The antiferromagnetic structures of KFeS2, RbFeS2, KFeSe2, and RbFeSe2 and the correlation between magnetic moments and crystal field calculations

Validation of Interstitial Iron and Consequences of Nonstoichiometry in Mackinawite (Fe1+xS)

“…Therefore, this structure can tolerate additional valence electrons without disrupting the two most significant orbital interactions. It is interesting that naturally occurring samples of the mineral mackinawite are known to contain small 33 All Fe atoms are nearly tetrahedrally coordinated by S atoms, so the 3d orbitals are separated into e-type and t 2 -type, based on the local coordinate system. Also, although the xz and yz orbitals in KFeS 2 are not strictly degenerate, they are illustrated as such for clarity.…”

“…The contour plot suggests three possible interstitial locations with (I) tetrahedral, (II) square pyramidal, and (III) trigonal planar sulfur coordination ( Figures 1 and 4). Position I sits at (1/ 33 reported a range of Fe−S distances in the ternary sulfides, AFeS 2 (A = K, Rb), to be 2.231−2.246 Å. Although the oxidation state of Fe in these compounds is 3+, they are rare examples of Fe atoms tetrahedrally coordinated by sulfide ligands.…”

Cs[FeSe2], Cs3[FeSe2]2, and Cs7[Fe4Se8]: Missing Links of Known Chalcogenido Ferrate Series

“…The general compound series A 1+x [Fe Figure 1): While oxido compounds of this type exhibit cristobalite-like networks of corner-sharing [FeO 4 ] tetrahedra, [20][21][22] the respective sulfido and selenido ferrates, which are observed for the whole alkali element series from Na (S) and K (Se) to Cs [5][6][7][8][9][4][5][6][7][8][9]23] contain linear chains of edge-sharing tetrahedra; tellurido ferrates(III) of this composition are unknown. The recently prepared first chain ferrates(II), Na 2 [FeS 2 ] and Na 2 [FeSe 2 ] [13,14] (x = 1, compound 5 in Figure 1), round out the series.…”

“…The latter Na salts crystallize in the K 2 [ZnO 2 ]-type structure and also contain linear tetrahedra chains. In-between (0.33 Յ x Յ 0.75), numerous mixed-valent sulfido and selenido ferrates with buckled chains of edge-sharing tetrahedra are reported: This encompasses the long-known salts A 3 [FeQ 2 ] 2 with an equiatomic Fe II /Fe III ratio (x = 0.5, compounds 6 and 7 in Figure 1), [10][11][12]24,25] the recently prepared compounds Rb 4 [FeS 2 ] 3 (x = 0.33) and K 7 [FeS 2 ] 4 (x = 0.75) and the two isotypic potassium and rubidium ferrates A 7 [FeS 2 ] 5 (x = 0.4). [4,26] In the structures of all mixed-valent S/Se chain compounds, the buckling of the chains is evidently controlled by the local coordination of the changing number of alkali cations with different sizes, but not by a charge ordering.…”

“…[1][2][3][4] The compounds with a Q:Fe ratio of 2:1 belong to two different classes: The large series of Fe III and Fe II/III mixed-valent chain ferrates exhibit hexagonal rod packings of linear or slightly buckled infinite chains of edge-sharing tetrahedra 1 ϱ [FeQ 4/2 ] n-. [5][6][7][8][9][10][11][12][4][5][6][7][8][9][10][11][12][13][14] The second class are salts containing cubane-type clusters . For numbers referring the structure type cf.…”