A relativistic DFT study on the structure and property of M(M = Ba, Sr) @ C74 (D3h)

The interaction between M (M = Ba, Sr) and C74 (D3h) was investigated by the relativistic DFT. With the representative patch of C74 (D3h), all the possible isomers, transition states, and energy barriers were studied. Optimized structures show that there are three equivalent isomers, with Ba or Sr located about 1.7 Å off-center. According to the minimum energy pathway, the possible movement trajectory of Ba or Sr in the C74 (D3h) cage was predicted. The energy barriers for Ba and Sr hopping from one stable site to another are 8.30 and 7.88 kcal mol−1, respectively. According to the trajectory, the NMR spectra of M@C74 (M = Ba, Sr) was predicted. When the Ba or Sr was encapsulated into the C74 cage, the symmetry of M@C74 (M = Ba, Sr) changes from D3h to C2v, and the blue shift of the Raman vibrational mode within 100–200 cm−1 of M@C74 was found.