Double-icosahedral Li clusters in a new binary compound Ba(19)Li(44): a reinvestigation of the Ba-Li phase diagram

The binary Ba-Li system was reinvestigated for compositions with less than 80 at. % Li. A new compound, Ba(19)Li(44), stable up to 126 degrees C, was found and structurally characterized. According to single-crystal X-ray diffraction data, the compound crystallizes in a new structure type with a tetragonal unit cell, space group I42d, a = 16.3911(5) Angstrom, c = 32.712(1) Angstrom, Z = 4, and V = 8788.7(5) Angstrom(3). It can be described as a complicated variant of the chalcopyrite structure. Typical for Li-rich phases, Ba(19)Li(44) contains icosahedron-based polytetrahedral clusters.     

The indium subnitrides Ae6In4(InxLiy)N(3-z)(Ae = Sr and Ba)

The indium nitrides Sr6In4(In(0.32)Li(0.92))N(2.49) and Ba6In(4.78)N(2.72) have been synthesized from an excess of molten sodium. They crystallize in a stuffed variant of the eta-carbide structure type in the cubic space group Fdm with Z = 8. The lattice parameters are a = 14.3752(4) and 15.216(1) A, with cell volumes 2970.6(2) and 3523.3(6) A3, respectively. In both compounds there are vacancies on some of the indium and nitrogen sites and, in the case of Sr6In4(In(0.32)Li(0.92))N(2.49), mixed lithium-indium occupancy of one metal site. It is demonstrated that the partial and mixed occupancies act to carefully tune to electron count to almost fulfill the bonding requirements of the stellar quadrangular subnets of both compounds. Four probe resistivity measurements performed upon a pellet of Sr6In4(In(0.32)Li(0.92))N(2.49) show it to have a room-temperature resistivity of 6.3 mOmega.cm with a weak temperature dependence.     

Topological relationships and building blocks in Zintl phases of the composition Ba(n+1)(Mg,Li)2nSi2(n+1)

The structures of two novel Zintl phases, Ba6Mg5.2Li2.8Si12 and BaMg0.1Li0.9Si2, are presented. Both compounds contain chains in cis-trans conformation. The silicon partial structure of Ba6Mg5.2Li2.8Si12 (C2/m; a = 1212.0(1), b = 459.78(4), c = 1129.10(9) pm; beta = 91.77(2) degrees; Z = 1) is built of unbranched, planar Si6 chains while BaMg0.1Li0.9Si2 (Pnma; a = 725.92(5), b = 461.36(3), c = 1169.08(8) pm; Z = 4) consists of infinite Si(n) chains. The compounds show all electronic and structural characteristics that are typical for the special subset of Zintl phases with highly charged planar anions. The structures of the new compounds, as well as that of Ba2Mg3Si4, can be derived from the common parent type BaMg2Si2. It is shown that a comprehensive picture of a chemical twinning based on BaMg2Si2 can be derived.     

Growth and Spectroscopic Investigations of Disordered Nd3+:Li3Ba2La3(MoO4)8 Crystal

Nd3+: Li3Ba2La3(MoO4)8 crystal has been grown from a flux of Li2MoO4 by the top seeded solution growth method (TSSG) and its structure was confirmed by X-ray diffraction. The polarized absorption spectra, fluorescence spectra and fluorescence decay curve of the crystal were measured. The main spectral parameters were calculated by the Judd-Ofelt theory and compared with other Nd-doped crystals. The broad absorption bands and the large absorption cross sections around 805 nm indicate that the crystal is very suitable for diode-laser pumping. The broad emission bands around 1060 nm show that the crystal is a potential medium for tunable and short pulse lasers. The quantum efficiency of the crystal is up to 95%, which is higher than the value for Nd3+:YVO4 and Nd3+:YAG and comparable to that of other disordered molybdate crystals. The excellent spectroscopic properties show that Nd3+:Li3Ba2La3(MoO4)8 crystal may be regarded as a potential solid state laser host material for diode laser pumping.     

