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Polymorphism is observed in the Y3+xRh4Ge13−x series. The decrease of Y-content leads to the transformation of the primitive cubic Y3.6Rh4Ge12.4 [x = 0.6, space group Pm3¯n, a = 8.96095(9) Å], revealing a strongly disordered structure of the Yb3Rh4Sn13 Remeika prototype, into a body-centred cubic structure [La3Rh4Sn13 structure type, space group I4132, a = 17.90876(6) Å] for x = 0.4 and further into a tetragonal arrangement (Lu3Ir4Ge13 structure type, space group I41/amd, a = 17.86453(4) Å, a = 17.91076(6) Å) for the stoichiometric (i.e. x =0)Y3Rh4Ge13. Analogous symmetry lowering is found within the Y3+xIr4Ge13−x series, where the compound with Y-content x = 0.6 is crystallizing with La3Rh4Sn13 structure type [a = 17.90833(8) Å] and the stoichiometric Y3Ir4Ge13 is isostructural with the Rh-analogue [a = 17.89411(9) Å, a = 17.9353(1) Å]. The structural relationships of these derivatives of the Remeika prototype are discussed. Compounds from the Y3+xRh4Ge13−x series are found to be weakly-coupled BCS-like superconductors with Tc = 1.25, 0.43 and 0.6, for x = 0.6, 0.4 and 0, respectively. They also reveal low thermal conductivity (

Electron-rich [Fe(CN)4]6− features a π-backbonding scheme with non-innocent CN-ligands exhibiting weak C–N bonds and a d10 configuration on iron.

The metastable type-II clathrate Na24-δ Ge136 was obtained from Na12 Ge17 by applying a two-step procedure. At first, Na12 Ge17 was reacted at 70 °C with a solution of benzophenone in the ionic liquid (IL) 1,3-dibutyl-2-methylimidazolium-bis(trifluoromethylsulfonyl) azanide. The IL was inert towards Na12 Ge17 , but capable of dissolving the sodium salts formed in the redox reaction. By annealing at 340 °C under an argon atmosphere, the X-ray amorphous intermediate product was transformed to crystalline Na24-δ Ge136 (δ≈2) and α-Ge in an about 1 : 1 mass ratio. The product was characterized by X-ray powder diffraction, chemical analysis, and 23 Na solid-state NMR spectroscopy. Metallic properties of Na24-δ Ge136 were revealed by a significant Knight shift of the 23 Na NMR signals and by a Pauli-paramagnetic contribution to the magnetic susceptibility. At room temperature, Na24-δ Ge136 slowly ages, with a tendency to volume decrease and sodium loss.

Yb3Co4Ge13 is the first example of a Remeika phase with a 3D + 3 [space group P3n(α,0,0)000(0,α,0)000(0,0,α)000; a = 8.72328(1) A, α = 0.4974(2)] modulated crystal structure. A slight shift of the composition towards higher Yb-content (i.e. Yb3.2Co4Ge12.8) leads to the disappearance of the satellite reflections and stabilization of the disordered primitive cubic [space group Pmn, a = 8.74072(2) A] Remeika prototype structure. The stoichiometric structurally modulated germanide is a metal with hole-like charge carriers, where Yb-ions are in a temperature-dependent intermediate valence state varying from +2.60 to +2.66 for the temperature range 85–293 K. The valence fluctuations have been investigated by means of temperature dependent X-ray absorption spectroscopy, magnetic susceptibility and thermopower measurements.

The clathrate-I borosilicide K8−xBySi46−y (0.8 ≤ x ≤ 1.2 and 6.4 ≤ y ≤ 7.2; space group Pmn) was prepared in sealed tantalum ampoules between 900 °C and 1000 °C. By high-pressure preparation at 8 GPa and 1000 °C, a higher boron content is achieved (x = 0.2, y = 7.8). Crystal structure and composition were established from X-ray diffraction data, chemical analysis, WDX spectroscopy, and confirmed by 11B and 29Si NMR, and magnetic susceptibility measurements. The compositions are electron-balanced according to the Zintl rule within one estimated standard deviation. The lattice parameter varies with composition from a = 9.905 A for K7.85(2)B7.8(1)Si38.2(1) to a = 9.968(1) A for K6.80(2)B6.4(5)Si39.6(5).

