New Zr₆MTe₂ (M = Mn, Fe, Co, Ni, Ru, Pt), Zr₆Fe_0.6Se_2.4, and Zr₆Fe_0.57S_2.43 Intermetallics:  Structural Links between Binary (Zr,Hf)₃M Alloys and Porous Metal-Rich Tellurides

Abstract

The synthesis of the group IV ternary chalcogenides Zr(6)MTe(2) (M = Mn, Fe, Co, Ni, Ru, Pt) and Zr(6)Fe(1)(-)(x)()Q(2+)(x)() (Q = S, Se) is reported, as are the single-crystal structures of Zr(6)FeTe(2), Zr(6)Fe(0.6)Se(2.4), and Zr(6)Fe(0.57)S(2.43). The structure of Zr(6)FeTe(2) was refined in the hexagonal space group P&sixmacr;2m (No. 189, Z = 1) with lattice parameters a = 7.7515(5) Å and c = 3.6262(6) Å, and the structures of Zr(6)Fe(0.6)Se(2.4) and Zr(6)Fe(0.57)S(2.43) were refined in the orthorhombic space group Pnnm (No. 58, Z = 4) with lattice parameters a = 12.737(2) Å, b = 15.780(2) Å, and c = 3.5809(6) Å and a = 12.519(4) Å, b = 15.436(2) Å, and c = 3.4966(6) Å, respectively. The cell parameters of Mn-, Co-, Ni-, Ru-, and Pt-containing tellurides were also determined. The Zr(6)ZTe(2) compounds are isostructural with Zr(6)CoAl(2), while Zr(6)Fe(1)(-)(x)()Q(2+)(x)() (Q = S, Se) were found to adopt a variant of the Ta(2)P-type structure. Chains of condensed M-centered, tetrakaidecahedra of zirconium constitute the basic structural unit in all these compounds. The modes of cross-linking that give rise to the Zr(6)FeTe(2) and Zr(6)Fe(1)(-)(x)()Q(2+)(x)() structures, differences among the title compounds, and the influence of chalcogen size differences are discussed. The stoichiometric nature of Zr(6)FeTe(2) and its contrast with sulfur and selenium congeners apparently result from a Te-Fe size mismatch. The importance of stabilization of both Zr(6)FeSe(2) and Zr(6)FeTe(2) compounds by polar intermetallic Zr-Fe bonding is underscored by a bonding analysis derived from electronic band structure calculations.

Structural analysis of Gd6FeBi2 from single-crystal X-ray diffraction methods and electronic structure calculations

“…A different variant of the the same crystallographic arrangement (Pearson code hP9, Wyckoff sequence g f d a) is known in the community as the ZrNiAl structure. Earlier studies on the tellurides Zr 6 T Te 2 suggest that such a structure is stabilized by the size mismatch between the late transition metals and main-group elements, and the strong bonding between early and late transition metals (Wang & Hughbanks, 1996).…”

New Ternary Lanthanide Transition-Metal Tellurides: Dy6MTe2, M=Fe, Co, Ni

“…The stability can usually be attributed to strong bonding between the interstitial, often a late transition metal, and a surrounding host metal from an early metal group, a circumstance that is another reminder of some early ideas of Brewer (1). Among the many reduced chalcogenides of the early transition metals that demonstrate these heterometal features are Ta M S (2, 3), Ta M Se (4), Ta MSe (5), Nb MS (6), Hf MTe (7), all with some combination of M"Fe, Co, Ni, Zr MTe (M"Mn, Fe, Co, Ni, Ru, Pt) (8), Hf MTe (9) (M"Mn}Fe), Nb Ni \V S >V (6), Ta MTe (M"Cr, Fe}Ni, Al, Si) (10,11), Sc Ni Te (12), Y M Te (M"Fe}Ni) (13), and Sc MTe (14) (M"Mn}Ni). Many of these phases also have a common structural motif, have tricapped trigonal prismatic clusters of the more active metal that share basal faces, and are centered by the late transition metal.…”

Tunable Magnetic Exchange between Rare-Earth Metal 5d and Iron 3d States: A Case Study of the Multiple Magnetic Transitions in Gd6FeBi2 and the Solid Solutions Dy6–xGdxFeBi2 (1 ≤ x ≤ 5) with Curie Temperatures in the Range 120–350 K

“…According to earlier reports on the isostructural tellurides Zr 6 T Te 2 , the “″6-1-2” structure is stabilized by the strong bonding between Zr and the transition metal T . By analogy, strong interactions between RE and T should also be expected in the isotypic RE 6 TX 2 .…”