bluuebunny/crossref_metadata_2025_split huggingface dataset:
On the crystal structure of γ-AgMg4
Authors: Kudla Christian , Prots Yurii , Leineweber Andreas , Kreiner Guido 
Published: February 2005

Abstract
The title compound with the trivial name γ-AgMg4 is obtained by melting the elements in weld-sealed tantalum ampoules and subsequent annealing. The alloys were characterized by chemical, metallographic, thermal and X-ray powder analyses. γ-AgMg4 is formed by a peritectoid reaction at 472(2) °C from ɛ′-Ag17Mg54 and δ-(Mg). The exact composition corresponds to the formulas AgMg4.08 or Ag9Mg36.7 with 80.3(1) at-% Mg concentration. The title compound is a complex metallic alloy phase due to the large number of atoms and intrinsic structural disorder. γ-AgMg4 crystallizes hexagonal in the space group P63/m with a = 12.4852(8) Å and c = 14.4117(9) Å in a unique structure type without a perceptible homogeneity range. The crystal structure has been studied including disorder phenomena by means of Rietveld refinements of X-ray and neutron powder diffraction data and X-ray single crystal structure analyses. The crystal structure is a hitherto unknown I3 cluster phase, i.e., an intermetallic compound with building blocks of three vertex connected icosahedra as the fundamental structural units joined via a small number of connection types (here B- and L-type). Channels along [001] reveal distinct structural disorder described as a packing of approximately 1.9 icosahedra, 1.3 tricapped trigonal prisms and 0.4 Frank-Kasper Z15 polyhedra per unit cell. The findings support the usefulness of the I3 cluster concept as a construction kit concerning not only simple subunits but also more complex “patches” with inherent structural disorder.
Metallic barrelane: crystal structure, physical properties and bonding analysis of La16Al13
Authors: Niewa Rainer , Kirchner Martin , Zhang Hui , Schnelle Walter , Grin Yuri 
Published: February 2005

Abstract
Single crystals of the new intermetallic compound La16Al13 were obtained by thermal treatment of (La3O)Al in sealed Ta ampoules at 973 K, powder material for physical properties measurements from melt beads of appropriate composition at 773 K, well below the peritectic temperature of 978 K of the decomposition into LaAl and liquid. La16Al13 crystallizes hexagonal (space group P-62m, a = 918.3(2) pm, c = 1123.8(3) pm, R
gt(F) = 0.0293, R
all(F) = 0.0299, wR(F
2) = 0.0621) with one formula unit per unit cell. The crystal structure can be described as built from layers of face-sharing Edshammar polyhedra (AlLa2La9/2)2 alternating with layers of barrelane-like Al11 cages linked by La. La16Al13 is a Pauli-paramagnet with metallic electrical resistivity. Electron localization function calculation reveals covalent interactions within the Al11 cages. The resulting large number of the ‘free’ charge carriers explains the metal-like transport and magnetic properties in good agreement with the experiments and electronic band-structure calculation.
Structural phase transition of CeAuGe at high pressure
Authors: Brouskov Valeri , Hanfland Michael , Pöttgen Rainer , Schwarz Ulrich 
Published: February 2005

Abstract
Structural properties of the ternary intermetallic compound CeAuGe were investigated at hydrostatic pressures up to 15 GPa with high-resolution angle dispersive X-ray powder diffraction using synchrotron radiation and the diamond anvil cell technique. At 8.7(7) GPa a first order phase transition is observed from a hexagonal NdPtSb-type arrangement into an orthorhombic high-pressure modification with a TiNiSi-type crystal structure. The transformation is associated with a 3% shortening of the lattice parameter perpendicular to the puckered layers [AuGe]n and an elongation of one of the lattice parameters within the plane of the layers. The changes of interatomic distances are more pronounced than the metrical alterations and indicate that a transition from layer-type poly anions into a 3D network [AuGe]n is associated with the structural transformation.
Incommensurately modulated CeSi1.82
Authors: Leisegang Tilmann , Meyer Dirk C. , Doert Thomas , Zahn Gernot , Weißbach Torsten , Souptel Dmitri , Behr Günter , Paufler Peter 
Published: February 2005

