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.     

Silicide und Germanide mit Gd6Cu8Ge8-Struktur

Zusammenfassung Die Verbindungen {Sc,Y,Tb,Dy,Ho,Er,Tm,Yb,Lu}₆Cu₈Si₈ sowie {Y,Yb}₆Cu₈Ge₈ werden hergestellt. Diese sind isotyp mit der Gd₆Cu₈Ge₈-Struktur. Die Gitterparameter werden ermittelt.

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Silicides and germanides with Gd₆Cu₈Ge₈-structure type

The compounds {Sc,Y,Tb,Dy,Ho,Er,Tm,Yb,Lu}₆Cu₈Si₈ and {Y,Yb}₆Cu₈Ge₈ have been prepared. They were found to be analogous with the Gd₆Cu₈Ge₈-structure type. The lattice parameters have been determined.

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Mit 1 Abbildung     

Die Kristallstruktur von Gd6Cu8Ge8 und isotypen Phasen

Zusammenfassung Die Verbindungen Gd(Dy, Er, Lu)₆Cu₈Ge₈ wurden hergestellt und ihre Struktur bestimmt. Gd₆Cu₈Ge₈ kristallisiert orthorhombisch in einem neuen Strukturtyp mita=14,000±0,008 Å,b=6,655±0,003 Å,c=4,223±0,004 Å, Raumgruppe D _2h ²⁵ -I mmm mit 2 Gd in 2 (d), 4 Gd in 4 (e), 8 Cu in 8 (n), 4 Ge in 4 (f) und 4 Ge in 4 (h), N=1. Die Struktur ist durch Verwandtschaft zum AlB₂- und CaZn₅-Typ gekennzeichnet. Die anderen genannten Phasen sind dem Gd₆Cu₈Ge₈ isotyp.

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Crystal structure of Gd₆Cu₈Ge₈, and of isotypic phases

The compounds Gd(Dy, Er, Lu)₆Cu₈Ge₈ have been prepared and their structure has been determined. Gd₆Cu₈Ge₈ crystallizes in a new structure type witha=14.000±0.008 Å,b=6.655±0.003 Å,c=4.223±0.004 Å, space group D _2h ²⁵ -I mmm with 2 Gd in 2 (d), 4 Gd in 4 (e), 8 Cu in 8 (n), 4 Ge in 4 (f) and 4 Ge in 4 (h), N=1. The structure is characterized by close relationship to the AlB₂ and CaZn₅ structure types. The other phases mentioned above are isotypic to Gd₆Cu₈Ge₈.

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Mit 4 Abbildungen     

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.     

Semiconducting behavior of type-I Si clathrate K8Ga8Si38

A ternary type-I Si clathrate K(8)Ga(8)Si(38) has been revealed to be an indirect band gap semiconducting material with an energy gap (E(g)) of approximately 0.10 eV, which is much smaller than the calculated E(g) value that is 0.15 eV wider than E(g) of elemental Si with the diamond-type structure.     

The Intermetallic Type-I Clathrate Na8Zn4Ge42

The new intermetallic type-I clathrate Na₈Zn₄Ge₄₂ was obtained by direct reaction of the elements, and its crystal structure was determined by means of single-crystal X-ray diffraction methods. The structure is described in space group Pm3 n (no. 223) with a = 10.6982(1) Å. A mixed Zn/Ge occupancy is found for one of the network sites (6c). Na₈Zn₄Ge₄₂ represents an air-stable electron-precise Zintl phase with exclusively Na cations located in the cavities of a polyanionic host network of four-connected Zn and Ge atoms.     

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.     

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.     

Structural relaxation of amorphous Ge38S62 studied by length dilatometry and calorimetry

The structural relaxation of Ge₃₈S₆₂ glass has been studied by length dilatometry and calorimetry. The Tool-Narayanaswamy-Moynihan model was applied on obtained data of structural relaxation and parameters of this model were determined: Δh*= 483±2 kJ mol^-1, ln(A/s)= -81±1, β= 0.7±0.1 and x=0.6±0.1. Both dilatometric and calorimetric relaxation data were compared on the basis of the fictive relaxation rate. It was found that the relaxation rates are very similar and well correspond to the prediction of phenomenological model. This revised version was published online in July 2006 with corrections to the Cover Date.