Double Tetrahedra Research Articles

Electronic Structure Analysis of the A10 Tt2 P6 System (A=Li-Cs; Tt=Si, Ge, Sn) and Synthesis of the Direct Band Gap Semiconductor K10 Sn2 P6.

Investigating the relationship between atomic and electronic structures is a powerful tool to screen the wide variety of Zintl phases for interesting (opto-)electronic properties. To get an insight in such relations, the A10 Tt2 P6 system (A=Li-Cs; Tt=Si-Sn) was picked as model system to analyse the influence of structural motives, combination of elements and their properties on type and width of the band gaps. Those compounds comprise two interesting structural motives of their anions, which are either monomeric trigonal planar TtP3 5- units which are isostructural to CO3 2- or [Tt2 P6 ]10- dimers which correspond to two edge-sharing TtP4 tetrahedra. The A10 Tt2 P6 compounds were structurally optimized for both polymorphs and subsequent frequency analysis, band structure as well as density of states calculations were performed. The Gibbs free energies were compared to determine temperature dependent stability, where Na10 Si2 P6 , Na10 Ge2 P6 and K10 Sn2 P6 were found to be candidates for a high temperature phase transition between the two polymorphs. Additionally, the unknown, but predicted compound K10 Sn2 P6 was synthesized and characterized by single crystal and powder x-ray diffraction. It crystalizes in the monoclinic space group P 21 /n and incorporates [Sn2 P6 ]10- edge sharing double tetrahedra. It was determined to be a direct band gap semiconductor with a band gap of 2.57 eV.

Finding Order in Disorder: The Highly Disordered Lithium Oxonitridophosphate Double Salt Li8+x P3 O10-x N1+x (x=1.4(5)).

The crystalline lithium oxonitridophosphate Li8+x P3 O10-x N1+x , was obtained in an ampoule synthesis from P3 N5 and Li2 O. The compound crystallizes in the triclinic space group P with a=5.125(2), b=9.888(5), c=10.217(5) Å, α=70.30(2), β=76.65(2), γ=77.89(2)°. Li8+x P3 O10-x N1+x is a double salt, the structure of which contains distinctive complex anion species, namely non-condensed P(O,N)4 tetrahedra, and P(O,N)7 double tetrahedra connected by one N atom. Additionally, there is mixed occupation of O/N positions, which enables further anionic species by variation of O/N occupancies. To characterize these motifs in detail, complementary analytical methods were applied. The double tetrahedron exhibits significant disorder in single-crystal X-ray diffraction. Furthermore, the title compound is a Li+ ion conductor with a total ionic conductivity of 1.2×10-7 S cm-1 at 25 °C, and a corresponding total activation energy of 0.47(2) eV.

Synthesis and Characterization of the Lithium-Rich Phosphidosilicates Li10Si2P6 and Li3Si3P7.

The lithium phosphidosilicates Li10Si2P6 and Li3Si3P7 are obtained by high-temperature reactions of the elements or including binary Li-P precursors. Li10Si2P6 (P21/n, Z = 2, a = 7.2051(4) Å, b = 6.5808(4) Å, c = 11.6405(7) Å, β = 90.580(4)°) features edge-sharing SiP4 double tetrahedra forming [Si2P6]10- units with a crystal structure isotypic to Na10Si2P6 and Na10Ge2P6. Li3Si3P7 (P21/m, Z = 2, a = 6.3356(4) Å, b = 7.2198(4) Å, c = 10.6176(6) Å, β = 102.941(6)°) crystallizes in a new structure type, wherein SiP4 tetrahedra are linked via common vertices and which are further connected by polyphosphide chains to form unique ∞2[Si3P7]3- double layers. The two-dimensional Si-P slabs that are separated by Li atoms can be regarded as three covalently linked atoms layers: a defect α-arsenic type layer of P atoms sandwiched between two defect wurzite-type Si3P4 layers. The single crystal and powder X-ray structure solutions are supported by solid-state 7Li, 29Si, and 31P magic-angle spinning NMR measurements.

