Andrzej Grzechnik et al 2007 J. Phys.: Condens. Matter 19 266219 doi:10.1088/0953-8984/19/26/266219
Crystal structure and stability of β-Na2ThF6 at non-ambient conditions
Andrzej Grzechnik1,5, Michael Fechtelkord2, Wolfgang Morgenroth3,4, Jose María Posse1 and Karen Friese1
Show affiliationsThe crystal structure and stability of β-Na2ThF6 at non-ambient conditions have been studied with calorimetric analysis, second harmonic generation measurements, and 19F and 23Na magic-angle spinning nuclear magnetic resonance (MAS NMR) spectroscopy, as well as synchrotron x-ray single-crystal and powder diffraction. The twinned structure (P321, Z = 1) is built of chains of capped trigonal prisms around the Th atoms formed along the c-axis through sharing of the basal faces. More distorted capped trigonal prisms around the Na atoms share their basal and equatorial faces with each other. The twin operation is a two-fold rotation around the c-axis. β-Na2ThF6 is stable in the temperature and pressure ranges of 100–954 K and 0.0001–6.4 GPa, respectively. The Na–F distances are more compressible than the Th–F distances. A hypothetical ferroelastoelectric and ferrobielastic 
phase transition is discussed.
- PACS
- Subjects
- Dates
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Issue 26 (4 July 2007)
Received 3 May 2007, in final form 28 May 2007
Published 15 June 2007
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Crystal structure and stability of β-Na2ThF6 at non-ambient conditions
Andrzej Grzechnik et al 2007 J. Phys.: Condens. Matter 19 266219
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