SP(3) HYBRIDIZED CARBONS ON BUCKMINSTERFULLERENE

Structural and electronic properties of buckminsterfullerene, C-60, and some of its Diels-Alder adducts, are briefly reviewed. The band structure of a novel fullerene polymer, found in Rb-C-60 and K-C-60 recently by Pekker et al. (Solid State Commun., 90 (1994) 349), is discussed. The hybridization on usual carbons of C-60 is analyzed by a simple procedure for constructing hybrids from minimal basis set atomic orbitals. It is found that the s-characters of the quasi-pi orbitals directed to the normal vectors on the C-60 Sphere are small. The three a hybrids can be specified as sp(2.5) orbitals on average, but they are rather different from each other, reflecting the nonequivalence of ''single'' and ''double'' C-C bonds in fullerenes. The so called sp(3) carbons in the Diels-Alder adducts and in the fullerene polymer are better described by sp(4.1) and sp(3.5) hybridizations, respectively.