(Non)Resonance Bonds in Molecular Dynamics Simulations: A Case Study concerning C60 Fullerenes

TL;DR

This paper studies how different bond types in C60 fullerenes affect their structural and electronic properties through molecular dynamics simulations.

Contribution

The study introduces a novel approach to analyzing resonance and non-resonance bonds in C60 fullerene polymorphs using specific simulation metrics.

Findings

Mixed bonds in C60 fullerenes significantly alter bond length entropy and vibrational stiffness.

Asymmetric bond redistribution affects electrostatic potential and dipole moment distributions.

Resonance bonds lead to distinct structural and energetic behaviors compared to integer bonds.

Abstract

In the case of certain chemical compounds, especially organic ones, electrons can be delocalized between different atoms within the molecule. These resulting bonds, known as resonance bonds, pose a challenge not only in theoretical descriptions of the studied system but also present difficulties in simulating such systems using molecular dynamics methods. In computer simulations of such systems, it is often common practice to use fractional bonds as an averaged value across equivalent structures, known as a resonance hybrid. This paper presents the results of the analysis of five forms of C60 fullerene polymorphs: one with all bonds being resonance, three with all bonds being integer (singles and doubles in different configurations), one with the majority of bonds being integer (singles and doubles), and ten bonds (within two opposite pentagons) valued at one and a half. The analysis involved the Shannon entropy value for bond length distributions and the eigenfrequency of intrinsic vibrations (first vibrational mode), reflecting the stiffness of the entire structure. The maps of the electrostatic potential distribution around the investigated structures are presented and the dipole moment was estimated. Introducing asymmetry in bond redistribution by incorporating mixed bonds (integer and partial), in contrast to variants with equivalent bonds, resulted in a significant change in the examined observables.

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