H. Oppermann

The crystal structure of Bi4O5I2 and its relation to the structure of Bi4O5Br2

Abstract The crystal structure of Bi4O5I2 has been solved from a 3:1 twinned crystal; accurate lattice parameters have been determined by a Rietveld refinement. Bi4O5I2 crystallizes with space group P21 (no. 4), Z=4, a=14.944(1), b=5.6983(3), c=11.263(1) Å, β= 99.81(1)°. Its structure is isotypic to the structure of the homologous Bi4O5Br2 for which more reliable lattice parameters have been determined by a Rietveld refinement. The effects of replacement of Br by I on the structure are discussed and compared with corresponding effects in the BiOX family (X = Cl, Br, I). A structural reason for the deviation of the twin supercells of the two compounds from orthogonality is discussed.

II. Zum System Bi2O3/Bi2Se3/Bi2Te3 – die Kristallstruktur von Bi2O2(TexSe1–x)

Entlang der quasibinaren Linie im Phasendiagramm Bi2O2Se/Bi2O2Te ist durch Festkorperreaktionen die Existenz einer luckenlosen Mischkristallreihe Bi2O2(TexSe1–x), 0 ≤= x ≤ 1 nachweisbar. Die Struktur der ternaren Randphase Bi2O2Se wurde anhand von Einkristallmessungen verfeinert. Fur Bi2O2Te und die weiteren Vertreter der Mischkristallreihe konnen die kristallografischen Daten uber Pulvermessungen erhalten werden: Bi2O2Se I4/mmm (No. 139); Z = 2; a = 3,887(1), c = 12,164(2) A, Bi2O2Te0,5Se0,5 I4/mmm (No. 139); Z = 2; a = 3,934(1), c = 12,454(2) A, Bi2O2Te I4/mmm (No. 139); Z = 2; a = 3,983(1), c = 12,699(2) A. Investigations of the Phase Relations in the Quaternary Systems Bi2O3/Bi2Ch/Bi2Ch (Ch = S, Se, Te) II. The System Bi2O3/Bi2Se3/Bi2Te3 – the Crystal Structure of Bi2O2(TexSe1–x) The existence of a complete series of mixed crystals Bi2O2(TexSe1–x), 0 ≤ x ≤ 1 in the pseudobinary system Bi2O2Se/Bi2O2Te has been detected by solid state reactions. The crystal structure of the ternary phase Bi2O2Se was refined on the basis of single crystal measurements. The crystallographic data for Bi2O2Te and for compositions of the mixed crystals were obtained using powder x-ray measurements: Bi2O2Se I4/mmm (No. 139); Z = 2; a = 3.887(1), c = 12.164(2) A, Bi2O2Te0,5Se0,5 I4/mmm (No. 139); Z = 2; a = 3.934(1), c = 12.454(2) A, Bi2O2Te I4/mmm (No. 139); Z = 2; a = 3.983(1), c = 12.699(2) A.

Untersuchungen zu Bismutseltenerdoxidhalogeniden der Zusammensetzung Bi2SEO4X (X = Cl, Br, I)

Die Bismutseltenerdoxidhalogenide Bi2SEO4X (SE = Y, La–Lu; X = Cl, Br, I) wurden festkorperchemisch aus stochiometrischen Gemengen BiOX, Bi2O3 und dem jeweiligen Seltenerdoxid SE2O3 synthetisiert und rontgenografisch, IR-spektroskopisch sowie mittels Massenspektrometrie und DTA/TG-Messungen charakterisiert. Die Kristallstruktur (tetragonal, P4/mmm, a ≈ 3,9 A, c ≈ 9 A) wurde durch Rietveld-Rechnungen verfeinert. Sie kann als Schichtstruktur aus [M3O4]+-Einheiten, die durch Halogen-Monoschichten getrennt sind, beschrieben werden. Die Seltenerd- und Bismutatome in Bi2SEO4X sind 8-fach koordiniert, die Struktur last sich vom Sillenit-Typ (LiBi3O4Cl) ableiten. Die Standardbildungsenthalpien wurden aus Losewarmen und die Standardentropien aus CP-Funktionen hergeleitet. Investigations on the Bismuth Rare-Earth Oxyhalides Bi2REO4X (X = Cl, Br, I) Compounds of the composition of Bi2REO4X (RE = Y, La–Lu; X =  Cl, Br, I) have been prepared by solid state reaction of stoichiometric mixtures of BiOX, Bi2O3, and RE2O3. They were characterized by X-ray powder diffraction, IR spectroscopy, mass spectrometry and DTA/TG measurements as well. The crystal structure (tetragonal, P4/mmm, a ≈ 3.9 A, c ≈ 9 A) was determined by the Rietveld method. In the structure [M3O4]+ layers are interleaved by single halogen layers. Rare-earth and bismuth atoms in Bi2REO4X are 8-coordinated. The structure can be derived from the LiBi3O4Cl2 type structure. The enthalpies of formation are derived from heats of solution. The standard entropies were calculated from low-temperature measurements of the specific heat capacities.

