Bis(ammonium) tris­(hexa­aqua­magnesium) tetra­kis(hydrogen phosphite)

The structure of the title compound, (NH₄)₂[Mg(H₂O)₆]₃(HPO₃)₄, consists of [Mg(H₂O)₆]²⁺ and (NH₄)⁺ cations and (HPO₃)²⁻ anions held together by an intricate network of hydrogen bonds involving all H atoms except for one linked directly to a P atom. The Mg²⁺ cations are octa­hedrally coordinated by six water mol­ecules. One of the Mg atoms is located on a site with 2/m symmetry, whereas the other Mg atom and the P and N atoms occupy sites with m symmetry.     

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.     

The new ternary phases of La3(Zn0.874Mg0.126)11 and Ce3(Zn0.863Mg0.137)11

The new ternary intermetallic title compounds, namely trilanthanum undeca(zinc/magnesium), La₃(Zn_0.874Mg_0.126)₁₁, (I), and tricerium undeca(zinc/magnesium), Ce₃(Zn_0.863Mg_0.137)₁₁, (II), are isostructural and crystallize in the orthorhombic La₃Al₁₁ structure type. These three phases belong to the same structural family, the representative members of which may be derived from the tetragonal BaAl₄ structure type by a combination of internal deformation and multiple substitution. Compared to the structure of La₃Al₁₁, in (I), a significant decrease of 11.9% in the unit‐cell b axis and an increase in the other two directions, of 3.6% along a and 5.2% along c, are observed. Such an atypical deformation is caused by the closer packing of atoms in the unit cell due to atom shifts that reflect strengthening of metallic‐type bonding. This structural change is also manifested in a significant difference in the coordination around the smaller atoms at the 8l Wyckoff position (site symmetry m). The Al atom in La₃Al₁₁ is in a tricapped trigonal prismatic environment (coordination number 9), while the Zn atoms in (I) and (II) are situated in a tetragonal antiprism with two added atoms (coordination number 10).     

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.     

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.     

Trivalent‐Intermediate Valent Cerium Ordering in Ce2RuZn4

The new intermetallic cerium compound Ce₂RuZn₄ was synthesized from the elements in a sealed tantalum tube in a water‐cooled sample chamber of an induction furnace. Ce₂RuZn₄ crystallizes with a new structure type: P4/nmm, Z = 2, a = 719.6(1), c = 520.2(1) pm, wR2 = 0.0816, 273 F² values and 15 variables. The structure contains two crystallographically independent cerium atoms: Ce1 with CN 16 (12 Zn + 4 Ce) and Ce2 with CN 14 (2 Ru + 8 Zn + 4 Ce). Based on the interatomic distances the two sites can be assigned to trivalent Ce1 and intermediate valent Ce2. The trivalent‐intermediate valent cerium ordering is underlined by magnetic susceptibility measurements. Ce₂RuZn₄ shows modified Curie‐Weiss behaviour in the temperature range 10–290 K with an experimental magnetic moment of 2.57(1) μ_B per formula unit. Thus only half of the cerium atoms are trivalent in Ce₂RuZn₄. A remarkable feature of the Ce₂RuZn₄ structure are short Ce2–Ru distances of 260 pm. The crystal chemistry of Ce₂RuZn₄ is discussed.     

Ca3GeO4Cl2 with a norbergite‐like structure

The title compound, tricalcium monogermanate dichloride, is orthorhombic and consists of one distinct Ge site on special position 4c, site symmetry m, and two different Ca sites, Ca1 and Ca2, one on general position 8d, site symmetry 1, and the other on special position 4c. Two of the O atoms occupy the 4c position (symmetry m); the third O atom is situated on the general 8d position, symmetry 1, as is the one distinct Cl position. By sharing common edges, the distorted Ca1 octahedra form infinite crankshaft‐like chains parallel to the b direction. Along a and c, these chains are connected to one another via common corners, thereby forming a three‐dimensional framework of edge‐ and corner‐sharing Ca1O₄Cl₂ octahedra. Triangular prisms of Ca2O₄Cl₂ polyhedra and GeO₄ tetrahedra fill the interstitial space within the Ca1 polyhedral framework. Relationships between the structures of the title compound and the humite‐type materials norbergite (Mg₃SiO₄F₂) and Mn₃SiO₄F₂ are discussed.     

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.     

Crystal,electronic structure and hydrogenation properties of the Mg5.57Ni16Ge7.43 cluster phase with a new type of polyhedron