When one becomes two: Ba12In4Se20, not quite isostructural to Ba12In4S19

The ternary selenide Ba12In4Se20 was synthesized by reaction of BaSe, In2Se3, and Se at 1023 K. Single-crystal X-ray diffraction revealed a trigonal structure (space group R3¯, Z = 6, a = 10.0360(6) Å, c = 78.286(4) Å at room temperature) consisting of one-dimensional stacks of InSe4 tetrahedra, In2Se7 double tetrahedra, selenide Se2– anions, and diselenide Se22– anions, with Ba2+ cations in the intervening spaces. The selenide Ba12In4Se20 can be derived from the corresponding sulfide Ba12In4S19 by replacing one monoatomic Ch2– anion with a diatomic Ch22– anion. An optical band gap of 1.70(2) eV, consistent with the dark red colour of the crystals, was deduced from the UV–vis–NIR diffuse reflectance spectrum.

Synthesis and Crystal Structures of Rb4Al2S5 and Cs4In2S5

AbstractTwo new alkali metal thiotrielates with the general composition M4T2S5 (M = Rb, Cs; T = Al, In) were obtained via the azide route and their crystal structures were determined from single‐crystal X‐ray diffraction data. Highly air sensitive Rb4Al2S5 crystallizes in pale red rods in the space group Pna21 (no. 33) with lattice constants a = 11.4450(5) Å, b = 11.4605(6) Å, c = 9.5727(4) Å, and a cell volume of V = 1255.6(1) Å3 with Z = 4. To the best of our knowledge, Rb4Al2S5 represents the first rubidium thioaluminate and a new structure type in the field of ternary alkali metal chalkogenometallates. Cs4In2S5 crystallizes isotypic to Rb4In2S5 in the space group P$\bar{1}$ (no. 2) with lattice constants a = 9.6871(3) Å, b = 11.1549(4) Å, c = 7.7879(3) Å, α = 110.731(3)°, β = 95.760(3)°, γ = 102.766(2)°, and a cell volume of V = 752.75(4) Å3 with Z = 2. The crystal structures of both solids consist of edge‐linked [T2S6]6– double tetrahedra, which build up one‐dimensional, polymeric 1∞[T2S54–] strands by trans‐corner sharing. The anionic chains are separated by rubidium and cesium cations, respectively. Aluminum as well as indium has a slightly distorted tetrahedral surrounding by sulfur, and the four independent rubidium atoms in Rb4Al2S5 feature distorted trigonal prismatic and distorted octahedral coordination spheres, respectively. In Cs4In2S5 the four different cesium positions show coordination numbers of six and seven. Cs4In2S5 was also characterized by Raman spectroscopy. The frequencies of In–S stretching modes are found in the range from 342 cm–1 to 292 cm–1.

Chains of Condensed IrIn7 Polyhedra in Ir2In12Ga4O15

AbstractThe new low valent iridiumindiumoxogallate Ir2In12Ga4O15 was prepared by heating intimate mixtures of Ir, In, In2O3, and Ga2O3 in a platinum crucible under an atmosphere of argon (1400 K, 70 h). The compound has an orange color. X‐ray powder diffraction patterns can be indexed on the basis of a primitive orthorhombic unit cell with lattice parameters a = 1954.5(1) pm, b = 674.0(1) pm, and c = 745.9(1) pm. The crystal structure of Ir2In12Ga4O15 was solved from powder diffraction data and refined using the Rietveld method (Pnn2, R(prof.) = 4.4 %, R(int.) = 2.5 %). Ir2In12Ga4O15 is according to [IrIn5In2/2]9+2[GaO4]5–2[Ga2O7]8– an ortho‐gallate‐pyro‐gallate with chains of corner sharing [IrIn7]9+ polyhedra, [GaO4]5–2 tetrahedra, and [Ga2O7]8– double tetrahedra. The Ir–In distances within the IrIn7 polyhedra are shorter than in Ir–In intermetallic phases and lie between 256–261 pm.

Synthesis, characterization, and properties of the first indium borogermanate incorporating an organic amine ligand: InBGe2O6(OH)2(CH3CH(NH2)CH2NH2)·2H2O

A new indium borogermanate incorporating an organic amine ligand, InBGe2O6(OH)2(CH3CH(NH2)CH2NH2)·2H2O, was synthesized under solvothermal conditions and characterized by infrared spectroscopy, thermogravimetric analysis, and emission spectroscopy. This compound is a new example of the combination of metal, boron, and germanium atoms into one structure in the presence of organic amine molecules. Its 2D sheets with one 3-, one 4-, and two types of 6-membered rings consist of In2O6N4 octahedral dimers, Ge2O6(OH) double tetrahedra, and BO3(OH) groups that are interconnected by water molecules to form a 3D supramolecular framework. Interestingly, the emission spectrum for this compound displays a strong broad band centered at 455nm.

