Zur Konstitution von Ba2WO3F4 und Ba2MoO3F4

On the Structure of Ba₂Wo₃F₄ and Ba₂MoO₃F₄ Ba₂[WO_2/2O₂F₂]F₂ has been prepared for the first time as colourless single crystals (from powder, Au-tube, 680°C, 90 d). It crystallizes in the monoclinic (C c) crystal system with a = 1151.1, b = 938.2, c = 718.8 pm, ß = 126.17°, Z = 4. d_x = 6.17, d_pyk = 6.13 g · cm^?3. (Fourcirclediffractometer PW 1100, Fa. Philips, MoKα-, ω-2Θ-scan, 1832 I₀(hkl) R = 8.3, R_w = 7.4%). Parameters see in the text. The isotypic Ba₂MoO₃F₄ has been prepared as powder (a = 1147.5, b = 937.0, c = 725.1 pm, ß = 126.42°). The structure shows chains of (WO_2/2O₂F₂) groups along [001]. To establish O^2? and F^? on the positions IR and Raman Spectra are employed. The Madelung Part of Lattice Energy, MAPLE, is calculated and discussed.     

The Crystal Structure of Ba3Cu2Al2F16: a Relative of Ba4Cu2Al3F21

Ba₃Cu₂Al₂F₁₆ is monoclinic: a = 7.334(1)Å, b = 5.320(2)Å, c = 16.022(1)Å, β = 96.34(1)°, Z = 2. Its crystal structure was solved in the space group P2₁ (No. 4) from synchrotron X‐ray single crystal data using 2685 unique reflections (2639 with F_o/σ(F_o) > 4). The final R factor is 0.044. The structure consists of a succession along the c‐axis of the cell of three layers of two different kinds of sheets developing in the (a, b) plane. The first one, formulated [(AlF₅)₂]_∞^4— and hereafter named A, is built up from infinite cis‐chains of aluminium‐fluorine octahedra [AlF₆], linked by two vertices and distanced by a. The second one, formulated [Cu₂AlF₁₁]_∞^4— and named B, is bidimensional. It is constituted of distorted copper‐fluorine octahedra [CuF₆], linked by edges, which form infinite chains interconnected by three vertices of isolated [AlF₆] octahedra. The stacking sequence of the sheets is (A, B, B)_∞. The barium ions, 12‐coordinated, are inserted between the sheets. The crystal structure of Ba₃Cu₂Al₂F₁₆ is closely related to that of Ba₄Cu₂Al₃F₂₁. Only the proportion and the stacking sequence of the two kinds of sheets in the c‐direction differ, according to two different compositions and two different symmetries.     

Spin dimer analysis of the magnetic structures of Ba3Cr2O8, Ba3Mn2O8, Na4FeO4, and Ba2CoO4 with a three-dimensional network of isolated MO4 (M = Cr, Mn, Fe, Co) tetrahedra

The spin exchange interactions of the magnetic oxides Ba3Cr2O8, Ba3Mn2O8, Na4FeO4, and Ba2CoO4 with a three-dimensional network of isolated MO4 (M = Cr, Mn, Fe, Co) tetrahedra were examined by performing spin dimer analysis on the basis of tight-binding electronic structure calculations. Although the shortest O...O distances between adjacent MO4 tetrahedra are longer than the van der Waals distance, our analysis shows that the super-superexchange interactions between adjacent MO4 tetrahedra are substantial and determine the magnetic structures of these oxides. In agreement with experiment, our analysis predicts a weakly interacting isolated AFM dimer model for both Ba3Cr2O8 and Ba3Mn2O8, the (0.0, 0.5, 0.0) magnetic superstructure for Na4FeO4, the (0.5, 0.0, 0.5) magnetic superstructure for Ba2CoO4, and the presence of magnetic frustration in Ba2CoO4. The comparison of the intra- and interdimer spin exchange interactions of Ba3Cr2O8 and Ba3Mn2O8 indicates that orbital ordering should be present in Ba3Cr2O8.     

Synthesis and Structure of Ba3La2（BO3）4 Crystal

1 INTRODUCTION At present the researches on more efficient solid-state laser materials become more important for the rapid development of diode-laser pumped solid-state laser. More researches have been devoted to the double borate compounds RX3(BO3)4 (R = Y, La, Gd and X = Y, Al, Sc), some of which exhibit good chemical and physical properties[1～10]. The rare earth and alkali-halide double borates M3Ln2(BO3)4 (M = Ca, Sr, Ba and Ln = LaLu and Y) were reported in literatures[11…     

