THE STRUCTURE OF Yb (ND₃)_5.7

Abstract

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Ammonia rotations in ytterbiumhexaammine

“…The combination of the structural 12 and dynamical results of the ytterbium-hexaammine leads to a consistent description of the dynamical processes of the ammonia.…”

“…Yb͑ND 3 ͒ 6 had been reported to show frozen-in orientational disorder of the ammonia down to 4 K. 3,4 More recent experiments with samples of different composition, Yb͑ND 3 ͒ x with xϭ5.5, 5.7, 5.9, 6.0, and 6.3, revealed a more complicated behavior. 12 At temperatures above 45 K in all samples a space group Im3m with a lattice constant a 0 Ϸ9.1 Å and orientational disorder were found. In one sample, Yb͑ND 3 ͒ 5.7 , this disorder phase was conserved at low temperatures Tϭ2 K, while all other samples exhibited a transition to a more ordered structure between Tϭ30 and 40 K. No obvious relation could be established between ammonia content and the lattice constant ͑e.g., ⌬xϳ⌬a 0 ͒.…”

“…A distance s ϭ3.16 Å between ytterbium ion and proton is taken from the structure analysis. 12,13 The result of the fit to the data at Tϭ35 K can hardly be distinguished from the continuous line ͑model I͒ in Fig. 4.…”