Polymeric fullerene chains in RbC60 and KC60

We present a detailed study of the structure of the polymer phase of AC60 (A=K, Rb) using data obtained from high-resolution neutron powder diffraction. We are able to obtain stable Rietveld refinements of both structures with no constraints on any carbon atom. KC60 has lattice parameters a=9.952 Å, b=9.091 Å, c=14.372 Å in space group Pnmn and RbC60 has a=10.125 Å, b=9.086 Å, c=14.207 Å and β=90.316° in space group I12/m1. We notice significant distortion throughout the ball from its original icosahedral symmetry. Coordinates of the atoms will allow more accurate theoretical calculation of the physical properties of these fullerides and might shed light on the differences among the cations and the dimensionality of their electronic properties.