Neutron diffraction study of the polymeric structure of

Abstract

High-resolution neutron powder diffraction is used to authenticate that the fulleride undergoes on cooling an incomplete structural phase transition from a primitive cubic to a monoclinic phase (space group , lattice constants at 2.5 K: a = 13.707(2) Å, b = 14.466(2) Å, c = 9.366(1) Å, ). Very short interfullerene C-C contacts are identified, providing evidence for the presence of bridging bonds whose distances refine to Å. The C-C bonds are inclined to the c axis by and lie within the bc plane. The stability of the ground state polymeric structure and the kinetics of the monomer polymer transformation are influenced by the charge state of the fulleride ions, the steric crowding associated with the dopant alkali ions and the relative orientational state adopted by neighbouring fullerides in the precursor monomer phase.