Die Kristallstruktur der Verbindungen V11Ge8, Cr11Ge8 und Mn11Ge8

The crystal structure of the isotypic compoundsT ₁₁Ge₈ (T=V, Cr, Mn) has been determined by means of direct methods fromWeissenberg data of a Cr₁₁Ge₈ single crystal. A finalR-value of 7.7% was obtained by least squares refinement based on 684 observed reflexions. The orthorhombic unit cell (Pnam-D _2h ¹⁶ ) with the dimensionsa-13.171,b=15.775 andc=4.939 Å contains 4 formula units Cr₁₁Ge₈. Atoms are arranged mainly in primary layers atz=1/4, 3/4 with nets comprising squares, pentagons and hexagons which are all centered by atoms of secondary layers atz≈0, 1/2. Secondary layer atoms formT—T-chains as well as Ge?Ge-chains inz-direction with short bond lengths (2.47 Å). The structural relationship between Cr₁₁Ge₈, Cr₅Ge₃ (W₅Si₃-type) and V₆Si₅ is discussed.     

Der Chemische Transport von Cr(Ge) (Mischkristall), Cr3Ge,Cr5Ge3, Cr11Ge8, CrGe,Cr11Ge19 und Ge(Cr) (Mischkristall)

Chemical Vapor Transport of Intermetallic Systems. Chemical Transport of Cr(Ge) (Mixed Crystal) Cr₃Ge, Cr₅Ge₃, Cr₁₁Ge₈, CrGe, Cr₁₁Ge₁₉ and Ge(Cr) (Mixed Crystal) All intermetallics in the Cr/Ge-system can be prepared by CVT-methods. The composition of the deposited crystals is influenced first and foremost by the composition of the starting material. Thermodynamic calculations allow to understand the process qualitatively.     

Prototype structure of Pb5Ge3O11

The prototypic structure of the optically active ferroelectric Pb₅Ge₃O₁₁ has been deduced from packing considerations and refined from single-crystal diffractometer data. Interleaving segments of the apatite and nasonite structures in layers perpendicular to c gives the lead germanate structure. The space group of the prototype is $\text{P}\text{6}$, with a = 10.190, c = 10.624 Å, and Z = 3. Atomic coordinates were refined to give an R-factor of 0.093 using 463 X-ray reflections. The structure contains tetrahedral GeO₄ groups and double tetrahedral Ge₂O₇ groups in equal numbers. Lead is found in both trigonal pyramid and trigonal prism configurations.     

Structure and Magnetic Properties of Ce3Ge0.66In4.34 and Ce11Ge4.74In5.26

New indides Ce₃Ge_0.66In_4.34 and Ce₁₁Ge_4.74In_5.26 were synthesized from the elements by arc‐melting and subsequent annealing at 870 K. Single crystals were grown through special annealing procedures in sealed tantalum tubes in a high‐frequency furnace. Both compounds were investigated on the basis of X‐ray powder and single crystal data: I4/mcm, La₃GeIn₄ type, a = 848.8(1), c = 1192.0(2) pm, Z = 4, wR2 = 0.0453, 499 F² values, 17 variables for Ce₃Ge_0.66In_4.34 and I4/mmm, Sm₁₁Ge₄In₆ type (ordered version of the Ho₁₁Ge₁₀ type), a = 1199.3(2), c = 1662.0(3) pm, wR2 = 0.0507, 1217 F² values, 41 variables for Ce₁₁Ge_4.74In_5.26. The Ce₃Ge_0.66In_4.34 structure shows a mixed Ge/In occupancy on the 4c Wyckoff position. This site is octahedrally coordinated by cerium atoms. These octahedra share all edges, leading to a three‐dimensional network. The latter is penetrated by a two‐dimensional indium substructure which consists of flattened tetrahedra at In–In distances of 291 and 300 pm. The Ce₁₁Ge_4.74In_5.26 structure contains three crystallographically independent germanium sites. The latter are coordinated by eight or nine cerium neighbors. These CN8 and CN9 polyhedra are condensed to a complex network which is penetrated by a three‐dimensional indium network with In–In distances of 301–314 pm. The 16m site shows a mixed In/Ge occupancy. Chemical bonding in both compounds is dominated by the p elements. Both ternaries studied exhibit localized magnetism due to the presence of Ce³⁺ ions. The compound Ce₃GeIn₄ remains paramagnetic down to 1.72 K, whereas Ce₁₁Ge₄In₆ orders ferromagnetically at T_C = 7.5 K.     