Rb8B8Si38 forms under high-pressure, high-temperature conditions at p = 8 GPa and T = 1273 K. The new compound (space group Pm3n, a = 9.9583(1) A) is the second example for a clathrate-I borosilicide. The phase is inert against strong acids and bases and thermally stable up to 1300 K at ambient pressure. (Rb+)8(B-)8(Si0)38 is electronically balanced, diamagnetic, and shows semiconducting behavior with moderate Seebeck coefficient below 300 K. Chemical bonding analysis by the electron localizability approach confirms the description of Rb8B8Si38 as Zintl phase.

A combined structural, magnetic and thermoelectric study of polycrystalline ternary MIn2S4 (M = Mn, Fe, Co, Ni) thiospinels is presented. All compounds crystallize with MgAl2O4-type structure. Rietveld refinement analysis confirmed that the preferred crystallographic position of transition metal element changes from mainly tetrahedral 8a for Mn to exclusively octahedral 16d for Ni (i.e. increase of the inversion parameter). Magnetic susceptibility measurements revealed M-elements to possess 2+ oxidation state in MIn2S4. All these compounds order antiferromagnetically with Neel temperatures T-N ranging from 5-13 K. The studied thiospinels are n-type semiconductors with large values of electrical resistivity rho > 0.6 omega center dot m at room temperature. An increase of the inversion parameter leads to a reduction of the determined activation energies, as well as to a more disorder-like behavior of thermal conductivity. The highest thermoelectric Figure of merit ZT was observed for MIn2S4 with M = Fe, Ni, which adopt inverse spinel structure.

Synthetic bulk and natural pyrite from the hydrothermal mine in Schonbrunn (Saxony, Germany) are confirmed to be stoichiometric FeS2 compounds and stable (for thermoelectric applications) up to ∼600 K by combined thermal, chemical, spectroscopic and X-ray diffraction analyses. Natural pyrite with a small amount (

A detailed study of polycrystalline indium-based In1-x□xIn2S4 (x = 0.16, 0.22, 0.28, and 0.33) thiospinel is presented (□- vacancy). Comprehensive investigation of synthesis conditions, phase composition and thermoelectric properties was performed by means of various diffraction, microscopic and spectroscopic methods. Single-phase α- and β-In1-x□xIn2S4 were found in samples with 0.16 ≤x≤ 0.22 and x = 0.33 (In2S3), respectively. In contrast, it is shown that In0.72□0.28In2S4 contains both α- and β-polymorphic modifications. Consequently, the thermoelectric characterization of well-defined α- and β-In1-x□xIn2S4 is conducted for the first time. α-In1-x□xIn2S4 (x = 0.16 and 0.22) revealed n-type semiconducting behavior, a large Seebeck coefficient (>|200|μV K-1) and moderate charge carrier mobility on the level of ∼20 cm2 V-1 s-1 at room temperature (RT). Decreases in charge carrier concentration (increase of electrical resistivity) and thermal conductivity (even below 0.6 W m-1 K-1 at 760 K) for larger In-content are observed. Although β-In0.67□0.33In2S4 (β-In2S3) is a distinct polymorphic modification, it followed the abovementioned trend in thermal conductivity and displayed significantly higher charge carrier mobility (∼104 cm2 V-1 s-1 at RT). These findings indicate that structural disorder in the α-modification affects both electronic and thermal properties in this thiospinel. The reduction of thermal conductivity counterbalances a lowered power factor and, thus, the thermoelectric figure of merit ZTmax = 0.2 at 760 K is nearly the same for both α- and β-In1-x□xIn2S4.

LuGe3 was obtained under high-pressure and high-temperature conditions at pressures between 8(1) and 14(2) GPa and at temperatures in the range from 1100(150) to 1500(150) K. The high-pressure phase is isotypic to DyGe3 and decomposes at ambient pressure and T = 690 K mainly into ( cF8)Ge and LuGe2- x. Chemical bonding analysis of LuGe3 reveals two-center electron-deficient Ge-Ge bonds, multicenter polar Lu-Ge interactions, and lone pairs on germanium. Magnetic susceptibility, specific heat, and electrical conductivity measurements indicate transition into a superconducting state below Tc = 3.3(3) K.

