Electrodynamic Response and Stability of Molecular Crystals

TL;DR

This paper demonstrates that electrodynamic dipolar interactions significantly influence the stability and dielectric properties of molecular crystals, emphasizing the importance of non-local response effects in accurate modeling.

Contribution

It introduces an accurate treatment of non-local electrodynamic response in density functional theory calculations for molecular crystals, improving agreement with experimental data.

Findings

Electrodynamic interactions are crucial for crystal stability.

Non-local response modeling aligns theoretical and experimental dielectric constants.

Cohesive properties are affected by collective response effects.

Abstract

We show that electrodynamic dipolar interactions, responsible for long-range fluctuations in matter, play a significant role in the stability of molecular crystals. Density functional theory calculations with van der Waals interactions determined from a semilocal "atom-in-a-molecule" model result in a large overestimation of the dielectric constants and sublimation enthalpies for polyacene crystals from naphthalene to pentacene, whereas an accurate treatment of non-local electrodynamic response leads to an agreement with the measured values for both quantities. Our findings suggest that collective response effects play a substantial role not only for optical excitations, but also for cohesive properties of non-covalently bound molecular crystals.