Tm2.22Co6Sn20 and TmLi2Co6Sn20 stannides as disordered derivatives of the Cr23C6 structure type

A new ternary dithulium hexacobalt icosastannide, Tm_2.22Co₆Sn₂₀, and a new quaternary thulium dilithium hexacobalt icosastannide, TmLi₂Co₆Sn₂₀, crystallize as disordered variants of the binary cubic Cr₂₃C₆ structure type (cF116). 48 Sn atoms occupy sites of m.m2 symmetry, 32 Sn atoms sites of .3m symmetry, 24 Co atoms sites of 4m.m symmetry, eight Li (or Tm in the case of the ternary phase) atoms sites of symmetry and four Tm atoms sites of symmetry. The environment of one Tm atom is an 18‐vertex polyhedron and that of the second Tm (or Li) atom is a 16‐vertex polyhedron. Tetragonal antiprismatic coordination is observed for the Co atoms. Two Sn atoms are enclosed in a heavily deformed bicapped hexagonal prism and a monocapped hexagonal prism, respectively, and the environment of the third Sn atom is a 12‐vertex polyhedron. The electronic structures of both title compounds were calculated using the tight‐binding linear muffin‐tin orbital method in the atomic spheres approximation (TB–LMTO–ASA). Metallic bonding is dominant in these compounds, but the presence of Sn—Sn covalent dumbbells is also observed.     

Crystal and electronic structures of La2LiGe6−x (x = 0.21) and La2LiGe4Si2

The synthesis and characterization of a new ternary dilanthanum lithium hexagermanide, La₂LiGe_6−x (x = 0.21), belonging to the Pr₂LiGe₆ structure type, and a quaternary dilanthanum lithium tetragermanium disilicide, La₂LiGe₄Si₂, which crystallizes as an ordered variant of this type, are reported. In both structures, Li is on a site of mmm symmetry. All other atoms are on sites of m2m symmetry. These structures are new representatives of a homologous linear structure series based on structural fragments of the AlB₂, CaF₂ and ZrSi₂ structure types. The observed 17‐vertex polyhedra are typical for La atoms and the environment of the Li atom is cubic. Two Ge atoms are enclosed in a tetragonal prism with one added atom (nine‐vertex polyhedron). The trigonal prismatic coordination is typical for Ge or Si atoms. The metallic nature of the bonding is indicated by the interatomic distances and electronic structure calculations.     

Grown from lithium flux,the ErCo5Si3.17 silicide is a combination of disordered derivatives of the UCo5Si3 and Yb6Co30P19 structure types

A ternary hexaerbium triacontacobalt enneakaidecasilicide, ErCo₅Si_3.17, crystallizes as a combination of disordered variants of the hexagonal UCo₅Si₃ (P6₃/m) and Yb₆Co₃₀P₁₉ (P) structure types and is closely related to the Sc₆Co₃₀Si₁₉ and Ce₆Rh₃₀Si₁₉ types. The Er, Co and three of the Si atoms occupy sites of m.. symmetry and a fourth Si atom occupies a site of .. symmetry. The environment of the Er atom is a 21‐vertex pseudo‐Frank–Kasper polyhedron. Trigonal prismatic coordination is observed for the Si atoms. The Co atoms are enclosed in heavily deformed cuboctahedra and 11‐vertex polyhedra. Crystallochemistry analysis and the data from electronic structure calculations (TB–LMTO–ASA) suggest that the Er atoms form positively charged cations which compensate the negative charge of the [Co₁₂Si₉]^m− polyanions.     

The Ce2Li0.39Ni1.61Si2 structure as a new derivative of the AlB2 family

A new quaternary dicerium lithium/nickel disilicide, Ce₂Li_0.39Ni_1.61Si₂, crystallizes as a new structure type of intermetallic compounds closely related to the AlB₂ family. The crystal–chemical interrelationships between parent AlB₂‐type, BaLiSi, ZrBeSi and the title compound are discussed using the Bärnighausen formalism. Two Ce atoms occupy sites of 3m. symmetry. The remainder, i.e. Ni, mixed Ni/Li and Si atoms, occupy sites of m2 symmetry. The environment of the Ce atom is an 18‐vertex polyhedron and the Ni, Ni/Li and Si atoms are enclosed in tricapped trigonal prisms. The title structure can be assigned to class No. 10 (trigonal prism and its derivatives) according to the Krypyakevich classification scheme [Krypyakevich (1977). In Structure Types of Intermetallic Compounds. Moscow: Nauka]. The electronic structure of the title compound was calculated using the tight‐binding linear muffin‐tin orbital method in the atomic spheres approximation (TB‐LMTO‐ASA). Metallic bonding is dominant in this compound. The strongest interactions are Ni—Si and Ce—Si.     

