Redetermination of the lanthanum iron sulfide La₅₂Fe₁₂S₉₀

Abstract

A redetermination of the structure of`La 32.66 Fe 11 S 60 ' in the trigonal space group R3m led to the new formula La 52 Fe 12 S 90 and to a rede®nition of the structure type. In the structure, the Fe 2+ cations occur in Fe 2 S 9 dimers of face-sharing octahedra (with 3m symmetry). The dimers are linked by face-and vertex-sharing bi-and tricapped LaS 6 trigonal prisms (with m symmetry) to form a three-dimensional network containing two types of cuboctahedral cavities. The larger cavities remain empty, while the smaller ones accommodate alternative sites for disordered La 3+ cations. CommentIn a search for materials with interesting magnetic properties, we have begun a reinvestigation of the R±Fe±S system (R = rare earth metal). With the larger rare-earth metals, phases of three different compositions are formed, viz. R 2 Fe 2À S 5 (R = La, Ce and Pr), R 3 Fe 2À S 7 (R = La, Ce, Pr and Nd) and R 52 Fe 12 S 90 (R = La, Ce, Pr and Nd) (Collin et al.

Ternary Erbium Chromium Sulfides: Structural Relationships and Magnetic Properties

“…In contrast, two different coordination environments may be identified for the rareearth cations. Er (1) 13 With the exception of S (11) and S(12), the structure exhibits pseudosymmetry, and therefore similarity restraints were applied to the anisotropic thermal parameters during the least-squares refinements. 17 However, application of Platon/Addsym 27,28 in order to identify missing symmetry elements indicates that there is an additional mirror plane, and that the structure is more correctly described in the centrosymmetric space group Cmcm.…”

Ce53Fe12S90X3 (X = Cl, Br, I): The First Rare-Earth Transition-Metal Sulfide Halides

“…Structure Determination. Analysis of the products by powder X-ray diffraction on a Siemens D5000 diffractometer revealed that the major phases, Ce 53 Fe 12 S 90 Cl 3 , Ce 53 Fe 12 S 90 Br 3 , and Ce 53 Fe 12 S 90 I 3 , adopt a structure related to the La 52 Fe 12 S 90 type. , While the Ce 53 Fe 12 S 90 I 3 sample was essentially phase pure (to the detection limits), the other samples contained varying amounts of Ce 10 S 14 O and FeS . The cell parameters of the three Ce 53 Fe 12 S 90 X 3 phases, refined by least-squares methods from their powder patterns indexed in R 3̄ m , using the program UNITCELL , are plotted in Figure .…”

“…No additional reflection conditions were observed. The centrosymmetric space group R 3̄ m was therefore chosen on the basis of the close relationship between the structures of Ce 53 Fe 12 S 90 X 3 and La 52 Fe 12 S 90 1 Crystallographic Data for Ce 53 Fe 12 S 90 X 3 (X = Cl, Br, I) formulaCe 53 Fe 12 S 90 Cl 3 Ce 53 Fe 12 S 90 Br 3 Ce 53 Fe 12 S 90 I 3 fw 11 088.31 11 221.69 11 362.66 space group R 3̄ m (No.…”

“…We have recently undertaken a reinvestigation of the ternary R − Fe−S system (R = rare-earth metal), with the goal of developing structure−property relationships for these mixed-metal compounds. Within this system, phases with compositions R 2 Fe 2 - δ S 5 (R = La, Ce, Pr), R 3 Fe 2 - δ S 7 (R = La, Ce, Pr, Nd; also formerly referred to as R 4 FeS 7 ), and R 52 Fe 12 S 90 (R = La, Ce, Pr, Nd; also formerly referred to as R 2 FeS 4 or R 32.66 Fe 11 S 60 ) have been reported for the larger rare-earth metals. − All possess crystal structures featuring FeS n polyhedra that are either isolated or condensed into dimers or chains. − These low-dimensional units are interconnected by trivalent rare-earth cations, allowing for complex magnetic coupling interactions involving the iron 3d n and rare-earth 4f n moments. However, the magnetic properties of the compounds containing nonmagnetic La III ions have been the most thoroughly studied to date. − Our main interest lies in the phase-pure preparation and structural and magnetic characterization of the latter (magnetic-moment-bearing) rare-earth analogues.…”

“…The crystal structure of “La 32.66 Fe 11 S 60 ” was then determined in the nonstandard monoclinic space group Bm , but it was later noted that trigonal symmetry had been overlooked . We recently redetermined the structure in R 3̄ m and suggested the new formula La 52 Fe 12 S 90 . In the structure, which is related to the prevalent Mn 5 Si 3 structure type, Fe 2 S 9 dimers and large cuboctahedral cavities alternate along the 3̄ axes.…”