Synthesis and Structure of Ba7F12Cl2

Crystals of ordered and disordered Ba₇F₁₂Cl₂ were prepared by flux growth and solid state reactions. These new structures were characterized by single crystal and powder X‐ray diffraction. The disordered variant which shows disorder on one of the cation sites was obtained from a BaF₂ + BaCl₂ + NaCl/NaF flux. It has hexagonal space group P6₃/m (176) with one formula unit per unit cell. The lattice constants are a = b = 1059.55(5) pm and c = 420.10(4) pm (at 21 °C). The structure was refined to R(R_w) = 0.026(0.030) for 346 independent reflections and 26 parameters. Slow cooling of a mixture of BaF₂ and LiCl yields the ordered variant. This one crystallizes in the hexagonal space group P6 (174) with one formula per unit cell. Lattice constants at 21 °C are a = b = 1063.46(2) pm and c = 417.52(1) pm. The structure was refined to R(R_w) = 0.017 (0.017) for 638 independent reflections and 45 parameters. The structural arrangement and the interatomic distances of the two variants are mutually similar. The barium atoms have coordination number nine. Propeller‐type arrangements with a chloride ion on the axis and the fluoride ions as blades are observed. These latter ones are interconnected into ‘channels' of tricapped fluoride prisms. Occupation disorder of the barium sites in the channels of the disordered variant makes the main difference between the two. An unexpectedly high X‐ray density obtained for both variants of Ba₇F₁₂Cl₂ can be correlated to the density of other barium fluorohalides having a coordination number of nine for the barium ion.     

ChemInform Abstract: Synthesis and Crystal Structure of [Cr(NH3)6] [Cr(NH3)2F4][BF4]2.

ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.     

Ba7Mn5Cr2O20: charge and chemical order

Ba7Mn5Cr2O2O20 adopts a structure containing an ordered array of Mn(IV), Mn(II) and Cr(V) cations and exhibits complex magnetic behaviour at low temperature.     

Ba4YZr3F23 and Ba4LnZr3F23: a new noncentrosymmetric potential host structure type for optical devices

The first ternary BaF₂–Ln(Y)F₃–ZrF₄ phases crystallizing near the composition range of fluoride glasses, namely Ba₄YZr₃F₂₃ (barium yttrium fluoridozirconate) and isotypic Ba₄LnZr₃F₂₃ (Ln = Yb, Er and Nd), have been synthesized. The crystal structure of Ba₄YZr₃F₂₃ cannot be correctly determined in the centrosymmetric space group Pnma (R1 = 0.09); it is preferably described in the noncentrosymmetric space group Pn2₁a (R1 = 0.028). All cations are located at y = 0.25–0.29 and 0.75–0.79. This new structure type is formed by infinite {[YZr₃F₂₃]^8?}_n columns associating, along [001], YF₉ tricapped trigonal prisms, ZrF₈ dodecahedra and ZrF₇ polyhedra. These columns are interconnected via BaF₁₀₊₁ and BaF₁₂ irregular polyhedra.     

Synthese und Kristallstruktur von [Cr(NH3)6][Cr(NH3)2F4][BF4]2

Synthesis and Crystal Structure of [Cr(NH₃)₆][Cr(NH₃)₂F₄][BF₄]₂ The action of ammonium fluoride on a mixture of boron and chromium in a sealed Monel ampoule at 300 °C yields single crystals of [Cr(NH₃)₆][Cr(NH₃)₂F₄][BF₄]₂. The crystal structure (tetragonal, P4/mbm, Z = 2, a = 1056.0(1), c = 781.7(1) pm; R₁ = 0.0414; wR₂ = 0.1087 for 411 reflections with I₀ > 2σ(I)) contains [Cr(NH₃)₆]³⁺ and [Cr(NH₃)₂F₄]^– octahedra and twice as many [BF₄]^– tetrahedra that are arranged in a quadrupled super‐structure of the CsCl‐type of structure.     

Zur Kristallstruktur von Ba3Al2F12

Concerning the Crystal Structure of Ba₃Al₂F₁₂ Preparing BaMnAlF₇ we obtained single crystals of Ba₃Al₂F₁₂ as a by‐product (a = 1020.3(2), b = 988.5(1), c = 952.2(1) pm, space group Pnnm, Z = 4). The redetermination confirmed the structure already known, but improved the results (R₁′ = 0.028 and wR₂ = 0.06 for 1908 and 2717 reflections, resp.). An interpretation is given for the relation of distances within the tetrameric anion [Al₄F₂₀]^8— (average Al—F: 180, 1 pm). The construction of the cationic frame [Ba₃F₂]⁴⁺ is discussed.     

Synthesis,Crystal Structure,and Properties of the Sodium Molybdate Fluoride Na3MoO4F

The compound Na₃MoO₄F was synthesized by high temperature solution methods. Single‐crystal X‐ray diffraction analysis reveals that Na₃MoO₄F crystallizes in the orthorhombic space group Pnma (No. 62) with lattice constants a = 5.588(2) Å, b = 7.515(3) Å, c = 12.876(5) Å, and Z = 4. The crystal structure consists of isolated MoO₄ groups and [FNa₃]_∞ chains, which are connected by Na–O bonds to form a three‐dimensional framework. A detailed structure comparison between Na₃MoO₄F and NaMoO₃F was carried out. IR spectroscopy and bond valence sum analysis of Na₃MoO₄F indicate that the structure is reasonable. In addition, the electronic structure was investigated by the first‐principles method.