The stannide Li4Rh3Sn5 was synthesized by induction-melting of the elements in a sealed tantalum ampoule. The sample was characterized by powder X-ray diffraction and the Li4Rh3Sn5 structure was refined from single-crystal X-ray diffractometer data: new type, orthorhombic space group Pnnm, a = 813.27(11), b = 2,259.6(3), c = 449.94(6) pm, wR2 = 0.0486, 1577 F-2 values and 64 variables. The rhodium and tin atoms form a rigid covalently bonded three-dimensional [Rh3Sn5] network with Rh-Sn distances ranging from 263 to 277 pm. Within this network, the tin atoms form two different substructures, i. e., angled Sn1-Sn4-Sn5 units and isolated Sn2 and Sn3 atoms. The lithium atoms fill cages within the [Rh3Sn5] network. They have coordination numbers 11, 12 and 13. Based on their different Li-7 resonance shifts two groups of distinct local environments can be identified in an intensity ratio of 3:1, namely the 4g Wyckoff sites Li1, Li2, and Li5, and the 2c Wyckoff sites Li3 and Li4. The whole Li4Rh3Sn5 structure can be described by condensation of the Li1@LiRh4Sn6, Li2@Li2Rh4Sn6, Li3@Li2Rh4Sn6, and Li4@Li2Rh4Sn6 polyhedra, including the Li5 atoms which are within the Li1 coordination sphere. The Sn-119 M & ouml;ssbauer spectrum of Li4Rh3Sn5 shows a superposition of two sub-signals in a ratio of 60:40. The two sub-signals with similar isomer shift are discernable through their quadrupole splitting parameters: similar to 1.93 mm s(-1) for the tin atoms of the angled Sn-3 unit, and similar to 1.20 mm s(-1) for the isolated tin atoms with a more symmetric electron density distribution.

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The new germanide TaRhGe was prepared from the elements by arc-melting and subsequent annealing at 1020 K for 10 days. TaRhGe crystallizes with the TiNiSi-type structure, space group Pnma, Z = 4, oP12, a = 640.2(2), b = 383.2(2), c = 741.7(2) pm, wR2 = 0.0550, 432 F-2 values, 20 parameters. The structure consists of a three-dimensional [RhGe] network of distorted RhGe4/4 tetrahedra with Rh-Ge distances ranging from 244 to 250 pm. The tantalum atoms are coordinated within this network by two folded and mutually tilted Rh3Ge3 hexagons. TaRhGe is Pauli-paramagnetic and shows no superconducting transition down to 3 K.

The stannides Li8Rh7Sn8 and Li1.23Rh1.77Sn were synthesized from the elements in sealed niobium ampoules. The structures were refined on the basis of single crystal X-ray diffractometer data: MnCu2Al type (Heusler phase), Fm (3) over barm, a = 615.5(4) pm, wR2 = 0.0319, 106F(2) values, 6 variables for Li1.23Rh1.77Sn and P (3) over bar m1, a = 894.4(4) pm, c = 1107.3(4) pm, wR2 = 0.0600, 1287F(2) values, 48 variables for Li8Rh7Sn8 which crystallizes with a new structure type. The rhodium site in Li1.23Rh1.77Sn shows Rh/Li mixing. The structure of Li8Rh7Sn8 contains two pronounced structural motifs. Layers of edge-sharing RhSn6 octahedra alternate with layers of six-membered rings of corner-sharing SnRh4 tetrahedra in UDUDUD orientation. The [Rh7Sn8](delta-) polyanionic network is characterized by covalent rhodium-tin bonding.

The silicide Li 13.7 Rh8Si 18.3 was synthesized from the elements in a sealed niobium ampoule at 1370 K followed by slow cooling. The sample was studied by powder and single-crystal X-ray diffraction. Li 13.7 Rh 8 Si 18.3 crystallizes with a non-centrosymmetric occupancy variant of the R-phase structureMg 32 ( Al, Zn) 49 : I23, a = 1306.9(2) pm, wR2 = 0.0447, 1286 F 2 values, and 53 variables. Striking structural motifs of the Li 13.7 Rh 8 Si 18.3 structure are M 12 icosahedra and M 60 buckyball-type clusters (M = Si + Rh), both partially built up from mixed-occupied sites.

The lithium-rich silicide Li4Pt3Si 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, wR2 = 0.0762, 525 F2 values and 21 variables. The striking structural motifs of the Li4Pt3Si 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 Pt3 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 7Li magic-angle spinning (MAS)–nuclear magnetic resonance (NMR) results. The two distinct lithium sites are well differentiated by their 7Li 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.

The lithium-rich silicide Li4.82(2)Pd2.90(2)Si2.28(2) was obtained by melting of palladium and silicon in an excess of lithium using a sealed niobium ampoule as container material. The structure of this new silicide was refined on the basis of single crystal X-ray diffractometer data: P43212, a = 679.1(1), c = 3774.7(8) pm, wR2 = 0.0712, Flack 0.03(11), 2072 F2 values, and 108 variables. The polar Li4.82(2)Pd2.90(2)Si2.28(2) structure consists of a complex three-dimensional [Pd2.90(2)Si2.28(2)] network which leaves larger channels along the c direction which are filled by the lithium atoms. One lithium site shows a mixed occupancy with silicon and two palladium sites show Pd/Si mixing, leading to the composition Li4.82(2)Pd2.90(2)Si2.28(2) for the investigated crystal.

