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The isotypic intermetallic compounds RE2RuMg2 (RE = Dy, Ho, Er, Tm, Lu) were synthesized from the elements in sealed niobium tubes in a muffle furnace with different annealing sequences. The polycrystalline samples were characterized through Guinier powder patterns. The structure of Er2RuMg2 was refined on the basis of single-crystal X-ray diffractometer data: ordered Os2Al3 type, I4/mmm, a = 338.44(5), c = 2029.4(4) pm, wR2 = 0.0237, 234F2 values, and 10 variables. The Er2RuMg2 structure is an i5 superstructure of the bcc packing with complete ordering of the erbium, ruthenium, and magnesium atoms. Layers of compressed, ruthenium-centered erbium cubes (290 pm Er-Ru) alternate with layers of edge-sharing magnesium tetrahedra (311 and 338 pm Mg-Mg); a new type of magnesium substructure. Temperature dependent magnetic susceptibility studies confirm the stable trivalent ground states of the rare earth elements. Lu2RuMg2 is a Pauli paramagnet and the remaining four compounds show Curie paramagnetism. Dy2RuMg2 and Ho2RuMg2 are accompanied by antiferromagnetic ordering at 8.9(1) and 3.6(1) K, respectively. [ABSTRACT FROM AUTHOR]

The intermetallic zinc compounds AAu4Zn2 ( A = Ca, Ce, Pr, Nd) were obtained by induction melting of the elements in sealed tantalum tubes. The samples were studied by X-ray diffraction on powders. The structures of the calcium and the cerium compound were refined from single crystal diffraction data: YbAl4Mo2 type, I4/ mmm, a = 692.8(1), c = 527.6(1) pm, wR2 = 0.0304, 244 F2 values and 11 variables for CaAu4.08Zn1.92 and a = 699.6(1), c = 531.2(1) pm, wR2 = 0.1152, 186 F2 values and 10 variables for CeAu4Zn2. The 4 d site of the calcium compound shows small mixed Zn/Au occupancy. The AAu4Zn2 structures consist of three-dimensional gold networks (272-286 pm Au-Au in CeAu4Zn2), which are penetrated by linear infinite zinc chains (266 pm Zn-Zn in CeAu4Zn2) that extend along the c axis. The calcium or rare earth atoms fill Au12 cavities within the networks. Temperature dependent magnetic susceptibility measurements reveal Pauli paramagnetism for CaAu4Zn2 and Curie-Weiss paramagnetism for the cerium, praseodymium, and neodymium compound, respectively. No magnetic ordering was evident down to 2.5 K. The static intermediate-valent compound Ce2RuZn4 crystallizes with a superstructure of CeAu4Zn2 ( klassengleiche subgroup P4/ nmm) with a different but fully ordered substitution on the transition metal sites. This structural relationship is discussed on the basis of a group-subgroup scheme. [ABSTRACT FROM AUTHOR]

The intermetallic compounds Sr2Au6.52Zn2.48, Sr2Au6Zn3, and Sr2Au6Ga3 were obtained by induction melting of the elements in sealed tantalum tubes. Their structures were studied by X-ray diffraction on powders and refined from single crystal diffraction data: R $\bar{3}$ c, a = 844.5(2), c = 2187.7(5) pm, wR2 = 0.0411, 936 F2 values and 20 variables for Sr2Au6.52Zn2.48; a = 841.6(2), c = 2191.5(7) pm, wR2 = 0.0126, 587 F2 values and 19 variables for Sr2Au6Zn3; and a = 841.9(2), c = 2191.1(7) pm, wR2 = 0.0199, 660 F2 values and 19 variables for Sr2Au6Ga3. The gold substructures of Sr2Au6Zn3 and Sr2Au6Ga3 can be considered as diamond polytypes with 6R stacking sequences (287-304 pm Au-Au in Sr2Au6Zn3). The cavities formed by this network are filled in an ordered manner by strontium atoms and Zn3 (281 pm Zn-Zn), respectively Ga3 (286 pm Ga-Ga) triangles in a 2:1 ratio. Consequently one can describe the Sr2Au6Zn3 and Sr2Au6Ga3 structures as ordered substitution variants of the Zintl phase CaIn2. This structural relationship is discussed on the basis of a group-subgroup Scheme. Sr2Au6.52Zn2.48 shows Zn/Au mixing on the triangle. [ABSTRACT FROM AUTHOR]