原子团簇Ge11同分异体的密度泛函研究

用分子图形软件设计出多种Ge_11原子团簇模型,使用B3LYP密度泛函方法进行几何构型优化和振动频率计算,比较了14种同分异构体的总能量,得到了新的基态构型。锗原子团簇的大部分原子以三、四、五和六配位成键。在Ge11原子团簇中,双角反四棱柱衍生出来的构型能量较低,它是设计大分子锗原子团簇初始模型的重要结构单元。由三棱柱演变的构型能量居中。带心结构和共边构型带有高配位原子,其总能量较高,是不稳定的结构。     

New compounds with Ge/Ge and Ge/C multiple bonds

Treatment of GeCl₂ · dioxane with the Grignard reagent RMgBr (R = 2,5-tBu₂C₆H₃) furnishes the tetraaryldigermene R₂GeGeR₂ (4). The X-ray structure analysis of 4 reveals a long GeGe double bond of 236.4 pm and the largest trans-bending angles of the substituents (42.6° and 37.2°) observed so far. The reaction of hexa-2,4-diyne with the germylene R₂Ge: (R = 2-tBu-4,5,6-Me₃C₆H) yields red crystals of the acetylene-bridged bis(germaethene) (Me)R₂GeC-CC-CGeR₂(Me) 7, the red colour of which indicates conjugation between the two double bonds.     

Synthesis,Structure, and High Temperature Thermoelectric Properties of Yb11Sb9.3Ge0.5

Zintl phase compounds with large unit cells and complex anionic structures such as Yb₁₁Sb₁₀ hold potential for being good thermoelectric materials. Single crystals of Ge‐doped Yb₁₁Sb₁₀ were synthesized using a molten Sn‐flux technique. Single crystal X‐ray diffraction data were obtained and resulted in a composition of Yb₁₁Sb_9.3Ge_0.5 which was verified by microprobe. Yb₁₁Sb_9.3Ge_0.5 is isostructural to Ho₁₁Ge₁₀, crystallizing in a body‐centered, tetragonal unit cell, space group I4/mmm, with Z = 4. The unit cell parameters of Yb₁₁Sb_9.3Ge_0.5 are a = 11.8813(4), c = 17.1276(13) Å with a volume of 2417.8(2) ų. These parameters correlate well with the structural refinement of previously published Yb₁₁Sb₁₀. The structure consists of 16 isolated Sb^3? anions, 8 dumbbells, 2 square planar rings and 44 Yb²⁺ cations. The Ge, doped in at 28 % occupancy, was found to be site specific, residing on the 2 square planar rings. Single crystal X‐ray diffraction is most consistent with the site that makes up the square ring being less than fully occupied. The doped compound is additionally characterized by X‐ray powder diffraction, differential scanning calorimetry and thermogravimetry. High temperature (300–1200 K) thermoelectric properties show that the doped compound has extremely low thermal conductivity (10–30 mW/cmK), lower than that of Yb₁₁Sb₁₀. Temperature dependent resistivity is consistent with a heavily doped semiconductor. Yb₁₁Sb_9.3Ge_0.5 shows p‐type behavior increasing from ～22 μV/K at room temperature to ～31 μV/K at 1140 K. The low value and the temperature dependence of the Seebeck coefficient suggest that bipolar conduction produces a compensated Seebeck coefficient and consequently a low zT.     