Synthesis, characterization, and electronic structure of Ba5In4Bi5: an acentric and one-electron deficient phase

The new ternary phase Ba(5)In(4)Bi(5) was synthesized by direct reaction of the corresponding elements at high temperature. It crystallizes in a noncentrosymmetric space group and represents a new structure type (tetragonal, P4nc with a=10.620(2) and c=9.009(2) A, Z=2). The structure is built of interconnected heteroatomic clusters of In(4)Bi(5), square pyramids with In(4)-bases and four exo-bonded bismuth atoms (bond to the In atoms). According to Wade's rule the compound is electron-deficient with one electron per cluster, that is, [In(4)Bi(5)](10-) instead of the expected [In(4)Bi(5)](11-) for a closed-shell species. The clusters are discussed also in light of the known heteroatomic deltahedral clusters with the same composition but different charge, [In(4)Bi(5)](3-). Band structure calculations on the new compound suggest substantial participation of barium in the overall bonding of the structure that "accounts" for the electron shortage     

Crystal Structure and Spectroscopic Properties of a New Ternary Tungstate Li3Ba2Ho3（WO4）8

A single crystal of Li3Ba2Ho3(WO4)8 was obtained from a flux of Li2WO4 under an air atmosphere. The structure of the pure crystal was determined by single-crystal X-ray diffraction method. It crystallizes in the monoclinic system, space group C2/c with a = 5.240(4), b = 12.790(10), c = 19.247(15), β = 91.921(15)°, V = 1289.1(18)3, Z = 2, Mr = 2773.09, Dc = 7.144 g/cm3, μ = 47.732 mm-1, Rint = 0.0693, F(000) = 2340, the final R = 0.0472 and wR = 0.1221 for 1535 observed reflections (I > 2σ(I)). The Li3Ba2Ho3(WO4)8 has a high structure disorder with one 8f site shared by Li(1) and Ho ions with occupancy of 0.25 and 0.75, respectively. The fundamental structure is constituted by distorted square antiprisms Ho/Li(1)O8 with C1 symmetry, distorted Li(2)O6 octahedra and BaO10 polyhedra. The optical properties were investigated by IR and absorption spectroscopy, and the emission cross sections and gain cross sections of 5I7 → 5I8 of Ho3+ were calculated.     

Ba11Cd8Bi14: bismuth zigzag chains in a ternary alkaline-earth transition-metal Zintl phase

A new transition-metal-containing Zintl phase, Ba11Cd8Bi14, has been synthesized by a Cd-flux reaction, and its structure has been determined by a single-crystal X-ray diffraction. Ba11Cd8Bi14 crystallizes in the monoclinic space group C2/m (No. 12, Z = 2) with a = 28.193(8) A, b = 4.8932(14) A, c = 16.823(5) A, and beta = 90.836(4) degrees , taken at -150 degrees C (R1 = 0.0407, wR2 = 0.1016). The structure can be described as being built of complex polyanionic [Cd8Bi14]22- layers running along the b axis, which are separated by the Ba2+ cations. An interesting feature of these layers is that they are composed of novel centrosymmetric chains of corner- and edge-shared CdBi4 tetrahedra, interconnected through exo-Bi-Bi bonds. These bonds connect terminal Bi atoms from adjacent chains in such a way that infinite zigzag chains of bismuth parallel to the same direction are formed. Electronic band structure calculations performed using the TB-LMTO-ASA method show a very small band gap, suggesting a narrow-gap semiconducting or poor metallic behavior for Ba11Cd8Bi14. The crystal orbital Hamilton population (COHP) analysis on the homo- and heteroatomic interactions in this structure is reported as well.     

Synthesis and crystal structure of lithium beryllium deuteride Li2BeD4

Single-phase ternary deuteride Li(2)BeD(4) was synthesized by a high-pressure high-temperature technique from LiD and BeD(2). The crystal structure of Li(2)BeD(4) was solved from X-ray and neutron powder diffraction data. The compound crystallizes in the monoclinic space group P2(1)/c with lattice parameters a = 7.06228(9) A, b = 8.3378(1) A, c = 8.3465(1) A, beta =93.577(1) degrees, and Z = 8. Its structure contains isolated BeD(4) tetrahedra and Li atoms that are located in the structure interstices. Li(2)BeD(4) does not undergo any structural phase transitions at temperatures down to 8 K.     

Li3[ScN2]: the first nitridoscandate(III)-tetrahedral Sc coordination and unusual MX2 framework

Li(3)[ScN(2)] was prepared from Li(3)N with Sc or ScN in a nitrogen atmosphere at 1020 K as a light yellow powder with an optical band gap of about 2.9 eV. The crystal structure was refined based on X-ray and neutron powder diffraction data (Ia$\bar 3$, Z=16, X-ray diffraction: R(profile)=0.078, R(Bragg)=0.070; Neutron diffraction: R(profile)=0.077, R(Bragg)=0.074; Rietfeld: a=1003.940(8) pm, Guinier: a=1004.50(3) pm). Li(3)[ScN(2)] is an isotype of Li(3)[AlN(2)] and Li(3)[GaN(2)] and crystallizes in an ordered superstructure of the Li(2)O structure type, leading to a three-dimensional framework of all-vertex-sharing tetrahedra 3[infinity[ScN[4/2][3-]]. Li is displaced from the center of a tetrahedron of N atoms in the direction of one trigonal face. Li(3)[ScN(2)] decomposes above 1050 K to form ScN and Li(3)N. Calculations of the periodic nodal surface (PNS) and of the electron localization function (ELF) support the picture of a covalent Sc-N network separated from isolated Li cations, whereby scandium d orbitals are involved in the chemical bonding.     

