Phasendiagramm des quasibinären Systems NiCr2S4–NiGa2S4, Kristallstruktur des NiGa2S4

Phase Relationship of the Quasibinary System NiCr₂S₄? ;NiGa₂S₄, Crystal Structure of NiGa₂S₄ The quaternary system NiCr_2–2xGa_2xS₄ was studied with the help of X-ray powder Guinier photographs of quenched samples. The crystal structure of ternary NiGa₂S₄, not found formerly, was determined using single crystal data. The structure (trigonal space group P3 m1, Z = 1, a = 362.49(2), c = 1199.56(5) pm) consists of hexagonal close-packed sulfur with Ni and Ga in one fourth of the octahedral and tetrahedral holes, respectively (FeGa₂S₄ type). The S? ;S distance of the S? ;Ni? ;S layered units is unusually small, vic. 321.1 pm. The infrared spectrum of NiGa₂S₄ and a group theoretical treatment of the FeGa₂S₄ type lattice modes are given. Up to 20 mol % Ga of the layered NiGa₂S₄ can be substituted by Cr whereby Ni is possibly transfered from octahedral to tetrahedral sites. The phase width of monoclinic Cr₃S₄ type NiCr₂S₄ is very small possibly due to the metal-metal interaction in this NiAs defect structure. In the range 0.18 ? x ? 0.35 quaternary spinel type mixed crystals are formed.     

Zur Kenntnis der Phasen A2−2xSn5+xCl12 (A = K,In)

On the A_2?2xSn_5+xCl₁₂ (A = K, In) Phases The refinement of the structure of A_2-2xSn_5+xCl₁₂ compounds (A = K⁺, In⁺) with single crystal data is reported. They crystallize with the Th₇S₁₂ type arrangement (a = 1192(2) pm, c = 428.9(8) pm (K-compound); a = 1189.8(6) pm, c = 431.2(3) pm (In-compound)) for which we propose the space group P6 . The possibility of meroedric twinning is discussed. Due to the composition of these compounds the structure is necessarily disordered and this leads to a wide range of homogeneity which can be influenced by the size and the polarity of the A type cation.     

IrIn7GeO8 = [IrIn6](GeO4)(InO4) und Verbindungen der Mischkristallreihe [IrIn6](Ge1+xIn1−4x/3O8) (0 ≤ x ≤ 0.75) – erste Oxide mit [IrIn6]‐Oktaedern

IrIn₇GeO₈ = [IrIn₆](GeO₄)(InO₄) and Compounds of the Solid Solution Series [IrIn₆](Ge_1+xIn_1?4x/3O₈) (0 ≤ x ≤ 0.75): First Oxides containing [IrIn₆] Octahedra The low valent indiumoxides IrIn₇GeO₈ = [IrIn₆](GeO₄)(InO₄) and [IrIn₆](Ge_1+xIn_1?4x/3O₈) (0 x ≤ 0.75) are formed by heating intimate mixtures of Ir, In, In₂O₃ and GeO₂ in corundum crucibles under an atmosphere of argon (1420 K, 70 h). The compounds are black and semiconducting. X‐ray powder diffraction patterns can be indexed on the basis of a face centered cubic unit cell with lattice parameters ranging from a = 1012.3(1) pm (x = 0) to a = 1007.3(1) pm (x = 0.75). Characteristic building units in [IrIn₆](Ge_1+xIn_1?4x/3O₈) are isolated [IrIn₆]⁹⁺ octahedra with short Ir‐In distances of 253.5 pm, which are linked via [GeO₄]^4? and [InO₄]^5? tetrahedra to a three dimensional framework. Starting from IrIn₇GeO₈ = [IrIn₆](GeO₄)(InO₄), the isoelectronic substitution of 4 In³⁺ ions by 3 Ge⁴⁺ ions and one Ge‐vacancy leads to the formation of a solid solution series [IrIn₆](GeO₄)_1+x(O₄)_x/3(InO₄)_1?4x/3, which shows a slight decrease in the cubic lattice parameter with increasing x. According to Rietveld refinements the structure of [IrIn₆](GeO₄)(InO₄) exhibits a statistical distribution of the tetrahedrally coordinated Ge and In atoms ( , R(prof.) = 4.4 %, R(int.) = 2.5 %). The crystal and electronic structures of [IrIn₆](GeO₄)(InO₄) are discussed on the basis of first principles electronic structure calculations.     

