  The current paper opens a series of papers that are aimed at the
determination of barriers that govern the covalent coupling between partners of
C60-based composites consisting of two or more fullerenes C60 (C60 dimer and
oligomers) (Part 1), C60 and single-walled carbon nanotube ([C60+(4,4)] carbon
nanobud) (Part 2), and C60 and graphene ([C60+(5,5)] and [C60+(9,8)] graphene
nanobuds) (Part 3). C60 dimers and oligomers are considered in the current
paper. The formation of composites is considered from the basic points related
to the regioselective chemical reactivity of the fullerene molecule atoms. The
dissonance between the predicted trimer and tetramer structures and
experimental observations is suggested to evidence the topological nature of
the C60 oligomerization. The barrier that governs the oligomer formation is
determined in terms of the coupling energy and is expanded over two
contributions that present the total energy of deformation of the composites'
components and the energy of covalent coupling . The computations were
performed by using the AM1 semiempirical version of unrestricted broken
symmetry Hartree-Fock approach.
