Cerium iron sulfide, Ce₃Fe_1.94S₇

Tricerium(III) diiron(II,III) hepta­sulfide, Ce₃Fe_1.94S₇, crystallizes in the polar hexagonal space group P6₃ and adopts the Ce₆Al_3.33S₁₄ structure type. The Fe atoms occupy both tetrahedral and octahedral sites. Isolated FeS₄ tetrahedra, all pointing in the same direction, are stacked along the threefold rotation axes. Chains of face-sharing FeS₆ octahedra propagate along the 6₃ axis. Vacancies resulting from the partial oxidation of Fe²⁺ to Fe³⁺ occur exclusively in the octahedral Fe sites. The Ce atoms are coordinated by [7+1] S atoms, which form bicapped trigonal prisms.