Synthesis, crystal and electronic structures of the new quaternary phases A5Cd2Sb5F (A = Sr, Ba, Eu), and Ba5Cd2Sb5O(x) (0.5<x<0.7)

A new family of quaternary fluoro-antimonides A(5)Cd(2)Sb(5)F (A = Sr, Ba, Eu) and oxyantimonides Ba(5)Cd(2)Sb(5)O(x) (0.5相似文献   

Li2B12Si2: the first ternary compound in the system Li/B/Si: synthesis, crystal structure, hardness, spectroscopic investigations, and electronic structure

We present the synthesis, crystal structure, hardness, IR/Raman and UV/Vis spectra, and FP-LAPW calculations of the electronic structure of Li(2)B(12)Si(2), the first ternary compound in the system Li/B/Si. Yellow, transparent single crystals were synthesized from the elements in tin as solvent at 1500 degrees C in h-BN crucibles in arc-welded Ta ampoules. Li(2)B(12)Si(2) crystallizes orthorhombic in the space group Cmce (no. 64) with a=6.1060(6), b=10.9794(14), c=8.4050(8) A, and Z=4. The crystal structure is characterized by a covalent network of B(12) icosahedra connected by Si atoms and Li atoms located in interstitial spaces. The structure is closely related to that of MgB(12)Si(2) and fulfils the electron-counting rules of Wade and Longuet-Higgins. Measurements of Vickers (H(V)=20.3 GPa) and Knoop microhardness (H(K)=20.4 GPa) revealed that Li(2)B(12)Si(2) is a hard material. The band gap was determined experimentally and calculated by theoretical means. UV/Vis spectra revealed a band gap of 2.27 eV, with which the calculated value of 2.1 eV agrees well. The IR and Raman spectra show the expected oscillations of icosahedral networks. Theoretical investigations of bonding in this structure were carried out with the FP-LAPW method. The results confirm the applicability of simple electron-counting rules and enable some structural specialties to be explained in more detail.     

Li24[MnN3]3N2 and Li5[(Li1-xMnx)N]3, two intermediates in the decomposition path of Li7[MnN4] to Li2[(Li1-xMnx)N]: an experimental and theoretical study

The crystal structure of Li7[Mn(V)N4] was re-determined. Isolated tetrahedral [Mn(V)N4](7-) ions are arranged with lithium cations to form a superstructure of the CaF2 anti-type (P4bar3n, No. 218, a = 956.0(1) pm, Z = 8). According to measurements of the magnetic susceptibility, the manganese (tetrahedral coordination) is in a d(2) S = 1 state. Thermal treatment of Li7[Mn(V)N4] under argon in the presence of elemental lithium at various temperatures leads to Li24[Mn(III)N3]3N2, Li5[(Li1-xMnx)N]3, and Li2[(Li1-xMn(I)x)N], respectively. Li24[Mn(III)N3]3N2 (P3bar1c, No. 163, a = 582.58(6) pm, c = 1784.1(3) pm, Z = 4/3) crystallizes in a trigonal unit cell, containing slightly, but significantly nonplanar trigonal [MnN3](6-) units with C3v symmetry. Measurements of the magnetic susceptibility reveal a d(4) S = 1 spin-state for the manganese (trigonal coordination). Nonrelativistic spin-polarized DFT calculations with different molecular models lead to the conclusion that restrictions in the Li-N substructure are responsible for the distortion from planarity of the [Mn(III)N3](6-). Li5[(Li1-xMnx)N]3 (x = 0.59(1), P6bar2m, No. 189, a = 635.9(3) pm, c = 381.7(2) pm, Z = 1) is an isotype of Li5[(Li1-xNix)N]3 with manganese in an average oxidation state of about +1.6. The crystal structure is a defect variant of the alpha-Li3N structure type with the transition metal in linear coordination by nitrogen. Li2[(Li1-xMn(I)x)N] (x = 0.67(1), P6/mmm, No. 191, a = 371.25(4) pm, c = 382.12(6) pm, Z = 1) crystallizes in the alpha-Li3N = Li2[LiN] structure with partial substitution of the linearly nitrogen-coordinated Li-species by manganese(I). Measurements of the magnetic susceptibility are consistent with manganese (linear coordination) in a low-spin d(6) S = 1 state.     

