The equilibrium sites of alkali cations in light alkali-doped C-60

By the analysis of limitations of the model proposed by Goze et al. the equ ilibrium sites of alkali cations in Na2RbC60 have been investigated using t he potential model consisting of short-range interatomic (ionic) potentials and long-range Coulomb interaction. It is shown that the cations in the oc tahedral coordination shift away from the center of the octahedral sites, w hile those in the tetrahedral coordination remain in the central positions. The result also shows the octahedral sites, as well as the tetrahedral sit es, are not all equivalent and can Le divided into two distinct sets in ori entationally ordered phase.