for our modeling purpose while keeping the band dispersions "exact". For this purpose, we can calculate the Wannier functions that we can later use as the bases to obtain the effective site-representation Hamiltonian matrix elements. These site-representation Hamiltonian matrix elements can then be used as a set of parameters to construct a tight-binding (TB) model Hamiltonian in k-representation. We may then use the TB model as the unperturbed Hamiltonian term, to which we may add some interaction terms to extend the model for specific purposes. In these two lectures, I will briefly review the DFT and the TB modeling concept using Wannier functions of selected atomic orbitals as the basis set. I will also demonstrate how we can perform the DFT calculations utilizing a software package such as Quantum Espresso and how we can extract the site-representation Hamiltonian matrix elements, i.e., the TB parameters, using a software package called Wannier.90. Further, I will show how to construct an interacting model based on the TB Hamiltonian with some interaction terms and the calculation of some dynamical physical quantities such as density of states (DOS) and optical responses using an algorithm employing Green function technique.

Presenter: Muhammad Aziz Majidi