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Figure 5
Thermal vibrational ellipsoids in cryolite at T = 880 K and T = 890 K, i.e. below and above the phase transition, respectively, as reported by Yang et al. (1993BB88). Colour code: Al is blue, Na1 and Na2 are red and yellow, and F is grey. At T = 890 K in the high temperature phase, neither the atomic positions nor the vibrational octahedra suggest static tilting.

IUCrJ
Volume 10| Part 3| May 2023| Pages 309-320
ISSN: 2052-2525
https://doi.org/10.1107/S2052252523002208