Guest displacement in silicon clathrates
Résumé
We study both theoretically and experimentally the structure of the doped silicon clathrate II NaxSi34. We find that contrary to published works, the sodium atoms do not retain the Td symmetry inside the Si28 cages and move about 1 Å away from the center of the cage. This displacement, in conjunction with that of a sodium atom in an adjacent Si28 cage, leads to a “dimerization” of sodium atoms. As a consequence, Rietveld refinements of x-ray diffraction spectra and transport, vibrational, and electronic properties must be revisited.
Domaines
Matériaux
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