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  • 1
    ISSN: 0044-2313
    Keywords: Dilithium manganese tetrabromide, Li2MnBr4 ; crystal structure ; neutron diffraction data ; MAPLE calculations ; Raman spectra ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Li2MnBr4(o-rh.) - an Ordered NaCl Defect Structure of the SnMn2S4 TypeNeutron diffraction data of Li2MnBr4 at 25°C are presented. The orthorhombic room-temperature polymorph of Li2MnBr4 (space group Cmmm, Z = 2, a = 777.78(4), b = 1106.58(5), and c = 388.18(2) pm, RI = 6.7%) crystallizes in an ordered NaCl defect structure (SnMn2S4 type). The tetragonally distorted MBr6 octahedra are elongated in the case of LiBr6 and compressed for MnBr6 owing to the different sharing of these units. The crystal structure of Li2MnBr4 oC14 (and those of alternative structure models with a larger pseudotetragonal cell) are discussed with respect to X-ray intensities, Madelung part of lattice energy (MAPLE), and the Raman spectra. The symmetry coordinates and vibrational modes of the \documentclass{article}\pagestyle{empty}\begin{document}$ (\mathop {\rm k}\limits^ \to = 0) $\end{document} phonons of Li2MnBr4 oC14 are given.
    Notes: Die Kristallstruktur der Raumtemperaturmodifikation von Li2MnBr4 wurde mit Hilfe von Neutronenpulvermessungen bestimmt. Li2MnBr4(o-rh.) (Raumgruppe Cmmm, Z = 2, a = 777,78(4), b = 1106,58(5) und c = 388,18(2) pm, RI = 6,7%) kristallisiert in einer geordneten NaCl-Defekt-(bzw. Über-)struktur (SnMn2S4-Typ). Die MBr6-Oktaeder sind (mit unterschiedlicher Verknüpfung) tetragonal gestaucht (Mn) bzw. gestreckt (Li). Die Kristallstruktur von Li2MnBr4 oC14 (sowie von alternativen Strukturmodellen einer größeren pseudotetragonalen Zelle) wird unter Einbeziehung der Röntgenintensitäten, von Madelungenergien (MAPLE) sowie der Ramanspektren diskutiert. Die Symmetriekoordinaten und Schwingungsformen der Gitterschwingungen \documentclass{article}\pagestyle{empty}\begin{document}$ (\mathop {\rm k}\limits^ \to = 0) $\end{document} des Li2MnBr4 oC14 werden mitgeteilt.
    Additional Material: 3 Ill.
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  • 2
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Zeitschrift für anorganische Chemie 619 (1993), S. 993-998 
    ISSN: 0044-2313
    Keywords: Bromozincates ; zinc ; olivine-type halides ; neutron diffraction ; fast ionic conductivity ; Raman spectra ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: New Halogenozincates M2IZnX4 (MI = Li, Na; X = Cl, Br) of Olivine TypeThe hitherto unknown tetrabromozincates Li2ZnBr4 and Na2ZnBr4 have been prepared. Quaternary halides Li2Zn(Cl, Br)4 and Li2Zn(Br, I)4 have been not obtained due to decomposition to mixtures of LiCl and ZnBr2, and LiBr and ZnI2. The crystal structures of the olivine-type bromides and of the high-temperature polymorph of Li2ZnCl4 have been determined by neutron powder diffraction using the Rietveld method (space group Pnma, Z = 4, a = 1 360.41(4), b = 788.47(2), c = 647.07(2) pm, RI = 9.07% (Li2ZnBr4), a = 1 446.32(5), b = 853.02(3), c = 676.61(2) pm, RI = 9.29% (Na2ZnBr4), a = 1 277.60(3), b = 741.76(2), c = 611.10(1) pm, RI = 7.63% (Li2ZnCl4)). The Raman spectra as well as the results of thermal analyses (DSC) and conductivity measurements (impedance spectroscopy) are presented and discussed. Contrary to Li2ZnCl4, Li2ZnBr4 and Na2ZnBr4 do not undergo any phase transition between 20°C and their melting points.