Zur Kenntnis des quaternären Systems Zn?In?S?Se Der Schnitt ZnIn2S4?Znln2Se4?In2S3?In2Se3

The Quaternary System ZnIn₂S₄? ZnIn₂Se₄? In₂Se₃? In₂S₃ The title system has been investigated on the indium rich side (ratio In/Zn ≥ 2) on samples quenched from 800°C to room temperature using x-ray methods. In this section 7 different phases could be identified the phase borders of which are given. ZnIn₂S₄-type and thiogallate type mixed crystals only show a small region of homogeneity while the monophase region of spinel type mixed crystals in the indiumsulfide rich part of the phase diagram has a larger extension. There is a new trigonal compound ZnIn₂S₂Se₂ (a_hex = 3.937, c_hex = 31.97 Å) with a large region of homogeneity. In the indiumselenide rich part there are two new phases: (i) Zn_0.4In₂Se_3.4 with unknown structure and (ii) a ternary phase of unknown structure in the system In₂S_3?xSe_x for 2.1 ≤ x ≤ 2.7.     

Kationenverteilung und Überstrukturordnung in ternären und quaternären Sulfidspinellen MIIMS4 – Einkristallstrukturuntersuchungen

Cation Distribution and Superstructure Ordering in Ternary and Quaternary Sulfide Spinels M^IIM₂^III S₄ – Single Crystal Structure Determinations The crystal structures of spinel type MIn₂S₄ (M ? Mn, Co, Ni), MCr_2?2xIn_2xS₄ (M ? Mn, Ni), and Cd_0.52Co_0,48Cr₂S₄ were reinvestigated by X-ray methods using single crystals grown by vapour phase transport technique. The indium sulfides possess a partially inverse distribution of the metal ions on the tetrahedral (8a) and octahedral sites (16d) of the structure. The degrees of inversion λ are 0.34 (MnIn₂S₄, a = 1072.0(1) pm, structural parameter u = 0.25726(2)), 0.84 (CoIn₂S₄, a = 1058.1(1) pm, u = 0.26921(5)) und 0.93 (NiIn₂S₄ a = 1050.5(1), u = 0.26040(3)). In the case of the chromium indium sulfide solid solutions, the degrees of inversion (and the structural parameters) increase (and decrease) linearly with increase in indium content x. ψ-scans of reflections not allowed in the space group Fd3 m do not prove simultaneous diffraction. Refinement of the structure of MnIn₂S₄ in space group F4 3m results in a partial superstructure ordering of Mn and In on the tetrahedral sites, 4a Mn_0.83In_0.17, 4c Mn_0.49In_0.51. In the case of Cd_0.52Co_0.48Cr₂S₄, superstructure ordering is like Cd_0.41Co_0.59 and Cd_0.62Co_0.38, respectively.     

