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The quaternary germanides RE3 TRh4Ge4 ( RE = Ce, Pr, Nd; T = Nb, Ta) were synthesized from the elements by arc-melting and subsequent annealing in a muffle furnace. The structure of Ce3TaRh4Ge4 was refined from single-crystal X-ray diffractometer data: new type, Pbam, a = 719.9(2), b = 1495.0(3), c = 431.61(8), wR2 = 0.0678, 1004 F2 values, and 40 variables. Isotypy of the remaining phases was evident from X-ray powder patterns. Ce3TaRh4Ge4 is a new superstructure variant of the aristotype AlB2 with an ordering of cerium and tantalum on the aluminum site, whereas the honey-comb network is built up by a 1:1 ordering of rhodium and germanium. This crystal-chemical relationship is discussed based on a group-subgroup scheme. The distinctly different size of tantalum and cerium leads to a pronounced puckering of the [Rh4Ge4] network, which shows the shortest interatomic distances (253-271 pm Rh-Ge) within the Ce3TaRh4Ge4 structure. Another remarkable structural feature concerns the tantalum coordination with six shorter Ta-Rh bonds (265-266 pm) and six longer Ta-Ge bonds (294-295 pm). The [Rh4Ge4] network fully separates the tantalum and cerium atoms (Ce-Ce > 387 pm, Ta-Ta > 431 pm, and Ce-Ta > 359 pm). The electronic density of states DOS from DFT calculations show metallic behavior with large contributions of localized Ce 4f as well as itinerant ones from all constituents at the Fermi level but no significant magnetic polarization on Ce could be identified. The bonding characteristics described based on overlap populations illustrate further the crystal chemistry observations of the different coordination of Ce1 and Ce2 in Ce3TaRh4Ge4. The Rh-Ge interactions within the network are highlighted as dominant. The bonding magnitudes follow the interatomic distances and identify differences of Ta bonding vs. Ce1/Ce2 bonding with the Rh and Ge substructures. [ABSTRACT FROM AUTHOR]

The quaternary germanides RE3 TRh4Ge4 ( RE = Ce, Pr, Nd; T = Nb, Ta) were synthesized from the elements by arc-melting and subsequent annealing in a muffle furnace. The structure of Ce3TaRh4Ge4 was refined from single-crystal X-ray diffractometer data: new type, Pbam, a = 719.9(2), b = 1495.0(3), c = 431.61(8), wR2 = 0.0678, 1004 F2 values, and 40 variables. Isotypy of the remaining phases was evident from X-ray powder patterns. Ce3TaRh4Ge4 is a new superstructure variant of the aristotype AlB2 with an ordering of cerium and tantalum on the aluminum site, whereas the honey-comb network is built up by a 1:1 ordering of rhodium and germanium. This crystal-chemical relationship is discussed based on a group-subgroup scheme. The distinctly different size of tantalum and cerium leads to a pronounced puckering of the [Rh4Ge4] network, which shows the shortest interatomic distances (253-271 pm Rh-Ge) within the Ce3TaRh4Ge4 structure. Another remarkable structural feature concerns the tantalum coordination with six shorter Ta-Rh bonds (265-266 pm) and six longer Ta-Ge bonds (294-295 pm). The [Rh4Ge4] network fully separates the tantalum and cerium atoms (Ce-Ce > 387 pm, Ta-Ta > 431 pm, and Ce-Ta > 359 pm). The electronic density of states DOS from DFT calculations show metallic behavior with large contributions of localized Ce 4f as well as itinerant ones from all constituents at the Fermi level but no significant magnetic polarization on Ce could be identified. The bonding characteristics described based on overlap populations illustrate further the crystal chemistry observations of the different coordination of Ce1 and Ce2 in Ce3TaRh4Ge4. The Rh-Ge interactions within the network are highlighted as dominant. The bonding magnitudes follow the interatomic distances and identify differences of Ta bonding vs. Ce1/Ce2 bonding with the Rh and Ge substructures. [ABSTRACT FROM AUTHOR]

Well-shaped needles of the metal-rich phosphide Ce2Ru12P7 were grown in a lead flux, while a polycrystalline sample became available through a ceramic route followed by arc-melting. Ce2Ru12P7 crystallizes with the hexagonal Zr2Fe12P7 type: P6̅, a = 940.7(2), c = 389.8(1) pm, wR2 = 0.0342, 1001 F2 values and 45 variables. Striking structural motifs in the Ce2Ru12P7 structure are tri-capped trigonal prisms that are centered by the phosphorus atoms: P1@Ru7Ce2, P2@Ru7Ce2 and P3@Ru9. Adjacent prisms are condensed via common edges to propeller-like building units. [ABSTRACT FROM AUTHOR]

