Eu7Ga6Sb8: A Zintl phase with Ga-Ga bonds and polymeric gallium antimonide chains

The Zintl phase Eu₇Ga₆Sb₈ was obtained from a direct element combination reaction at 900°C. It crystallizes in the orthorhombic space group Pbca (No. 61) with a=15.6470(17) Å, b=17.2876(19) Å, c=17.9200(19) Å, and Z=8. In Eu₇Ga₆Sb₈, the anionic framework forms infinite chains of [Ga₆Sb₈]¹⁴⁻ which are arranged side by side to make a sheet-like arrangement but without linking. The sheets of chains are separated by Eu²⁺ atoms and also within the sheet, Eu²⁺ atoms fill the spaces between two chains. The chain is made up of homoatomic tetramers (Ga₄)⁶⁺ and dimers (Ga₂)⁴⁺ connected by Sb atoms. The compound is a narrow band-gap semiconductor with E_g∼0.6 eV and satisfies the classical Zintl concept. Extended Hückel band structure calculations confirm that the material is a semiconductor and suggest that the structure is stabilized by strong Ga-Ga covalent bonding interactions. Magnetic susceptibility measurements for Eu₇Ga₆Sb₈ show that the Eu atoms are divalent and the compound has an antiferromagnetic transition at 9 K.     

The novel silicide Eu3Si4: structure, chemical bonding, magnetic behavior and electrical resistivity

The novel binary europium silicide Eu₃Si₄ was synthesized from the elements. Its crystal structure is a derivative of the Ta₃B₄ type: space group Immm, a=4.6164(4) Å, b=3.9583(3) Å, c=18.229(1) Å, Z=2. In the structure, the silicon atoms form one-dimensional bands of condensed hexagons. Deviating from the prototype structure, a partial corrugation of the initially planar bands may be concluded from the analysis of the experimental electron density in the vicinity of the Si1 atoms. In the paramagnetic region, Eu₃Si₄ shows a 4f⁷ electronic configuration for the europium atoms. Two consecutive magnetic ordering transitions were found at 117 and 40 K. The first one is attributed to a ferromagnetic ordering of the Eu2 atoms; the second one is caused by a ferromagnetic ordering of the Eu1 atoms resulting in a ferrimagnetic ground state with a net magnetization of 7 μ_B at 1.8 K. The temperature dependence of the electrical resistivity reflects the metallic character of the investigated compound. Furthermore, the pronounced changes of the dρ/dT slope confirm the magnetic transitions. From bonding analysis with the electron localization function, Eu₃Si₄ shows a Zintl-like character and its electronic count balance can be written as (Eu^1.83+)₃(Si1^0.95−)₂(Si2^1.8−)₂, in good agreement with its magnetic behavior in the paramagnetic region.     

Synthesis, structure and physical properties of the new Zintl phases Eu11Zn6Sb12 and Eu11Cd6Sb12

Reported are the syntheses, crystal structure determinations from single-crystal X-ray diffraction, and magnetic properties of two new ternary compounds, Eu₁₁Cd₆Sb₁₂ and Eu₁₁Zn₆Sb₁₂. Both crystallize with the complex Sr₁₁Cd₆Sb₁₂ structure type—monoclinic, space group C2/m (no. 12), Z=2, with unit cell parameters a=31.979(4) Å, b=4.5981(5) Å, c=12.3499(14) Å, β=109.675(1)° for Eu₁₁Zn₆Sb₁₂, and a=32.507(2) Å, b=4.7294(3) Å, c=12.4158(8) Å, β=109.972(1)° for Eu₁₁Cd₆Sb₁₂. Their crystal structures are best described as made up of polyanionic and ribbons of corner-shared ZnSb₄ and CdSb₄ tetrahedra and Eu²⁺ cations. A notable characteristic of these structures is the presence of Sb-Sb interactions, which exist between two tetrahedra from adjacent layers, giving rise to unique channels. Detailed structure analyses shows that similar bonding arrangements are seen in much simpler structure types, such as Ca₃AlAs₃ and Ca₅Ga₂As₆ and the structure can be rationalized as their intergrowth. Temperature-dependent magnetization measurements indicate that Eu₁₁Cd₆Sb₁₂ orders anti-ferromagnetically below 7.5 K, while Eu₁₁Zn₆Sb₁₂ does not order down to 5 K. Resistivity measurements confirm that Eu₁₁Cd₆Sb₁₂ is poorly metallic, as expected for a Zintl phase.     

