A meta-generalized gradient approximation-based time-dependent and dielectric function dependent method for optical properties of solid materials

TL;DR

This paper introduces a new computational method combining metaGGA functionals and a dielectric function model to accurately and efficiently predict optical properties like absorption spectra and exciton characteristics in solid materials.

Contribution

The paper presents a novel metaGGA-based time-dependent and dielectric function dependent approach for calculating optical properties of solids, improving accuracy and efficiency over existing methods.

Findings

Qualitative agreement of absorption spectra with experiments.

Accurate exciton binding energies, often better than GW-BSE.

Nanosecond-scale intrinsic exciton lifetimes predicted.

Abstract

Accurate and efficient calculation of optical response properties of solid materials is still challenging. We present a meta-generalized gradient approximation (metaGGA) density functional based time-dependent and dielectric function dependent method for calculating optical absorption, exciton binding energy and intrinsic exciton lifetime for bulk solids and two-dimensional (2D) monolayer materials. This method uses advanced metaGGA functionals to describe the band structures, and a dielectric function mBSE (model Bethe-Salpeter equation) to capture the screening effect accurately and efficiently and the interaction between electrons and holes. The calculated optical absorption spectra of bulk Si, diamond, SiC, MgO, and monolayer MoS2 qualitatively agree with experimental results. The exciton binding energies of the first prominent peak in the optical absorption spectra of the direct band gap solids Ar, NaCl and MgO from mBSE qualitatively agree with those from standard GW-BSE. For monolayer MoS2, mBSE predicts quantitatively accurate binding energy for the first prominent peak, better than GW-BSE does. The calculated intrinsic exciton lifetimes for materials considered here show magnitudes of several nanoseconds for most bright excitons. The presented mtaGGA-mBSE method is established as a computationally efficient alternative for optical properties of materials with an overall qualitative accuracy.