Search

The equiatomic gallides REAuGa (RE = La, Ce, Pr, Nd, Sm) were synthesized from the elements by arc‐melting. Small single crystals were grown by slowly cooling the samples from 1073 K to room temperature at a rate of 3 K·h–1. The REAuGa structures were reinvestigated from single‐crystal X‐ray diffractometer data. The five gallides adopt the non‐centrosymmetric EuAuGe type structure, space group Imm2, a superstructure variant of KHg2. The symmetry reductions lead to the formation of trillings and inversion twins. The domain ratios were precisely determined from the single crystal data. The striking structural motifs of the REAuGa structures are slightly puckered Au3Ga3 layers with strong covalent Au–Ga bonding. Stacking of these layers in AA′ sequence (A and A′ are related by mirror planes) leads to weak Au–Au (aurophilic bonding) and Ga–Ga interlayer interactions (319 and 283 pm in SmAuGa). Temperature dependent magnetic susceptibility measurements revealed Curie–Weiss behavior for CeAuGa and NdAuGa, whereas SmAuGa exhibits the typical van Vleck paramagnetism caused by contributions of the excited states. Antiferromagnetic ground states were observed for CeAuGa, NdAuGa, and SmAuGa below the respective Néel temperatures of 2.8, 9.5 and 24.1 K. LaAuGa is Pauli paramagnetic. [ABSTRACT FROM AUTHOR]

The lutetium‐rich indide Lu13Ni6In was synthesized from the elements by arc‐melting and subsequent annealing in a sealed niobum container. At room temperature, the Lu13Ni6In structure is centrosymmetric, space group R3m, a = 919.74(10), c = 1828.9(2) pm, wR2 = 0.0996, 666 F2 values, 43 variables. It exhibits strong anisotropic displacement parameters U33 for the Lu1 and U22 for the Ni atoms. In going to low‐temperature, Lu13Ni6In shows a phase transition (loss of the inversion symmetry) along with an ordering of Lu1. The structure was refined from 90 K single‐crystal X‐ray diffractometer data for an inversion twin: R3m, a = 918.97(4), c = 1820.27(7) pm, wR2 = 0.0890, 1288 F2 values, 56 variables. The low‐temperature Lu13Ni6In structure can be described as a condensation of In@Lu12 icosahedra, Ni2@Lu6 trigonal prisms, and Ni@Lu4 tetrahedra to layers that are stacked in ABC sequence. The driving force for superstructure formation is a strengthening of Lu–Ni bonding. Temperature dependent magnetic susceptibility measurements show Pauli paramagnetic behavior. [ABSTRACT FROM AUTHOR]

Na3GaF6 and Na3GaF6:Mn4+ samples were obtained from NaNO3 and Ga(NO3)3·9H2O in hydrofluoric acid using K2MnF6 or NaMnO4 as manganese sources. The structure of Na3GaF6 was studied by single crystal X-ray diffraction at 90, 293, 440 and 500 K, confirming the monoclinic cryolite type structure, space group P21/c. The gallium atoms show slightly distorted octahedral coordination by fluorine atoms, similar to the Na1 atoms. Coordination number 8 is observed for Na2. Both sodium sites are clearly distinguished by 23Na MAS-NMR spectroscopy. Above 400 K the spectra reveal distinct chemical exchange effects, signifying sodium ion hopping between these two sites. At the same time static 19F NMR spectra indicate pronounced motional narrowing effects in this temperature region. The nearly invariant 69Ga MAS-NMR spectra suggest that any reorientational motion involving the GaF63− ions (if present) occurs with preservation of the center of mass of these octahedra. [ABSTRACT FROM AUTHOR]

The germanides YPtGe2 and GdPtGe2 were synthesized from REGe2 precursor compounds and platinum by arc-melting and their structures were studied on the basis of temperature-dependent single crystal X-ray diffraction data. At room temperature both germanides adopt the orthorhombic YIrGe2 type structure, space group Immm, with enhanced U11 displacement parameters for the Ge1 atoms. Below 174 and 145 K, respectively, satellite reflections emerge in the diffraction patterns, giving rise to modulations. The low-temperature structures were refined in the superspace group Pnnn(1/2,1/2,γ)qq0 (48.1.11.3). The structural phase transition is also evident in the magnetic susceptibility, specific heat and resistivity data. The high- and low-temperature modifications are discussed on the basis of a group–subgroup scheme. [ABSTRACT FROM AUTHOR]

