Symmetry of the electronic and geometric structures of metallofullerene M@C74 (M = Be, Mg, Ca, Sr, and Ba) in terms of vibronic coupling

Motion of the encapsulated metal in M@C74 (M = Be, Mg, Ca, Sr, and Ba) is studied in terms of vibronic coupling using group theory approach. The selection rule for the symmetry of metal motion is presented. This agrees well with experimental findings for Ca@C74. The metal motion can be regarded as a pseudo-Jahn–Teller effect. The electronic structures and adiabatic potential surfaces of M@C74 are calculated using the tight-binding approximation.