title: Orientational Disorder of C60 in Li2CsC60.
abstract: The x-ray diffraction of the nonsuperconducting ternary fulleride Li(2)CsC(60) reveals at room temperature a face-centered-cubic (Fm3m) disordered structure that persists to a temperature of 13 Kelvin. The crystal structure is best modeled as containing quasispherical [radius of 3.556(4) angstroms] C(60)(3-) ions, in sharp contrast to their orientational state in superconducting face-centered-cubic K(3)C(60) (merohedral disorder) and primitive cubic Na(2)CsC(60) (orientational order). The orientational disorder of the carbon atoms on the C(60)(3-) sphere was analyzed with symmetry-adapted spherical-harmonic functions. Excess atomic density is evident in the <111> directions, indicating strong bonding Li(+)-C interactions, not encountered before in any of the superconducting alkali fullerides. The intercalate-carbon interactions and the orientational state of the fullerenes have evidently affected the superconducting pair-binding mechanism in this material.
authors.forename: I
authors.initials: I
authors.lastname: Hirosawa
authors.forename: K
authors.initials: K
authors.lastname: Prassides
authors.forename: J
authors.initials: J
authors.lastname: Mizuki
authors.forename: K
authors.initials: K
authors.lastname: Tanigaki
authors.forename: M
authors.initials: M
authors.lastname: Gevaert
authors.forename: A
authors.initials: A
authors.lastname: Lappas
authors.forename: J K
authors.initials: JK
authors.lastname: Cockcroft