Optical to UV spectra and birefringence of SiO$_2$ and TiO$_2$: First-principles calculations with excitonic effects

TL;DR

This paper introduces a first-principles computational method to accurately predict optical and UV spectra, including excitonic effects, for materials like SiO2 and TiO2, aiding understanding of their optical properties.

Contribution

It combines Bethe-Salpeter equation calculations with density-functional theory to model optical spectra and birefringence in materials, demonstrating its effectiveness on SiO2 and TiO2 phases.

Findings

Accurate optical spectra including excitonic effects are achieved.

Birefringence in TiO2 is effectively interpreted.

Method validated with bulk Si calculations.

Abstract

A first principles approach is presented for calculations of optical -- ultraviolet (UV) spectra including excitonic effects. The approach is based on Bethe-Salpeter equation calculations using the \textsc{NBSE} code combined with ground-state density-functional theory calculations from the electronic structure code \textsc{ABINIT}. Test calculations for bulk Si are presented, and the approach is illustrated with calculations of the optical spectra and birefringence of $\alpha$-phase SiO$_2$ and the rutile and anatase phases of TiO$_2$. An interpretation of the strong birefringence in TiO$_2$ is presented.