Encapsulation of Hydrogen Molecules in C50 Fullerene: An ab Initio Study of Structural, Energetic, and Electronic Properties of H2@C50 and 2H2@C50 Complexes

Various DFT functionals, including those containing long-range interactions and dispersion, together with HF and MP2 theoretical methods, were used to identify the number of H 2 molecules that can be encapsulated inside a C 50 cage. It is demonstrated that the 2H 2 @C 50 complex is thermodynamically unstable based on its positive complexation energy. Some discrepancies, however, were found with respect to the stability of the H 2 @C 50 complex. Indeed, SVWN5, PBEPBE, MP2, B2PLYP, and B2PLYPD calculations confirmed that the H 2 @C 50 complex is thermodynamically stable, while HF, BP86, B3LYP, BHandHLYP, LC-wPBE, CAM-B3LYP, and wB97XD showed that this complex is thermodynamically unstable. Nevertheless, examination of strain and dispersion energies further supported the fact that one H 2 molecule can indeed be encapsulated inside the C 50 cage. Other factors, such as the host-guest interactions and bond dissociation energy, were analyzed and discussed.