The infinite double‐stranded chain polymer catena‐poly­[[bis­(dicyan­amido)­zinc(II)]‐di‐μ‐1,2‐bis(1,2,4‐triazol‐1‐yl)­ethane‐κ4N4:N4′]

The coordination geometry of the Zn^II atom in the title complex, [Zn(C₂N₃)₂(C₆H₈N₆)₂]_n or [Zn(dca)₂(bte)₂]_n, where bte is μ‐1,2‐bis(1,2,4‐triazol‐1‐yl)­ethane and dca is dicyan­amide, is distorted compressed octahedral, in which the Zn^II atom lies on an inversion center and coordinates four N atoms from the triazole rings of four symmetry‐related bte ligands and two N atoms from two symmetry‐related monodentate dca ligands. The structure is polymeric, with 18‐membered spiro‐fused rings extending in the b direction and each 18‐membered ring involving two inversion‐related bte mol­ecules.     

Ce20Mg19Zn81: a new structure type with a giant cubic cell

Icosacerium nonadecamagnesium henoctacontazinc, Ce₂₀Mg₁₉Zn₈₁, synthesized by fritting of the pure elements with subsequent arc melting, crystallizes with an unusually large cubic unit cell [space group F3m, a = 21.1979 (8) Å] and represents a new structure type among the technologically important family of ternary rare earth–transition metal–magnesium intermetallics. The majority of atoms (two Ce and five Zn) display .3m site symmetry, two Ce and one Mg atom occupy three 2.mm positions, one Mg and one Zn have 3m site symmetry, one Mg and three Zn atoms sit in ..m positions, and one Zn atom is in a general position. The Ce₂₀Mg₁₉Zn₈₁ structure can be described using the geometric concept of nested polyhedral units, by which it consists of four different polyhedral units, viz.A (Zn+Zn₄+Zn₄+Zn₁₂+Ce₆), B (Mg+Zn₁₂+Ce₄+Zn₂₄+Ce₄), C (Zn₄+Zn₁₂+Mg₆) and D (Zn₄+Zn₄+Mg₁₂+Ce₆), with the outer construction unit being an octahedron or tetrahedron. All interatomic distances in the structure indicate metallic‐type bonding.     

Geometric and topological analysis of icosahedral structures of samson Mg2Zn11 (cP39) Phases, K6Na15Tl18H (cP40), and Tm3In7Co9 (cP46): Nanocluster precursors, self-assembly mechanism, and superstructure ordering

Geometric and topological analysis and 3D reconstruction of self-assembly of icosahedral structures of Samson Mg₂Zn₁₁ clusters (space group Pm[`3]Pm\bar 3, cP39, 10 compounds) and the K<sub>6</sub>Na<sub>15</sub>Tl<sub>18</sub>H and Tm<sub>3</sub>In<sub>7</sub>Co<sub>9.29</sub> structures were performed by computer methods (the TOPOS program package). The complete decomposition of the 3D graph of the crystal structures into cluster substructures showed the existence of the crystal-forming nanocluster precursor A comprising 45 atoms (A-45). The S-6 cluster spacers were identified in Mg<sub>2</sub>Zn<sub>11</sub>, and the S-7 cluster spacers were found in K<sub>6</sub>Na<sub>15</sub>Tl<sub>18</sub>H. In Tm<sub>3</sub>In<sub>7</sub>Co<sub>9.29</sub>, the S-6 and S-7 cluster spacers with the centers statistically occupying the same position were determined. The A-45, S-6 (octahedron), and S-7 (centered octahedron) clusters have symmetry [`3]m\bar 3m. The A-45 nanocluster contains an inner Zn(Zn)₁₂ template icosahedron and an external quasi-spherical shell composed of 32 atoms (deltahedron D32). A-45 is equivalent to the Bergman cluster used as the approximant of the local structure of quasicrystals. For deltahedron D32, the existence of a hierarchical structure was identified as a result of self-assembly involving two types of cyclic clusters: K-7 with an atom in the center of the sixth ring and three-atom cyclic clusters K-3. The atoms of the K-3 and K-7 clusters occupy all possible positions over the 12 vertices and 20 faces of an icosahedron and thereby form an edge net of bonds made of triangles. For the K₆(Na₁₄MTl₁₈) structures (M = Mg, An, Cd, Hg), the cluster nature of superstructure ordering of three chemically different atoms (14Na, M, and 18Tl) over 33 positions of the Zn atoms in the unit cell of the basis Mg₂Zn₁₁(Mg₆Zn₃₃) structure was considered.     

