Abstract
Samples of Rb3C 60 (NH/D3) x and one of Li2·8C60(NH3)3·7 were prepared and examined by X-ray and neutron powder diffraction. A pattern of the lithium compound can be fitted to an Imm (a = 11·843(2) A) cell in which there are orientationally disordered C60 molecules and the lithium and ammonia are coordinated together and occupy the tetrahedral holes. However, some patterns from samples of different history and heat treatment show extra reflection peaks. They can be indexed as a Pm1 supercell of the Imm cubic cell. The Rb3C60(NH/D3) x patterns are more complex but can be indexed using two commensurate modulations. The relative amount in any one sample of these two commensurate modulations vary depending on method of preparation, annealing and sample ageing. The modulations are conceptually derived from a hypothetical Imm (a = 12·10 A) cell. However, the modulations are so large in amplitude that the observed intensities no longer resemble the pattern from a hypothetical Imm structure. Their position, inten...
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