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High temperature powder diffraction and solid state DFT study of β‐cryolite (Na 3 AlF 6 )
Author(s) -
Smrčok Ľ.,
Kucharík M.,
Tovar M.,
Žižak I.
Publication year - 2009
Publication title -
crystal research and technology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.377
H-Index - 64
eISSN - 1521-4079
pISSN - 0232-1300
DOI - 10.1002/crat.200900141
Subject(s) - rietveld refinement , cryolite , crystallography , neutron diffraction , powder diffraction , chemistry , zigzag , polyhedron , diffraction , energy minimization , fluorine , crystal structure , computational chemistry , geometry , physics , aluminium , mathematics , organic chemistry , optics
Neutron and synchrotron powder diffraction data for β‐cryolite were collected within 550‐800(880) °C. Atomic coordinates of Al, F and Na atoms were obtained by both neutron Rietveld refinement and energy minimization in solid state at DFT level of theory. It was shown that although Rietveld refinements with fluorine atoms statically displaced from the 24 e to the 96 k special position of the Fm ‐3 m space group provide a reasonable fit to the experimental data, the refined structure differ from that obtained by the total energy minimization. The structure with the minimum of the total energy corresponds to the low temperature α‐phase with a zigzag arrangement of the polyhedra built around the Al and Na atoms. (© 2009 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)