Crystal structure and luminescence of Sr0.99Eu0.01AlSiN3

Strontium europium aluminum silicon nitride, Sr_0.99Eu_0.01AlSiN₃, was synthesized by heating a mixture of binary nitrides at 2173 K and a N₂ gas pressure of 190 MPa. Single crystals of Sr_0.99Eu_0.01AlSiN₃ approximately 30 μm were obtained. The structure was confirmed to be an isotypic structure of CaAlSiN₃ in the orthorhombic space group Cmc2₁, analyzed by single-crystal X-ray diffraction. The lattice parameters are a=9.843(3), b=5.7603(16), c=5.177(2) Å, cell volume=293.53(17) Å³. It shows an orange-red photoluminescence by 5d→4f transition of Eu²⁺ at around 610 nm under excitation ranging from ultraviolet to 525 nm. The photoluminescence intensity, temperature characteristics, and oxidative stability were comparable or superior to those of CaAlSiN₃:Eu²⁺ phosphor.     

Synthesis, structure and properties of SrAu3In3 and EuAu3In3—New indides with gold zig-zag chains

New indides SrAu₃In₃ and EuAu₃In₃ were synthesized by induction melting of the elements in sealed tantalum tubes. Both indides were characterized by X-ray diffraction on powders and single crystals. They crystallize with a new orthorhombic structure type: Pmmn, Z=2, a=455.26(9), b=775.9(2), c=904.9(2) pm, wR2=0.0425, 485 F² values for SrAu₃In₃ and a=454.2(2), b=768.1(6), c=907.3(6) pm, wR2=0.0495, 551 F² values for EuAu₃In₃ with 26 variables for each refinement. The gold and indium atoms build up three-dimensional [Au₃In₃] polyanionic networks, which leave distorted hexagonal channels for the strontium and europium atoms. Within the networks one observes Au2 atoms without Au-Au contacts and gold zig-zag chains (279 pm Au1-Au1 in EuAu₃In₃). The Au-In and In-In distances in EuAu₃In₃ range from 270 to 290 and from 305 to 355 pm. The europium atoms within the distorted hexagonal channels have coordination number 14 (8 Au+6 In). EuAu₃In₃ shows Curie-Weiss behavior above 50 K with an experimental magnetic moment of 8.1(1) μB/Eu atom. ¹⁵¹Eu Mössbauer spectra show a single signal at δ=−11.31(1) mm/s, compatible with divalent europium. No magnetic ordering was detected down to 3 K.     

Deuterium ordering in Laves-phase deuteride YFe2D4.2

The structure of Laves-phase deuteride YFe₂D_4.2 has been investigated by synchrotron and neutron (ToF) powder diffraction experiments between 60 and 370 K. Below 323 K, YFe₂D_4.2 crystallizes in a fully ordered, monoclinic structure (s.g. Pc, Z=8, a=5.50663(4), b=11.4823(1), c=9.42919(6) Å, β=122.3314(5)°, V=503.765(3) Å³ at 290 K) containing 4 yttrium, 8 iron and 18 deuterium atoms. Most D-D distances are, within the precision of the diffraction experiment, longer than 2.1 Å; the shortest ones are of 1.96 Å. Seven of eight iron atoms are coordinated by deuterium in a trigonal bipyramid, similar to that in TiFeD_1.95−2. The eighth iron atom is coordinated by deuterium in a tetrahedral configuration. The coordination of iron by deuterium, and the iron-deuterium distances point to the importance of the directional bonding between iron and deuterium atoms. The lowering of crystal symmetry due to deuterium ordering occurs at much higher temperature than the magnetic ordering, and is therefore one of the parameters that are at the origin of the magnetic transition at lower temperatures.     