The germanides YPtGe2 and GdPtGe2 were synthesized from REGe2 precursor compounds and platinum by arc-melting and their structures were studied on the basis of temperature-dependent single crystal X-ray diffraction data. At room temperature both germanides adopt the orthorhombic YIrGe2 type structure, space group Immm, with enhanced U11 displacement parameters for the Ge1 atoms. Below 174 and 145 K, respectively, satellite reflections emerge in the diffraction patterns, giving rise to modulations. The low-temperature structures were refined in the superspace group Pnnn(1/2,1/2,γ)qq0 (48.1.11.3). The structural phase transition is also evident in the magnetic susceptibility, specific heat and resistivity data. The high- and low-temperature modifications are discussed on the basis of a group–subgroup scheme. [ABSTRACT FROM AUTHOR]

Two different samples of Ce3Rh4Ge4 were synthesized from different starting compositions by melting of the elements in an arc-melting furnace followed by annealing sequences in a sealed tantalum ampoule in a muffle furnace. The structures of two different stacking variants were refined on the basis of temperature dependent single-crystal X-ray diffractometer data. At high temperature Ce3Rh4Ge4 adopts the U3Ni4Si4 type structure with strongly enhanced anisotropic displacement parameters for the Rh1 atoms. For the two different crystals, additional reflections start to appear at different temperatures. The first crystal showed additional reflections already at room temperature (stacking variant I) and the second one showed additional reflections emerging below 270 K (stacking variant II). Stacking variant I could be described with the (3+1)D superspace group I2/m(α0γ)00; α=1/2a*, γ=1/2c*; (Z=2), 1252 F2 values, 48 variables, wR=0.0306 for the main and wR=0.0527 for 440 1st order satellite reflections, similar to Pr3Rh4Ge4. For stacking variant II the (3+1)D superspace group is Immm(α00)00s; α=1/2a*; (Z=2). The structure could be refined with 1261 F2 values, 53 variables and residuals of wR=0.0331 for the main reflections and wR=0.1755 (R1obs=0.0788) for the 1st order satellite reflections, [a=406.2(1), b=423.7(1) and c=2497.1(1) pm]. The commensurate description could be transformed to a three-dimensional (3D) supercell with space group Pnma and Z=4: a=812.5(1), b=423.7(1), c=2497.1(2) pm, 1261 F2 values, 69 variables and wR=0.0525. The relation of the U3Ni4Si4 type structure, the (3+1)D modulated and the 3D supercells are discussed on the basis of group-subgroup schemes. Ab initio electronic structure calculations are in line with the diffraction experiments, revealing the lowest total energy for the Pnma phase. [ABSTRACT FROM AUTHOR]

Two different samples of Ce3Rh4Ge4 were synthesized from different starting compositions by melting of the elements in an arc-melting furnace followed by annealing sequences in a sealed tantalum ampoule in a muffle furnace. The structures of two different stacking variants were refined on the basis of temperature dependent single-crystal X-ray diffractometer data. At high temperature Ce3Rh4Ge4 adopts the U3Ni4Si4 type structure with strongly enhanced anisotropic displacement parameters for the Rh1 atoms. For the two different crystals, additional reflections start to appear at different temperatures. The first crystal showed additional reflections already at room temperature (stacking variant I) and the second one showed additional reflections emerging below 270 K (stacking variant II). Stacking variant I could be described with the (3+1)D superspace group I2/m(α0γ)00; α=1/2a*, γ=1/2c*; (Z=2), 1252 F2 values, 48 variables, wR=0.0306 for the main and wR=0.0527 for 440 1st order satellite reflections, similar to Pr3Rh4Ge4. For stacking variant II the (3+1)D superspace group is Immm(α00)00s; α=1/2a*; (Z=2). The structure could be refined with 1261 F2 values, 53 variables and residuals of wR=0.0331 for the main reflections and wR=0.1755 (R1obs=0.0788) for the 1st order satellite reflections, [a=406.2(1), b=423.7(1) and c=2497.1(1) pm]. The commensurate description could be transformed to a three-dimensional (3D) supercell with space group Pnma and Z=4: a=812.5(1), b=423.7(1), c=2497.1(2) pm, 1261 F2 values, 69 variables and wR=0.0525. The relation of the U3Ni4Si4 type structure, the (3+1)D modulated and the 3D supercells are discussed on the basis of group-subgroup schemes. Ab initio electronic structure calculations are in line with the diffraction experiments, revealing the lowest total energy for the Pnma phase. [ABSTRACT FROM AUTHOR]