    Notes: Die Darstellung der bisher nicht bekannten Tetrabromozinkate Li2ZnBr4 und Na2ZnBr4 wird beschrieben. Quaternäre Halogenide des Typs Li2Zn(Cl, Br)4 bzw. Li2Zn(Br, I)4 konnten nicht erhalten werden. Es erfolgt Entmischung zu LiCl und ZnBr2 bzw. LiBr und ZnI2. Die Kristallstrukturen der im Olivintyp kristallisierenden Bromide und der Hochtemperaturform von Li2ZnCl4 wurden auf der Basis von Neutronenpulver-Messungen nach der Rietveld-Methode bestimmt (Raumgruppe Pnma, Z = 4, a = 1 360,41(4), b = 788,47(2), c = 647,07(2) pm, RI = 9,07% (Li2ZnBr4), a = 1 446,32(5), b = 853,02(3), c = 676,61(2) pm, RI = 9,29% (Na2ZnBr4), a = 1 277,60(3), b = 741,76(2), c = 611,10(1) pm, RI = 7,63% (Li2ZnCl4)). Raman-Spektren sowie das Ergebnis thermoanalytischer Untersuchungen (DSC) und Leitfähigkeitsmessungen (Impedanz-Spektroskopie) werden mitgeteilt. Li2ZnBr4 und Na2ZnBr4 zeigen im Gegensatz zu Li2ZnCl4 zwischen 20°C und dem Schmelzpunkt keine Phasenumwandlung.
    Additional Material: 5 Ill.
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  • 3
    ISSN: 0044-2313
    Keywords: Magnesium iodate ; crystal structure ; Raman spectra ; high temperature Raman- and X-ray studies, thermal analyses ; lone-pair radius of iodine(V) ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Magnesium Iodate Decahydrate Mg(IO3)2 · 10 H2O - Crystal Structure, Raman Spectra, Thermal Decomposition, Lone-Pair Radius of Iodine(V)Mg(IO3)2 · 10 H2O crystallizes in the triclinic space group P1 (a = 654.25(9), b = 1109.8(2), c = 1176.7(2) pm; α = 105.470(8), β = 104.086(8), γ = 101.744(8)°; Z = 2). The structure has been determined by single-crystal X-ray diffraction at 273 K, and refined to a final R value of 0.0272 for 4372 observed reflections (I 〉 2σ(I)). The magnesium ions are coordinated to six different H2O molecules forming a slightly distorted octahedron with Mg—O distances varying between 202.2(2) and 211.6(3) pm. The hexaaquamagnesium ions are arranged parallel to (010). The two kinds of iodate ions and the four different “free” water molecules are filled between the layers thus formed.There are twenty independent hydrogen bonds with O … O distances from 268.7(3) to 287.6(4) pm. On the basis of all intermolecular I … I distances of iodates reported in the literature, 180 pm are recommended as van-der-Waals radius resp. lonepair radius of iodine(V). DSC and Raman spectroscopic experiments as well as high-temperature Raman and X-ray measurements were performed and are discussed with respect to the energetic and geometric distortion of the IO3- ions and the dehydration of the decahydrate via the tetrahydrate (308 K) to Mg(IO3)2 (428 K).
    Notes: Mg(IO3)2 · 10 H2O kristallisiert in der triklinen Raumgruppe P1 (a = 654,25(9), b = 1109,8(2), c = 1176,6(2) pm; α = 105,470(8), β = 104,086(8), γ = 101,744(8)°; Z = 2). Die Kristallstruktur wurde mit Hilfe von Röntgen-Einkristalldaten (MoKα) bestimmt (R = 2,72%, 4372 symmetrieunabhängige Reflexe mit I 〉 2σ(I)). Sie ist aus oktaedrischen [Mg(H2O)6]2+- und pyramidalen IO3--Ionen sowie 4 weiteren Kristallwassermolekülen aufgebaut. Die O … O-Abstände der Wasserstoffbrücken der 20 verschiedenen Wasserstoffatome betragen 268,7(3) - 287,6(7) pm. Aufgrund der intermolekularen I … I-Abstände der bisher bekannten Iodatstrukturen werden 180 pm als van-der-Waals- bzw. lone-pair-Radius von Iod(V) vorgeschlagen. Raman-Spektren von Mg(IO3)2 · 10 H2O und das Ergebnis von DSC-Messungen sowie Röntgen- und Raman-Heizaufnahmen werden mitgeteilt und in Hinblick auf die Verzerrung der Iodationen und die Dehydratation des Decahydrats über das Tetrahydrat (308 K) zu Mg(IO3)2 (428 K) diskutiert.
    Additional Material: 9 Ill.
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