Synthesis, crystal structures, magnetic and electric transport properties of Eu11InSb9 and Yb11InSb9

Two new rare-earth metal containing Zintl phases, Eu₁₁InSb₉ and Yb₁₁InSb₉ have been synthesized by reactions of the corresponding elements in molten In metal to serve as a self-flux. Their crystal structures have been determined by single crystal X-ray diffraction—both compounds are isostructural and crystallize in the orthorhombic space group Iba2 (No. 45), Z=4 with unit cell parameters a=12.224(2) Å, b=12.874(2) Å, c=17.315(3) Å for Eu₁₁InSb₉, and a=11.7886(11) Å, b=12.4151(12) Å, c=16.6743(15) Å for Yb₁₁InSb₉, respectively (Ca₁₁InSb₉-type, Pearson's code oI84). Both structures can be rationalized using the classic Zintl rules, and are best described in terms of discrete In-centered tetrahedra of Sb, [InSb₄]⁹⁻, isolated Sb dimers, [Sb₂]⁴⁻, and isolated Sb anions, Sb³⁻. These anionic species are separated by Eu²⁺ and Yb²⁺ cations, which occupy the empty space between them and counterbalance the formal charges. Temperature-dependent magnetic susceptibility and resistivity measurements corroborate such analysis and indicate divalent Eu and Yb, as well as poorly metallic behavior for both Eu₁₁InSb₉ and Yb₁₁InSb₉. The close relationships between these structures and those of the monoclinic α-Ca₂₁Mn₄Sb₁₈ and Ca₂₁Mn₄Bi₁₈ are also discussed.     

Chemical bonding in EuTGe (T=Ni, Pd, Pt) and physical properties of EuPdGe

EuPdGe was prepared from the elements by reaction in a sealed tantalum tube in a high-frequency furnace. Magnetic susceptibility measurements show Curie-Weiss behavior above 60 K with an experimental magnetic moment of 8.0(1)μ_B/Eu indicating divalent europium. At low external fields antiferromagnetic ordering is observed at T_N=8.5(5) K. Magnetization measurements indicate a metamagnetic transition at a critical field of 1.5(2) T and a saturation magnetization of 6.4(1)μ_B/Eu at 5 K and 5.5 T. EuPdGe is a metallic conductor with a room-temperature value of 5000±500 μΩ cm for the specific resistivity. ¹⁵¹Eu Mössbauer spectroscopic experiments show a single europium site with an isomer shift of δ=−9.7(1) mm/s at 78 K. At 4.2 K full magnetic hyperfine field splitting with a hyperfine field of B=20.7(5) T is observed. Density functional calculations show the similarity of the electronic structures of EuPdGe and EuPtGe. T-Ge interactions (T=Pd, Pt) exist in both compounds. An ionic formula splitting Eu²⁺T⁰Ge²⁻ seems more appropriate than Eu²⁺T²⁺Ge⁴⁻ accounting for the bonding in both compounds. Geometry optimizations of EuTGe (T=Ni, Pt, Pd) show weak energy differences between the two structural types.     

