Rotational dynamics and polymerization of C-60 in C-60-cubane crystals: A molecular dynamics study

摘要

We report classical and tight-binding molecular dynamics simulations of the C-60 fullerene and cubane molecular crystal in order to investigate the intermolecular dynamics and polymerization processes. Our results show that, for 200 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 (less than or similar to 1 ps), small amplitude hindered rotational motions (librations) at intermediate times, and rotational diffusive dynamics at long times (greater than or similar to 10 ps). The mechanisms underlying these dynamics are presented. Random copolymerizations 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.