Large single crystals of Li2(Ca3N)2[Ga4] and Li2(Sr3N)2[Ga4] up to several mm in size were grown from mixtures of the respective elements and binary alkaline-earth metal nitrides in reactive lithium melts employing a modified high-temperature centrifugation-aided filtration (HTCAF) technique. The main structural features of these isotypic phases are stella quadrangula building units [Ga4]Li4/2 and octahedra (Nae6/2), which form two independent interpenetrating networks. The phases crystallize in the η-carbide structure and represent diamagnetic small bandgap semiconductors. Real-space chemical bonding analysis indicates predominantly ionic bonding.

The title compound was synthesized by a reaction of the elemental educts in a corundum crucible at 1200 °C under an Ar atmosphere. The excess of Ga used in the initial mixture served as a flux for the subsequent crystal growth at 600 °C. The crystal structure of Yb4Ga24Pt9 was determined from single-crystal X-ray diffraction data: new prototype of crystal structure, space group C2/m, Pearson symbol mS74, a = 7.4809(1) A, b = 12.9546(2) A, c = 13.2479(2) A, β = 100.879(1)°, V = 1260.82(6) A3, RF = 0.039 for 1781 observed reflections and 107 variable parameters. The structure is described as an ABABB stacking of two slabs with trigonal symmetry and compositions Yb4Ga6 (A) and Ga12Pt6 (B). The hard X-ray photoelectron spectrum (HAXPES) of Yb4Ga24Pt9 shows both Yb2+ and Yb3+ contributions as evidence of an intermediate valence state of ytterbium. The evaluated Yb valence of ∼2.5 is in good agreement with the results obtained from the magnetic susceptibility measurements. The compound is a bad metallic conductor.

The phase and chemical compositions of the mineral chalcopyrite from the sulfide footwall vein in La Cantera (Zacatecas, Mexico) is examined by powder X-ray diffraction, energy dispersive X-ray spectroscopy, and chemical ICP-OES analyses. The influence of the detected impurities on the thermoelectric parameters (i.e. thermopower, electrical and thermal conductivities) is discussed. Thermoelectric figure of merit, ZT, of the studied natural minerals is found to be of the same order of magnitude (ca. 10–3) as reported for CuFeS2 synthesized in the laboratory.

Na16Cs8Li x Ge136−x (x≈2.8, space group Fd3̅m) is the first intermetallic type-II clathrate with a lithium-substituted framework. The phase was obtained from the elements in sealed Ta ampoules by annealing at 650°C for 5 days. Samples were investigated by synchrotron X-ray powder diffraction, solid-state NMR, microstructure and chemical analysis. The substitution of Ge by Li atoms causes a marked shrinking of the lattice parameter. Studies by 7Li NMR confirmed the presence of Li in the clathrate phase and the 23Na and 133Cs NMR spectra consistently showed distinct changes as compared to the ternary Na16Cs8Ge136. The SEDOR technique revealed a distance between Li and Cs atoms in agreement with the result of crystal structure refinement, indicating Li substitution at site 96g. The distinct Knight shift of all NMR signals implies metallic behaviour of the clathrate phase, measurements of the magnetic susceptibility indicate diamagnetic behaviour.

The unprecedented, fully deprotonated form of acetonitrile, the acetonitriletriide anion CCN3−, is experimentally realized for the first time in the stabilizing bulk host framework of the Ba5[TaN4][C2N] nitridometalate via a one-pot synthesis from the elements under moderate conditions (920 K). The molecular structure of this long-sought acetonitrile derivative is confirmed by X-ray diffraction, as well as NMR, IR, and Raman spectroscopy. The anion is isoelectronic to the CO2 molecule, and, in contrast to acetonitrile (H3C−C≡N), the electron pairs are shifted towards two double bonds, that is, [C=C=N]3−.

