Crystal structure and electronic transport of Dy@C82 -: art. no. 115410

The crystal structure of Dy@C-82 isomer I at 298 K has been determined by Rietveld refinement for x-ray powder diffraction with synchrotron radiation. Isomer I shows a simple cubic structure (sc: Pa (3) over bar) with a lattice constant a of 15.78(1) Angstrom. The C-2 axis of a C-2v-C-82 cage aligns along the [111] direction of this crystal lattice. The C-82 cage is orientationally disordered to satisfy a (3) over bar symmetry along [111], which is requested in this space group. The large thermal parameter for the Dy atom estimated from the x-ray diffraction probably reflects a large disorder caused by a floating motion of the Dy atom inside the C-82 cage as well as a ratchet-type motion of the Dy@C-82 molecule. The electronic transport of thin film of Dy@C-82 shows a semiconducting behavior. The energy gap E-g is estimated to be 0.2 eV. Further, the variation of valence from Dy3+ to Dy2+ is found by metal doping into the Dy@C-82 crystals.