Crystal Structure and SHG Characterization of γ-BiSeO3Cl

Abstractγ-BiSeO3Cl crystals were grown and characterized by x-ray microanalysis and second harmonic generation. The structure of γ-BiSeO3Cl was determined by single-crystal x-ray diffraction: sp. gr. Pna21, a = 11.707(4) Å, b = 7.047(5) Å, c = 5.315(1) Å, Z = 4, R1 = 0.564, wR2 = 0.1272. The structures and second-order nonlinear responses of α- and γ-BiSeO3Cl are discussed in comparison with those of MTeO3X (M = Bi, rare earth; X = Cl, Br, I) oxyhalides.

Zum chemischen Transport von Bismutoxidhalogeniden BiOX (X = Cl, Br, I) mit Halogen, Halogenwasserstoff sowie Wasser und Bestimmung der Molwärmen von BiOX

Aus dem Vergleich des berechneten und experimentellen Transportverhaltens von BiOX (X = Cl, Br, I) mit X2, HX und H2O wird gezeigt, dass der chemische Transport von BiOCl, BiOBr und BiOI mit X2 und HX mit den bekannten Gasspezies verstanden werden kann. Aus den hohen Transportraten der BiOX mit H2O wird die Existenz von Gaskomplexen Bi(OH)2X gefolgert und ihre Bildungsenthalpien und Standardentropien hergeleitet:δH(Bi(OH)2Clg,298) = –128,5 ± 7,0 kcal/mol, S°(Bi(OH)2Clg,298) = 83,1 ± 5,0 cal/K · mol.δH(Bi(OH)2Brg,298) = –118,5 ± 7,5 kcal, S°(Bi(OH)2Brg,298) = 86,0 ± 5,0 cal/K · mol.δH(Bi(OH)2Ig,298) = –102,5 ± 8,0 kcal/mol, S°(Bi(OH)2Ig,298) = 87,6 ± 5,0 cal/K · mol. Die Standardentropien der BiOX wurden aus Tieftemperatur-Cp-Messungen erhalten:S°(BiOClf,298) = 24,30 ± 0,05 cal/K · mol,S°(BiOBrf,298) = 25,93 ± 0,05 cal/K · mol,S°(BiOIf,298) = 28,55 ± 0,05 cal/K · mol. Chemical Transport of Bismuth Oxide Halides BiOX (X = Cl, Br, I) with X2, HX and H2O, and Determination of the Molar Enthalpies of BiOX By comparison of calculated and experimental chemical transport behaviour of BiOX (X = Cl, Br, I) with X2, HX, and H2O it was shown, that we understand the transport of BiOCl, BiOBr and BiOI with X2 and HX in terms of the well known gaseous spezies in the systems. The existence of gaseous complexes Bi(OH)2X is be concluded from high transport rates of BiOX with water, and their enthalpies and entropies were derived. The molar enthalpies and standard entropies of BiOX were determined by low temperature Cp measurements. (Data see Inhaltsubersicht)

Phase barograms - phase diagrams by total pressure measurements

The measurement of the total vapour pressure of binary, quasi-binary and ternary systems gives us information for the determination of the existence of phases, the existence range of phases and their coexistence and solubility ranges by the investigation of the barograms of the systems, too. By determination of the existence fields we obtain the decomposition mechanism and the dominant gaseous species and from the temperature function of the equilibrium constant we calculate the reaction enthalpy and reaction entropy and from these the enthalpy of formation and the standard entropy. The possibilities of the method are demonstrated on the ternary system Bi/Se/O.

