Titre du document / Document title

The crystal structure of synthetic simmonsite, Na₂LiAlF₆

Auteur(s) / Author(s)

ROSS Kirk C. ⁽¹⁾ ; MITCHELL Roger H. ⁽¹⁾ ; CHAKHMOURADIAN Anton R. ⁽²⁾ ;

Affiliation(s) du ou des auteurs / Author(s) Affiliation(s)

⁽¹⁾ Department of Geology, Lakehead University, 955 Oliver Road, Thunder Bay, Ont., P7B 5E1, CANADA
⁽²⁾ Department of Geological Sciences, University of Manitoba, Winnipeg, Man., R3T 2N2, CANADA

Résumé / Abstract

The structure of the synthetic fluoroperovskite, Na₂LiAlF₆ (simmonsite), has been determined by powder X-ray diffraction using the Rietveld method of structure refinement. The compound adopts space group P2₁/n [#14; a = 5.2842(1); b = 5.3698(1); c = 7.5063(2) Å; β = 89.98(1)°; Z = 4), and is a member of the cryolite (Na₂NaAlF₆) structural group characterized by ordering of the B-site cations (Li, Al) and tilting of the BF₆ octahedra according to the tilt scheme a^-b^-c⁺. Rotations of the B-site polyhedra are less (Φ_Li = 14.9°; Φ_Al = 17.0°) than those found in cryolite (Φ_Na = 18.6; Φ_Al = 23.5°) because of the larger difference in the ionic radii of the B-site cations in cryolite as compared to those in simmonsite. Na at the A-site is displaced from the special position resulting in 10- and 8-fold coordination in simmonsite and cryolite, respectively. By analogy with the synthetic compound, naturally occurring simmonsite is considered to adopt space group P2_1/n (#14) and not the P2₁(#4) or P2_1/m(#11) space groups.

Revue / Journal Title

Journal of solid state chemistry   ISSN 0022-4596   CODEN JSSCBI 

Source / Source

2003, vol. 172, n^o1, pp. 95-101 [7 page(s) (article)] (20 ref.)

Langue / Language

Anglais

Editeur / Publisher

Elsevier, San Diego, CA, ETATS-UNIS  (1969) (Revue)

Mots-clés anglais / English Keywords

Inorganic compounds ; Aluminium fluorides ; Lithium fluorides ; Sodium fluorides ; Perovskites ; Synthetic mineral ; Crystal structure ; XRD ; Experimental study ;

Mots-clés français / French Keywords

Composé minéral ; Al F Li Na ; Na2LiAlF6 ; Simmonsite ; Aluminium fluorure ; Lithium fluorure ; Sodium fluorure ; Perovskites ; Minéral synthétique ; Structure cristalline ; Diffraction RX ; Etude expérimentale ;

Mots-clés espagnols / Spanish Keywords

Mineral sintético ;

Mots-clés d'auteur / Author Keywords

Perovskite ; Cryolite ; Simmonsite ; Rietveld refinement ;

Localisation / Location

INIST-CNRS, Cote INIST : 14677, 35400011833465.0150