The ternary germanide Mg_5.57Ni₁₆Ge_7.43 (cubic, space group Fmm, cF116) belongs to the structural family based on the Th₆Mn₂₃-type. The Ge1 and Ge2 atoms fully occupy the 4a (mm symmetry) and 24d (m.mm) sites, respectively. The Ni1 and Ni2 atoms both fully occupy two 32f sites (.3m symmetry). The Mg/Ge statistical mixture occupies the 24e site with 4m.m symmetry. The structure of the title compound contains a three-core-shell cluster. At (0,0,0), there is a Ge1 atom which is surrounded by eight Ni atoms at the vertices of a cube and consequently six Mg atoms at the vertices of an octahedron. These surrounded eight Ni and six Mg atoms form a [Ge1Ni₈(Mg/Ge)₆] rhombic dodecahedron with a coordination number of 14. The [GeNi₈(Mg/Ge)₆] rhombic dodecahedron is encapsulated within the [Ni₂₄] rhombicuboctahedron, which is again encapsulated within an [Ni₃₂(Mg/Ge)₂₄] pentacontatetrahedron; thus, the three-core-shell cluster [GeNi₈(Mg/Ge)₆@Ni₂₄@Ni₃₂(Mg/Ge)₂₄] results. The pentacontatetrahedron is a new representative of Pavlyuk's polyhedra group based on pentagonal, tetragonal and trigonal faces. The dominance of the metallic type of bonding between atoms in the Mg_5.57Ni₁₆Ge_7.43 structure is confirmed by the results of the electronic structure calculations. The hydrogen sorption capacity of this intermetallic at 570 K reaches 0.70 wt% H₂.     

The crystal structure of Mg51Zn20

The crystal structure of Mg₅₁Zn₂₀, a phase designated conventionally as “Mg₇Zn₃,” has been determined by the single-crystal X-ray diffraction method. It was solved by the examination of a Patterson synthesis, and refined by the ordinary Fourier and least-squares method; the R value obtained was 4.8% for 1167 observed reflections. The crystal is orthorhombic, space group Immm, with a = 14.083(3), b = 14.486(3), c = 14.025(3) Å, and Z = 2. There are 18 independent atomic sites, Zn1Zn6, Mg1Mg10, A, and B, and the last two sites are statistically occupied by Zn and Mg atoms with the occupancies; 0.46(2)Zn7 + 0.52(2)Mg11 and 0.24(2)Zn8 + 0.74(2)Mg12, for A and B, respectively. The structure of the crystal is described as an arrangement of icosahedral coordination polyhedra, to which all the atomic sites but Zn3 site belong. In this arrangement the Zn atoms other than the Zn3 and Zn8(B) center the icosahedral coordination polyhedra with coordination number 12. The Zn3, Zn8 atoms, and all the Mg atoms except Mg11(A) are located at the centers of various coordination polyhedra with the coordination numbers from 11 to 15. The distances between neighboring atoms are 2.71–3.07, 2.82–3.65, and 2.60–3.20 Å for ZnZn, MgMg, and ZnMg, respectively.     

Lanthanum tetrazinc,LaZn4

The structure of lanthanum tetrazinc, LaZn₄, has been determined from single‐crystal X‐ray diffraction data for the first time, approximately 70 years after its discovery. The compound exhibits a new structure type in the space group Cmcm, with one La atom and two Zn atoms occupying sites with m2m symmetry, and one Zn atom occupying a site with 2.. symmetry. The structure is closely related to the BaAl₄, La₃Al₁₁, BaNi₂Si₂ and CaCu₅ structure types, which can be presented as close‐packed arrangements of 18‐vertex clusters, in this case LaZn₁₈. The kindred structure types contain related 18‐vertex clusters around atoms of the rare earth or alkaline earth metal.     

New quaternary carbide Mg1.52Li0.24Al0.24C0.86 as a disorder derivative of the family of hexagonal close‐packed (hcp) structures and the effect of structure modification on the electrochemical behaviour of the electrode

Magnesium alloys are the basis for the creation of light and ultra‐light alloys. They have attracted attention as potential materials for the accumulation and storage of hydrogen, as well as electrode materials in metal‐hydride and magnesium‐ion batteries. The search for new metal hydrides has involved magnesium alloys with rare‐earth transition metals and doped by p‐ or s‐elements. The synthesis and characterization of a new quaternary carbide, namely dimagnesium lithium aluminium carbide, Mg_1.52Li_0.24Al_0.24C_0.86, belonging to the family of hexagonal close‐packed (hcp) structures, are reported. The title compound crystallizes with hexagonal symmetry (space group Pm2), where two sites with m2 symmetry and one site with 3m. symmetry are occupied by an Mg/Li statistical mixture (in Wyckoff position 1a), an Mg/Al statistical mixture (in position 1d) and C atoms (2i). The cuboctahedral coordination is typical for Mg/Li and Mg/Al, and the C atom is enclosed in an octahedron. Electronic structure calculations were used for elucidation of the ability of lithium or aluminium to substitute magnesium, and evaluation of the nature of the bonding between atoms. The presence of carbon in the carbide phase improves the corrosion resistance of the Mg_1.52Li_0.24Al_0.24C_0.86 alloy compared to the ternary Mg_1.52Li_0.24Al_0.24 alloy and Mg.     

