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.     

Li12Cu12.60Al14.37: a new ternary derivative of the binary Laves phases

New ternary dodecalithium dodecacopper tetradecaaluminium, Li₁₂Cu_12.60Al_14.37 (trigonal, Rm, hR39), crystallizes as a new structure type and belongs to the structural family that derives from binary Laves phases. The Li atoms are enclosed in 15‐ and 16‐vertex and the Al3 atom in 14‐vertex pseudo‐Frank–Kasper polyhedra. The polyhedra around the statistical mixtures of (Cu,Al)1 and (Al,Cu)2 are distorted icosahedra. The electronic structure was calculated by the TB–LMTO–ASA (tight‐binding linear muffin‐tin orbital atomic spheres approximation) method. The electron localization function, which indicates bond formation, is mostly located at the Al atoms. Thus, Al—Al bonding is much stronger than Li—Al or Cu—Al bonding. This indicates that, besides metallic bonding which is dominant in this compound, weak covalent Al—Al interactions also exist.     

LiBC3: a new borocarbide based on graphene and heterographene networks

Li–B–C alloys have attracted much interest because of their potential use in lithium‐ion batteries and superconducting materials. The formation of the new compound LiBC₃ [lithium boron tricarbide; own structure type, space group P m 2, a = 2.5408 (3) Å and c = 7.5989 (9) Å] has been revealed and belongs to the graphite‐like structure family. The crystal structure of LiBC₃ presents hexagonal graphene carbon networks, lithium layers and heterographene B/C networks, alternating sequentially along the c axis. According to electronic structure calculations using the tight‐binding linear muffin‐tin orbital‐atomic spheres approximations (TB–LMTO–ASA) method, strong covalent B—C and C—C interactions are established. The coordination polyhedra for the B and C atoms are trigonal prisms and for the Li atoms are hexagonal prisms.     

Li4Ge2B as a new derivative of the Mo2B5 and Li5Sn2 structure types

Binary and multicomponent intermetallic compounds based on lithium and p‐elements of Groups III–V of the Periodic Table are useful as modern electrode materials in lithium‐ion batteries. However, the interactions between the components in the Li–Ge–B ternary system have not been reported. The structure of tetralithium digermanium boride, Li₄Ge₂B, exhibits a new structure type, in the noncentrosymmetric space group R3m, in which all the Li, Ge and B atoms occupy sites with 3m symmetry. The title structure is closely related to the Mo₂B₅ and Li₅Sn₂ structure types, which crystallize in the centrosymmetric space group Rm. All the atoms in the title structure are coordinated by rhombic dodecahedra (coordination number = 14), similar to the atoms in related structures. According to electronic structure calculations using the tight‐binding–linear muffin‐tin orbital–atomic spheres approximation (TB–LMTO–ASA) method, strong covalent Ge—Ge and Ge—B interactions were established.     

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.     

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.     

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.     

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.     

Li8Cu12+xAl6−x (x = 1.16): a new structure type related to Laves phases

The new ternary lithium copper aluminide Li₈Cu_12+xAl_6−x (x = 1.16) crystallizes in the P6₃/mmc space group with six independent atom positions of site symmetries m. (Al/Cu mixture), m2 (Li atoms), 3m. (Al/Cu mixture and Li atoms) and .m. (Cu atoms). The compound is a derivative of the K₇Cs₆ binary structure type and is related to the binary MgZn₂ Laves phase and the LiCuAl₂, MgCu_1.07Al_0.93 and Mg(Cu_1−xAl_x)₂ (x = 0.465) ternary Laves phases. The coordination polyhedra of the atoms in this structure are icosahedra (Cu atoms), slightly distorted icosahedra and bicapped hexagonal antiprisms (Al/Cu statistical mixture), and Frank–Kasper and distorted Frank–Kasper polyhedra (Li atoms). All interatomic distances indicate metallic type bonding.     

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.     

Li9Al4Sn5 as a new ordered superstructure of the Li13Sn5 type

Alloys from the ternary Li–Al–Sn system have been investigated with respect to possible applications as negative electrode materials in Li‐ion batteries. This led to the discovery of a new ternary compound, a superstructure of the Li₁₃Sn₅ binary compound. The ternary stannide, Li₉Al₄Sn₅ (nonalithium tetraaluminium pentastannide; trigonal, P m 1, hP18 ), crystallizes as a new structure type, which is an ordered variant of the binary Li₁₃Sn₅ structure type. One Li and one Sn site have m . symmetry, and all other atoms occupy sites of 3m . symmetry. The polyhedra around all types of atoms are rhombic dodecahedra. The electronic structure was calculated by the tight‐binding linear muffin‐tin orbital atomic spheres approximation method. The electron concentration is higher around the Sn and Al atoms, which form an [Al₄Sn₅]^m− polyanion.     

