Excited state properties of point defects in semiconductors and insulators investigated with time-dependent density functional theory

TL;DR

This paper develops an efficient hybrid TDDFT method for calculating excited state properties of large solid-state systems, emphasizing the importance of structural relaxations in defect-related optical properties.

Contribution

It introduces a spin-conserving and spin-flip hybrid TDDFT formulation with analytical forces, enabling large-scale excited state calculations in solids.

Findings

Accurate excited state energies for point defects in semiconductors and insulators.

Structural relaxations significantly influence optical absorption and emission.

Implementation on GPU and CPU accelerates large-scale computations.

Abstract

We present a formulation of spin-conserving and spin-flip, hybrid time-dependent density functional theory (TDDFT), including the calculation of analytical forces, which allows for efficient calculations of excited state properties of solid-state systems with hundreds to thousands of atoms. We discuss an implementation on both GPU and CPU based architectures, along with several acceleration techniques. We then apply our formulation to the study of several point defects in semiconductors and insulators, specifically the negatively charged nitrogen-vacancy and neutral silicon-vacancy centers in diamond, the neutral divacancy center in 4H silicon carbide, and the neutral oxygen-vacancy center in magnesium oxide. Our results highlight the importance of taking into account structural relaxations in excited states, in order to interpret and predict optical absorption and emission mechanisms in spin-defects.