The intermetallic compounds Sr2Au6.52Zn2.48, Sr2Au6Zn3, and Sr2Au6Ga3 were obtained by induction melting of the elements in sealed tantalum tubes. Their structures were studied by X-ray diffraction on powders and refined from single crystal diffraction data: R $\bar{3}$ c, a = 844.5(2), c = 2187.7(5) pm, wR2 = 0.0411, 936 F2 values and 20 variables for Sr2Au6.52Zn2.48; a = 841.6(2), c = 2191.5(7) pm, wR2 = 0.0126, 587 F2 values and 19 variables for Sr2Au6Zn3; and a = 841.9(2), c = 2191.1(7) pm, wR2 = 0.0199, 660 F2 values and 19 variables for Sr2Au6Ga3. The gold substructures of Sr2Au6Zn3 and Sr2Au6Ga3 can be considered as diamond polytypes with 6R stacking sequences (287-304 pm Au-Au in Sr2Au6Zn3). The cavities formed by this network are filled in an ordered manner by strontium atoms and Zn3 (281 pm Zn-Zn), respectively Ga3 (286 pm Ga-Ga) triangles in a 2:1 ratio. Consequently one can describe the Sr2Au6Zn3 and Sr2Au6Ga3 structures as ordered substitution variants of the Zintl phase CaIn2. This structural relationship is discussed on the basis of a group-subgroup Scheme. Sr2Au6.52Zn2.48 shows Zn/Au mixing on the triangle. [ABSTRACT FROM AUTHOR]

Abstract: The title compounds were prepared by induction levitation melting of the elemental components and subsequent annealing. UMnGe (Pnma, a = 686.12(9), b = 425.49(6) and c = 736.5(1) pm) adopts the orthorhombic structure of TiNiSi and U2Mn3Ge (P63/mmc, a = 524.3(2) and c = 799.2(3) pm) possesses the hexagonal Mg2Cu3Si-type structure (ordered variant of the hexagonal Laves phase MgZn2). Both structures were refined from X-ray powder data to residuals of R I = 0.021 and 0.014 for UMnGe and U2Mn3Ge, respectively. The manganese and germanium atoms in UMnGe build up a three-dimensional [MnGe] network of ordered Mn3Ge3 hexagons with Mn–Ge distances ranging from 248 to 259 pm. The uranium atoms are coordinated by two tilted Mn3Ge3 hexagons. The manganese atoms in U2Mn3Ge build up Kagomé networks with 252 and 272 pm Mn–Mn distances which are connected via the germanium atoms (254 pm Mn–Ge) to a three-dimensional network. A remarkable feature of the U2Mn3Ge structure is a short U–U distance of 278 pm between adjacent cavities of the [Mn3Ge] network. From DFT based electronic structure calculations both germanides are found more cohesive than the Laves phase UMn2, thus underpinning the substantial role of Mn–Ge bonding. Calculations for both germanides show ferrimagnetic ground states with antiparallel spin alignments between U and Mn. The valence bands show bonding characteristics for interactions of atoms of different chemical natures and significant Mn–Mn bonding in U2Mn3Ge. Preliminary investigation of UMnGe by magnetization measurements confirms an antiferromagnetic arrangement below T N = 240 K. [Copyright &y& Elsevier]