Structure determination and relative properties of novel cubic borates MM'4(BO3)3 (M = Li, M' = Sr; M = Na, M' = Sr, Ba)

A series of novel borates, MM'4(BO3)3 (M = Li, M' = Sr; M = Na, M' = Sr, Ba), have been successfully synthesized by standard solid-state reaction. The crystal structures have been determined from powder X-ray diffraction data. They crystallize in the cubic space group Iad with large lattice parameters: a = 14.95066(5) A for LiSr4(BO3)3, a = 15.14629(6) A for NaSr4(BO3)3, and a = 15.80719(8) A for NaBa4(BO3)3. The structure was built up from 64 small cubic grids, in which the M' atoms took up the corner angle and the BO3 triangles or MO6 cubic octahedra filled in the interspaces. The isolated [BO3]3- anionic groups are perpendicular to each other, distributed along three 100 directions. The anisotropic polarizations were counteracting, forming an isotropic crystal. Sr and Ba atoms were found to be completely soluble in the solid solution NaSr(4-)xBax(BO3)3 (0 < or = x < or = 4). The photoluminescence of samples doped with the ions Eu2+ and Eu3+ was studied, and effective yellow and red emission was detected, respectively. The results are consistent with the crystallographic study. The DTA and TGA curves of them show that they are chemically stable and congruent melting compounds.     

Atomic interactions in the p-type clathrate I Ba8Au5.3Ge40.7

Single crystals of Ba(8)Au(5.3)Ge(40.7) [space group Pm(3)n (No. 223), a = 10.79891(8) ?] were prepared by a Bridgman technique. The crystal structure refinement based on single-crystal X-ray diffraction data does not reveal any vacancies in the Au/Ge framework or in the cages. In addition to the ionic bonding between Ba and the anionic framework, a direct interaction between Ba and Au atoms was identified in Ba(8)Au(5.3)Ge(40.7) by applying the electron localizability indicator. As expected by the chemical-bonding picture, Ba(8)Au(5.3)Ge(40.7) is a diamagnet and shows p-type electrical conductivity with a hole carrier concentration of 7.14 × 10(19) cm(-3) at 300 K and very low lattice thermal conductivity of ≈0.6 W m(-1) K(-1) at 500 K. The thermoelectric figure of merit ZT of single crystals of Ba(8)Au(5.3)Ge(40.7) attains 0.3 at 511 K and reaches 0.9 at 680 K in a polycrystalline sample of closely similar composition. This opens up an opportunity for tuning of the thermoelectric properties of materials in the Ba-Au-Ge clathrate system by changing the chemical composition.     

Synthesis and Crystal Structure of a 3-D Hydrogen-bonded Supramolecular Decavanadate Compound [Habo]6[V10O28]·2C3H7OH·2H2O

A new inorganic-organic hybrid supramolecular compound [Habo]6[V10O28]·solvents and its crystal structure was reported as follows: monoclinic, space group P21/n, a =11.419(9), b = 16.811(16), c = 15.521(12) (A), β= 102.98(2)°, V= 2903(4) (A)3, Z = 4, C15H46N3O19V5,Mr = 827.25, Dc = 1.893 g/cm3, λ(MoKα) = 0.71073 A,μ = 1.636 mm-1, F(000) = 1696, the final R =0.0696 and wR = 0.1361 for 4641 observed reflections with I ＞ 2σ(I). The compound is based on decavanadate clusters [V 1oO28]6-. The hydrogen bonding interactions among Habo+ cations, solvents and decavanadate clusters extend 1 into a three-dimensional supramolecular architecture.     

Synthesis, Crystal Structures and Characterization of Ba5LiTiNb9O30

A new niobate compound with the chemical composition of Ba5LiTiNb9O30 was synthesized by doping Li^ into the system BaO-TiO2-Nb2O5 in conventional solid state reaction method. The crystalline structure was determined by X-ray diffraction analysis (XRD). The results showed that crystal structure of Ba5LiTiNb9O30 belongs to tetragonal tungsten bronze structure with space group P4bm and its unit cell parameters: a=b=1.2512(2) nm, c=0.4008(5)nm. The microstructure of reaction products was observed by scanning electron microscopy (SEM).     

