Coarse-grained electrostatic interactions of coronene: Towards the crystalline phase

TL;DR

This study compares two coarse-grained models for electrostatic interactions in coronene molecules, assessing their ability to reproduce experimental crystalline phase properties through molecular dynamics simulations.

Contribution

The paper introduces and evaluates two electrostatic modeling approaches for coronene, enhancing coarse-grained simulations of aromatic molecular crystals.

Findings

The ring-charge distribution model aligns well with experimental data.

The quadrupole-based model shows limitations at large distances.

Both models help understand the crystalline phase formation.

Abstract

In this article we present and compare two different, coarse-grained approaches to model electrostatic interactions of disc-shaped aromatic molecules, specifically coronene. Our study builds on previous work [J. Chem. Phys. 141, 214110 (2014)] where we proposed, based on a systematic coarse-graining procedure starting from the atomistic level, an anisotropic effective (Gay-Berne-like) potential capable of describing van-der-Waals contributions to the interaction energy. To take into account electrostatics, we introduce, first, a linear quadrupole moment along the symmetry axis of the coronene disc. The second approach takes into account the fact that the partial charges within the molecules are distributed in a ring-like fashion. We then reparametrize the effective Gay-Berne-like potential such that it matches, at short distances, the ring-ring potential. To investigate the validity of these two approaches, we perform many-particle Molecular Dynamics (MD) simulations, focusing on the crystalline phase (karpatite) where electrostatic interaction effects are expected to be particularly relevant for the formation of tilted stacked columns. Specifically, we investigate various structural parameters as well as the melting transition. We find that the second approach yields consistent results with those from experiments despite the fact that the underlying potential decays with the wrong distance dependence at large molecule separations. Our strategy can be transferred to a broader class of molecules, such as benzene or hexabenzocoronene.