BiGaIn2S6 – Synthese,Struktur und Eigenschaften

BiGaIn₂S₆ – Synthesis, Structure, and Properties The novel compound BiGaIn₂S₆ was obtained in the quaternary system Bi–Ga–In–S. BiGaIn₂S₆ forms red transparent platelets and exhibits a range of homogeneity between BiGa₁In₂S₆ and BiGa_0.8In_2.2S₆. The compound is a semiconductor with E_g(opt.) = 1.9 eV. – BiGaIn₂S₆ crystallizes monoclinically forming a new structure type (a = 1112.0 pm, b = 380.6 pm, c = 1228.0 pm, β = 116.30°, Z = 2, space group P2₁/m, no. 11). The S atoms form strongly corrugated 2 D fragments of the (hc)₂ sphere packing type. The In atoms occupy octahedral holes (d(In–S) = 262 pm) and the Ga atoms tetrahedral holes (d(Ga–S) = 234 pm) inside the 2 D-layers. The Bi atoms on the top of trigonal BiS₃ pyramids (d(Bi–S) = 265 pm) are at the periphery of the layers and have four additional S ligands from the neigbouring layer at much larger distances (d(Bi–S) = 319 pm). – The bonding of a Bi^III sulfide is analyzed for the first time by the Electron Localization Function (ELF).     

Structure and magnetic properties of RE2CuIn3 (RE=Ce, Pr, Nd, Sm and Gd)

The ternary copper indides RE₂CuIn₃≡RECu_0.5In_1.5 (RE=Ce, Pr, Nd, Sm and Gd) were synthesized from the elements in sealed tantalum tubes in an induction furnace. They crystallize with the CaIn₂-type structure, space group P6₃/mmc, with a statistical occupancy of copper and indium on the tetrahedral substructure. These indides show homogeneity ranges RECu_xIn_2−x. Single crystal structure refinements were performed for five crystals: CeCu_0.66In_1.34 (a=479.90(7) pm, c=768.12(15) pm), PrCu_0.52In_1.48 (a=480.23(7) pm, c=759.23(15) pm), NdCu_0.53In_1.47 (a=477.51(7) pm, c=756.37(15) pm), SmCu_0.46In_1.54 (a=475.31(7) pm, c=744.77(15) pm), and GdCu_0.33In_1.67 (a=474.19(7), c=737.67(15) pm). Temperature-dependent susceptibility measurements show antiferromagnetic ordering at T_N=4.7 K for Pr₂CuIn₃ and Nd₂CuIn₃ and 15 K for Sm₂CuIn₃. Fitting of the susceptibility data of the samarium compound revealed an energy gap ΔE=39.7(7) K between the ground and the first excited levels.     

Über die Decamethylferroceniumpolyiodide [(Me5C5)2Fe]Ix mit x = 3, 5 und 6,5. Darstellung und strukturelle Charakterisierung eines Triiodids (DMFc)I3, eines Pentaiodids (DMFc)I5 und eines Hexacosaiodids (DMFc)4I26

Studies on Polyhalides. 30 On Decamethylferriciniumpolyiodides [(Me₅C₅)₂Fe]I_x with x = 3, 5, 6.5: Preparation and Crystal Structures of a Triiodide (DMFc)I₃, a Pentaiodide (DMFc)I₅ and a Hexacosaiodide (DMFc)₄I₂₆ Decamethylferrocene (DMFc) may be oxidized by iodine analogous to ferrocene (Fc) to the decamethylferrocenium ion (DMFc)⁺ and precipitated as the crystalline solids decamethylferrocenium triiodide (DMFc)I₃, decamethylferrocenium pentaiodide (DMFc)I₅ and tetracisdecamethylferrocenium hexacosaiodide (DMFc)₄I₂₆. The two compounds with higher iodine content are new. These are characterized by X-ray diffraction methods on single crystals. The structures are built up from complex cations of expected geometry and isolated or remarkably connected polyiodide ions. Decamethylferrocenium triiodide C₂₀H₃₀FeI₃ crystallizes monoclinically in C2/m with a = 1489.9(4) pm, b = 1133.0(2) pm, c = 765.9(3) pm, β = 111.76(3)° and Z = 2. The crystal structure follows the CsCl-type and contains isolated triiodide ions of the linear symmetric form. Decamethylferrocenium pentaiodide C₂₀H₃₀FeI₅ crystallizes monoclinically in P2₁/c with a = 1130.0(2) pm, b = 1442.6(1) pm, c = 1716.6(2) pm, β = 96.62(1)° and Z = 4. The crystal structure may be deduced from the primitiv quadratic bundle of alternating cationic and anionic rods. It contains exceptionally isolated somewhat opened out pentaiodide ions. Tetrakisdecamethylferrocenium hexacosaiodide (C₂₀H₃₀Fe)₄I₂₆ crystallises monoclinically in P2₁/n with a = 1331.3(8) pm, b = 1319.4(4) pm, c = 3564(2) pm, β = 90.84(5)° and Z = 2. The crystal structure of this compound with unusual composition may be described as an inclusion compound with channels for the cations. The outstanding anionic grating may be derived from the primitive cubic lattice of iodide ions with iodine bridges on all edges by removing systematically 1/12 of the iodine molecules.     

