Search

Investigations in the ternary system Eu–Al–Pt led to the discovery of Eu4Al13Pt9, a new representative exhibiting a coloring variant of the Ho4Ir13Ge9 type structure. The orthorhombic structure was refined based on single crystal X-ray diffraction data (Pmmn, Wyckoff sequence e 9 b 3 a 5, a = 415.38(1), b = 1149.73(2), c = 1994.73(5) pm, wR2 = 0.0622, 1901 F 2 values, 88 variables) and full atomic ordering was observed for all atoms. The structure features a complex [Al13Pt9] δ– network with the Eu atoms occupying hexagonal prismatic cavities. The bonding situation of this new platinide was investigated via quantum-chemical calculations. According to Density Functional Theory (DFT) the title compound has to be described as a polar intermetallic material with a covalently bonded [Al13Pt9] δ– polyanion showing strong Pt–Al alongside weak Al–Al and Pt–Pt bonding and Eu cations in the cavities.

Three new iridium aluminum intermetallics CaAl4Ir2, SrAl4Ir2, and EuAl4Ir2 were synthesized from the elements using silica or tantalum ampoules. They crystallize in the tetragonal crystal system with space group P4/ncc and lattice parameters of a = 782.20(1) and c = 779.14(2) pm for CaAl4Ir2, a = 797.62(1) and c = 772.75(2) pm for SrAl4Ir2, and finally a = 791.78(5) and c = 773.31(5) pm for EuAl4Ir2. All compounds crystallize isostructurally and adopt a new structure type that can be derived from the KAu4In2 type structure. To compare the structures from a crystallographic point of view, a group–subgroup relation between KAu4In2 and EuAl4Ir2 as well as KAu4In2 and KAu4Sn2 have been established using the Bärnighausen formalism. Finally, quantum-chemical calculations have been conducted, showing that in all three title compounds, a polyanionic [Al4Ir2]δ– network exists with significant (polar) bonding interactions, while the respective Caδ+, Srδ+, and Euδ+ cations are located in octagonal channels. Graphical abstract

Single crystals of a new samarium platinum indide have been synthesized in a high-frequency furnace under flowing argon atmosphere. The crystal structure of SmPt2In2 was determined from single-crystal X-ray data (R1 = 0.0416 for 1049 F values and 63 variables). It belongs to the CePt2In2 structure type with the following crystallographic parameters: P21/m, mP20, Z = 4, a = 10.0561(8), b = 4.4214(2), c = 10.1946(8) Å, β = 116.492(5)°, V = 405.68(5) Å3. Physical properties were studied and the crystal chemical discussion is supported by electronic structure calculations.

The title compounds have been synthesized by reaction of the elements in sealed tantalum crucibles in a muffle furnace using special annealing sequences. The crystal structures of YbNi2.31Al2.69 (R1 = 0.0100 for 212 F 2 values and 18 variables) and for ErNi2.23Al2.77 (R1 = 0.0154 for 255 F 2 values and 18 variables) were refined from single crystal X-ray data. They belong to the YNi2Al3 type (i3 superstructure of CaCu5) with the following crystallographic parameters: space group P 6 / m m m $P6/mmm$ , Pearson symbol hP18, Z = 3, a = 8.2723(12), c = 4.0672(8) Å, V = 241.03(8) Å3 for YbNi2.31Al2.69 and a = 8.9109(13), c = 4.0669(8) Å, V = 279.66(8) Å3 for ErNi2.23Al2.77. The crystal chemical discussion is supported by electronic structure calculations.

The new ternary compound La3Ni4Al2 has been synthesized and the crystal structure has been studied by X-ray single crystal diffraction. La3Ni4Al2 is the first aluminide, crystallizing in the La3Ni4Ga2-type. The crystal structure of La3Ni4Al2 consists of La-layers and hetero-atomic Ni/Al layers, sequentially alternating along the a axis (pseudo-hexagonal c axis). According to electronic structure calculations using the tight-binding linear muffin-tin orbital method in the atomic-sphere approximation (TB-LMTO-ASA), strong Al–Ni interactions have been established. The coordination polyhedra for the Al atoms are cuboctahedra, whereas the bicapped square prism and bicapped square antiprism are typical for nickel atoms. The lanthanum atoms are enclosed in pseudo Frank–Kasper polyhedra.

The equiatomic rare earth iridium indides REIrIn (RE=La, Pr, Nd, Er–Yb) were synthesized by reaction of the elements in induction or muffle furnaces and were characterized through X-ray powder patterns. The structures of LaIr0.86In1.14, PrIr0.89In1.11, NdIr0.94In1.06, ErIrIn (all ZrNiAl type, P6̅2m), and YbIrIn (TiNiSi type, Pnma) were refined from single crystal X-ray diffractometer data. Refinements of the occupancy parameters revealed small degrees of solid solutions with indium substitution on the iridium sites. Chemical bonding analyses and electronic structure calculations indicate the dominance of metallic bonding in addition to partial ionic interactions between the cations and polyanions, as well as covalent contributions between the indium and iridium atoms.