Rotational dynamics and polymerization of C$_{60}$ in C$_{60}$-cubane crystals: A molecular dynamics study

TL;DR

This study uses molecular dynamics simulations to explore the rotational behavior of C60 fullerenes and the polymerization of C60-cubane crystals, revealing temperature-dependent dynamics and phase coexistence.

Contribution

It provides detailed insights into the intermolecular dynamics and polymerization mechanisms in C60-cubane crystals through classical and tight-binding simulations.

Findings

C60 fullerenes exhibit free, hindered, and diffusive rotational motions at different timescales.

Copolymerization occurs at higher temperatures, forming disordered structures.

Radial distribution and electronic density of states show coexistence of amorphous and crystalline phases.

Abstract

We report classical and tight-binding molecular dynamics simulations of the C$_{60}$ fullerene and cubane molecular crystal in order to investigate intermolecular dynamics and polymerization processes. Our results show that, for 200 K and 400 K, cubane molecules remain basically fixed, presenting only thermal vibrations, while C$_{60}$ fullerenes show rotational motions. Fullerenes perform "free" rotational motions at short times ($\lesssim$ 1 ps), small amplitude hindered rotational motions (librations) at intermediate times, and rotational diffusive dynamics at long times ($\gtrsim$ 10 ps). The mechanisms underlying these dynamics are presented. Random copolymerization among cubanes and fullerenes were observed when temperature is increased, leading to the formation of a disordered structure. Changes in the radial distribution function and electronic density of states indicate the coexistence of amorphous and crystalline phases. The different conformational phases that cubanes and fullerenes undergo during the copolymerization process are discussed.