Half Antiperovskites VI: On the Substitution Effects in Shandites InxSn2–xCo3S2

In the shandite type solid solution In_xSn_2–xCo₃S₂ the transition from half metal ferromagnetic Sn₂Co₃S₂ to the new thermoelectric InSnCo₃S₂ is related to A = In, Sn on different crystallographic sites. Effects and origin of crystal and electronic structure changes induced by A = In are now investigated within the solid solution 0 ≤ x ≤ 2 including In₂Co₃S₂. Effects are studied from X‐ray data, ¹¹⁹Sn Mößbauer spectroscopy, and ab initio calculations. Their origin is explored by DFT modeling on site preference of In and Sn in a supercell, electric field gradients (EFG), spin polarization, band structures, and direct space analyses (ELF, AIM). Indium is found to cause the crystal structure distortion on one A site, the electronic structure distortion to the other, as a consequence of inverted anisotropic bonding.     

Untersuchungen an Polyhalogeniden. XXVI [1]. Über N-Propylurotropiniumpolyiodide UrPrIx mit x = 5 und 7: Strukturelle Charakterisierung eines Pentaiodids und eines Heptaiodids

Studies on Polyhalides. 26. On N-Propylurotropinium Polyiodides UrPrI_x with x = 5 and 7: Crystal Structures of a Pentaiodide and a Heptaiodide The salts UrPrI_x with x = 5 and 7 are formed by the reaction of N-propylurotropinium iodide UrPrI with excess iodine I₂ at room temperature from aqueous solution. N-propylurotropinium pentaiodide C₉H₁₉N₄I₅ crystallizes monoclinically in P2₁/n with a = 1007.6(3) pm, b = 1362.5(3) pm, c = 2899.0(9) pm, β = 91.49(3)º and Z = 8. The crystal structure is built up from parallel chains of cations UrPr⁺ and pairs of V-shaped pentaiodide anions I₅^? along [0 1 0]. N-propylurotropinium heptaiodide C₉H₁₉N₄I₇ crystallizes triclinically in P1 with a = 970.4(1) pm, b = 971.1(1) pm, c = 1357.8(2) pm, α = 106.83(1)º, β = 92.28(1)º, γ = 105.17(1)º and Z = 2. The crystal structure is stacked by alternating cationic and anionic double layers along [0 0 1]. The heptaiodide layer shows a two-dimensional network.     

Die Pentatelluride M2Te5 (M = Al,Ga, In): Polymorphie,Strukturbeziehungen und Homogenitätsbereiche