The compounds MNi21B20 (M = In, Sn) have been synthesized and their cubic crystal structure determined (space group Pm[3 with combining macron]m, lattice parameters a = 7.1730(1) Å and a = 7.1834(1) Å, respectively). The structure can be described as a hierarchical partitioning of space based on a reo-e net formed by Ni3 species with large cubical, cuboctahedral and rhombicuboctahedral voids being filled according to [Ni1@Ni38], [M@Ni312], and [Ni26@B20@Ni324], respectively. The [Ni6@B20] motif inside the rhombicuboctahedral voids features an empty [Ni6] octahedron surrounded by a [B20] cage recently described in E2Ni21B20 (E = Zn, Ga). Position-space bonding analysis using ELI-D and QTAIM space partitioning as well as 2- and 3-center delocalization indices gives strong support to an alternative chemical description of space partitioning based on face-condensed [B@Ni6] trigonal prisms as basic building blocks. The shortest B–B contacts display locally nested 3-center B–B–Ni bonding inside each trigonal prism. This clearly rules out the notion of [Ni6@B20] clusters and leads to the arrangement of 20 face-condensed [B@Ni23Ni33] trigonal prisms resulting in a triple-shell like situation Ni26@B20@Ni324(reo-e), where the shells display comparable intra- and inter-shell bonding. Both compounds are Pauli paramagnets displaying metallic conductivity.

The intermetallic phase [Li x Ba8−x ][Li y Si46−y ] is the first example of a clathrate-I silicide containing lithium with the peculiarity that the Li atoms occupy both cage and framework positions. The phase was obtained by ambient-pressure solid-state reactions at 400°C between Ba4Li2Si6 and the binary clathrate phase Ba8−x Si46 applying different experimental approaches. In this reaction, Li atoms substitute Si atoms of the framework at site 6c (space group Pm3̅n) and fill up the Ba-deficient dodecahedral Si20 cages at site 2a. The presence of Li atoms in the clathrate phase was proven by combined X-ray powder diffraction, 7Li and 29Si solid-state NMR analyses. Incorporation of lithium markedly increased the lattice parameter of the clathrate phase, e.g. from a=10.3200(2) Å for Ba7.48(2)Si46 to a=10.3715(3) Å for [Li0.59(2)Ba7.41(2)][Li2.3(1)Si43.7(1)]. The critical temperature T c for the transition to the superconducting state decreased from 7.7 K to 3.2 K upon Li incorporation.

We report the high-pressure high-temperature synthesis (P = 15 GPa, T = 1300 K) of BaGe3(tI32) adopting a CaGe3-type crystal structure. Bonding analysis reveals layers of covalently bonded germanium dumbbells being involved in multicenter Ba-Ge interactions. Physical measurements evidence metal-type electrical conductivity and a transition to a superconducting state at 6.5 K. Chemical bonding and physical properties of the new modification are discussed in comparison to the earlier described hexagonal form BaGe3(hP8) with a columnar arrangement of Ge3 triangles.

Polycrystalline samples of the solid solution Pb1−xEuxTe were prepared by the spark-plasma technique. In contrast to the literature data, the homogeneity range of the solid solution amounts only to 0 ≤ x ≤ 0.02 under the selected preparation conditions. The implementation of Eu into the PbTe lattice was monitored by refinement of the lattice parameters. The thermoelectric properties of the prepared materials were investigated above room temperature. In samples with compositions x ≤ 0.04, the solid solution Pb1−xEuxTe reveals a metal–semiconductor transition around 500 K going in parallel to the p–n transition in the conductivity. No significant influence of the europium substitution on the thermoelectric figure-of-merit was observed in stoichiometric bulk materials. Introduction to the international collaboration Collaboration between Prof. Yuri Grin's group at Max-Planck Institute of Chemical Physics of Solids and Prof. Jing-Tai Zhao's group at Shanghai University (at Shanghai Institute of Ceramics, Chinese Academy of Sciences before 2014) in the field of Solid State Chemistry and Physics of intermetallic compounds started from 1999 followed by an establishment of a Partner Group between the Max-Planck Society and Chinese Academy of Sciences. The collaboration is highly recognized, in particular the studies on exploration of novel high-performance thermoelectric materials – so-called “122” Zintl phases – in pnictide systems and germanium clathrates. The long-term collaboration generated more than 30 joint publications in international journals and many presentations at national and international conferences, more than 10 co-supervised students and postdocs, and a series of workshops on X-ray Crystallography in Shanghai and Dresden.

