Structure and physical properties of Cs3+alpha C60 (alpha=0.0-1.0) under ambient and high pressures

The intermediate phases Cs3+alphaC60 (alpha=0.0-1.0), have been prepared, and their structure and physical properties are studied by x-ray powder diffraction, Raman, ESR, electric conductivity, and ac susceptibility measurements under ambient and high pressures. The x-ray powder diffraction pattern of Cs3+alphaC60 (alpha=0.0-1.0) can be indexed as a mixture of the body-centered-orthorhombic (bco) and cubic (A15) phases. The A15 phase diminishes above 30 kbar. The broad ESR peak due to the conduction electron (c-ESR) is observed only for the phases around alpha=0.0 in Cs3+alphaC60. The resistivity of the Cs3+alphaC60 (alphanot equal0) sample follows the granular metal theory and/or Sheng model even in the sample exhibiting a broad ESR peak. No superconducting transition is observed up to 10.6 kbar in Cs3+alphaC60 (alphanot equal0). These results present that bco phase of Cs3+alphaC60 (alpha=0) is a final candidate for a pressure-induced superconductor.</p

Structural and electronic properties of Ce@C_<82>

X-ray diffraction patterns for a solid sample of Ce@C_ that contains a mixture of two isomers, I and II, can be indexed in a face-centered cubic lattice with a lattice constant of 15.88(5)Å, while x-ray diffraction patterns for Ce@C_ isomer I alone indicate a simple cubic lattice with a lattice constant of 15.78(1) Å. Rietveld refinement for the x-ray diffraction pattern of the latter, Ce@C_ isomer I, has been carried out with a space group of Pa3^- . Thin films of Ce@C_ were first prepared by thermal deposition under ~10^ Torr. The Raman spectra for these thin films show a peak ascribable to a Ce-C_ cage-stretching mode at ~160 cm^, implying that the valence of Ce in this structure is ＋3. This valence of ＋3 is supported by Ce L_III-edge XANES for a thin film of Ce@C_ . Furthermore, the local structure around the Ce ion could be determined by Ce L_III-edge EXAFS for a thin-film. Transport properties of a thin film of Ce@C_ have been studied by a four-probe method, and these demonstrate a semiconducting behavior with a small gap of 0.4 eV