SrZn11: a new binary compound with the BaCd11 structure

Single crystals of strontium undecazinc, SrZn₁₁, were obtained when decomposing SrZn₂ under conditions of high pressure and high temperature. The new binary Sr–Zn compound crystallizes in the space group I4₁/amd (BaCd₁₁ structure type) with one Sr position (m2) and three Zn sites (m2, .2/m., 1). The structure is described in terms of all‐face‐capped Zn₈ tetrahedra as the central building unit, defined by the Zn atoms on .2/m. and 1. The building units are condensed into chains by the central tetrahedra sharing edges, and the chains are interconnected by shared capping atoms. The resulting three‐dimensional framework of Zn atoms yields channels that are occupied by Sr and Zn atoms on the high‐symmetry m2 positions.     

Rhombohedral boron subnitride,B13N2, by X‐ray powder diffraction

The structure of the title compound consists of distorted B₁₂ icosahedra linked by N—B—N chains. The compound crystallizes in the rhombohedral space group Rm (No. 166). The unit cell contains four symmetry‐independent atom sites, three of which are occupied by boron [in the 18h, 18h (site symmetry m) and 3b (site symmetry m) Wyckoff positions] and one by nitrogen (in the 6c Wyckoff position, site symmetry 3m). Two of the B atoms form the icosahedra, while N atoms link the icosahedra together. The main feature of the structure is that the 3b position is occupied by the B atom, which makes the structure different from those of B₆O, for which these atom sites are vacant, and B_4+xC_1−x, for which this position is randomly occupied by both B and C atoms.     

Tb2Ni2Mg3: a new structure type derived from the Ru3Al2B2 type

Single crystals of diterbium dinickel trimagnesium, Tb₂Ni₂Mg₃, were synthesized from the elements by induction melting. The novel compound crystallizes in the space group Cmmm with one Mg atom of site symmetry mmm and the Tb, Ni and other Mg atom in m2m positions. This ternary compound represents a new structure type that is derived from Ru₃Al₂B₂ by way of Wyckoff site distribution. The two‐layer structure of Tb₂Ni₂Mg₃ is a new representative of a homologous linear structure series of general formula R′_k+nX_2nR′′_2m+k based on structural fragments of the α‐Fe, CsCl and AlB₂ structure types. The Tb atoms in the structure are enclosed in 17‐vertex polyhedra, while rhombododeca­hedra and distorted rhombododeca­hedra surround the Mg atoms, and equatorially tricapped trigonal prisms form around the Ni atoms. All inter­atomic distances indicate metallic type bonding.     

Monoclinic PZN‐8%PT [Pb(Zn0.3066Nb0.6133Ti0.08)O3] at 4 K

The structure of the relaxor ferroelectric Pb(Zn_0.3066Nb_0.6133Ti_0.08)O₃ (lead zinc niobium titanium trioxide), known as PZN‐8%PT, was determined at 4 K from very high resolution neutron powder diffraction data. The material is known for its extraordinary piezoelectric properties, which are closely linked to the structure. Pseudo‐cubic lattice parameters have led to considerable controversy over the symmetry of the structure. We find the structure to be monoclinic in the space group Cm (No. 8), with the Zn, Nb and Ti cations sharing the octahedrally coordinated B site (site symmetry m, special position 2a) and Pb occupying the 12‐coordinate A site (site symmetry m, special position 2a). O atoms occupy a disorted octahedron around the B site (site symmetry m and special position 2a, and site symmetry 1 and general position 4b). Atomic coordinates have been determined for the first time, allowing the direction of spontaneous polarization to be visualized.     

