Hole Localization in Molecular Crystals From Hybrid Density Functional Theory

TL;DR

This paper introduces a computational approach using hybrid density functional theory to accurately model hole trapping and polaron formation in organic molecular crystals, aligning well with experimental ionization potentials.

Contribution

It presents a novel scheme for tuning exchange in hybrid DFT to eliminate self-interaction errors in modeling hole localization in molecular crystals.

Findings

Accurate ionization potentials for localized and delocalized holes

Self-trapped molecular polarons form in perfect crystals

Method validated against experimental data

Abstract

We use first-principles computational methods to examine hole trapping in organic molecular crystals. We present a computational scheme based on the tuning of the fraction of exact exchange in hybrid density functional theory to eliminate the many-electron self-interaction error. With small organic molecules, we show that this scheme gives accurate descriptions of ionization and dimer dissociation. We demonstrate that the excess hole in perfect molecular crystals form self-trapped molecular polarons. The predicted absolute ionization potentials of both localized and delocalized holes are consistent with experimental values.