The germanides RE3Pt4Ge6 (RE = Y, Pr, Nd, Sm, Gd-Dy) have been synthesized by arc-melting of the elements followed by inductive annealing to improve the crystallinity and allow for structural order. The compounds have been studied by powder X-ray diffraction; additionally the structure of Y3Pt4Ge6 has been refined from single-crystal X-ray diffractometer data. It exhibits a (3 + 1)D modulated structure, indicating isotypism with Ce3Pt4Ge6. The crystal structure can be described as an intergrowth between YIrGe2- and CaBe2Ge2-type slabs along [100]. Temperature-dependent magnetic susceptibility measurements showed Pauli paramagnetism for Y3Pt4Ge6 and Curie-Weiss paramagnetism for Pr3Pt4Ge6 and Nd3Pt4Ge6. Sm3Pt4Ge6 exhibits van Vleck paramagnetism, while antiferromagnetic ordering at TN = 8.1(1) K and TN = 11.0(1) K is observed for Gd3Pt4Ge6 and Tb3Pt4Ge6, respectively. [ABSTRACT FROM AUTHOR]

The stannide Sm2Rh3Sn5 was obtained by arcmelting of the elements and subsequent annealing at 1070 K in a silica tube. Sm2Rh3Sn5 crystallizes with the orthorhombic Y2Rh3Sn5 type structure, space group Cmc21, Z = 4: a = 444.46(8), b = 2636.2(4), c = 718.3(1) pm, wR = 0.0711, 1761 F² values and 61 variables. The three crystallographically independent rhodium atoms show tricapped trigonal prismatic coordination by samarium and tin atoms. Sm2Rh3Sn5 can be considered as a simple 1:1 intergrowth structure of TiNiSi- and NdRh2Sn4-related slabs of compositions SmRhSn and SmRh2Sn4. Temperature dependent magnetic susceptibility data revealed van Vleck type behavior caused by the proximity of the exited 6H7/2 state to the 6H5/2 ground state of Sm3+, and an antiferromagnetic ordering occurs at TN = 3.5(5) K. [ABSTRACT FROM AUTHOR]

The five ternary intermetallic compounds M2Pt6Al15 (M = Ca, Sc, Y, La, Lu) were prepared from the elements by arc-melting. The crystal structure was determined via single crystal X-ray diffraction. The title compounds crystallize in a superstructure of the RE0.67Pt2Al5 type structure (P63/mmc) in the monoclinic crystal system with space group P121/m1 (Sc2Pt6Al15: a = 734.19(2), b = 1628.96(10), c = 734.19(2) pm, β = 119.999(3)°; wR = 0.0356, 3034 F2 values, 68 variables). The superstructure can be derived by the superspace formalism using (3 + 2)D or (3 + 1)D interpretations of the diffraction data. The structural relation to the subcell structure is discussed on the basis of a group-subgroup scheme. In the crystal structure strongly bonded [Pt2Al4]δ- slabs are alternatingly stacked with ordered layers containing M atoms and Al3 triangles. [ABSTRACT FROM AUTHOR]