A new tetragonal structure type for Li2B2C

The ternary dilithium diboron carbide, Li₂B₂C (tetragonal, space group Pm2, tP10), crystallizes as a new structure type and consists of structural fragments which are typical for structures of elemental lithium and boron or binary borocarbide B₁₃C₂. The symmetries of the occupied sites are .m. and 2mm. for the B and C atoms, and m2 and 2mm. for the Li atoms. The coordination polyhedra around the Li atoms are cuboctahedra and 15‐vertex distorted pseudo‐Frank–Kasper polyhedra. The environment of the B atom is a ten‐vertex polyhedron. The nearest neighbours of the C atom are two B atoms, and this group is surrounded by a deformed cuboctahedron with one centred lateral facet. Electronic structure calculations using the TB–LMTO–ASA method reveal strong B...C and B...B interactions.     

catena‐Poly[[[4‐bromo‐2‐(2‐pyridyl­methyl­imino­meth­yl)­phenol­ato]­zinc(II)]‐μ‐chloro]

The title complex, [Zn(C₁₃H₁₀BrN₂O)Cl]_n, is a chloride‐bridged polynuclear zinc(II) compound. Each Zn^II ion is five‐coordinated in a square‐pyramidal configuration, with one O and two N atoms of one Schiff base and one bridging Cl atom defining the basal plane, and another bridging Cl atom occupying the apical position. The novelty of the compound lies in the bridging by chlorine of two square‐pyramidal Zn atoms, so that the bridging atom is apical for one Zn ion and basal for the other. This structural arrangement has not been observed before. The linked moieties form polymeric zigzag chains running along the a axis.     

Poly[μ4‐sulfido‐tris(thiocyanato‐κN)tris(μ3‐1,2,4‐triazolato‐κ3N1:N2:N4)tetrazinc(II)]: a three‐dimensional zinc sulfide coordination polymer

The title compound, [Zn₄(C₂H₂N₃)₃(NCS)₃S]_n, is a three‐dimensional coordination polymer consisting of tetrahedral SZn₄ clusters bridged by triazole ligands. In the tetrahedral unit, three Zn atoms are connected to six bridging triazolate ligands, whereas the fourth Zn atom (site symmetry 3m) is bonded to three terminal thiocyanate anions that protrude into the void space created by the Zn–triazolate network. The network prototype is simple cubic, but a strong distortion along a body diagonal and the imposition of a polar direction by the arrangement of the molecular constituents lead to the trigonal space group R3m. This study demonstrates the use of the 3‐mercapto‐1,2,4‐triazole ligand as an effective source for sulfide ions in the synthesis of sulfide‐based coordination polymers.     

Thallium selenate (Tl2SeO4) in a paraelastic phase by X‐ray powder diffraction

The structure of thallium selenate, Tl₂SeO₄, in a paraelastic phase (above 661 K) has been analysed by Rietveld analysis of the X‐ray powder diffraction pattern. Atomic parameters based on the isomorphic K₂SO₄ crystal in the paraelastic phase were used as the starting model. The structure was determined in the hexagonal space group P6₃/mmc, with a = 6.2916 (2) Å and c = 8.1964 (2) Å. From the Rietveld refinement it was found that two orientations are possible for the SeO₄ tetrahedra, in which one of their apices points randomly up and down with respect to [001]. One Tl atom lies at the origin with symmetry, the other Tl and one of the O atoms occupy sites with 3m symmetry, the Se atom is at a site with symmetry and the remaining O atom is at a site with m symmetry. Furthermore, it was also found that the Tl atoms display anomalously large positional disorder along [001] in the paraelastic phase.     

Two alkali metal chlorites,LiClO2 and KClO2

The structures of tetragonal (P4₂/ncm) lithium chlorite, LiClO₂, and orthorhombic (Cmcm) potassium chlorite, KClO₂, have been determined by single‐crystal X‐ray analyses. In LiClO₂, the Li atom is at a site of symmetry, while in KClO₂, the K atom is at a site with 2/m symmetry. In both compounds, the unique Cl and O atoms are at sites with mm and m symmetry, respectively. The structure of LiClO₂ consists of layers of Li⁺ cations coordinated by ClO₂⁻ anions. In contrast, the structure of KClO₂ contains pseudo‐layers of K⁺ and ClO₂⁻ ions containing four short K—O distances. The Li⁺ and K⁺ cations are surrounded by four and eight chlorite O atoms in tetrahedral and distorted cubic coordination environments, respectively.     

Ba[Co3(VO4)2(OH)2] with a regular Kagomé lattice

The new layered title compound, barium di‐μ‐hydroxido‐di‐μ‐vanadato‐tricobaltate(II), was prepared under low‐temperature hydrothermal conditions. Its crystal structure comprises Co²⁺ and O²⁻ ions in the Kagomé geometry. The octahedral Co₃O₆(OH)₂ Kagomé layers, made up of edge‐shared CoO₄(OH)₂ octahedra with Co on a site of 2/m symmetry, alternate along the c axis with barium vanadate heteropolyhedral layers, in which Ba is on a site of m symmetry and V is on a site of 3m symmetry. All three O atoms and the H atom also occupy special positions: two O atoms and the H atom are on sites with 3m symmetry and one O atom is on a site with m symmetry. Ba[Co₃(VO₄)₂(OH)₂] represents the first compound from the four‐component BaO–CoO–V₂O₅–H₂O system and its structure is topologically related to the minerals vesignieite, Ba[Cu₃(VO₄)₂(OH)₂], and bayldonite, Pb[Cu₃(AsO₄)₂(OH)₂].     