New quaternary palladium arsenide oxides Nd10Pd3As8O10 and Sm10Pd3As8O10 were synthesized from the rare earth (RE) elements, appropriate rare earth oxides, arsenic and palladium sponge at maximum annealing temperatures of 1223 K. The structure of the neodymium compound was refined from X-ray single crystal diffractometer data at different temperatures. The samarium compound was found to be isotypic on the basis of Guinier powder diffraction. Both compounds are isotypic with Nd10Au3As8O10 and consist of stacked, formal polycationic [RE10O10]10+ and polyanionic [Pd3(As2)4]10− layers. In contrast to the well-known, tetrahedrally coordinated rare earth oxide layers with basically ionic bonding, the palladium arsenide layers exhibit rather covalent character, which is underlined by XPS data. Electrical resistivity measurements indicate semiconducting properties for Nd10Pd3As8O10 and additionally show an anomaly at approximately 160 K, which results from a structural phase transition, clarified by X-ray single crystal diffractometer data. The phase transition originates from out of plane distortions of the palladium atoms, which show structural order around 160 K. Specific heat measurements and temperature dependent magnetic susceptibility data (including low field measurements) do not show any corresponding anomaly, referring to a very small structural change, which mainly effects electrical conductivity in the present palladium arsenide substructure. Nd10Pd3As8O10 exhibits Curie–Weiss paramagnetism and shows no magnetic order down to 2.5 K. Electronic band structure calculations predict a metallic state – probably due to the very small gap – and confirm the covalent character of the [Pd3As8] layer. [ABSTRACT FROM AUTHOR]

The rare earth-based zinc compounds RE13Pd25+ xZn28- x ( RE = Y, Ho-Lu) were synthesized from the elements in sealed niobium ampoules with a maximum reaction temperature of 1470 K followed by different annealing sequences. The structures of all compounds were refined from single crystal X-ray diffraction data, indicating substantial Zn/Pd mixing on one 8 c and one 24 g zinc site. Exemplarily, the homogeneity range of the solid solution Yb13Pd25+ xZn28- x was manifested from samples of different starting compositions and five single crystal data sets. The RE13Pd25+ xZn28- x structures are cubic, space group I4̅3 m with lattice parameters ranging from 1295 to 1307 pm, as a function of the rare earth element and the Zn/Pd mixing. Hierarchically, one can derive the RE13Pd25+ xZn28- x structures from the simple bcc packing. A group-subgroup scheme was developed for this new 4 × 4 × 4 tungsten superstructure which shows vacancy ordering and dumbbell formation. Temperature dependent magnetic susceptibility measurements show diamagnetism for a Lu13Pd29Zn24 sample and Curie-Weiss paramagnetism for Tm13Pd29Zn24 down to 3 K. [ABSTRACT FROM AUTHOR]

CeCoGa was synthesized by melting of the elements in an arc-melting furnace as well as in a sealed niobium tube in an induction furnace. A further annealing step improves the purity and crystallinity of the samples significantly. Its structure was refined on the basis of single-crystal X-ray diffractometer data at different temperatures. Already at room temperature CeCoGa crystallizes in a superstructure of the HT-CeCoAl type. This superstructure can be described in the (3+1)D superspace group C2/ m(α0γ)00; α=2/3, γ=1/3 with a temperature independent q-vector ( Z=4). For the 300 K data (also for 90 K) the commensurate modulated structure could be refined with 1336 F2 values, 56 variables and residuals of wR=0.0348 for the main and wR=0.0605 for the satellites of 1st order [ a=1101.7(1), b=436.0(1) and c=482.4(1) pm, β=103.2(1)°]. Furthermore a description in a transformed 3D supercell with the space group C2/ m and Z=12 is possible. For the 90 K data this 3D supercell was refined with 1289 F2 values, 56 variables and a residual of wR=0.0409 [ a=1618.8(1), b=435.3(1) and c=1094.1(1) pm, β=119.3(1)°]. The relation of the HT-CeCoAl type structure, the (3+1)D modulated and the 3D supercell structure are discussed on the basis of a group-subgroup relation. By thermal analysis and magnetic measurements the phase transition temperature to the HT-CeCoAl type structure is stated slightly above 475 K. Furthermore intermediate cerium valence was identified by the magnetic susceptibility. [ABSTRACT FROM AUTHOR]

The first ternary compound in the Sr-Pt-Al system, SrPt2Al2, was synthesized by melting of the elements in a sealed niobium tube in a high frequency furnace. The structure of SrPt2Al2 was determined by single-crystal X-ray diffraction on the basis of data sets recorded at 90, 150, 210, 270 and 300 K. The compound crystallizes in an incommensurately modulated (3+2)D structure being related to the tetragonal primitive CaBe2Ge2 type structure. The structure was refined in the orthorhombic superspace group Pmmn( α,0,0)0 s0(0, β,0) s00 ( α=0.222(1) a*, β=0.224(1) b*, a= b=436.89(5), c=1010.16(13) pm at 90 K) with RM=0.0403, RS,1=0.0597 and RS,2=0.2046. The structural relation with CaBe2Ge2 along with a refinement in the tetragonal superspace group P4/ nmm( α,0,0)0000(0, α,0)00 s0 is discussed with respect to the temperature dependence of the q-vectors and by group-subgroup relations. The modulation, from the standpoint of the crystal chemistry, is mainly caused by the distortion of the Pt arrangements within the pseudo-tetragonal ab plane. [ABSTRACT FROM AUTHOR]