Synthesis, crystal structure and magnetic properties of U2Co6Al19

The new compound U₂Co₆Al₁₉ was prepared by reaction of the elemental components in an arc-melting furnace followed by a heat treatment at 1050°C for 500 h. Its chemical composition was checked by energy-dispersive X-ray analyses and its crystal structure was determined by single crystal X-ray diffraction experiments. It crystallizes with four formula units in the monoclinic space group C2/m in a unit cell of dimensions a=17.4617(3)Å, b=12.0474(2)Å, c=8.2003(1)Å, β=103.915(1)°. The crystal structure of U₂Co₆Al₁₉ can be regarded as a superstructure of NdCo_4−xGa₉ structure type. This complex structure consists of a three-dimensional Co-Al framework delimiting tunnels where the U atoms reside. The shortest U-U distances are found in the c direction with alternating values of 3.98(1) and 4.22(1) Å. Temperature-dependent magnetization shows a first peak at 12.5 K and a weak ferromagnetic character below the temperature T_C=8 K. Magnetization at 1.9 K reaches almost saturation in 5 T with the moment of 0.36 μ_B/U atom. The complex magnetic behavior of U₂Co₆Al₁₉ may be ascribed to a canted spin structure resulting from an antiparallel arrangement of the magnetic moments not fully compensated at low temperature. At higher temperature, the compound displays simple paramagnetic behavior.     

New Compounds of the ThCr2Si2-Type and the Electronic Structure of CaM2Ge2 (M: Mn-Zn)

Two new compounds were synthesized by heating mixtures of the elements at 975-1025 K and characterized by single-crystal X-ray methods. CaZn₂Si₂ (a=4.173(2) Å, c=10.576(5) Å) and EuZn₂Ge₂ (a=4.348(2) Å, c=10.589(9) Å) crystallize in the ThCr₂Si₂-type structure (space group I4/mmm; Z=2). Magnetic susceptibility measurements of EuZn₂Ge₂ show Curie-Weiss behavior with a magnetic moment of 7.85(5)μ_B/Eu and a paramagnetic Curie temperature of 10(1) K. EuZn₂Ge₂ orders antiferromagnetically at T_N=10.0(5) K and undergoes a metamagnetic transition at a low critical field of about 0.3(2) T. The saturation magnetization at 2 K and 5.5 T is 6.60(5) μ_B/Eu. ¹⁵¹Eu Mössbauer spectroscopic experiments show one signal at 78 K at an isomer shift of −11.4(1) mm/s and a line width of 2.7(1) mm/s compatible with divalent europium. At 4.2 K full magnetic hyperfine field splitting with a field of 26.4(4) T is detected. The already known compounds CaM₂Ge₂ (M: Mn-Zn) also crystallize in the ThCr₂Si₂-type structure. Their MGe₄ tetrahedra are strongly distorted with M=Ni and nearly undistorted with M=Mn or Zn. According to LMTO electronic band structure calculations, the distortion is driven by a charge transfer from M-Ge antibonding to bonding levels.     

Quaternary selenostannates Na2−xGa2−xSn1+xSe6 and AGaSnSe4 (A=K, Rb, and Cs) through rapid cooling of melts. Kinetics versus thermodynamics in the polymorphism of AGaSnSe4

The quaternary alkali-metal gallium selenostannates, Na_2−xGa_2−xSn_1+xSe₆ and AGaSnSe₄ (A=K, Rb, and Cs), were synthesized by reacting alkali-metal selenide, Ga, Sn, and Se with a flame melting-rapid cooling method. Na_2−xGa_2−xSn_1+xSe₆ crystallizes in the non-centrosymmetric space group C2 with cell constants a=13.308(3) Å, b=7.594(2) Å, c=13.842(3) Å, β=118.730(4)°, V=1226.7(5) Å³. α-KGaSnSe₄ crystallizes in the tetragonal space group I4/mcm with a=8.186(5) Å and c=6.403(5) Å, V=429.1(5) Å³. β-KGaSnSe₄ crystallizes in the space group P2₁/c with cell constants a=7.490(2) Å, b=12.578(3) Å, c=18.306(5) Å, β=98.653(5)°, V=1705.0(8) Å³. The unit cell of isostructural RbGaSnSe₄ is a=7.567(2) Å, b=12.656(3) Å, c=18.277(4) Å, β=95.924(4)°, V=1741.1(7) Å³. CsGaSnSe₄ crystallizes in the orthorhombic space group Pmcn with a=7.679(2) Å, b=12.655(3) Å, c=18.278(5) Å, V=1776.1(8) Å³. The structure of Na_2−xGa_2−xSn_1+xSe₆ consists of a polar three-dimensional network of trimeric (Sn,Ga)₃Se₉ units with Na atoms located in tunnels. The AGaSnSe₄ possess layered structures. The compounds show nearly the same Raman spectral features, except for Na_2−xGa_2−xSn_1+xSe₆. Optical band gaps, determined from UV-Vis spectroscopy, range from 1.50 eV in Na_2−xGa_2−xSn_1+xSe₆ to 1.97 eV in CsGaSnSe₄. Cooling of the melts of KGaSnSe₄ and RbGaSnSe₄ produces only kinetically stable products. The thermodynamically stable product is accessible under extended annealing, which leads to the so-called γ-form (BaGa₂S₄-type) of these compounds.     