Tb2–xNdxZn17–yNiy (x = 0.5, y = 4.83): a new intermetallic with a maximum disordered structure and its hydrogen storage properties

The ternary Tb_2–xNd_xZn_17–yNi_y (x = 0.5, y = 4.83) disordered phase belongs to the structural family based on the rhombohedral Th₂Zn₁₇ structure type. The structure is maximally disordered since all the sites are occupied by statistical mixtures of atoms. The Tb/Nd mixture of atoms occupies the 6c site (site symmetry 3m). The statistical mixtures Ni/Zn consisting of more Ni atoms are located in the 6c and 9d (symmetry .2/m) sites. In the following 18f (site symmetry .2) and 18h (site symmetry .m) sites are located Zn/Ni statistical mixtures which consist of more Zn atoms. Zn/Ni atoms form three-dimensional networks with hexagonal channels that fill statistical mixtures of Tb/Nd and Ni/Zn. The Tb_2–xNd_xZn_17–yNi_y compound belongs to the family of intermetallic phases capable of absorbing hydrogen. In the structure, there are three types of voids, namely, 9e (site symmetry .2/m), 3b (site symmetry m) and 36i (site symmetry 1), in which hydrogen can be inserted, and the maximum total absorption capacity can reach 1.21 wt% H₂. Electrochemical hydrogenation shows that the phase absorbs 1.03% of H₂, which indicates partial filling of the voids with H atoms.     

Polymeric aqua(nitrilotriacetato)erbium(III)

In the structure of the title compound, [Er(C₆H₆NO₆)(H₂O)]_n, the Er atoms are eight‐coordinated by one N atom and six O atoms from three symmetry‐related nitrilo­tri­acetate (NTA) ligands, and by one O atom of a water mol­ecule, adopting a distorted square‐antiprismatic geometry. The Er atoms are linked by the NTA ligands into layers, which are interconnected via O—H?O hydrogen bonds between the water mol­ecules and the carboxyl­ate O atoms. The asymmetric unit contains one Er atom, one NTA ligand and one water mol­ecule, all of which are located in general positions.     

Eine neue Kolorierungsvariante des α‐Mn‐Strukturtyps mit Hauptgruppenelementen in K5Pb24 – Kristallstruktur,Supraleitung und Struktur‐Eigenschafts‐Beziehung

Novel Coloring of the α‐Mn Structure Type with Main Group Elements in K₅Pb₂₄ – Crystal Structure, Superconductivity, and Structure Property Relationship K₅Pb₂₄ was synthesized from the elements in a welded niobium ampoule at 800 °C. The crystal structure was determined from X‐ray single crystal data. Space group I 4 3m, a = 12.358(1) Å, Z = 2, Pearson symbol cI58. The structure of K₅Pb₂₄ shows an ordered atomic distribution on the four crystallographic sites of the α‐Mn structure type. The aristotype is decomposed into cluster units consisting of 48 Pb atoms. The structural subunits are built from four 16‐vertex Frank Kasper polyhedra, which consist of 15 Pb and one K atom (K1). The 16‐vertex polyhedra are centered with another K atom (K2). Four such polyhedra share a common corner (K1) and several edges. 18 shared edges form a truncated tetrahedra of twelve Pb atoms. These atoms form together with four K1 atoms (located in the center of the Frank Kasper polyhedra) a Friauf polyhedra. The result is a ‘supratetrahedra‘ of 48 Pb atoms enclosing five K atoms. The body centered arrangement of this units results in a three‐dimensional framework of Pb atoms. The title compound is the lead‐richest phase of the K/Pb system. Superconducting properties are observed from temperature dependent susceptibility measurements. Field dependent measurements reveal a hard type II superconductor. LMTO and EH band structure calculations verify the metallic behavior. An analysis of the density of states with the help of the electron localization function (ELF) shows the presence of lone pairs in this intermetallic phase. The role of lone pairs is discussed with respect to the superconducting property.