Probing atomic-scale interactions of Kr and Xe encapsulation in C60

Le résumé fourni par la source

The encapsulation of rare gases within carbon cages like C 60 holds significant importance in molecular engineering, particularly for nuclear waste treatment and gas separation technologies. By employing density functional theory (DFT), first-principles molecular dynamics (FPMD), and interaction region indicator (IRI) function, this study comprehensively explores the encapsulation mechanisms of krypton (Kr) and xenon (Xe) in C60 fullerene. Results reveal that Kr@C60 exhibits a Gibbs free energy of −1.3234 × 10 7 kJ·mol −1 , which is 119 % lower than that of Xe@C60 (−6.0387 × 10 6 kJ·mol −1 ). This difference is attributed to Kr's broader Van der Waals interaction and higher polarizability. Frontier-orbital analysis reveals almost identical HOMO–LUMO gaps (ΔE ≈ 2.738 eV), yet the quadrupole-type polarizability tensor of Kr induces smaller surface polarity index (12.88952 kJ·mol −1 for Xe@C60 vs. 12.91007 kJ·mol −1 for Kr@C60), translating into a 0.14 % expansion of the cage and a 6.74 % reduction in negative-surface variance. Consequently, Xe@C60 presents a smoother electrostatic landscape that minimizes desorption bottlenecks. FPMD trajectories collected over 5000 frames at 300 K reveal that both Kr and Xe atoms remain stably localized within the octahedral void at the center of the C60 crystal lattice, executing near-spherical excursions confined to 0.6 Å; notably, Kr exhibits a marginally slower and more strongly correlated motion than Xe. This work not only clarifies long-standing controversies regarding the encapsulation mechanisms of heavy rare gases but also establishes a framework for predicting fullerene adsorption properties, advancing the translation of molecular sciences into industrial-scale gas management.

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