Synthesis and Crystal Structures of Ca4SiN4 and New Polymorph of Ca5Si2N6

Single crystals of Ca4SiN4 were found in the product prepared by heating Ba, Ca, Si, NaN3, and Na at 900 °C. Ca4SiN4 [space group P2(1)/c (No. 14), Z = 4, a = 9.1905(4) Å, b = 5.9775(3) Å, c = 11.0138(7) Å, β = 116.4054(17)°] is isotypic with Ca4GeN4 and K4SiO4. Isolated [SiN4](8-) tetrahedra were identified in the structure by single-crystal X-ray diffraction. After reheating the product at 900 °C, a new polymorph of Ca5Si2N6 crystallized. The space group of the polymorph [C2/m (No. 12), Z = 4, a = 6.2712(5) Å, b = 10.0175(8) Å, c = 12.0287(8) Å, β = 99.303(2)°] is different from C2/c previously reported for Ca5Si2N6, while both polymorphs are composed of Ca(2+) and edge-sharing double tetrahedra [Si2N6](10-).

Low-Temperature Properties of the Quantum Heisenberg Antiferromagnet on Some One-Dimensional Lattices Containing Equilateral Triangles

We consider the quantum Heisenberg antiferromagnet in a magnetic field on two one-dimensional lattices containing equilateral triangles (a chain of corner-sharing double tetrahedra and a frustrated three-leg ladder) which support localized-magnon states. By mapping of the localized-magnon degrees of freedom on a classical lattice gas we obtain high-field thermodynamic quantities of the models at low temperatures.

Lithium Argyrodites with Phosphorus and Arsenic: Order and Disorder of Lithium Atoms, Crystal Chemistry, and Phase Transitions

Crystal chemical data of high- (HT) and low-temperature (LT) modifications of lithium argyrodites with the compositions Li(7)PCh(6) (Ch=S, Se), Li(6)PCh(5)X (X=Cl, Br, I), Li(6)AsS(5)Br, and Li(6)AsCh(5)I (Ch=S, Se) based on single-crystal, powder X-ray (113 K<T<503 K) and neutron measurements (5 K<T<293 K) are presented. In the HT modifications, the Li atoms are strongly disordered over a fraction of the available tetrahedral holes, whereas in the LT modifications they occupy ordered crystallographic positions with a pronounced site preference that is analysed on a crystal chemical basis. The Ch/X partial structures remain nearly unchanged upon the reversible phase transitions. Crystal chemical and crystallographic relations between HT and LT modifications based on the Frank-Kasper model of tetrahedral close packing are discussed. X-ray single-crystal data for HT-Li(6)PS(5)I show the electron density of the disordered Li to be smeared out over an extended region preferably inside face-sharing double tetrahedra. A series of temperature-dependent powder neutron data for Li(6)PS(5)I gives clear evidence for an HT/LT phase transition at approximately 175 K with an ordering of the Li atoms in different polyhedra with coordination numbers between three and four.

Sr5Ge2N6 – A Nitridogermanate with Edge‐sharing Double Tetrahedra

AbstractThe new nitridogermanate Sr5Ge2N6 was obtained as a coarsely crystalline product by Na‐flux technique employing a reaction of Sr, Na, NaN3 and GeO2 in weld shut tantalum‐tubes at temperatures up to 760 °C. The crystal structure was determined by single‐crystal X‐ray methods: (Sr5Ge2N6, space group C2/c (no. 15), a = 1040.8(2), b = 652.08(13), c = 1356.5(3) pm, β = 100.29(3)°, V = 905.8(3)·106 pm3, Z = 4, 1240 observed reflections, 61 parameters, R1 = 0.031). In the solid, there are edge‐sharing [Ge2N6]10− double tetrahedra surrounded by Sr2+ ions. Sr5Ge2N6 was found to be isotypic with Ca5Si2N6.

La6C2Br9: La-Tetraederdoppel mit endohedralen C4–-Ionen / La6C2Br9: La Bitetrahedral Clusters with Endohedral C4− Ions

Monophasic La6C2Br9 was prepared by heating a mixture of LaBr3, lanthanum metal and carbon in a molar ratio of 3 : 3 : 2 at 840 °C for 5 d. The crystal structure was investigated by X-ray single crystal diffraction (space group C2/c, a = 14.234(3), b = 10.858(2), c = 14.588(3) Å , β = 106.80(3) °). In the structure the La atoms form edge-sharing double tetrahedra. The La tetrahedra are centered by single carbon atoms. The yellow crystals of La6C2Br9 are transparent and electrically insulating.

