Arsenides continue to captivate the fields of inorganic chemistry and condensed matter physics. In this work we present the discovery of two new members of this family─U8Co42As25 and UCo3As2─which were synthesized in single crystalline form. U8Co42As25 is the first representative of the Y8Co41As25structure type (space group P63/m, Pearson symbol hP75, a = 17.7460(5) Å, c = 3.8120(1) Å), while UCo3As2 adopts HoCo3P2 type of structure (space group Pmmn, Pearson symbol oP36, a = 3.8611(2) Å, b = 10.8414(6) Å, c = 12.7297(6) Å). Both materials order antiferromagnetically─U8Co42As25 at TN = 26 K and UCo3As2 at TN = 67 K.

Noncentrosymmetric crystal structures are of significant interest due to the peculiar physical phenomena they frequently promote. Among mercury-based compounds, only a few noncentrosymmetric materials are known, with the vast majority remaining unexplored. In this work, we examine the family of noncentrosymmetric mercurides Na11Hg52 and A11-xHg54+x (A = Ca or Sr). All three materials are identified as new superconductors. The values of the critical temperatures are fairly modest, ranging from 1.7 K (Ca11-xHg54+x) to 3.1 K (Na11Hg52). We postulate that the superconductivity of noncentrosymmetric Na11Hg52 and A11-xHg54+x (A = Ca or Sr) compounds is likely conventional.

Abstract The Nowotny chimney–ladder (NCL) phase in the Fe–Ge system near Fe2Ge3 composition is a promising thermoelectric material owing to its characteristic coexistence of degenerate electronic transport and strongly suppressed lattice thermal conductivity, yet the structural and compositional origins of this behavior remain incompletely understood. Synchrotron diffraction shows that samples prepared with nominal Fe2Ge3 composition crystallize as an incommensurately modulated NCL phase close to FeGe1.52. From the superspace description, we derive and refine for the first time a three-dimensional commensurate approximant, Fe27Ge41 (tP272). Chemical-bonding analysis based on the model of Fe2Ge3 reveals a three-dimensional framework of heteroatomic multiatomic Fe–Ge interactions without homoatomic Fe–Fe or Ge–Ge bonds. DFT calculations for the Fe27Ge41 approximant show that slight Ge excess in comparison with Fe2Ge3 shifts the Fermi level into the conduction band, yielding a nominal carrier concentration of ∼1021 cm–3, consistent with Hall measurements, and explaining the degenerate n-type behavior without extrinsic donors. The electronic structure is characterized by a high density-of-states effective mass (∼11 me), arising from convergence of flat conduction bands near the Fermi level. Despite high elastic moduli and a moderate Grüneisen parameter, the lattice thermal conductivity is low (∼1.8 W m–1 K–1 at 300 K), corresponding to an estimated phonon mean free path of approximately 8 Å. The failure of the Debye–Callaway model to reproduce this value indicates additional phonon scattering, which may be related to the incommensurate structure and bonding inhomogeneity. Overall, the incommensurate Fe–Ge NCL phase combines degenerate electronic transport with phonon-glass-like thermal behavior.

The Cu-Te system contains particularly complex copper chalcogenides due to their intricate crystal structures and multiple phase transitions. This study investigates the structural transitions of Cu3-x Te2 through high-resolution synchrotron measurements conducted from room temperature (RT) up to 693 K. At room temperature, Cu3-x Te2 displays incommensurately modulated orthorhombic structure with lattice parameters a = 4.00912(1) & Aring;, b = 12.22806(3) & Aring;, and c = 3.98424(1) & Aring;, along with a modulation wavevector q = 0.3999(1)c*. A transformation to a tetragonal structure (space group P4/nmm; a = 4.01877(2) & Aring;, c = 6.11105(3) & Aring;) occurs at similar to 423 K, followed by a transition to a hexagonal structure (space group P 6 m2; a = 7.28869(1) & Aring; and c = 7.85504(1) & Aring;) at similar to 623 K. Both transitions are reversible upon cooling. High-resolution transmission electron microscopy (HRTEM) and high-resolution annular dark field scanning TEM (HR-ADF STEM) reveal nanoscale origin of the modulation. Most notably a robust doubling along c and occasional longer-period supercells, linked to ordering of the copper sublattice with fractional occupancy. Density functional theory (DFT), quantum theory of atoms in molecules (QTAIM), and electron localizability indicator (ELI-D) reveal very small charge transfer and the emergence of lone-pair-like basins on Te upon Cu vacancy formation, suggesting that ordering/reordering of Te lone pairs coupled to Cu vacancy ordering drives the orthorhombic <-> tetragonal <-> hexagonal transformations. The high-temperature hexagonal modification exhibits a well-ordered Te framework but a highly disordered Cu sublattice, reminiscent of fast-ion conductors such as Cu2Se, indicating potential ionically dynamic behavior and motivating transport studies toward superionic functionality.