On the effect of Ga and In substitutions in the Ca11Bi10 and Yb11Bi10 bismuthides crystallizing in the tetragonal Ho11Ge10 structure type

The Ga‐ and In‐substituted bismuthides Ca₁₁Ga_xBi_10–x, Ca₁₁In_xBi_10–x, Yb₁₁Ga_xBi_10–x, and Yb₁₁In_xBi_10–x (x < 2) can be readily synthesized employing molten Ga or In metals as fluxes. They crystallize in the tetragonal space group I4/mmm and adopt the Ho₁₁Ge₁₀ structure type (Pearson code tI84; Wyckoff sequence n2 m j h2 e2 d). The structural response to the substitution of Bi with smaller and electron‐poorer In or Ga has been studied by single‐crystal X‐ray diffraction methods for the case of Ca₁₁In_xBi_10–x [x = 1.73 (2); octabismuth undecacalcium diindium]. The refinements show that the In atoms substitute Bi only at the 8h site. The refined interatomic distances show an unconventional – for this structure type – bond‐length distribution within the anionic sublattice. The latter can be viewed as consisting of isolated Bi³⁻ anions and [In₄Bi₈²⁰⁻] clusters for the idealized Ca₁₁In₂Bi₈ model. Formal electron counting and first‐principle calculations show that the peculiar bonding in this compound drives the system toward an electron‐precise state, thereby stabilizing the observed bond‐length pattern.     

RADIATION-INDUCED CHANGES IN THE STRUCTURE AND FERROELECTRIC PROPERTIES OF Pb5Ge3O11 SINGLE CRYSTALS

Journal of Structural Chemistry - Perfect stoichiometric Pb5Ge3O11 single crystals are irradiated with 60Co γ-rays (1·106&nbsp;Rad) and high-energy electrons (0.13 e/cm2, 0.89 e/cm2,...     

High-pressure synthesis and electrical properties of Mn3Ge5 with Mn11Si19-type structure

The new germanium-rich manganese germanide, Mn₃Ge₅, was synthesized at 600–1000°C and 4 GPa using a Belt-type apparatus. The crystal structure of Mn₃Ge₅ was identified as possessing the Mn₁₁Si₁₉ type with a tetragonal cell (Schoenflies symbolD_2d). The electrical resistivity of Mn₃Ge₅ increased with increasing temperature and saturated above 200 K. The thermoelectric power was 50–70 μV/K and its sign was positive. These data indicated that Mn₃Ge₅ was ap-type semiconductor or a semimetal.     

从含锗蒸馏渣中回收锗的工艺方法探讨

通过大量的生产试验，寻找一种利用经蒸馏提纯生产锗后的蒸馏渣回收生产锗的工艺方法。     

Compound formation in the System PbGeO3?Pb5Ge3O11

Compound formation in the system PbGeO₃? Pb₅Ge₃O₁₁ was studied by thermal analysis and high-temperature X-ray diffraction. New modifications of PbGeO₃ and Pb₅Ge₃O₁₁ were prepared by the simultaneous hydrolysis of lead and germanium alkoxides, followed by washing and drying; the former has a hexagonal unit cell with a = 15.573 Å and c = 7.240 Å, and the latter has an orthorhombic crystal structure with a = 5.081 Å, b = 7.301 Å and c = 8.817 Å. They are transformed to the known monoclinic and hexagonal modifications at 575 to 610°C and 410 to 450°C, respectively. No compound of Pb₃Ge₂O₇ was confirmed. The structures of germanate groups in the lead germanate compounds are discussed on the basis of the infrared spectral data.     

Ge9=Ge9=Ge9=Ge9]8-: a linear tetramer of nine-atom germanium clusters,a nanorod

A tetramer of nine-atom deltahedral germanium clusters and charge 8-, [Ge9=Ge9=Ge9=Ge9]8- , has been characterized as a (Rb-18C6)(+) salt (18C6 = 18-crown-6 polyether). The clusters are connected by pairs of parallel bonds, and the electrons are delocalized over the whole anion. The size of the tetramer is of nanorod dimensions, ca. 2 nm.     