Crystal structure of BaMg2Si2O7 and Eu luminescence

Crystal structure of BaMg₂Si₂O₇ was determined and refined by a combined powder X-ray and neutron Rietveld method (monoclinic, C2/c, no. 15, Z=8, a=7.24553(8) Å, b=12.71376(14) Å, c=13.74813(15) Å, β=90.2107(8)°, V=1266.44(2) Å³; R_p/R_wp=3.38%/4.77%). The structure contains a single crystallographic type of Ba atom coordinated to eight O atoms with C₁ (1) site symmetry. Under 325-nm excitation Ba_0.98Eu_0.02Mg₂Si₂O₇ exhibits an asymmetric emission band around 402 nm. The asymmetric shape of the emission band is likely associated with a small electron-phonon coupling in BaMg₂Si₂O₇. The integrated intensity of the emission band was observed to remain constant over the temperature range 4.2-300 K.     

Synthesis, structure and magnetic properties of the new mixed-valence vanadate Na2SrV3O9

The new complex oxide Na₂SrV₃O₉ was synthesized and investigated by means of X-ray diffraction, electron microscopy and magnetic susceptibility measurements. This oxide has a monoclinic unit cell with parameters a=5.416(1) Å, b=15.040(3) Å, c=10.051(2) Å, β=97.03(3)°, space group P2₁/c and Z=4. The crystal structure of Na₂SrV₃O₉, as determined from X-ray single-crystal data, is built up from isolated chains formed by square V⁴⁺O₅ pyramids. Neighboring pyramids are linked by two bridging V⁵⁺O₄ tetrahedra sharing a corner with each pyramid. The Na and Sr atoms are situated between the chains. Electron diffraction and HREM investigations confirmed the crystal structure. The temperature dependence of the susceptibility indicates low-dimensional magnetic behavior with a sizeable strength of the magnetic intra-chain exchange J of the order of 80 K, which is very likely due to superexchange through the two VO₄ tetrahedra linking the magnetic V⁴⁺ cations.     

Crystal structure and properties of the new vanadyl(IV)phosphates Na2MVO(PO4)2, M=Ca and Sr

Two new complex vanadyl(IV)phosphates Na₂MVO(PO₄)₂ (M=Ca, Sr) were synthesized in evacuated quartz ampoules and investigated by means of X-ray diffraction, electron microscopy, DTA, ESR and magnetic susceptibility measurements. The crystal structure of Na₂SrVO(PO₄)₂ was solved ab initio from X-ray powder diffraction data. Both compounds are isostructural: a=10.5233(3) Å, b=6.5578(2) Å, c=10.0536(3) Å and a=10.6476(3) Å, b=6.6224(2) Å, c=10.2537(3) Å for Ca and Sr, respectively; S.G. Pnma, Z=4. The compounds have a three-dimensional structure consisting of V⁴⁺O₆ octahedra connected by PO₄ tetrahedra via five of the six vertexes forming a framework with cross-like channels. The strontium and sodium atoms are located in the channels in an ordered manner. Electron diffraction as well as high-resolution electron microscopy confirmed the structure solution. The new vanadylphosphates are Curie-Weiss paramagnets in a wide temperature range down to 2 K with θ=12 and 5 K for Ca and Sr phases, respectively.     