The intermetallic compounds ScPdZn and ScPtZn were prepared from the elements by high-frequency melting in sealed tantalum ampoules. Both structures were refined from single crystal X-ray diffractometer data: YAlGe type, Cmcm, a = 429.53(8), b = 907.7(1), c = 527.86(1) pm, wR2 = 0.0375, 231 F2 values, for ScPdZn and a = 425.3(1), b = 918.4(2), c = 523.3(1) pm, wR2 = 0.0399, 213 F2 values for ScPtZn with 14 variables per refinement. The structures are orthorhombically distorted variants of the AlB2 type. The scandium and palladium (platinum atoms) build up ordered networks Sc3Pd3 and Sc3Pt3 (boron networks) which are slightly shifted with respect to each other. These networks are penetrated by chains of zinc atoms (262 pm in ScPtZn) which correspond to the aluminum positions, i.e. Zn(ScPd) and Zn(ScPt). The corresponding group-subgroup scheme and the differences in chemical bonding with respect to other AlB2-derived REPdZn and REPtZn compounds are discussed. 45Sc solid state NMR spectra confirm the single crystallographic scandium sites. From electronic band structure calculations the two compounds are found metallic with free electron like behavior at the Fermi level. A larger cohesive energy for ScPtZn suggests a more strongly bonded intermetallic than ScPdZn. Electron localization and overlap population analyses identify the largest bonding for scandium with the transition metal (Pd, Pt). [ABSTRACT FROM AUTHOR]

The new antimonides RE8Rh17Sb14 (RE = La, Ce, Pr, Nd) were synthesised by arc-melting. Crystals can be grown in a high-frequency furnace. The RE8Rh17Sb14 phases were characterized by powder X-ray diffraction. They crystallize with a tetragonal, CaBe2Ge2-related superstructure which was refined for Ce8Rh17Sb14 on the basis of single crystal X-ray diffractometer data: I4cm, a = 1239.8 (3), c = 2101.8 (8) pm, wR = 0.065, 2924 F values, and 109 parameters. The rhodium and antimony atoms and vacancies show full ordering on the [Be2Ge2] substructure, leading to a composition of Ce8Rh17Sb14≡CeRh2.13Sb1.75. The superstructure formation is discussed on the basis of a group-subgroup scheme together with the related structures of CePt2+xSb2−y, CeNi1.91As1.94 and URh1.6As1.9. Temperature dependent susceptibility measurements show Pauli paramagnetism for La8Rh17Sb14 and Curie–Weiss paramagnetism for RE8Rh17Sb14 (RE = Ce, Pr, Nd). No magnetic ordering was detected down to 2.5 K. [ABSTRACT FROM AUTHOR]

The intermetallic compounds RECuMg and REPdMg ( RE=La, Ce) were prepared and characterized by magnetic susceptibility and heat-capacity measurements. They crystallize with an ordered USi type structure (space group P4/ mbm) and the cerium compounds contain stable trivalent cerium ions, which undergo antiferromagnetic ordering at ∼7.5 and ∼4 K, respectively. In high magnetic fields CeCuMg exhibits spin reorientation with critical field strength of 40 kOe at 5 K. The data are compared to the non-magnetic isotypic compounds La TMg ( T=Cu, Ni, Pd) and to the already reported intermediate valent CeNiMg. [ABSTRACT FROM AUTHOR]

The lithium-rich silicide LiPtSi was synthesised from the elements by high-temperature synthesis in a sealed niobium ampoule. Its structure was refined on the basis of single-crystal X-ray diffraction data: R32, a = 693.7(2), c = 1627.1(4) pm, w R2 = 0.0762, 525 F values and 21 variables. The striking structural motifs of the LiPtSi structure are silicon atoms with a slightly distorted trigonal prismatic platinum coordination with short Si-Pt distances (238-246 pm). Always two trigonal prisms are condensed via a common Pt triangle, and these double units built up a three-dimensional network by condensation via common corners. The channels left by this prismatic network are filled by two crystallographically independent lithium sites in a 3:1 ratio. The single crystal X-ray data were fully confirmed by neutron powder diffraction and Li magic-angle spinning (MAS)-nuclear magnetic resonance (NMR) results. The two distinct lithium sites are well differentiated by their Li isotropic chemical shift and nuclear electric quadrupolar interaction parameters. MAS-NMR spectra reveal signal coalescence effects above 300 K, indicating chemical exchange between the lithium sites on the millisecond timescale. The spectra can be simulated with a simple two-site exchange model. From the resulting temperature-dependent correlation times, an activation energy of 50 kJ/mol is extracted. [ABSTRACT FROM AUTHOR]