Li12Cu16+xAl26−x (x = 3.2): a new intermetallic structure type

The new ternary lithium copper aluminide, Li₁₂Cu_16+xAl_26−x (x = 3.2), dodecalithium nonadecacopper tricosaaluminide, crystallizes in a new structure type with space group P4/mbm. Among nine independent atomic positions, two Al (one of which is statistically disordered with Cu) and three Li atoms have point symmetry m.2m, two statistically disordered Al/Cu atoms are in m.. sites, one Al atom is in a 4/m.. site and one Cu atom occupies a general site. The framework of Li₁₂Cu_16+xAl_26−x consists of pseudo‐Frank–Kasper polyhedra enclosing channels of hexagonal prisms occupied by Li atoms. The crystallochemical peculiarity of this new structure type is discussed in relation to the derivatives from Laves phases (LiCuAl₂ and Li₈Cu_12+xAl_6−x) and to the well known CaCu₅ structure.     

PbCa2[Al8O15] with a novel three‐dimensional aluminate anion

The asymmetric unit of the title compound, lead(II) dicalcium octaaluminate, contains one Pb, one Ca, four Al and eight O atoms, with the Pb atom and one O atom situated on mirror planes. Three Al atoms exhibit slightly distorted tetrahedral coordinations with a mean Al—O bond length of 1.76 Å. The fourth Al atom is in a considerably distorted trigonal–bipyramidal coordination with a mean Al—O bond length of 1.89 Å. One AlO₄ tetrahedron forms infinite chains parallel to [100] via corner‐sharing. These chains are linked by parallel chains of edge‐sharing AlO₅ trigonal bipyramids into layers A of six‐membered double rings extending parallel to (010). The second layer B is made up of the remaining two AlO₄ tetrahedra. These tetrahedra share corners, resulting in likewise six‐membered double rings. Finally, the parallel layers A and B are linked into a three‐dimensional framework by common corners. Charge compensation is achieved by the Pb²⁺ and Ca²⁺ cations, which are situated in the cavities of the anionic framework, and which are surrounded by seven and six O atoms, respectively, both within highly irregular coordination polyhedra.     

Synthesis and crystal structure of three nido 11‐vertex platinaborane clusters

The reaction of [PtCl₂(PPh₃)₂] with closo‐B₁₀H₁₀^2? in ethanol under reflux conditions gave two nido 11‐vertex platinaundecaborane clusters: [(PPh₃)₂PtB₁₀H₁₀‐8,10‐(OEt)₂]·CH₂Cl₂ (1) and [(PPh₃)₂PtB₁₀H₁₁‐11‐OEt]·CH₂Cl₂ (2) . A novel B₁₀H₁₀^2? deboronated nido 11‐vertex diplatinaundecaborane [(µ‐PPh₂)(PPh₃)₂Pt₂B₉H₆‐3,9,11‐(OEt)₃]·CH₂Cl₂ (3) was obtained when the same reaction was carried out under solvothermal conditions. All of these compounds were characterized by infrared spectroscopy, NMR spectroscopy, elemental analysis and single‐crystal X‐ray diffraction. Both clusters 1 and 2 have a nido 11‐vertex {PtB₁₀} polyhedral skeleton in which the Pt atom lies in the open PtB₄ face. Each Pt atom connects with four B atoms and two P atoms of the PPh₃ ligands. Cluster 3 has a nido 11‐vertex {Pt₂B₉} polyhedral skeleton in which two Pt atoms sit in neighbouring positions of the open Pt₂B₃ face, bridged by a PPh₂ group. Each Pt atom connects three B atoms and a P atom of the PPh₃ ligand. Copyright © 2005 John Wiley & Sons, Ltd.     

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.     

Tuning Hydrogen Storage in Lithium‐Functionalized BC2N Sheets by Doping with Boron and Carbon

First‐principles calculations are used to explore the strong binding of lithium to boron‐ and carbon‐doped BC₂N monolayers (BC₂NB_C and BC₂NC_N, respectively) without the formation of lithium clusters. In comparison to BC₂N and BC₂NC_B, lithium‐decorated BC₂NB_C and BC₂NC_N systems possess stronger s–p and p–p hybridization and, hence, the binding energy is higher. Lithium becomes partially positively charged by donating electron density to the more electronegative atoms of the sheet. Attractive van der Waals interactions are responsible for binding hydrogen molecules around the lithium atoms. Each lithium atom can adsorb three hydrogen molecules on both sides of the sheet, with an average hydrogen binding energy of approximately 0.2 eV, which is in the range required for practical applications. The BC₂NB_C–Li and BC₂NC_N–Li complexes can serve as high‐capacity hydrogen‐storage media with gravimetric hydrogen capacities of 9.88 and 9.94 wt %, respectively.     