In solid-state compounds, the valence of europium can sometimes be mixed, which is especially favored in structures with several positions for the europium atoms. In this work, we study the Eu-based intermetallic noncentrosymmetric system Eu11-x Hg54+x , which has 65 atoms per unit cell and 4 distinct crystallographic positions for europium and 14 positions for mercury. Our detailed analysis of the magnetism of large single crystals suggests that europium in Eu11-x Hg54+x might be present in two valence states, resulting in a fragile magnetic ground state. Due to the cage-like structure with a large distance between the Eu atoms, those atoms are weakly ferromagnetically coupled and Eu11-x Hg54+x orders at low temperatures, below T 1 = 5.5 K, with a subsequent spin reorientation at T 2 = 4.3 K. There is no sign of magnetic frustration. Interestingly, the magnetic ordering of the europium substructure results in a magnetization pole reversal with a delicate ferrimagnetic ground state. Additional magnetic phases can be induced by the application of a modest external magnetic field.

The preparation of Zintl phases with pronounced spin-orbit coupling has received substantial scientific interest because of their distinctive electronic properties. In the context of superconductivity and topological phenomena related to band inversion, intermetallic compounds of bismuth have come into focus recently. While bismuth forms a rich variety of Zintl phases with the heavier alkaline-earth metals, there are significantly fewer magnesium compounds. Here we show that high-temperature high-pressure synthesis opens a convenient route for the preparation of Mg5Bi3Hx already at moderate conditions. The compound (space group Pnma, a = 11.5399(3) Å, b = 8.9503(2) Å and c = 7.8770(2) Å) adopts a Ca5Sb3F crystal structure. The minute amounts of hydrogen could only be detected by thermal decomposition of the compound in combination with mass spectroscopy of the gas phase. Direct space analysis of the chemical bonding allowed for allocating the hydrogen position at a partially occupied interstitial site and reveals strongly polar Mg-Bi and Mg-H bonds in accordance with the Zintl concept. Calculated band structures exhibit substantial electronic reorganization upon hydrogen insertion. The combination of advanced analytical tools in concert with modern quantum chemical techniques provides an efficient approach to allocate trace amounts of interstitial atoms stabilizing intermetallic phases.

This work presents a study on a new thorium iron arsenide, Th2Fe12As7, a second discovered compound in the ternary system. It crystallizes in the noncentrosymmetric hexagonal Zr2Fe12P7 structure type (space group P6, a = 9.5506(4) Å and c = 3.8645(2) Å). The bonding analysis of Th2Fe12As7 reveals that the structure can be represented by a trigonal prismatic environment of the As atoms, which are the geometric locations of anionic components of the structure. The cationic components of the structure are represented by the Th species. Furthermore, the bonding analysis revealed a new feature─a three-dimensional framework of two-atomic bonds between the Fe atoms, which─in the sense of effective charges─is essentially neutral. It plays the role of a bonding mediator within the [Fe-As] framework. Th2Fe12As7 is a metallic paramagnet down to the lowest measured temperature, 0.4 K.

Three new representatives of the ZrSO structure type (space group P213, Pearson symbol cP12, also known under the notation LaIrSi)-BaGaPd (a = 6.8660 & Aring;), BaGaPt (a = 6.8370 & Aring;), and SrGaPt (a = 6.6144 & Aring;)-are prepared by direct reaction of elements with the subsequent homogenization heat treatment at 600 degrees C for 500 h. The crystal structure is studied using X-ray single crystal (BaGaPd) or powder (BaGaPt and SrGaPt) diffraction data. The crystal structures of ZrSO type are crystallographically ordered superstructures of the binary prototype SrSi2. Analysis of chemical bonding using quantum chemical techniques in position space reveals the key role of the 3D (anionic) network of covalently-bonded Ga and transition-metal atoms TM in {Ba, Sr}[GaTM] or silicon atoms in Sr[Si2] for the organization of the crystal structures of SrSi2- and ZrSO-types.