The Pentatellurides M₂Te₅ (M = Al, Ga, In): Polymorphism, Structural Relations, and Homogeneity Ranges The hitherto unknown crystal structure of the black solid Al₂Te₅ is solved by Rietveld refinement of X-Ray powder data: a = 1359.29(3) pm, b = 415.27(1) pm, c = 983.92(2) pm, β = 126.97(1)°, space group: C2/m (no. 12), Z = 2. In contrast to Ga₂Te₅ and In₂Te₅Al₂Te₅ is very sensitive to hydrolysis. It can formally be described as Te[AlTe_3/3Te_1/1]₂, containing layers made up of chains of cis-edge-sharing AlTe₄ tetrahedra [AlTe_3/3Te_1/1] and additional Te atoms. In₂Te₅-I and In₂Te₅-II are characterized by layers with a similar topology, Ga₂Te₅ however is different. It has no layer structure, but contains chains of trans-edge-sharing GaTe₄-tetrahedra and additional Te-atoms according to the formulation Te[GaTe_4/2]₂. It can be regarded as a variant of the TlSe type structure. From heterogeneous samples with the nominal composition In_0.5Ga_1.5Te₅ single crystals of a new stacking variant (In₂Te₅-III) of the In₂Te₅ structure type can be isolated. The composition of the crystals, determined by single crystal structure analysis, is In_0.77Ga_1.23Te₅, with a = 1613.2(3) pm, b = 424.6(1) pm, c = 1330.5(2) pm, β = 97.39(1)°, space group C2/c (Nr. 15), Z = 4. This structure type is not yet known for unsubstituted In₂Te₅. The range of homogeneity for Ga₂Te₅ with respect to the substitution of Gallium by Indium is given by Ga_2-xIn_xTe₅ (x < 0.4). Within the limits of experimental error however a substitution of Te in Ga₂Te₅ by Se cannot be detected.     

Exploring the Cu‐In‐S System under Solvothermal Conditions near the Composition CuIn5S8

Solvothermal syntheses of copper‐indium‐sulfides performed with different Cu:In:S ratios afforded crystallization of nanocrystalline Cu‐In‐S phases with compositions close to CuInS₂, CuIn₃S₅, and CuIn₇S₁₁. Each sample shows a different and distinguishable morphology. The minority component CuInS₂ with wurtzite‐type structure crystallizes as thin plates, which are preferably stacked parallel to black stacks. The component with composition CuIn₃S₅ forms isolated few nm thin layers being arranged like the petals of a flower growing from a common point. Finally, red CuIn₇S₁₁ is obtained as nanobelts with individual diameters of about 20 nm and lengths up to more than 1 μm. According to electron diffraction patterns and X‐ray diffractometry the structures of CuIn₃S₅ and CuIn₇S₁₁ cannot be assigned to known bulk phases of the Cu‐In‐S system, however first structure models are proposed.     

Zur Kenntnis des quasi-binären Systems InCl?SnCl2 und eine Anmerkung zum System KCl?SnCl2

On the Quasi-binary System InCl? SnCl₂ and a Remark on the System KCl? SnCl₂ We report the phase diagrams of the quasi-binary systems InCl/SnCl₂ and KCl/SnCl₂ derived from DTA and X-ray investigations. In both systems we find a nonstoichiometric phase having the formula A_2?2xSn_5+xC₁₂ (with 0 ? x ? 0.15 for A = In and 0 ? x ? 0.14 for A ? K), a peritectic ASn₂Cl₅ compound and a dystectic 1:1 phase. The nonstoichiometric phases are both isotypic with Th₇S₁₂. KSn₂Cl₅ crystallizes with a tetragonal NH₄Pb₂Br₅-type structure (sp. gr. 14/mcm; a = 803.55(3), c = 1387.5(5) pm) and InSn₂Cl₅ with a monoclinic NH₄Pb₂Cl₅-type arrangement (sp. gr. P2₁/c; a = 891.7(3), b = 800.2(3), c = 1251.0(4) pm, β = 89.55(5)°). The lattice constants for InSnCl₃ (a = 1680(3), b = 799.2(9), c = 845.4(10) pm, β = 90.8(1)°) were derived by indexing the X-ray powder diagram. In addition the InCl? SnCl₂ system contains a peritectic In₄SnCl₆ phase (sp. gr. Pmma; a = 1270(2), b = 2515(3), c = 1456 (1) pm, (single crystal data)) and a dystectic In₉SnCl₁₁ compound (tetragonal primitive; a = 864.6(2), c = 1219.3(6) pm (derived from indexed powder data)).     

