The hopping interaction energy between C60 clusters as a function of their relative orientation is studied with a tight-binding model derived from an ab initio calculation. Different structures are compared, and factors determining the cluster orientation and the lattice are discussed both without and with doping. Comparison with experiment suggests that chemical bonding (hopping) is important for the cluster orientation and the cohesive energy.
 

Physical Review Letters, 67 3002-5, 1991.