Abstract
An incommensurately modulated structure of CeSi1.82 as determined by single-crystal X-ray diffraction at room temperature is reported. The observed satellite reflections reduce the orthorhombic symmetry of the X-ray pattern to a monoclinic one. This suggests the description of the modulated structure in the monoclinic superspace group I2/b(αβ0)00. The modulation wave vector was determined to q = 0.410(1) · a* + 0.610(1) · b*. The refinement was done using harmonic modulation functions for the displacement and the occupation probability of the atoms, the quality parameters converged to R
obs = 3.33% (R
obs = 2.56% for the main reflections, R
obs = 8.88% for the 1st order satellite reflections and R
obs = 33.06% for the 2nd order satellite reflections). The origin of the observed satellite reflections is attributed to a modulation of the partly occupied Si site caused by composition changes within the crystal.
Crystal structures of M2[B10H10] (M = Na, K, Rb) via real-space simulated annealing powder techniques
Authors: Hofmann K. , Albert Barbara 
Published: February 2005

Abstract
Alkali metal decahydro-closo-decaborates M2[B10H10] (M = Na, Rb, Cs) were synthesised by ion-exchange and characterised via infrared and 11B-NMR spectroscopy. The crystal structures of Na2[B10H10], K2[B10H10], and Rb2[B10H10] were determined from X-ray powder diffraction data using real-space techniques. The compounds crystallise in the monoclinic space group P21/n (no. 14) with the lattice constants: Na2[B10H10]: a = 1028.28(6) pm, b = 1302.18(5) pm, c = 667.34(3) pm, β = 93.754(3)°; K2[B10H10]: a = 1285.54(8) pm, b = 1117.84(7) pm, c = 682.27(4) pm, β = 93.357(3)°; Rb2[B10H10]: a = 1320.04(7) pm, b = 1136.88(6) pm, c = 704.23(4) pm, β = 94.158(3)°. The hydroborate anions are arranged almost hexa gonally with alkali metal cat ions in the tetrahedral interstices.
Solvothermal synthesis, phase transition and crystal structure of β- and γ-CuPb3Br7
Authors: Oldag Thorsten , Keller Hans-Lothar 
Published: February 2005

Abstract
Single crystals of CuPb3Br7 were solvothermally synthesized starting with CuBr and PbBr2 in diethylene glycol at a temperature of 453 K. Two reversible phase transitions were observed with the DSC method at temperatures of 156 K and 433 K. The crystal structures of the low and medium temperature modifications were determined with single crystal X-ray diffraction method. Both modifications can be derived from the Sr7Pt3 type structure and can be differentiated by minor atomic displacements and partial occupation of the additional copper positions.
[Ba2(C2H6O2)4][Ge2(C2H4O2)6] · 2.5 C2H6O2 – an ethanediolato complex of germanium. Synthesis, thermal decomposition and crystal structure
Authors: Jäger Lothar , Lorenz Volker , Wagner Christoph , Müller Thomas , Abicht Hans-Peter 
Published: February 2005

Abstract
[Ba2(C2H6O2)4][Ge2(C2H4O2)6] · 2.5 C2H6O2 (3a) is isolated from the reaction of GeO2 · aq with Ba(OH)2 · 8 H2O in glycol (1,2-ethanediol). 3a crystallizes in the space group P-1 with a = 10.324(2) Å, b = 13.932(3) Å, c = 15.800(3) Å, α = 102.86(2)°, β = 91.33°, γ = 109,47° and V = 2077.2(7) Å3. With increasing temperature 3a looses glycol and forms step by step [Ba(C2H6O2)2][Ge(C2H4O2)3] (3b), Ba[Ge(C2H4O2)3] (3c) and finally hexagonal BaGeO3 (4).
Synthesis and crystal structure of {[Li(NH3)4]2[18-crown-6]}[Li(NH3)4]2(Sn3
ph
6)2 · 4 NH3
Authors: Wiesler Katharina , Korber Nikolaus 
Published: February 2005