Powder x-ray diffraction and Raman spectroscopy studies showed In-rich thiospinels with the chemical formula In1 y ❑yIn2S4 xTex (y approximate to 0.16, 0.22 and x approximate to 0.1, 0.2) to be composed of the cubic a-modification [space group (SG) Fd3m] with a minor admixture of tetragonal fl -phase (SG I41/amd). Tellurium incorporation in the crystal structures is confirmed by Rietveld refinements, energy dispersive x-ray-and Raman spectroscopies. All samples are found to be indirect band gap semiconductors with an Eoptg approximate to 2 eV, which decreases with increasing Tecontent. The thiospinels with y approximate to 0.16, 0.22 and x approximate to 0.1 revealed by two orders of magnitude enhanced charge carrier concentration (i.e., n approximate to 1018 cm  3) and approximate to 6-9 times larger charge carrier mobilities (mu) than corresponding binary specimens. A kink at 200 K in p(T) is found to originate from a stepper increase of n. The Seebeck coefficient is negative for all samples indicating electrons to be the dominant charge carriers. The total thermal conductivity of the compounds is almost completely phonon (Kph) mediated. The Debye-Callaway fits of Kph reveal an enhanced point-defect scattering in the In2.78S4 xTex series compared to In2.84S4 xTex, in accordance with the higher vacancy concentration (i.e., smallery). The Balkanski-Klemens analysis of the temperature dependent Raman shifts indicated domination of three-phonon scattering mechanism agreeing with the lowered Kph values. The appearance of low-energy optical modes confirms the In1-atoms, randomly occupying [In1S4]-tetrahedra, to reveal a 'rattling' motion and thus, to be a probable source of enhanced anharmonic effects limiting Kph. Te-doping of In-rich thiospinels (y approximate to 0.16, 0.22) results in the improvement of the electrical transport characteristics and simultaneously in an increase of their thermal conductivities due to smaller vacancy concentration. The possible reduction of Kph and the improvement of the TE performance are discussed.

The phase transition beta'->gamma in Ag8SnSe6 argyrodite was studied by means of high-temperature X-ray diffraction, differential scanning calorimetry and dilatometry. The cell parameters of Ag8SnSe6 were determined and their temperature dependence in the range 295-420 K analyzed. The changes of entropy (Delta trS = 29.0 & sdot;10- 3 J/K) and enthalpy (Delta trH = 10.3 J/g) at the phase transition beta'->gamma at 356 K in Ag8SnSe6 were determined.

By combining experimental and computational studies, the orthorhombic stannide CeMgSn with a TiNiSi-type structure has been characterized as a potential hydrogen storage material. Experimental studies of the formed monohydride CeMgSnH including hydrogen absorption-desorption, thermal desorption spectroscopy, synchrotron and neutron powder diffraction (298 and 2 K), magnetization, and Sn-119 M & ouml;ssbauer spectroscopic measurements are discussed in parallel with ab initio electronic structure calculations. A small, 1.27 vol %, expansion of the unit cell of CeMgSn during its transformation into a thermally stable CeMgSnH monohydride is caused by an ordered insertion of H atoms into half of the available Ce3Mg tetrahedral interstices leaving the CeMg3 tetrahedra unoccupied. The bonding in CeMgSnH is dominated by strong Ce-Sn and Mg-Sn interactions which are almost not altered by hydrogenation, whereas the H atoms carry a small negative charge and show bonding interactions with Ce and Mg. Hydrogenation causes a conversion of the antiferromagnetic CeMgSn into ferromagnetic CeMgSnH with the Ce moments aligned along [001] with a magnetic moment of 1.4(3) mu(B). The Sn-119 isomer shifts and the values of quadrupole splitting in the M & ouml;ssbauer spectra suggest a similar s-electron density distribution for the Ce- and La-containing REMgSnH monohydrides.

Intermetallic compounds R 2 Ni 2 M ( R = rare-earth metal, M = p-element) with the W 2 CoB 2 structure type (space group Immm ) form hydrides at low hydrogen pressures (below 1 bar H 2 ). The nature of the p-element is an important parameter affecting the activity towards hydrogen. Nd 2 Ni 2 Sn forms the hydride Nd 2 Ni 2 SnH 4.5 when heated to 393 K. Hydrogenation results in substantial anisotropic cell volume expansion ( Delta V / V = 15.7 %) and monoclinic distortion of the crystal lattice (space group C 2/ m ). Hydrogen can occupy sites inside three different Nd - Ni tetrahedra. Partial spontaneous hydrogen desorption leaves one of the tetrahedral sites vacant and the monoclinic distortion is removed. Magnetic exchange interactions are weakened upon hydrogenation, and the magnetic ordering temperature drops from 21 K in Nd 2 Ni 2 Sn to 5 K in its hydride. The variations in magnetism can be explained in terms of changes of the closest environment of the metal atoms, as well as by the usual decrease of the concentration of conduction electrons affecting the RKKY exchange interaction.

Changes in the dielectric properties of two-dimensional (2D) microsized molybdenum disulfide powders in response to ambient air humidity at room temperature were studied (impedance spectroscopy, 1 Hz–20 MHz). The microsized 2H-MoS2 powders were found to absorb significant amounts of moisture (0.43–2.88 wt.