Magnetic properties and Eu Mössbauer effects of mixed valence europium copper sulfide, Eu2CuS3

Ternary europium copper sulfide Eu₂CuS₃ have been investigated by X-ray diffraction, ¹⁵¹Eu Mössbauer spectroscopy, magnetic susceptibility, magnetization, and specific heat measurements. In this compound, Eu²⁺ and Eu³⁺ ions occupy two crystallographically independent sites. The ¹⁵¹Eu Mössbauer spectra indicate that the Eu²⁺ and Eu³⁺ ions exist in the molar ratio of 1:1, and the Debye temperatures of Eu²⁺ and Eu³⁺ are 180 and 220 K, respectively. In its magnetic susceptibility, the divergence between the zero-field cooled and field cooled susceptibilities appears below 3.4 K. The specific heat has a λ-type anomaly at the same temperature. From the field dependence of magnetization at 1.8 K, the Eu²⁺ ion was found to be in the ferromagnetic state with the saturation magnetization M_S=6.7 μ_B.     

Hydro(solvo)thermal synthesis and structural characterization of a new organically templated gallophosphate: [H3N(CH2)2NH3]1/2·[Ga5 (PO4)4(OH)4]

A new three-dimensional open-framework gallophosphate: [H₃N(CH₂)₂NH₃]_1/2·[Ga₅ (PO₄)₄(OH)₄] has been prepared by hydro(solvo)thermal synthesis in presence of ethylenediamine (en) as structure-directing agent. Its structure was determined by means of single-crystal X-ray diffraction analysis with the following crystal data: monoclinic space group C2/m, a=10.1604(9) Å, b=12.0085(15) Å, c=7.1892(7) Å, β=90.797(6)°, V=877.08(16) Å³, Z=2, R₁=0.0264, wR₂=0.0764. The total numbers of measured reflections and unique reflections were 3508 and 1300, respectively. It is built up from a new secondary building unit (SBU) Ga₄P₄O₂₀(OH)₄, in which Ga atoms exhibit distorted trigonal bipyramidal coordination and P atoms are in tetrahedral coordination. The SBU Ga₄P₄O₂₀(OH)₄ are linked into a layer by bridge oxygen atoms. The GaO₄(OH)₂ octahedra link the layers into a three-dimentional framework. Diprotonated ethylenediamine was found in the channel of the framework. The material was characterized by IR spectroscopy, ¹H NMR spectra, thermogravimetric and differential thermal analyses and elemental analysis.     

R12Pt7In (R=Ce, Pr, Nd, Gd, Ho)—new derivatives of the Gd3Ga2-type

A new compound Ce₁₂Pt₇In was synthesized and its crystal structure at 300 K has been determined from single crystal X-ray data. It is tetragonal, space group I4/mcm, Z=4, with the lattice parameters: a=12.102(1) Å and c=14.542(2) Å, wR2=0.1102, 842 F² values, 33 variable parameters. The structure of Ce₁₂Pt₇In is a fully ordered ternary derivative of the Gd₃Ga₂-type. Isostructural compounds has been found to form with Pr (a=11.976(1) Å, c=14.478(2) Å), Nd (a=11.901(1) Å, c=14.471(2) Å), Gd (a=11.601(3) Å, c=14.472(4) Å), and Ho (a=11.369(1) Å, c=14.462(2) Å). Magnetic properties of Ce₁₂Pt₇In, Pr₁₂Pt₇In and Nd₁₂Pt₇In were studied down to 1.7 K. All three ternaries order magnetically at low temperatures with complex spin arrangements. The electrical resistivity of Ce₁₂Pt₇In and Nd₁₂Pt₇In is characteristic of rare-earth intermetallics.     

