Ce4Ag3Ge4O(0.5)--chains of oxygen-centered [OCe2Ce(2/2)] tetrahedra embedded in a [CeAg3Ge4] intermetallic matrix.
The oxidation of an intermetallic phase under high-pressure/high-temperature conditions led to the synthesis of Ce4Ag3Ge4O(0.5) exhibiting [OCe2Ce(2/2] tetrahedral chains, in which the oxygen atoms statistically occupy the tetrahedral centres. Starting from a 1:1:1 CeAgGe precursor (NdPtSb type), a multianvil high-pressure/high-temperature experiment at 11.5 GPa and 1250-1300 °C revealed Ce4Ag3Ge4O(0.5), crystallizing in the space group Pnma with the following lattice parameters: a = 2087.3(4), b = 439.9(1), and c = 1113.8(2) pm. Magnetic measurements showed Curie-Weiss behavior above 100 K with an experimental magnetic moment of 2.42 µB per Ce atom, close to the value for the free Ce(3+) ion, clearly indicating trivalent cerium in Ce4Ag3Ge4O(0.5). Full potential GGA+U band structure calculations resulted in metallic properties and a magnetic ground state with one unpaired 4f-electron per cerium in agreement with the experiments.
Chemistry of layered d-metal pnictide oxides and their potential as candidates for new superconductors
Abstract Layered d-metal pnictide oxides are a unique class of compounds which consist of characteristic d-metal pnictide layers and metal oxide layers. More than 100 of these layered compounds, including the recently discovered Fe-based superconducting pnictide oxides, can be classified into nine structure types. These structure types and the chemical and physical properties of the characteristic d-metal pnictide layers and metal oxide layers of the layered d-metal pnictide oxides are reviewed and discussed. Furthermore, possible approaches to design new superconductors based on these layered d-metal pnictide oxides are proposed.
Darstellung und Kristallstruktur neuer AM2X2-Verbindungen in den Systemen Erdalkalimetall-Platinmetall-Germanium†
Vier neue ternare Verbindungen im System Erdalkalimetall-Platinmetall-Germanium konnten dargestellt und rontgenographisch charakterisiert werden. BaRu2Ge2 kristallisiert orthorhombisch, Raumgruppe Fddd, a=634,4(1) pm, b=1 056,5(3) pm, c=1 273,1(3) pm. Im ThCr2Si2-Typ (tetragonal, Raumgruppe 14/mmm) kristalisieren SrRu2Ge2 (a=430,6(1) pm, c=1 030,3(2) pm), BaRh2Ge2 (a=418,9(5) pm, c=1 175,7(10) pm) und SrRh2Ge2 (a=418,3(3) pm, c=1 071,8(6) pm). 
 
 
 
Preparation and Crystal Structure of New AM2X2 Compounds in the Systems Earthalkali Metal/Platinum Metal/Germanium. 
 
 
 
Four new ternary compounds in the systems earthalkali metal/platinum metal/germanium have been prepared and characterised by single crystal X-ray investigation. BaRu2Ge2 crystallizes orthorhombically, space group Fddd, a=634.4(1) pm, b=1 056.5(3) pm, c=1 273,1(3) pm. SrRu2Ge2 (a=430.6(1) pm, c=1 030.3(2) pm), BaRh2Ge2 (a=418.9(5) pm, c=1 175.7(10) pm) and SrRh2Ge2 (a=418.3(3) pm, c=1 071.8(6) pm) crystallize in the ThCr2Si2-type structure (tetragonal, space group I4/mmm).