Gasphasengleichgewichte quaternärer Bismut-Selen-Oxidchloride

Die Existenz der Verbindungen Bi4O4SeCl2, Bi10O12SeCl4 und Bi22O28SeCl8 im System Bi2O3/Bi2Se3/BiCl3 wurde durch Festkorperreaktionen und Chemischen Transport nachgewiesen. Daruber hinaus wurden die Festkorper-Gasphasengleichgewichte fur die Verbindungen massenspektrometrisch untersucht. Dabei wurde die Gasspezies BiSeCl erstmals experimentell nachgewiesen und ihre Geometrie und thermochemischen Eigenschaften uber ab-initio Molekulberechnungen charakterisiert. Weiterfuhrende thermodynamische Modellierungen der heterogenen Gleichgewichte unterstutzen das Verstandnis der experimentellen Ergebnisse zur Gasphasenzusammensetzung sowie zum Chemischen Transport. Gas-Phase Equilibria of Quaternary Bismuth Selenium Oxidechlorides The existence of new compounds Bi4O4SeCl2, Bi10O12SeCl4, and Bi22O28SeCl8 in the pseudoternary area Bi2O3/Bi2Se3/BiCl3 has been established by solid state and chemical vapour transport reactions. Furthermore, heterogeneous equilibria between solid state and vapour phase have been studied by mass-spectrometric measurements. The novel gas-molecule BiSeCl has been detected. The results of ab initio calculations for structure and refining of thermochemistry of this molecule are given: (Bi–Se) = 2,44 A; (Bi–Cl) = 2,49 A; (Se–Bi–Cl) = 106,0°; Thermodynamics: δH°B,298 (BiSeClg) = 6,0 kcal/mol; S°298 (BiSeClg) = 75,8 cal/mol K; Cp (BiSeClg) = 13,583 + 0,64 · 10–3 · T – 0,41 · 105 · T–2 – 0,35 · 10–6 · T2 cal/mol K. Finally, the composition of the gaseous phase has been calculated and estimations about chemical vapour transport were carried out by thermodynamic modelling.

Synthesis and powder X-ray diffraction analysis of new mixed rare-earth and selenium oxychlorides with composition LnSeO3Cl

A series of new mixed rare-earth and selenium oxychlorides with composition LnSeO3Cl (Ln = La, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Yb, or Y) were prepared by annealing together LnOCl and SeO2 in sealed silica tubes. The resulting compounds were characterized by powder X-ray diffraction. The unit cell parameters of the phases were determined. Lanthanum—europium oxychlorides crystallized in the tetragonal system to give the Sillen phases analogously to tellurium compounds with the similar formula, whereas Tb—Yb and Y oxychlorides crystallized in the orthorhombic system. It is likely that the latter oxychlorides are not layered compounds.

Thermische Zersetzung und Lösungskalorimetrie von Ammoniumsamariumbromiden

für Naturforschung in cooperation with the Max Planck Society for the Advancement of Science under a Creative Commons Attribution 4.0 International License. Dieses Werk wurde im Jahr 2013 vom Verlag Zeitschrift für Naturforschung in Zusammenarbeit mit der Max-Planck-Gesellschaft zur Förderung der Wissenschaften e.V. digitalisiert und unter folgender Lizenz veröffentlicht: Creative Commons Namensnennung 4.0 Lizenz. Thermische Zersetzung und Lösungskalorimetrie von Ammoniumsamariumchloriden

Bestimmung der Bildungsenthalpie von SmOCl durch Lösungskalorimetrie

Determination of the Enthalpy of Formation of SmOCl by Solution Calorimetry The enthalpy of formation of SmOCl (ΔH(SmOClf, 298) = —239.9 ± 0.5 kcal/mol) was determined from the heat of solution of SmOCl (ΔHL(SmOClf298) = —31.24 ± 0.15 kcal/mol) on the base of the enthalpies of formation of Sm2O3 and SmCl3 and their heats of solution in 4n HCl.