Sc3RuC4 and Sc3OsC4 were synthesized by arc-melting and subsequent annealing. At room temperature, they crystallize with the Sc3CoC4 structure, space group Immm. At 223 and 255 K, Sc3RuC4 and Sc3OsC4, respectively, show a monoclinic distortion caused by a pair-wise displacement of the one-dimensional [Ru(C2)2]δ− and [Os(C2)2]δ− polyanions, which are embedded in a scandium matrix. Superstructure formation leads to shorter Ru−Ru and Os−Os distances of 316 pm between adjacent [Ru(C2)2]δ− and [Os(C2)2]δ− polyanions. Each ruthenium (osmium) atom is covalently bonded to four C2 pairs with Ru−C (Os−C) distances of 220−222 pm. A comparison of the C−C bond distances at room temperature in Sc3TC4 with T representing a group 8 transition metal (Fe, Ru, Os) reveals a minimum in the case of the 4d metal Ru: 144.98(11) pm (Fe), 142.8(7) pm (Ru), and 144.6(4) pm (Os). Analysis of the local electronic structure of the [T(C2)2] moieties hints at a complex interplay between chemical bonding and relativistic effects, which is responsible for the V-shaped pattern of the C−C bond distances (long, short, and long for T = Fe, Ru, and Os, respectively). Relativistic effects lead to a strengthening of covalent T−C bonding. This is shown on the basis of periodic DFT calculations by a significant increase of the charge density at the T−C bond critical points (0.55 < 0.57 < 0.64 eÅ−3) down the row of group 8 elements. These structural characteristics and topological features do not change in the corresponding low-temperature phases of Sc3RuC4 and Sc3OsC4. However, topological analyses of theoretical charge density distributions reveal distinct changes of the valence shell charge concentrations at the transition metal centers due to the monoclinic distortions. Presumably, the local electronic situation at the transition metals reflects the origin and extent of these monoclinic distortions. At 223 and 255 K, Sc3RuC4 and Sc3OsC4, respectively, show a monoclinic distortion caused by a pair-wise displacement of their one-dimensional [Ru(C2)2]δ− and [Os(C2)2]δ− polyanions. Superstructure formation leads to shorter Ru−Ru and Os−Os distances of 316 pm between adjacent [Ru(C2)2]δ− and [Os(C2)2]δ− polyanions. Analysis of the local electronic structure of the [T(C2)2] moieties hints at a complex interplay between chemical bonding and relativistic effects. [ABSTRACT FROM AUTHOR]

The gadolinium–rhodium–indide Gd3Rh1.940(7)In4 was prepared by arc-melting of the elements and subsequent annealing in a corundum crucible in a sealed silica tube. Gd3Rh1.940(7)In4 adopts the hexagonal Lu3Co1.87In4 type, space group $P{\bar 6}$, a = 781.4(5), c = 383.8(3) pm, wR2 = 0.0285, BASF = 0.375(1) (merohedric twinning via a twofold axis ( xx0)), 648 F2 values, 22 variables. The structure is derived from the well known ZrNiAl type through an ordering of rhodium and indium atoms on the Ni2 sites. The Rh/In ordering forces a reduction of the space group symmetry from $P{\bar 6}62m$ to $P{\bar 6}$, leading to merohedric twinning for the investigated crystal. The Rh1 site has an occupancy of only 94.0(7)%. The investigated crystal had a composition Gd3Rh1.940(7)In4. The main geometrical motif are three types of centered, tricapped trigonal prisms, i.e., [Rh1In26Gd3], [Rh2Gd6In23], and [In1Gd6In23]. The shortest interatomic distances occur for Rh–In (276–296 pm) followed by In–In (297 pm). Together, the rhodium and indium atoms build up a three-dimensional [Rh1.940(7)In4] network, in which the gadolinium atoms fill slightly distorted pentagonal channels. The crystal chemistry of Gd3Rh1.940(7)In4 is discussed on the basis of a group-subgroup scheme. [ABSTRACT FROM AUTHOR]

