Crystal structure of the Fe-member of usovite

Crystals of the title compound, with the idealized composition Ba(2)CaFeAl(2)F(14), dibarium calcium iron(II) dialuminium tetra­deca­fluoride, were obtained serendipitously by reacting a mixture of the binary fluorides BaF(2), CaF(2) and AlF(3) in a leaky steel reactor. The compound crystallizes in the usovite structure type (Ba(2)CaMgAl(2)F(14)), with Fe(2+) cations replacing the Mg(2+) cations. The principal building units are distorted [CaF(8)] square-anti­prisms (point group symmetry 2), [FeF(6)] octa­hedra (point group symmetry -1) and [AlF(6)] octa­hedra that are condensed into undulating (2) (∞)[CaFeAl(2)F(14)](4−) layers parallel (100). The Ba(2+) 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 Ba(2)Ca(1.310 (15))Fe(0.690 (15))Al(2)F(14) [model (I)] and Ba(2)CaFe(0.90 (1))Al(2)F(14) [model (II)].