Syntheses and structures of novel complex Yb(II) fluorides: YbBeF4, YbAlF5 and LiYbAlF6

Light green powder samples and single crystals of YbBeF₄, YbAlF₅, and LiYbAlF₆ have been prepared by heating appropriate mixtures of YbF₂ and BeF₂, YbF₂ and AlF₃, or YbF₂, LiF, and AlF₃ at 750 °C under argon in a closed silica ampoule. YbBeF₄ crystallises monoclinic with a = 667.4(2), b = 691.1(2), c = 640.2(2) pm, β = 103.87(2)°, YbAlF₅ crystallises tetragonal with a = 1380.3(3), c = 701.3(3) pm, and LiYbAlF₆ crystallises trigonal with a = 504.2(2) and c = 986.8(1) pm. YbBeF₄ is the first fluoroberyllate, which adopts the monazite type structure, YbAlF₅ is isotypic with BaTiF₅ and LiYbAlF₆ crystallises in the LiCaAlF₆ type structure. In all three fluorides the Yb atoms are in the oxidation state +2 and the Yb-F distances range from 232 to 280 pm. Measurements of the magnetic susceptibilities have shown that YbBeF₄, YbAlF₅ and LiYbAlF₆ are diamagnetic. The structures of YbBeF₄, YbAlF₅ and LiYbAlF₆ are discussed in comparison to the corresponding fluoroberyllates and -fluoroaluminates with Sr and Ca.     

Homologous Silver Bismuth Chalcogenide Halides (N,x)P. II. The (2, x)P and (3, x)P Structure Families of Modular Compounds with Tunable Composition and Structure

The crystal structures of two members of the solid solution series Ag_3xBi_5?3xS_8?6xCl_6x?1 (x = 0.52 (I) , x = 0.67 (II) ) and three compounds of the Ag_4xBi_6?4xQ_10?8xBr_8x?2 series (Q = S: x = 0.70 (III) , x = 0.84 (IV) ; Q = Se: x = 0.72 (V) ) were determined by single‐crystal X‐ray diffraction. The compounds crystallize in the monoclinic space group C2/m (No. 12) with a = 1326.7(3), b = 403.9(1), c = 1176.7(2) pm, β = 107.83(3)° for (I) ; a = 1325.4(3), b = 403.3(1), c = 1170.6(2) pm, β = 108.14(3)° for (II) ; a = 1338.9(4), b = 407.7(1), c = 1426.4(4) pm, β = 113.95(2)° for (III) ; a = 1346.7(4), b = 409.3(1), c = 1440.7(4) pm, β = 114.40(1)° for (IV) ; and a = 1370.9(2), b = 417.64(4), c = 1480.4(2) pm, β = 114.92(2)° for (V) . (I) and (II) adopt the PbBi₄S₇ structure type, (III) to (V) crystallize in the CuBi₅S₈ type. All five compounds belong to the homologous series with general formula [BiQX]₂[Ag_xBi_1?xQ_2?2xX_2x?1]_N+1 (Q = S, Se; X = Cl, Br; 1/2 ≤ x ≤ 1)), which resemble minerals of the pavonite series. They are characterized by the parameters N and x and are denoted ^{(N, x)}P. In the crystal structures, two kinds of layered modules alternate along [001]. Modules of type A uniformly consist of paired rods of face‐sharing monocapped trigonal prisms around Bi atoms with octahedra around mixed occupied metal positions (M = Ag/Bi) between them. Modules of type B are composed of chains of edge‐sharing [MZ₆] octahedra (M = Ag/Bi; Z = Q/X). These NaCl‐type fragments are of thickness N = 2 in Ag_3xBi_5?3xS_8?6xCl_6x?1 and N = 3 in Ag_4xBi_6?4xQ_10?8xBr_8x?2. All structures exhibit Ag/Bi disorder in octahedrally coordinated metal positions and Q/X mixed occupation of some anion positions.     

