Development of a ReaxFF potential for lanthanum-based endohedral metallofullerenes and molecular dynamics simulations of their formation mechanism

In this study, we develop a reactive force field (ReaxFF) for CLa interactions to investigate the formation mechanism of lanthanum-based endohedral metallofullerenes (La-EMFs). Geometric structures, charge distributions, bond energies, bond angle energies, and torsion angle energies of representative La-EMFs are obtained by density functional theory (DFT) calculations and are served as the foundation for force field training and validation. The obtained ReaxFF_CLa force field accurately reproduces DFT results. Utilizing this force field, we investigate the effects of carbon-to‑lanthanum (C:La) atomic ratio, temperature, and helium gas on the formation of La-EMFs. Key findings include: (1) Optimal conditions for forming La-EMFs are a C:La ratio of 12.5:1 and a temperature of 2600 K; (2) He gas promotes cage formation and suppresses cage expansion. This study reveals the underlying mechanism of lanthanide encapsulation, and identifies optimized conditions valuable for developing efficient synthesis strategies.