MOMENTUM DENSITY OF KXC60. G. Loupias, Ch. Bellin, M. Marangolo, J. Moscovici, S. Erwin, S. Rabii, C. Hérold, J.F. Marêché, P. Lagrange. Université Pierre et Marie Curie (Paris 6), 4, place Jussieu 75252 Paris Cedex 05.
Compton scattering measurements have been demonstrated to provide an accurate check of valence electron densities of solids, in the electronic ground-state. Since the scattering is incoherent, this technique, which is a bulk probe, is insensitive to crystal defects.
Compton profiles, i.e. energy-loss spectra of scattered photons were measured on powder samples, using 16keV monochromatic beam provided by the french synchrotron facility. All the KxC60 samples (x=3,4, and 6) were intercalated by C. Hérold et al. and kept under vacuum. For comparison, C60 powder was measured in same experimental conditions. Average calculated Compton profiles are simulated by S. Rabii from the ab initio and all-electron SCF energy band structure calculatied by S. Erwin within the local-density approximation (LDA).
In order to describe the electronic structures, differences between KxC60 and C60 measured Compton profiles are compared with theoretical profile differences. Since Compton scattering is particularly sensitive to the hybridization between carbon and alkali orbitals as it was demonstrated in the case of graphite intercalation compounds, the distorsion of C60 molecule is discussed as a function of x. In addition, "charge transfer" between the intercalate and the C60 molecules as well as magnitude of e--e- correlations (essential to understand the superconductivity) are studied in this set of materials.
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