Gallium substitutions as a means to stabilize alkaline-earth and rare-earth metal pnictides with the cubic Th3P4 type: Synthesis and structure of A7Ga2Sb6 (A=Sr, Ba, Eu)

Three new compounds—Sr_7.04(2)Ga_1.94(2)Sb₆, Ba_7.02(3)Ga_1.98(3)Sb₆ and Eu_7.04(3)Ga_1.90(3)Sb₆—have been synthesized from reactions of the corresponding elements using gallium as a metal flux. Their crystal structures (space group I4¯3d (No. 220), Z=2 with unit cell parameters: a=9.9147(9) Å for the Sr-compound; a=10.3190(9) Å for the Ba-compound; and a=9.7866(8) Å for the Eu-compound) have been established by single-crystal X-ray diffraction. The structures are best described as Ga-stabilized derivatives of the hypothetical Sr₄Sb₃, Ba₄Sb₃ and Eu₄Sb₃ phases with the cubic Th₃P₄ type. Such an inclusion of interstitial Ga atoms in this atomic arrangement results in the formation of isolated [Ga₂Sb₆]¹⁴⁻ fragments, isoelectronic and isostructural with the [Sn₂Te₆]⁶⁻ anions in the K₃SnTe₃ type, and allows for the attainment of a charge-balanced electron count. In that sense, the Sr₄Sb₃, Ba₄Sb₃ and Eu₄Sb₃ binaries, which are expected to be electron-deficient and are currently unknown, can be “turned” into Sr₇Ga₂Sb₆, Ba₇Ga₂Sb₆ and Eu₇Ga₂Sb₆, whose structures are readily rationalized following the Zintl concept.     

Yb5Ni4Sn10 and Yb7Ni4Sn13: New polar intermetallics with 3D framework structures

The title compounds have been obtained by solid state reactions of the corresponding pure elements at high temperature, and structurally characterized by single-crystal X-ray diffraction studies. Yb₅Ni₄Sn₁₀ adopts the Sc₅Co₄Si₁₀ structure type and crystallizes in the tetragonal space group P4/mbm (No. 127) with cell parameters of a=13.785(4) Å, c=4.492 (2) Å, V=853.7(5) Å³, and Z=2. Yb₇Ni₄Sn₁₃ is isostructural with Yb₇Co₄InGe₁₂ and crystallizes in the tetragonal space group P4/m (No. 83) with cell parameters of a=11.1429(6) Å, c=4.5318(4) Å, V=562.69(7) Å³, and Z=1. Both structures feature three-dimensional (3D) frameworks based on three different types of one-dimensional (1D) channels, which are occupied by the Yb atoms. Electronic structure calculations based on density functional theory (DFT) indicate that both compounds are metallic. These results are in agreement with those from temperature-dependent resistivity and magnetic susceptibility measurements.     

Ga-Ga bonding and tunnel framework in the new Zintl phase Ba3Ga4Sb5

A new Zintl phase Ba₃Ga₄Sb₅ was obtained from the reaction of Ba and Sb in excess Ga flux at 1000°C, and its structure was determined with single-crystal X-ray diffraction methods. It crystallizes in the orthorhombic space group Pnma (No. 62) with a=13.248(3) Å, b=4.5085(9) Å, c=24.374(5) Å and Z=4. Ba₃Ga₄Sb₅ has a three-dimensional [Ga₄Sb₅]⁶⁻ framework featuring large tunnels running along the b-axis and accommodating the Ba ions. The structure also has small tube-like tunnels of pentagonal and rhombic cross-sections. The structure contains ethane-like dimeric Sb₃Ga-GaSb₃ units and GaSb₄ tetrahedra that are connected to form 12- and 14-membered tunnels. Band structure calculations confirm that the material is a semiconductor and indicate that the structure is stabilized by strong Ga-Ga covalent bonding interactions.