Crystal structure of the Fe-member of usovite

Acta Crystallographica Section E: Crystallographic Communications

Weil, M.¹ 

[1] Institute for Chemical Technologies and Analytics, Division of Structural Chemistry, Vienna University of Technology, Getreidemarkt 9/164-SC, A-1060 Vienna, Austria

关键词: CRYSTAL STRUCTURE;    USOVITE;    FE-CONTAINING USOVITE;    DISORDER;    FLUORIDES;   

DOI  :  10.1107/S2056989015009251

学科分类：数学（综合）

来源: International Union of Crystallography

【 摘 要 】

Crystals of the title compound, with the idealized composition Ba2CaFeAl2F14, dibarium calcium iron(II) dialuminium tetra­deca­fluoride, were obtained serendipitously by reacting a mixture of the binary fluorides BaF2, CaF2 and AlF3 in a leaky steel reactor. The compound crystallizes in the usovite structure type (Ba2CaMgAl2F14), with Fe2+ cations replacing the Mg2+ cations. The principal building units are distorted [CaF8] square-anti­prisms (point group symmetry 2), [FeF6] octa­hedra (point group symmetry -1) and [AlF6] octa­hedra that are condensed into undulating 2∞[CaFeAl2F14]4− layers parallel (100). The Ba2+ cations separate the layers and exhibit a coordination number of 12. Two crystal structure models with a different treatment of the disordered Fe site [mixed Fe/Ca occupation, model (I), versus underoccupation of Fe, model (II)], are discussed, leading to different refined formulae Ba2Ca1.310 (15)Fe0.690 (15)Al2F14 [model (I)] and Ba2CaFe0.90 (1)Al2F14 [model (II)].

【 授权许可】

CC BY