Abstract: The rare earth transition metal carbides Sc3RhC4 and Sc3IrC4 were synthesized by arc-melting of cold-pressed pellets of the elements (ideal atomic ratio) under an atmosphere of purified argon. The structures of the two carbides were investigated by X-ray diffraction on both powders and single crystals. Sc3RhC4 and Sc3IrC4 crystallize with a pronounced Sc3CoC4 type subcell, space group Immm. Weak additional reflections indicated the formation of a superstructure by doubling the subcell along with a monoclinic distortion. The superstructure of Sc3RhC4 and Sc3IrC4 was refined from X-ray single crystal diffractometer data: , , , , , , 821 values for Sc3RhC4 and , , , , , 816 values for Sc3IrC4 with 32 variables per refinement. The formation of the superstructure is explained on the basis of a group-subgroup scheme. Both structures are composed of one-dimensional infinite polyanionic layers [T(C2)2] n (, Ir) that are separated by the scandium atoms. While these polyanionic layers are planar in the Sc3CoC4 type structure, a slight puckering occurs in Sc3RhC4 and Sc3IrC4. An ionic formula splitting can to a first approximation be written as (3Sc3+)[TC4]9−. Chemical bonding in Sc3RhC4 and Sc3IrC4 is briefly discussed. [Copyright &y& Elsevier]

Zr5Ir2In4 was synthesized by reaction of the elements in a glassy carbon crucible in a water-cooled sample chamber of an induction furnace. The sample was characterized by X-ray diffraction on both powder and single crystals. Zr5Ir2In4 crystallizes with a pronounced Lu5Ni2In4 type subcell, space group Pbam, a = 1739.5(6), b = 766.3(2), c = 338.9(2) pm. Weak additional reflections force a doubling of the subcell c axis. The superstructure of Zr5Ir2In4 is of a new type: Pnma, a = 1739.5(6), b = 677.8(2), c = 766.3(2) pm, wR2 = 0.0529, 1592 F2 values, and 60 variable parameters. The group-subgroup scheme for the klassengleiche symmetry reduction is presented. The formation of the superstructure is most likely due to a puckering effect (size of the iridium atoms). The crystal chemistry of Zr5Ir2In4 is briefly discussed. [ABSTRACT FROM AUTHOR]

The intermetallic compounds IrIn2-xMgx (x=0.53, 0.70) and Mg3-xInxIr (x=0.80, 0.97) were synthesized by induction melting of the elements in glassy carbon crucibles in a water-cooled sample chamber. All compounds were investigated by X-ray powder diffraction and the structures have been refined on the basis of single-crystal diffractometer data: Mg2Cu type, Fddd, a=981.9(3), b=528.8(1), c=1799.2(4) pm, wR2=0.0620, 507 Fo2 values, 19 variables for IrIn1.47Mg0.53, a=980.8(1), b=528.1(1), c=1797.3(3) pm, wR2=0.0924, 502 Fo2 values, 19 variables for IrIn1.30Mg0.70, and Cu3P type, P63cm, a=788.7(2), c=836.6(2) pm, wR2=0.0403, 715 Fo2 values, 29 variables for Mg2.03In0.97Ir, a=788.6(1), c=832.7(2) pm, wR2=0.0407, 489 Fo2 values, 30 variables for Mg2.20In0.80Ir. The Mg2Cu type structure of IrIn2 has two crystallographically different indium sites which both show mixed In/Mg occupancy. For both crystals a higher magnesium substitution occurs for the In1 site. In the Cu3P type structure of Mg2.03In0.97Ir and Mg2.20In0.80Ir, all four magnesium sites show Mg/In mixing. The by far highest indium occupancy is observed for the Mg1 sites, i.e. 59% in Mg2.03In0.97Ir and 50% in Mg2.20In0.80Ir. The crystal chemistry of these intermetallic compounds is briefly discussed. [Copyright &y& Elsevier]