Oxidative Coupling of Ge94‐ Zintl Anions ‐ Hexagonal Rod Packing of Linear [Ge9=Ge9=Ge9=Ge9]8‐

The compound [K(18‐crown‐6)]₈[Ge₉=Ge₉=Ge₉=Ge₉] ˙ 8en ( 1 ) featuring a [Ge₉=Ge₉=Ge₉=Ge₉]^8‐cluster anion was synthesized from K₄Ge₉ for the first time. The X‐ray single crystal analysis shows that, in many respects such as bond connection and packing style, compound 1 is quite different from the previously reported compounds [Rb(18‐crown‐6)]₈[Ge₉=Ge₉=Ge₉=Ge₉] ˙ 2en ( 2 ) and [Rb(18‐crown‐6)]₈[Ge₉=Ge₉=Ge₉=Ge₉] ˙ 6en ( 3 ). Crystal packing of 1 gives strong indications that the highly charged nano‐rods self assembly in a hexagonal rod packing.     

Theoretical Study of Pd11Si6 Nanosheet Compounds Including Seven‐Coordinated Si Species and Its Ge Analogues

Nanosheet compounds Pd₁₁(SiiPr)₂(SiiPr₂)₄(CNtBu)₁₀ ( 1 ) and Pd₁₁(SiiPr)₂(SiiPr₂)₄(CNMes)₁₀ ( 2 ), containing two Pd₇(SiiPr)(SiiPr₂)₂(CNR)₄ plates (R=tBu or Mes) connected with three common Pd atoms, were investigated with DFT method. All Pd atoms are somewhat positively charged and the electron density is accumulated between the Pd and Si atoms, indicating that a charge transfer (CT) occurs from the Pd to the Si atoms of the SiMe₂ and SiMe groups. Negative regions of the Laplacian of the electron density were found between the Pd and Si atoms. A model of a seven‐coordinated Si species, that is, Pd₅(Pd?SiMe), is predicted to be a stable pentagonal bipyramidal molecule. Five Pd atoms in the equatorial plane form bonding overlaps with two 3p orbitals of the Si atom. This is a new type of hypervalency. The Ge analogues have geometry and an electronic structure similar to those of the Si compounds. But their formation energies are smaller than those of the Si analogues. The use of the element Si is crucial to synthesize these nanoplate compounds.     

Use of a summation technique for evaluation of the phase transition in lead germanate,Pb5Ge3O11

A computer technique is outlined to increase the signal: noise ratio of DSC results for transformations involving small changes of energy. The method is applied to determine the transformation temperature of the ferroelectric-paraelectric transformation of lead germanate, Pb₅Ge₃O₁₁, either pure or doped with Nd³⁺ or with Nd³⁺+K⁺.

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Zusammenfassung Eine Computermethode wird angegeben, die es erlaubt, das Signal: Rausch-Verhältnis bei DSC-Messungen von Umwandlungen mit geringer Energie zu erhöhen. Diese Methode wird verwendet, um die Temperatur der Umwandlung ferroelektrisch-paraelektrisch an Bleigermanat Pb₅Ge₃O₁₁, rein oder dotiert mit Nd³⁺ oder mit Nd³⁺ +K⁺, zu bestimmen.

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Thanks are due to Dr. H. D. Kürsten, who prepared the crystals.     

ChemInform Abstract: Complex Intermetallic Compounds: CaNi5Ge3, Ca15Ni68Ge37, and Ca7Ni49Ge22. Three Multifaceted Ni—Ge Framework Structures Combining the Structural Motifs of Ni3Ge and CaNi2Ge2.

The title compounds are prepared by arc‐melting of the elements followed by heating in Ta ampules (950—1150 °C, 1—12 h).