Issue 6, 2000
From the journal:

Journal of Materials Chemistry

Kosmas Prassides,*a   Craig M. Brown,ab   Serena Margadonna,a   Konstantinos Kordatos,a   Katsumi Tanigaki,c   Emmanuelle Suard,b   A. José Dianouxb  and  Kenneth D. Knudsend  

* Corresponding authors

a School of Chemistry, Physics and Environmental Science, University of Sussex, Brighton, UK

b Institute Laue-Langevin, Grenoble, France

c Faculty of Science, Osaka-city University, PREST, JST, 3-3-138 Sugimoto, Sumiyoshi-ku, Osaka, Japan

d European Synchrotron Radiation Facility, Grenoble, France

Abstract

Neutron and synchrotron X-ray powder diffraction and inelastic neutron scattering (INS) studies of Na2RbC60 in both its polymeric and monomeric phases have been performed as a function of temperature, with particular attention paid to the cooling protocol. The powder diffraction measurements on cooling confirm the slow transformation of the primitive cubic high temperature phase to the monoclinic low temperature phase in the vicinity of 250 K. Rietveld refinements of both the X-ray and neutron data show that over half of the sample transforms to the polymer in the temperature range 180–200 K, this fraction rising to 64(2)% at base temperature. On heating, the percentage of the monomer phase increased from 230 K at the expense of the polymer, with a full transformation occurring by 277 K. A final phase transition to the disordered fcc structure occurs over a range of temperatures from 299 to 317 K. Study of the time evolution of the monomer → polymer transformation at 180 and 200 K allowed us to extract an estimate of the activation barrier to interball C–C bond formation as 0.16(2) eV, comparable to the magnitude of the reorientational potential in the precursor monomer phase. INS spectra in the temperature range 100 to 320 K confirm the reduction of symmetry from the primitive cubic phase through splittings of the intramolecular vibrational modes. The polymeric nature of interfullerene bonding in Na2RbC60 is also confirmed via direct observation of excess scattered intensity in the 8–25 meV region of the generalised phonon density-of-states (GDOS).

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Article information

DOI
https://doi.org/10.1039/B000418I
Article type
Paper
Submitted
14 Jan 2000
Accepted
07 Mar 2000
First published
11 May 2000

J. Mater. Chem., 2000,10, 1443-1449

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Powder diffraction and inelastic neutron scattering studies of the Na2RbC60 fulleride

K. Prassides, C. M. Brown, S. Margadonna, K. Kordatos, K. Tanigaki, E. Suard, A. J. Dianoux and K. D. Knudsen, J. Mater. Chem., 2000, 10, 1443 DOI: 10.1039/B000418I

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