Tetrahedra and Vertex‐Sharing Double Tetrahedra in the Ammonium Iodomercurates(II) (NH4)7[HgI4]2 [Hg2I7](H2O) and (NH4)3[Hg2I7

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Trigonal Na3Li(SeO4)2·6H2O crystal – a novel SRS‐active material with high Raman gain coefficient

AbstractWe discovered and characterized the χ (3)‐active Na3Li(SeO4)2·6H2O crystal with considerably high Raman gain coefficients for laser physics and nonlinear optics. (© 2007 WILEY‐VCH Verlag GmbH &amp; Co. KGaA, Weinheim)magnified imageSection of the crystal structure of Na3Li(SeO4)2·6H2O, representing one sheet of [Na3O7(H2O)6] groups together with the linking tetrahedral groups [SeO4] and the double tetrahedra [O3SeOLi(H2O)3], that are formed by [SeO4] and [LiO(H2O)3]. Hydrogen atoms are marked with spheres. (© 2007 WILEY‐VCH Verlag GmbH &amp; Co. KGaA, Weinheim)

Tetrahedra and Vertex‐Sharing Double Tetrahedra in the Ammonium Iodomercurates(II) (NH4)7[HgI4]2[Hg2I7](H2O) and (NH4)3[Hg2I7

AbstractThe new ammonium iodomercurates(II), (NH4)7[HgI4]2[Hg2I7](H2O) (1) and (NH4)3[Hg2I7] (2) contain isolated tetrahedra and vertex‐sharing double tetrahedra as the anions. The crystal structures were determined from single‐crystal X‐ray diffraction data: 1: orthorhombic, Pnma (no. 62), a = 2175.9(2), b = 1781.8(2), c = 1256.2(2) pm, Z = 4. R1 [I0&gt;2σ(I0)] = 0.0520; 2: monoclinic, P21/c (no. 14), a = 1259.0(2), b = 773.2(1), c = 2172.4(3) pm, β = 101.18(2)°, Z = 4, R1 [I0&gt;2σ(I0)] = 0.0308.

Crystal structure and vibrational spectroscopy of the new acidic diphosphate (NH4)2Zn(H2P2O7)2 · 2 H2O

Abstract The hydrated ammonium hemizinc dihydrogen diphosphate (NH4)2Zn(H2P2O7)2 · 2 H2O was synthesized. It crystallizes in the triclinic system, space group P-1, Z = 1, with the following unit-cell-parameters: a = 7.0026(2) Å, b = 7.3297(2) Å, c = 7.7885(3) Å, α = 81.229(1)°, β = 71.064(1)°, γ = 88.172(1)°, V = 373.64(2) Å3. The structure was obtained by single-crystal X-ray diffractometry, and a full-matrix least-squares refinement based on F 2 gave a final R 1 index of = 0.0447 (wR 2 = 0.1336), utilizing 2055 observed reflections with I &gt; 2σ(I). The crystal packing consists in a three-dimensional network made by layers parallel to ab plane of ZnO6 octahedra sharing four vertices with H2P2O7 double tetrahedra: (NH4)+ cations fill up the cavities between tetrahedra and octahedra; strong hydrogen bonds stabilize the framework. The dihydrogendiphosphate anion (H2P2O7)2- shows bent eclipsed conformation and the Zn2+ ion lies on inversion centre. Raman and infrared spectra of (NH4)2Zn(H2P2O7)2 · 2 H2O have been collected and interpreted using factor group analysis. No coincidences observed between most of Raman and IR spectral bands confirmed the centrosymmetric structure of the title compound; the vibrational spectra point to a bent POP bridge angle.

Porous titanosilicate nanorods in the structure of yuksporite, (Sr,Ba)2K4(Ca,Na)14(□,Mn,Fe) {(Ti,Nb)4(O,OH)4[Si6O17]2[Si2O7]3}(H2O,OH)n, resolved using synchrotron radiation

