Angle-resolved effective potentials for disk-shaped molecules

TL;DR

This paper develops a method to derive angle-resolved effective pair potentials for uniaxial, disk-shaped molecules like coronene, capturing temperature and angle dependencies to improve coarse-grained simulations.

Contribution

It introduces a novel approach combining umbrella sampling and steered dynamics to derive angle-resolved potentials, emphasizing their importance for accurate modeling of crystal and fluid states.

Findings

Angle-resolved potentials are crucial for accurate crystal structure modeling.

Temperature and angle dependencies significantly affect the effective potentials.

The developed potentials improve the representation of many-body and thermodynamic properties.

Abstract

We present an approach for calculating coarse-grained angle-resolved effective pair potentials for uniaxial molecules. For integrating out the intramolecular degrees of freedom we apply umbrella sampling and steered dynamics techniques in atomistically-resolved molecular dynamics (MD) computer simulations. Throughout this study we focus on disk-like molecules such as coronene. To develop the methods we focus on integrating out the van-der-Waals and intramolecular interactions, while electrostatic charge contributions are neglected. The resulting coarse-grained pair potential reveals a strong temperature and angle dependence. In the next step we fit the numerical data with various Gay-Berne-like potentials to be used in more efficient simulations on larger scales. The quality of the resulting coarse-grained results is evaluated by comparing their pair and many-body structure as well as some thermodynamic quantities self-consistently to the outcome of atomistic MD simulations of many-particle systems. We find that angle-resolved potentials are essential not only to accurately describe crystal structures but also for fluid systems where simple isotropic potentials start to fail already for low to moderate packing fractions. Further, in describing these states it is crucial to take into account the pronounced temperature dependence arising in selected pair configurations due to bending fluctuations.