A large variety of chemical and physical properties are exhibited by mercurides and amalgams. In this work, we have successfully examined seven strontium mercurides: SrHg11, SrHg8, Sr10Hg55, SrHg2, SrHg, Sr3Hg2, and Sr3Hg. The interest in the mercury-rich region is motivated by the large number of mercury-based superconductors that have high mercury content. At the same time, the preparation on the mercury-rich side of the binary phase diagram is experimentally non-trivial, due to the high vapor pressure of mercury and extreme air-sensitivity of mercury-rich compounds. By employing a set of specialized techniques, we were able to discover superconductivity in three mercury-strontium compounds – SrHg11 (Tc=3.2±0.3 K, Hc2=0.18±0.05 T), SrHg8 (Tc=3.0±0.1 K, Hc2=0.35±0.02 T), and Sr10Hg55 (Tc=2.2±0.25 K, Hc2=0.54±0.05 T).

This work presents a study on a new uranium iron arsenide UFe5As3. By implementing Bi-flux synthesis, we were able to grow mm-sized single crystals of this compound, which show twinning. UFe5As3 is one of only two known uranium iron arsenides. It adopts a monoclinic, UCr5P3-type crystal structure (space group P21/m, Pearson symbol mP18, a = 7.050(2) Å, b = 3.8582(9) Å, c = 9.634(1) Å, β = 100.25(1)°). The magnetic susceptibility of UFe5As3 indicates it to be an antiferromagnet with TN = 47 K and μeff = 4.94 μB per formula unit, signaling that both U and Fe are likely magnetic in this material. The material appears to be anisotropic, with a small (likely ferromagnetic) spin reorientation transition around T = 29 K. The Sommerfeld coefficient γ0 = 135 mJ mol-1 K-2 suggests enhanced effective electron mass in UFe5As3, while electrical resistivity indicates metallic, Kondo-like behavior.

Samples of the pseudo-binary system Na2-xLixGa7 (x <= 1) were synthesized from the elements at 300 degrees C in sealed Ta ampoules or by the reaction of Na2Ga7 with LiCl. The peritectic formation temperature decreases with increasing Li content from 501(2) degrees C (x = 0) to 489(2) degrees C (x = 1). The boundary compositions Na2Ga7 and Na1Li1Ga7 crystallize with different structure types related by a group-subgroup relation. While the Na-rich compositions (x <= 0.5) represent a substitutional solid solution (space group Pnma), the Li-rich compositions feature an unconventional replacement mechanism in which Li atoms occupying interstitial positions induce vancancies at the Na positions (space group Cmce). The crystal structure of Na1Li1Ga7 (a = 8.562(1) & Aring;, b = 14.822(2) & Aring;, c = 11.454(2) & Aring;; Z = 8) was determined from X-ray single-crystal diffraction data, and reveals an anionic framework comprising 12-bonded Ga-12 icosahedra and 4-bonded Ga atoms, with alkali-metal atoms occupying channels and cavities. The arrangement of cations makes NaLiGa7 a new structure type within the MgB12Si2 structure family. Band structure calculations for the composition NaLiGa7 predict semiconducting behavior consistent with the balance [Na+](2)[Li+](2)[(Ga-12)(2-)][Ga-](2), considering closo Wade clusters [(12b)Ga-12](2-) and Zintl anions [(4b)Ga](-). Susceptibility measurements indicate temperature-independent diamagnetic behavior.

Single‐phase MoNi 4 was prepared by multi‐step long‐term thermal treatment. The crystal structure was re‐evaluated by single‐crystal and powder X‐ray as well as powder neutron diffraction resulting in space group I 4/ m and lattice parameters of a =5.7300(6) Å and c =3.5649(6) Å. Despite the formation by complex solid‐state reaction, the crystal structure of MoNi 4 is fully ordered, whereby the single‐crystalline micro‐domains feature sizes below 20 μm. The ordering is supported by the strong charge transfer from Mo to Ni hindering the formation of anti‐sites. Two types of four‐atomic bonds stabilize the crystal structure. The bonding is isotropic, allowing cleavage in different crystallographic directions with mostly nickel atoms on the surface. In combination with the negative effective charge of the nickel species, this enables to shed more light on the behaviour of MoNi 4 in catalytic processes.

The new ternary intermetallic compound ZrAl0.23Ge1.77 was observed after annealing at 600°C, and its crystal structure was determined by X-ray single-crystal diffraction. The structure (own structure type, Pearson symbol tI32-8, space group I41/amd, a = 3.8013(2), c = 29.893(3) Å, Z = 4) is a variant with partial positional disorder of the pseudo-binary structure type Zr0.75AlSi1.25. The structures are members of the family of linear intergrowth structures composed of AlB2-type slabs (layers of centered trigonal prisms) and CaF2-type slabs (layers of empty “half octahedra”), here in the ratio 1:2. The structure of ZrAl0.23Ge1.77 is characterized by statistical occupation by Al and Ge of one of the sites forming the CaF2-type slabs and positional disorder of the Ge atoms that form zig-zag chains along the crystallographic direction [100].