The equiatomic intermetallic phases CaAgIn [a = 482.75(7), b = 750.0(1), c = 835.5(1) pm], SrAgIn [a = 495.86(5), b = 794.71(9), c = 851.89(9) pm], LaAgIn [a = 489.99(5), b = 767.93(9), c = 837.53(9) pm], and EuAgIn [a = 493.02(7), b = 781.6(1), c = 844.2(1) pm] were synthesized from the elements in sealed niobum containers. They crystallize with the EuAuGe type structure, space group Imm2. The four structures were refined from single-crystal Xray data. The silver and indium atoms build up orthorhombically dis torted, puckered Ag3In3 hexagons, which are stacked in AA' sequence, leading to direct Ag-Ag and In--In interlayer bonding (e.g. 303 and 304 pm in CaAgIn). Temperature dependent magnetic susceptibility measurements show a magnetic moment of 7.40(1) μB per europium atom. EuAgIn orders antiferromagnetically at 5.7(5) K. The divalent nature of europium is also evident from 151Eu Mössbauer spectra: δ = -10.50(1) mm·s-1 at 78 K. [ABSTRACT FROM AUTHOR]

The intermetallic phase ErPd2Al3 was obtained by arc-melting of the elements and subsequent annealing for crystal growth. The sample was studied by X-ray diffraction on powders and single crystals. The structure of ErPd2Al3 was refined from X-ray diffraction data and revealed a superstructure of PrNi2Al3 - a CaCu5 derivative ( P6/ m, a=1414.3(1), c=418.87(3) pm wR=0.0820, 1060 F2 values, 48 variables. The same superstructure was subsequently found for PrNi2Al3 ( P6/ m, a=1407.87(4), c=406.19(2) pm, wR=0.0499, 904 F2 values, 47 variables). In the crystal structure, the aluminium and transition metal atoms form a polyanionic network according to [ T2Al3] δ− , while rare earth atoms fill cavities within the networks. They are coordinated by six transition metal and twelve aluminum atoms. In contrast to the PrNi2Al3 type structure reported so far, two crystallographic independent rare-earth sites are found of which one (1 b) is shifted by 1/2 z, causing a distortion in the structure along with a recoloring of the T and Al atoms in the network. [ABSTRACT FROM AUTHOR]

The intermetallic phase ErPd2Al3 was obtained by arc-melting of the elements and subsequent annealing for crystal growth. The sample was studied by X-ray diffraction on powders and single crystals. The structure of ErPd2Al3 was refined from X-ray diffraction data and revealed a superstructure of PrNi2Al3 - a CaCu5 derivative ( P6/ m, a=1414.3(1), c=418.87(3) pm wR=0.0820, 1060 F2 values, 48 variables. The same superstructure was subsequently found for PrNi2Al3 ( P6/ m, a=1407.87(4), c=406.19(2) pm, wR=0.0499, 904 F2 values, 47 variables). In the crystal structure, the aluminium and transition metal atoms form a polyanionic network according to [ T2Al3] δ− , while rare earth atoms fill cavities within the networks. They are coordinated by six transition metal and twelve aluminum atoms. In contrast to the PrNi2Al3 type structure reported so far, two crystallographic independent rare-earth sites are found of which one (1 b) is shifted by 1/2 z, causing a distortion in the structure along with a recoloring of the T and Al atoms in the network. [ABSTRACT FROM AUTHOR]

The quaternary gold arsenide oxides Ce9Au5− xAs8O6 and Pr9Au5− xAs8O6 were synthesized from the rare earth elements ( RE), rare earth oxides, arsenic and gold powder at maximum annealing temperatures of 1173 K. The structures were refined from single crystal X-ray diffractometer data: Pnnm, a=1321.64(6) pm, b=4073.0(3), c=423.96(2), wR2=0.0842, 3106 F2 values, 160 variables for Ce9Au4.91(4)As8O6 and Pnnm, a=1315.01(4), b=4052.87(8), c=420.68(1) pm, wR2=0.0865, 5313 F2 values, 160 variables for Pr9Au4.75(1)As8O6. They represent a new structure type and show a further extension of pnictide oxide crystal chemistry. A complex polyanionic gold arsenide network [Au5As8]15− (with some disorder in the gold substructure) is charge compensated with polycationic strands of condensed edge-sharing O@ RE4/4 and O@ RE4/3 tetrahedra ([ RE4O3]212+) as well as RE3+ cations in cavities. [ABSTRACT FROM AUTHOR]