Geometrical structures,electronic states,and stability of NinAl clusters

Density‐functional with generalized gradient approximation (GGA) for the exchange‐correlation potential has been used to calculate the energetically global‐minimum geometries and electronic states of Ni_nAl (n = 2–8) neutral clusters. Our calculations predict the existence of a number of previously unknown isomers. All structures may be derived from a substitution of a Ni atom at marginal positions by an Al atom in the Ni_n+1 cluster. Aluminum atom remains on the surface of the geometrical configurations. Moreover, these species prefer to adopt three‐dimensional (3D) spacial forms at the smaller number of nickel atoms compared with the pure Ni_n+1 (n ≥ 3) configuration. Atomization energies per atom for Ni_nAl (n = 2–8) have the same trend as the binding energies per atom for Ni_n (n = 3–9). The stabilization energies reveal that Ni₅Al is the relatively most stable in this series. In comparison with the magnetic moment of pure metal nickel (0.6 μ_B), the average magnetic moment of Ni atom increases in Ni Al clusters except the Ni₃Al. Moreover, except the case of Ni₅Al, Ni average magnetic moment decreases when alloyed with Al atoms than that in pure Ni clusters, which originate the effective charge transferring from Al to Ni atoms. © 2009 Wiley Periodicals, Inc. Int J Quantum Chem, 2010     

Syntheses of Halogenated Polyhedral Phosphaboranes: Crystal Structure of conjuncto‐3,3′‐(closo‐1,2‐P2B4Br3)2

Co‐pyrolysis of B₂Br₄ with PBr₃ at 480 °C gave, in addition to the main product closo‐1,2‐P₂B₄Br₄, conjuncto‐3,3′‐(1,2‐P₂B₄Br₃)₂ ( 1 ) and the twelve‐vertex closo‐1,7‐P₂B₁₀Br₁₀ ( 2 ), both in low yields. X‐ray structure determination for 1 [triclinic, space‐group P1 with a = 7.220(2) Å, b = 7.232(2) Å, c = 8.5839(15) Å, α = 97.213(15)°, β = 96.81(2)°, γ = 94.07(2)° and Z = 1] confirmed that 1 adopts a structure consisting of two symmetrically boron–boron linked distorted octahedra with the bridging boron atoms in the 3,3′‐positions and the phosphorus atoms in the 1,2‐positions. The intercluster 2e/2c B–B bond length is 1.61(3) Å. The shortest boron–boron bond within the cluster framework is 1.68(2) Å located between the boron atoms antipodal to the phosphorus atoms. The icosahedral phosphaborane 2 was characterized by ¹¹B‐¹¹B COSY NMR spectroscopy showing cross peaks indicative for the isomer with the phosphorus atoms in 1,7‐positions. Both the X‐ray data of 1 and the NMR spectroscopic data of 1 and 2 give further evidence for the influence of an antipodal effect of heteroatoms to cross‐cage boron atoms and, vice versa, of an additional shielding of the phosphorus atoms caused by B‐Hal substitution at the boron positions trans to phosphorus.     

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.     

Tetraaqua‐1κO,2κ3O‐(μ‐2,4‐dinitrophenolato‐1κ2O1,O2:2κO1)(2,4‐dinitrophenolato‐1κ2O1,O2)dilithium(I): a dinuclear lithium(I) complex

The title complex, [Li₂(C₆H₃N₂O₅)₂(H₂O)₄], contains two kinds of Li atoms, viz. five‐coordinated and four‐coordinated. The five‐coordinated Li ion has a tetragonal–pyramidal geometry, with a water molecule in the apical position and four O atoms from two 2,4‐dinitrophenolate (2,4‐DNP) ligands in the basal plane. The four‐coordinated Li ion has a tetrahedral geometry, with three water molecules and one phenolate O atom of a 2,4‐DNP ligand. The Li ions are bridged by a phenolate O atom, giving the complex a dinuclear structure. The crystal packing is stabilized by O—H...O hydrogen‐bonding interactions involving the water molecules and nitro O atoms.