The crystal structure of yuksporite, (Sr,Ba) 2 K 4 (Ca,Na) 14 (⃞ ,Mn,Fe){(Ti,Nb) 4 (O,OH) 4 [Si 6 O 17 ] 2 [Si 2 O 7 ] 3 }(H 2 O,OH) n , where n ∼ 3 [monoclinic, P2 1 /m, a = 7.126(3), b = 24.913(6), c = 17.075(7) Å, β = 101.89(3)°, V = 2966.4(17) Å 3 ] has been solved using X-ray synchrotron radiation data collected from a needle-like crystal with dimensions of 6 × 6 × 50 µm 3 at the Swiss-Norwegian beamline BM01 of the European Synchrotron Research Facility (ESRF, Grenoble, France). The structure was refined to R 1 = 0.101 on the basis of 2359 unique observed reflections with |F o | ≥ 4σ F . The structure of yuksporite is based upon titanosilicate nanorods elongated along a and with an elliptical cross-section of ca. 16 × 19 Å = 1.6 × 1.9 nm. Silicate tetrahedra form double xonotlite-like chains 1 ∞ [Si 6 O 17 ] oriented parallel to (001). Two 1 ∞ [Si 6 O 17 ] chains are linked into a rod via TiO 6 octahedra and Si 2 O 7 double tetrahedra. The {(Ti,Nb) 4 (O,OH) 4 [Si 6 O 17 ] 2 [Si 2 O 7 ] 3 } nanorods are porous. The internal pores are defined by eight-membered rings (8MR) with open diameters of 3.2 Å. The interior of the titanosilicate nanorods is occupied by Sr, Ba, K, and Na cations and H 2 O molecules. The nanorods are separated by walls of Ca coordination polyhedra that are parallel to (010) and link the rods into a three-dimensional structure.

In1.06Ho0.94Ge2O7: A Thortveitite‐Type Compound.

AbstractFor Abstract see ChemInform Abstract in Full Text.

Two new ammonium diphosphates: crystal structure of Mn0.5NH4H2P2O7·H2O and MnNaNH4P2O7·3H2O

Abstract Two new ammonium diphosphates, Mn0.5NH4H2P2O7·H2O (1) and MnNaNH4P2O7·3H2O (2), have been synthesized and investigated by single crystal X-ray diffraction. Compound (1) crystallizes in the triclinic space group P1̅, and the unit cell dimensions are a = 7.0029(2) Å, b = 7.4401(2) Å, c = 7.8771(2) Å, α = 80.444(1)°, β = 71.359(1)°, γ = 87.408(1)°, V = 383.48(2) Å3, Z = 2; compound (2) crystallizes in the monoclinic space group Cc, with the following unit cell dimensions: a = 10.1124(4) Å, b = 16.4448(7) Å, c = 5.6000(3) Å, β = 104.304(2)°, V = 902.39(7) Å3, Z = 4. Final residuals are: R = 0.0281 and w R = 0.0769, by using 2356 reflections with I &gt; 2σ(I), for (1); R = 0.0301 and w R = 0.0682, by using 2322 reflections with I &gt; 2σ(I), for (2). The crystal packing of Mn0.5NH4H2P2O7·H2O consists of layers parallel to ac plane formed by MnO6 regular octahedra, H2P2O7 double tetrahedra and ammonium cations. Strong hydrogen bonds embed the dihydrogendiphosphate groups in the framework. The crystal packing of MnNaNH4P2O7·3H2O is made up of layers of P2O7 double tetrahedra, NaO7 monocapped octahedra and MnO6 regular octahedra down c. Water and ammonium cations molecules fill up the cavities between the above mentioned polyhedra. Strong hydrogen bonds complete the network.

In1.06Ho0.94Ge2O7: a thortveitite-type compound.

A new indium holmium digermanate, In(1.06)Ho(0.94)Ge(2)O(7), with a thortveitite-type structure, has been prepared as a polycrystalline powder material by high-temperature solid-state reaction. This new compound crystallizes in the monoclinic system (space group C2/c, No. 15). The structure was characterized by Rietveld refinement of powder laboratory X-ray diffraction data. The In(3+) and Ho(3+) cations occupy the same octahedral site, forming a hexagonal arrangement on the ab plane. In their turn, the hexagonal arrangements of (In/Ho)O(6) octahedral layers are held together by sheets of isolated diortho groups comprised of double tetrahedra sharing a common vertex. In this compound, the Ge(2)O(7) diortho groups lose the ideal D(3d) point symmetry and also the C(2h) point symmetry present in the thortveitite diortho groups. The Ge-O-Ge angle bridging the diortho groups is 160.2 (3) degrees, compared with 180.0 degrees for Si-O-Si in thortveitite (Sc(2)Si(2)O(7)). The characteristic mirror plane in the thortveitite space group (C2/m, No. 12) is not present in this new thortveitite-type compound and the diortho groups lose the C(2h) point symmetry, reducing to C(2).