The quaternary gold arsenide oxides Ce9Au5− xAs8O6 and Pr9Au5− xAs8O6 were synthesized from the rare earth elements ( RE), rare earth oxides, arsenic and gold powder at maximum annealing temperatures of 1173 K. The structures were refined from single crystal X-ray diffractometer data: Pnnm, a=1321.64(6) pm, b=4073.0(3), c=423.96(2), wR2=0.0842, 3106 F2 values, 160 variables for Ce9Au4.91(4)As8O6 and Pnnm, a=1315.01(4), b=4052.87(8), c=420.68(1) pm, wR2=0.0865, 5313 F2 values, 160 variables for Pr9Au4.75(1)As8O6. They represent a new structure type and show a further extension of pnictide oxide crystal chemistry. A complex polyanionic gold arsenide network [Au5As8]15− (with some disorder in the gold substructure) is charge compensated with polycationic strands of condensed edge-sharing O@ RE4/4 and O@ RE4/3 tetrahedra ([ RE4O3]212+) as well as RE3+ cations in cavities. [ABSTRACT FROM AUTHOR]

Pr3Rh4Ge4 was synthesized by melting of the elements in an arc-melting furnace followed by annealing in a sealed tantalum ampoule in a muffle furnace. Structure refinement was based on temperature dependent single-crystal X-ray diffractometer data. At ambient temperature Pr3Rh4Ge4 adopts the U3Ni4Si4 type structure with strongly enhanced anisotropic displacement parameters for Rh1. Below 230 K additional reflections start to appear and at 110 K the structure could be described with the (3+1)D superspace group I2/ m(α0γ)00; α=1/2, γ=1/2; ( Z=2). This commensurately modulated structure could be refined with 1448 F2 values, 39 variables and residuals of wR=0.0417 for the main reflections and wR=0.1520 for the satellites of 1st order, [ a=408.36(2), b=421.12(3) and c=2504.4(2) pm]. The commensurate description could be transformed to a 3D supercell with space group A2/ m and Z=4: a=816.72(2), b=421.12(3), c=2537.5(1) pm, β=99.26(1)°, 1448 F2 values, 69 variables and wR=0.0499. The relation of the U3Ni4Si4 type structure, the (3+1)D modulated and the 3D supercell is discussed on the basis of a group-subgroup scheme. Temperature dependent magnetic susceptibility data reveal Curie-Weiss paramagnetism with an experimental moment of 3.72(2) μB/Pr atom and a Weiss constant of -12.6(5) K. No magnetic ordering is evident down to 3 K. [ABSTRACT FROM AUTHOR]

Pr3Rh4Ge4 was synthesized by melting of the elements in an arc-melting furnace followed by annealing in a sealed tantalum ampoule in a muffle furnace. Structure refinement was based on temperature dependent single-crystal X-ray diffractometer data. At ambient temperature Pr3Rh4Ge4 adopts the U3Ni4Si4 type structure with strongly enhanced anisotropic displacement parameters for Rh1. Below 230 K additional reflections start to appear and at 110 K the structure could be described with the (3+1)D superspace group I2/ m(α0γ)00; α=1/2, γ=1/2; ( Z=2). This commensurately modulated structure could be refined with 1448 F2 values, 39 variables and residuals of wR=0.0417 for the main reflections and wR=0.1520 for the satellites of 1st order, [ a=408.36(2), b=421.12(3) and c=2504.4(2) pm]. The commensurate description could be transformed to a 3D supercell with space group A2/ m and Z=4: a=816.72(2), b=421.12(3), c=2537.5(1) pm, β=99.26(1)°, 1448 F2 values, 69 variables and wR=0.0499. The relation of the U3Ni4Si4 type structure, the (3+1)D modulated and the 3D supercell is discussed on the basis of a group-subgroup scheme. Temperature dependent magnetic susceptibility data reveal Curie-Weiss paramagnetism with an experimental moment of 3.72(2) μB/Pr atom and a Weiss constant of -12.6(5) K. No magnetic ordering is evident down to 3 K. [ABSTRACT FROM AUTHOR]