Conventional and density-fitting local Møller–Plesset theory calculations of C60 and its endohedral H2@C60 and 2H2@C60 complexes

The geometries of C60 and the H2@C60 and 2H2@C60 complexes have been fully optimized at the density-fitting local second-order Møller–Plesset (DF-LMP2) level of theory and compared to their conventional MP2 counterparts. A slight elongation of the HH bond is found in H2@C60, which leads to a red shift of the HH vibrational frequency, relative to that of free H2, consistent with reported experimental data. The 2H2@C60 is characterized by a slight cage expansion and a blue CC vibrational frequency shift. The DF-LMP2/cc-pVTZ complexation energies are equal to −5.6 and +3.0 kcal/mol, for one and two encapsulated H2 molecules, respectively, and agree well with former theoretical estimates.