Mechanismus der Entmischung von Chromindiumsulfid-Spinellmischkristallen. Transmissionselektronenmikroskopische Untersuchungen (HRTEM)

Mechanism of the Decomposition of Chromium Indium Sulfide Spinel Solid Solutions – Transmission Electron Microscope Studies (HRTEM) The mechanism of the probably spinodal decomposition of the spinel type solid solutions MCr_2?2xIn_2xS₄ with M = Fe, Co below 850 and 1000°C, respectively, was studied by high resolution transmission electron microscope technique (HRTEM). The decomposition starts by migration of the metal ions in the tetrahedral 8a sites of the spinel structure to the 16c interstitial sites forming lamellar domains of NaCl structure and NaCl superstructure (Zr₃S₄ or LiVO₂ type), respectively.     

Band‐Edge Electronic Structure of β‐In2S3: The Role of s or p Orbitals of Atoms at Different Lattice Positions

As a promising solar‐energy material, the electronic structure and optical properties of Beta phase indium sulfide (β‐In₂S₃) are still not thoroughly understood. This paper devotes to solve these issues using density functional theory calculations. β‐In₂S₃ is found to be an indirect band gap semiconductor. The roles of its atoms at different lattice positions are not exactly identical because of the unique crystal structure. Additonally, a significant phenomenon of optical anisotropy was observed near the absorption edge. Owing to the low coordination numbers of the In3 and S2 atoms, the corresponding In3‐5s states and S2‐3p states are crucial for the composition of the band‐edge electronic structure, leading to special optical properties and excellent optoelectronic performances.     

Preparation and crystal structure of Nb6.74 Ta5.26S4 – a new compound in the ternary system Ta?Nb?S

Nb_6.74Ta_5.26S₄ has been prepared by high temperature techniques. The crystal structure has been determined from single crystal X-ray diffraction data (R/R_w = 0.0588/0.0655). The compound crystallizes in the orthorhombic space group Pnma with unit cell dimensions a = 959.11 (26) pm, b = 336.37 (10) pm, and c = 3282.51 (74) pm. The orthorhombic cell contains four formula units. Its structure is similar to that of Nb-rich sulfides, rather than to that of Ta-rich sulfides. The metal coordinations are capped distorted cubic prisms and pentagonal prisms while the coordinations of sulfur are capped trigonal prisms.     

Ca3Ni8In4—An Ordered Noncentrosymmetric Variant of the BaLi4 Type

The title compound was synthesized by reacting the elements in an arc-melting apparatus under purified argon and subsequent annealing at 870 K. Ca₃Ni₈In₄ was investigated using X-ray diffraction on both powders and single crystals: P6₃mc, a=898.9(1) pm, c=752.2(2) pm, wR2=0.0591, 327 F² values, and 35 parameters. This structure is an ordered, noncentrosymmetric variant of the BaLi₄ type. The nickel and indium atoms build a complex three-dimensional [Ni₈In₄] polyanion in which the calcium atoms fill distorted hexagonal channels. To a first approximation the formula may be written as (3 Ca²⁺)⁶⁺ [Ni₈In₄]⁶⁻. Within the polyanion the Ni1, Ni3, and Ni4 atoms form one-dimensional cluster units which extend in the c direction while the Ni2 atoms have only indium neighbors in a distorted tetrahedral coordination. The Ni–Ni distances in the cluster range from 241 to 266 pm. The cluster units are surrounded and interconnected by indium atoms. The group– subgroup relation from centrosymmetric BaLi₄ to noncentrosymmetric Ca₃Ni₈In₄ is presented. Chemical bonding in Ca₃Ni₈In₄ and the structural relation with Lu₃Co_7.77Sn₄, Ca₃Au_6.61Ga_4.39, and Co₂Al₅ is briefly discussed.