THE STRUCTURE OF Yb (ND3)5.7
Résumé
Neutron powder diffraction was performed on five Yb(ND3)x samples prepared with x = 5.5, 5.7, 5.9 6.0 and 6.3. Two different low temperature (2 K) structures are observed ; one (i) mainly showing peaks of a bcc lattice with a0 = 9.076 Å but also weak sc peaks, the other (ii) presenting bcc peaks only with a0 = 9.111 Å. At 17 K the sc peaks in (i) vanish, which indicates the presence of an order- disorder phase transition. For the orientationally disordered structure (ii), Yb(ND3)5.7, showing more disorder at low temperature, a structure refinement with cubic harmonic functions is given.
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