Ba2AgInS4 and Ba4MGa5Se12 (M = Ag, Li): syntheses, structures, and optical properties

The first two members in alkaline-earth/group XI/group XIII/chalcogen system, namely Ba(2)AgInS(4) and Ba(4)AgGa(5)Se(12), were synthesized along with a Li analogue Ba(4)LiGa(5)Se(12). Ba(2)AgInS(4) crystallizes in space group P2(1)/c. It contains [AgInS(4)](4-) layers built from AgS(3) triangles and InS(4) tetrahedra with Ba(2+) cations inserted between the layers. Ba(4)AgGa(5)Se(12) and Ba(4)LiGa(5)Se(12) adopt two closely-related structure types in space group P4[combining macron]2(1)c with structural difference originating from the different positions of Ag and Li in them. The three-dimensional framework in Ba(4)AgGa(5)Se(12) is composed of GaSe(4) tetrahedra with the Ba and Ag atoms occupying the large and small channels respectively, whereas that in Ba(4)LiGa(5)Se(12) is built from LiSe(4) and GaSe(4) tetrahedra with channels to accommodate the Ba atoms. As deduced from the diffuse reflectance spectra measurement, the optical band gaps were 2.32 (2) eV, 2.52 (2) eV, and 2.65 (2) eV for Ba(2)AgInS(4), Ba(4)AgGa(5)Se(12), and Ba(4)LiGa(5)Se(12), respectively.     

Synthesis and Structure of Ba[ZrN2] and Ba2[NbN3]

Ba₃N₂ reacts at 950°C under pure N₂ with Zr to yield dark red, air-sensitive Ba[ZrN₂]. This new compound crystallizes in the tetragonal space group P4/nmm with a = 416.10(2), c = 839.2(1) pm and Z = 2. The crystal structure was solved and refined using X-ray and neutron powder diffraction data. In the nitrido zirconate [ZrN₂]^2? the Zr atoms exhibit a square-pyramidal coordination by five N atoms at distances of 201(3) and 220.2(2) pm. The pyramids share all the edges in the basal plane to form layers parallel to (001) with their apices alternately pointing up and down. The Ba²⁺ cations are integrated into these layers at the levels of the pyramidal apices. The structure can be interpreted as a stuffed PbFCl type. Ba₂[NbN₃] is formed by the reaction of Ba₃N₂ and NbN or of Ba and Nb at 1 000°C under N₂. Isostructural to Ba₂[TaN₃] it crystallizes in the monoclinic space group C2/c with a = 613.2(3), b = 1 176.8(3), c = 1 322.9(4) pm, β = 91.65(2)°, Z = 8. The nitrido niobate anions form chains of corner sharing NbN₄ tetrahedra with distances Nb? N between 188(1) and 199.9(9) pm.     

Crystal growth of two new photoluminescent oxides: Sr3Li6Nb2O11 and Sr3Li6Ta2O11

Single crystals of Sr3Li6M2O11 (M = Nb, Ta) were grown out of a high-temperature Sr(OH)2/LiOH/KOH flux. The single crystal X-ray diffraction data were indexed to the orthorhombic Pmma system, with a = 10.5834(15) A, b = 8.3103(13) A, c = 5.8277(8) A, V = 512.55(13) A(3), and Z = 2 for Sr3Li6Nb2O11 and a = 10.5936(6) A, b = 8.3452(5) A, c = 5.8271(4) A, V = 515.15(6) A(3), and Z = 2 for Sr3Li6Ta2O11. The crystal structure consists of sheets of interconnected SrO8 polyhedra that are separated by M-O layers and an intervening LiO(x) polyhedral framework, representing a new structural type. The M-O layers exhibit a rare occurrence of both five- and six-coordinated M(5+) ions in the same structure. The oxides, upon excitation at 250 nm, exhibit violet emission at room temperature.     

Ba2F2Fe2+ 0.5Fe3+ S3: a two-dimensional inhomogeneous mixed valence iron compound

The structure of the new mixed valence compound Ba2F2Fe1.5S3 was solved by means of single crystal X-ray analysis. It crystallizes in an orthorhombic cell, in the Pnma space group with the cell parameters a = 12.528(3) A, b = 18.852(4) A, and c = 6.0896(12) A. The structure is formed by the alternated stacking of fluorite type [Ba2F2]2+ blocks and the newly discovered [Fe1.5S3]2- blocks. This [Fe1.5S3]2- block exhibits a mixed valence of iron with Fe(+II) located in octahedrons and Fe(+III) in tetrahedrons. Preliminary susceptibility measurements suggest a low dimensional antiferromagnetic behavior.