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要旨:
The band structure of Ba5C60 has been studied by a crystal orbital (CO) approach of the intermediate neglect of differential overlap (INDO) type. Two crystal structures have been considered: (i) a f.c.c. one as realized in Ca5C60 and (ii) a structure derived from the b.c.c. arrangement of Ba6C60 with one Ba site unoccupied. It is demonstrated that the solid state electronic structure of the alkaline-earth-doped fulleride depends on details of the crystal structure. The f.c.c. arrangement shows a quasi-degeneracy between a metallic and a Mott-like configuration, while a finite band gap is realized in the b.c.c.-like arrangement. The Ba atoms transfer slightly more than one electron to the C60 soccerball. The metal-C60 hybridization thus is rather strong.
