Proton Quantum Effects on Electronic Excitation in Hydrogen-bonded Organic Solid: A First-Principles Green's Function Theory Study

TL;DR

This study uses first-principles Green's function theory combined with nuclear-electronic orbital methods to explore how proton quantum effects influence electronic excitations and exciton behavior in hydrogen-bonded organic solids, specifically eumelanin.

Contribution

It introduces a novel theoretical approach to examine proton quantum effects on excitons in hydrogen-bonded organic materials, addressing a gap in current modeling techniques.

Findings

Proton quantum effects significantly alter exciton properties.

Hydrogen bonds induce molecular-level anisotropy in excitons.

Proton quantization effects can be linked to structural features.

Abstract

Nuclear quantum effects of protons on electronic excitations in hydrogen-bonded organic materials remains underexplored. In theoretical studies, modeling excitons in these extended systems is particularly difficult because they tend to have a large exciton binding energy and sometimes exhibit charge transfer character. We demonstrate how first-principles Green's function theory combined with the nuclear-electronic orbital method enables us to examine the nature of excitons in a prototypical organic solid of eumelanin, for which the extensive hydrogen bonds have been proposed to facilitate the formation of delocalized excitons. We investigate how the quantization of protons impacts electronic excitations. We discuss the extent to which the resulting proton quantum effects can be described as being derived from structure and how they induce molecular-level anisotropy for the excitons in the organic solid.