A new intermetallic compound AlPd15B7 was synthesized by arc-melting the stoichiometric mixture of the elements. Single crystal X-ray diffraction data of ternary metal-rich boride reveal a new type of structure with the space group Ia3d and the lattice parameter a = 16.4466(3) Å. It adopts a filled anti-Yb3Rh4Sn13-type structure, where the positions corresponding to 3Yb, 4Rh and 13Sn atoms are occupied by 3Pd, 4B, and 1Al + 12 Pd, respectively and 3B additionally at interstitial sites. Magnetic susceptibility, electrical resistivity, and specific heat measurements reveal bulk superconductivity with a critical temperature Tc ≈ 2.9 K. Electronic structure calculations show that Pd 4d and B 2p states dominate the density of states (DOS) at the Fermi level EF.

The clathrate-I Ba8–xSi46 was manufactured from BaSi2 and α-Si by high-pressure high-temperature synthesis at 5 GPa and 900 °C and by redox reaction from Ba4Li2Si6. The transport properties were measured on specimens from the high-pressure high-temperature synthesis. The composition of the Ba8–xSi46 phase [space group Pmn, a = 10.3051(1) A] corresponds to x = 0.8(2) according to the refined lattice parameter, the value determined from full-profile refinement of powder X-ray diffraction data amounts to x = 0.73(1), and the chemical analysis results in x = 1.0(1), yielding the average composition Ba7.2(2)Si46. The electrical transport properties of the phase with x = 0.8 were determined in the temperature range 2–300 K using a polycrystalline bulk specimen. The material is a metallic conductor with ρ(300 K) = 3.3 μΩ m and S(300 K) = –6.8 μV K–1. The thermal conductivity shows a relatively large – for an intermetallic clathrate – value of about 8 W·K–1 m–1.

The metastable binary compound hp-CuBi was obtained from the direct chemical reaction between copper and bismuth at a pressure of 5 GPa and a temperature of 720 K. The atomic arrangement comprises slabs of puckered Cu layers sandwiched between Bi planes. The QTAIM charges calculated for compounds of bismuth with transition metals reveal negligible charge transfer for hp-CuBi. Analysis of the chemical bonding with position-space techniques discloses multicenter interactions within the Bi-Cu-Bi slabs and lone-pair interactions of the van der Waals type between these entities. hp-CuBi exhibits metal-type electrical conductivity with superconductivity below Tc =1.3 K.

The mixed-valent nitridomanganate Ba4[Mn3N6] was prepared using a gas–solid high temperature route. The crystal structure was determined employing high resolution synchrotron powder diffraction data: space group Pbcn, a = 9.9930(1) Å, b = 6.17126(8) Å, c = 14.4692(2) Å, V = 892.31(2) Å3, Z = 4. The manganese atoms in the structure of Ba4[Mn3N6] are four-fold coordinated by nitrogen forming infinite corrugated chains of edge-sharing [MnN4] tetrahedra. The chains demonstrate a complete charge order of Mn species. Magnetization measurements and first principle calculations indicate quasi-one dimensional magnetic behavior. In addition, chemical bonding analysis revealed pronounced Mn–Mn interactions along the chains.

The clathrate-I phase Ba8AlxSi46-x has been structurally characterized at the composition x = 6.9 (space group Pm3[combining macron]n, no. 223, a = 10.4645(2) Å). A crystal structure model comprising the distribution of aluminium and silicon atoms in the clathrate framework was established: 5.7 Al atoms and 0.3 Si atoms occupy the crystallographic site 6c, while 1.2 Al atoms and 22.8 Si atoms occupy site 24k. The atomic distribution was established based on a combination of (27)Al and (29)Si NMR experiments, X-ray single-crystal diffraction and wavelength-dispersive X-ray spectroscopy.