Structure and properties of Ce3Pd3Bi4, CePdBi, and CePd2Zn3

The intermetallic cerium compounds Ce₃-Pd₃Bi₄, CePdBi, and CePd₂Zn₃ were synthesized from the elements in sealed tantalum ampoules in an induction furnace. The compounds were characterized by X-ray powder and single crystal diffraction: CeCo₃B₂ type (ordered version of CaCu₅), P6/mmm, a = 538.4(4), c = 427.7(4) pm, wR2 = 0.0540, 115 F ² values, 9 variables for CePd₂Zn₃ and Y₃Au₃Sb₄ type, I [`4]{\bar 4} 3d, a = 1005.2(2) pm, w R2 = 0.0402, 264 F ² values, 9 variables for Ce₃Pd₃Bi₄, and MgAgAs type, a = 681.8(1) pm for CePdBi. The bismuthide structures are build up from three-dimensional networks of corner-sharing PdBi₄ tetrahedra with Pd–Bi distances of 281 (Ce₃Pd₃Bi₄) and 296 pm (CePdBi), respectively. The cerium atoms are located in larger voids of coordination number 12 (Ce₃Pd₃Bi₄) and 10 (CePdBi). In CePd₂Zn₃ the cerium atoms fill larger channels within the three-dimensional [Pd₂Zn₃] network with 18 (6 Pd + 12 Zn) nearest neighbors. The three compounds contain stable trivalent cerium with experimental magnetic moments of μ_eff = 2.70(2), 2.48(1), and 2.49(1) μ_B/Ce atom for CePd₂Zn₃, Ce₃Pd₃Bi₄, and CePdBi, respectively. Susceptibility and specific heat data gave no hint for magnetic ordering down to 2.1 K.     

A disordered cerium(IV) phosphate with a tunnel structure,K4CeZr(PO4)4

Tetra­potassium cerium(IV) zirconium tetra­kis­(mono­phos­phate) crystallizes in the tetra­gonal system (space group I4₁/amd). A complex disorder in K₄CeZr(PO₄)₄ involves the mixing of Ce and Zr atoms on a single site with m2 symmetry and the splitting of P‐ and O‐atom positions, equivalent to a rotation of the phosphate groups, to yield eight‐ and sixfold coordination environments around Ce and Zr, respectively. The K atoms are located in tunnels running parallel to the a and b axes.     

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.     

Lithium barium silicate,Li2BaSiO4, from synchrotron powder data

The structure of lithium barium silicate, Li₂BaSiO₄, has been determined from synchrotron radiation powder data. The title compound was synthesized by high‐temperature solid‐state reaction and crystallizes in the hexagonal space group P6₃cm. It contains two Li atoms, one Ba atom (both site symmetry ..m on special position 6c), two Si atoms [on special positions 4b (site symmetry 3..) and 2a (site symmetry 3.m)] and four O atoms (one on general position 12d, and three on special positions 6c, 4b and 2a). The basic units of the structure are (Li₆SiO₁₃)⁵⁻ units, each comprising seven tetrahedra sharing edges and vertices. These basic units are connected by sharing corners parallel to [001] and through sharing (SiO₄)⁴⁻ tetrahedra in (001). The relationship between the structures and luminescence properties of Li₂SrSiO₄, Li₂CaSiO₄ and the title compound is discussed.     

Disodium tetrakis(hexanoato‐O)zinc(II)

The structure of the title compound, Na₂[Zn(C₆H₁₁O₂)₄], consists of two‐dimensional polymeric sheets. The Zn²⁺ ions are approximately tetrahedrally coordinated by O atoms from different hexanoate anions. Both Na⁺ ions are six‐coordinated by carboxyl­ate O atoms. One of the hexanoate O atoms is attached to one Zn²⁺ ion and one Na⁺ ion, and the remaining O atom is attached to two Na⁺ ions.     

ZnTe6O13, a new ZnO–TeO2 phase

Our investigations into the ZnO–TeO₂ system have produced a new phase, zinc(II) hexatellurium(IV) tridecaoxide, ZnTe₆O₁₃, with trigonal (R) symmetry, synthesized by repeated heating and cooling to a maximum temperature of 1053 K. The asymmetric unit consists of a Zn atom coordinated in a distorted octahedral fashion by two unique tellurium(IV) oxide units that form trigonal–bipyramidal TeO₄ and TeO₃₊₁ corner‐ and edge‐shared polyhedra. Except for the Zn and an O atom, which occupy 6c positions, all atoms occupy 18f general positions.     

Adsorption and migration growth of the Ce,O, and F adatoms on the CeO2 (111) surface: A density functional theory study

In order to investigate the microscopic behavior of the crystal surface growth of the fluorinated cerium dioxide polishing powder, the adsorption and migration of the Ce, O, and F atoms on the CeO₂ (111) surface were studied by using density functional theory with Hubbard correction +U. The adsorption energies of three single atoms at five high-symmetry sites and the migration activation energies along the migration pathway on the CeO₂ (111) surface were calculated. Results show that the most stable adsorption sites of the Ce, O, and F atoms were the O_h, Ce_bri, and Ce_t sites, respectively. The Ce atom migrated from the O_h to the O_t site. The O atom migrated from the Ce_bri to the O_bri site. The F atom migrated from the Ce_t to the O_h site. The migration activation energies of the Ce, O, and F atoms along the migration pathways were 1.526, 0.597, and 0.263 eV, respectively. The F adatom does not change the spatial configuration of the Ce and the O atoms. When the O vacancy occurs on the CeO₂ (111) surface, the F adatom can make up for the O vacancy defect.