The silicide LiRh2Si2 was synthesized from the elements in a sealed niobium ampoule and was characterized by X-ray powder and single-crystal diffraction: FeMo2B2 type (ordered version of U3Si2), P4/mbm, a = 698.1(5), c = 274.6(4) pm, wR2 = 0.0842, 186 F-2 values and I I variables. The rhodium and silicon atoms build up a covalently bonded three-dimensional [Rh2Si2] network (244-248 pin Rh-Si), in which the lithium atoms fill larger channels which extend along the c axis. A similar structural arrangement occurs in LiY2Si2, however, the strong difference in size between rhodium and yttrium leads to different distortions. LiRh2Si2 and LiY2Si2 are isopointal rather than isotypic. The crystal chemistry and bonding peculiarities of both silicides are discussed on the basis of ab initio electronic structure calculations. Li-7 solid-state NMR studies on LiRh2Si2 revealed restricted motional narrowing due to lithium atomic diffusion in the temperature range 170-450 K.

Zeitschrift für anorganische und allgemeine ChemieVolume 634, Issue 11 p. 2034-2034 Poster The new Silicide Li4Pt3Si - Synthesis and Crystal Structure Tim Dinges, Tim Dinges Institut für Anorganische und Analytische Chemie, Westfälische Wilhelms-Universität Münster, Corrensstraße 30, 48149 MünsterSearch for more papers by this authorRolf-Dieter Hoffmann, Rolf-Dieter Hoffmann Institut für Anorganische und Analytische Chemie, Westfälische Wilhelms-Universität Münster, Corrensstraße 30, 48149 MünsterSearch for more papers by this authorRainer Pöttgen, Corresponding Author Rainer Pöttgen pottgen@uni-muenster.de Institut für Anorganische und Analytische Chemie, Westfälische Wilhelms-Universität Münster, Corrensstraße 30, 48149 MünsterInstitut für Anorganische und Analytische Chemie, Westfälische Wilhelms-Universität Münster, Corrensstraße 30, 48149 MünsterSearch for more papers by this author Tim Dinges, Tim Dinges Institut für Anorganische und Analytische Chemie, Westfälische Wilhelms-Universität Münster, Corrensstraße 30, 48149 MünsterSearch for more papers by this authorRolf-Dieter Hoffmann, Rolf-Dieter Hoffmann Institut für Anorganische und Analytische Chemie, Westfälische Wilhelms-Universität Münster, Corrensstraße 30, 48149 MünsterSearch for more papers by this authorRainer Pöttgen, Corresponding Author Rainer Pöttgen pottgen@uni-muenster.de Institut für Anorganische und Analytische Chemie, Westfälische Wilhelms-Universität Münster, Corrensstraße 30, 48149 MünsterInstitut für Anorganische und Analytische Chemie, Westfälische Wilhelms-Universität Münster, Corrensstraße 30, 48149 MünsterSearch for more papers by this author First published: 28 August 2008 https://doi.org/10.1002/zaac.200870052Citations: 1AboutPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL Share a linkShare onFacebookTwitterLinked InRedditWechat No abstract is available for this article.Citing Literature Volume634, Issue11September 2008Pages 2034-2034 RelatedInformation

The feasibility of growing alkali halides in the hypothetical 5-5 structure type on a specially prepared substrate of LiNbO 3 has been investigated. The highest degree of steering towards this structure is achieved by growing NaBr on a LiNbO 3 (001)-surface, where the outermost layer of oxygen atoms is followed by a layer of niobium atoms. The kinetic stability, against transition into the rock salt structure, of the 5-5 structure grown on the substrate is enhanced compared to the bulk 5-5 phase, but the 5-5 structure will nevertheless still be metastable compared to the rock salt structure type that constitutes the thermodynamically stable bulk phase of NaBr under standard conditions

Computer simulation techniques have been used to investigate the defect chemistry of perovskite-structured ionic conductors based upon AZrO(3)(A = Ca, Ba) and LaMO(3)(M = Sc, Ga). Our studies have examined dopant site-selectivity, oxide ion migration and dopant-defect association at the atomic level. The energetics of dopant incorporation in AZrO(3) show strong correlation with ion size. We predict Y(3+) to be one of the most favourable dopants for BaZrO(3) on energetic grounds, which accords with experimental work where this cation is the commonly used acceptor dopant for effective proton conduction. Binding energies for hydroxy-dopant pairs in BaZrO(3) are predicted to be favourable with the magnitude of the association increasing along the series Y < Yb < In < Sc. This suggests that proton mobility would be very sensitive to the type of acceptor dopant ion particularly at higher dopant levels. Oxygen vacancy migration in LaScO(3) is via a curved pathway around the edge of the ScO(6) octahedron. Dopant-vacancy clusters comprised of divalent dopants (Sr, Ca) at the La site have significant binding energies in LaScO(3), but very low energies in LaGaO(3). This points to greater trapping of the oxygen vacancies in doped LaScO(3), perhaps leading to higher activation energies at increasing dopant levels in accord with the available conductivity data.

Computer modelling techniques have been used to investigate the defect and oxygen transport properties of the Aurivillius phase Bi4Ti3O12. A range of cation dopant substitutions has been considered including the incorporation of trivalent ions (M3+=Al, Ga and In). The substitution of In3+ onto the Bi site in the [Bi2O2] layer is predicted to be the most favourable. The calculations suggest that lanthanide (Ln3+) doping at the dilute limit preferentially occurs in the [Bi2O2] layer, with probable distribution over both the [Bi2O2] and the perovskite A-site at higher dopant levels. It is predicted that the reduction process involving Ti3+ and oxygen vacancy formation is energetically favourable. The energetics of oxide vacancy migration between various oxygen sites in the structure have been investigated.