Pure samples of CaPdSn, CaPtSn, SrPtSn, SrAuSn and BaAuSn can be prepared by reacting the elements in glassy carbon crucibles or in sealed tantalum tubes in a water-cooled sample chamber of a high-frequency furnace. The stannides have been investigated by X-ray diffraction on powders. Single crystal data yielded: TiNiSi type, Pnma, a=764.16(7), b=470.74(4), c=799.64(7) pm, wR2=0.0622, 469 F2 values, 20 variables for SrPtSn, and CaCuGe type, Pnma, a=2341.4(3), b=481.80(5), c=826.7(1) pm, wR2=0.1368, 1136 F2 values, 56 variables for SrAuSn. The platinum (gold) and tin atoms form two-dimensional layers of puckered Pt3Sn3 and Au3Sn3 hexagons with short Pt&z.sbnd;Sn (276 and 278 pm) and Au&z.sbnd;Sn (279–286 pm) intralayer distances. These condensed two-dimensionally infinite nets are interconnected to each other via Pt&z.sbnd;Sn contacts (279 pm) in SrPtSn. In SrAuSn very weak interlayer Au&z.sbnd;Sn (312 pm) and Au&z.sbnd;Au (340 pm) contacts occur, but stronger Sn&z.sbnd;Sn (304 pm) interactions. The SrAuSn structure is a superstructure of SrPtSn resulting from an isomorphic transition of index 3 from Pnma to Pnma. The KHg2 type subcell of BaAuSn was determined from Guinier powder data: Imma, a=493.5(1), b=817.2(1), c=844.5(1) pm. 119Sn Mo¨ssbauer spectra of TiNiSi type CaPdSn and CaPtSn show a single signal at 77 K at isomer shifts of δ=1.964(5) and 1.857(4) mm s−1, respectively, subject to quadrupole splitting of ΔEQ=0.94(3) and 0.89(1) mm s−1. SrAuSn shows two superimposed signals in a ratio of 2:1 at 77 K: δ1=2.03(5), δ2=2.12(5) mm s−1, ΔEQ1=0.9(1) and ΔEQ2=0.6(2) mm s−1. [ABSTRACT FROM AUTHOR]

Ca3Rh4In12 was prepared under multianvil high-pressure (10.5 GPa) high-temperature (1370 K) conditions from the precursor compound CaRhIn2. The new indide was investigated by X-ray diffraction on powders and single crystals: Gd3Ru4Al12 type, P63/mmc, a=944.5(3), c=1042.7(4) pm, wR2=0.0343, 379 F2 values and 26 variables. Ca3Rh4In12 belongs to a family of hexagonal structures, i.e., ErZn5, EuMg5.2, Gd3Ru4Al12, Sc3Ni11Si4 and Sc3Ni11Ge4 with very similar structures. So far, Ca3Rh4In12 is the only compound of this family with complete long-range order and no mixed occupancies. The two rhodium atoms have eight indium neighbours in a distorted cube-like coordination. These distorted RhIn8 cubes share six common edges parallel to the ab-plane and two common corners along the c direction resulting in a complex three-dimensional [Rh4In12] network in which the calcium atoms fill larger voids. The Rh&z.sbnd;In and In&z.sbnd;In distances range from 261 to 286 pm and from 303 to 368 pm, respectively. Considering the strong Rh&z.sbnd;In and In&z.sbnd;In interactions as well as the electropositive character of the calcium atoms, electron counting can be written as (3Ca2+)6+[Rh4In12]6−. The rhodium–indium substructure of Ca3Rh4In12 is discussed in comparison with the various rhodium–indium networks in the structures of RhIn, RhIn3, CaRhIn, CaRhIn2, Sr2Rh2In3, SrRhIn2, CaRhIn4, EuRh2In8 and HoRhIn. [ABSTRACT FROM AUTHOR]