Abstract
{[Li(NH3)4]2[18-crown-6]}[Li(NH3)4]2(Sn3
ph
6)2 · 4 NH3 was prepared by reacting diphenyltin dichloride with lithium and 18-crown-6 in liquid ammonia. The crystal structure was obtained from low temperature single crystal X-ray data (P21/a, Z = 2, a = 18.483(5) Å, b = 13.240(2) Å, c = 22.919(5) Å; β = 103.65(3)°). The structure is built from previously unknown catena-hexaphenyltristannandiide anions, Sn3
ph
6, isolated tetraamminelithium complexes, and novel {[Li(NH3)4]2[18-crown-6]}2+ cations. In the latter divalent cation, two tetraamminelithium complexes coordinate to both sides of the crown ether via hydrogen bonds.
Nd(NH2SO3)(SO4) · 1.5 H2O: a non-centrosymmetric amidosulfate-sulfate of neodymium
Authors: Wickleder Mathias S. 
Published: February 2005

Abstract
The thermal decomposition of Nd(NH2SO3)3 · 2 H2O in a closed tube leads to violet single crystals of Nd(NH2SO3)(SO4) · 1.5 H2O. The compound crystallizes with the space group P1 (Z = 2, a = 689.2, b = 691.4, c = 962.0 pm, α = 109.64, β = 97.00, γ = 109.62°). The triclinic unit cell can be transformed into the respective bodycentered setting I1 (Z = 2, a = 977.9, b = 795.6, c = 1113.0 pm, α = 90.69, β = 115.06, γ = 88.98°) leading to a nearly monoclinic unit cell for the compound. In the crystal structure of Nd(NH2SO3)(SO4) · 1.5 H2O two Nd3+ ions are present. Nd(1)3+ is coordinated by four NH2SO3
– and two SO4
2– ions, and one H2O molecule. Owing to the chelating attack of the sulfate groups, the CN is nine. Nd(2)3+ is surrounded by four monodentate SO4
2– and two NH2SO3
– groups. Two H2O ligands fill up the coordination sphere and lead to a CN of eight. The linkage of the polyhedra leads to a three-dimensional network.
Synthesis of InxGa1–xN solid solutions
Authors: Kinski Isabel , Maurer Florian , Winkler Holger , Riedel Ralf 
Published: February 2005

Abstract
For the growth of group-III nitride thin films as well as GaN and AlN bulk phases precursors are widely used. Here, we introduce bulk phases of pure GaN, InN and solid solutions of InxGa1–xN synthesized by pyrolysis of molecular precursors in ammonia atmosphere. The dimeric [M(NMe2)3]2 (M = Al, Ga) is an oftentimes discussed precursor for conversion into group-III nitrides, while the other here presented gallium and indium amide derivatives have not been reported as appropriate precursors in literature so far. The given molecular structure of the precursors lead to a homogeneous distribution of Gallium and Indium on the cation positions in the solid solutions. GaN and InN and their solid solutions crystallizing in the wurtzite structure type follow Vegard’s law and therefore the lattice constant a
0 gives a hint about the degree of cations substitution in the structure. For the investigations of the synthesized bulk phases XRD, SEM and TEM coupled with EDX were used.
Chemical analyses and X-ray diffraction investigations of human hydroxyapatite minerals from aortic valve stenoses
Authors: Stork Ludwig , Müller Paul , Dronskowski Richard , Ortlepp Jan R. 
Published: February 2005

Abstract
A total of 23 solid, mineral-like samples from calcified aortic valves of human origin have been investigated by means of classic analytical techniques (atomic absorption spectroscopy) and powder X-ray diffraction methods (Rietveld approach). The calcification goes back to hexagonal Ca-deficient hydroxyapatite, and there is a large variance in absolute hydroxyapatite contents as well as in crystalline qualities. The source of the calcium deficiency has been traced back to the 4f calcium site of the crystal structure in P63/m, and the calcium loss is compensated by hydroxy group deficiencies. Despite no correlation between analytically and diffractionally determined calcium contents, the crystallinities of the samples and the sharpnesses of their Bragg peaks seem to be related with the sub-occupancy of the 4f calcium site.
M4,667Ch[SiO4]3 (M = Nd, Sm; Ch = O, S): structural comparison of two apatite-type lanthanoid chalcogenide ortho-oxosilicates
Authors: Hartenbach Ingo , Schleid Thomas 
Published: February 2005

Abstract
The lanthanoid chalcogenide ortho-oxosilicates M4.667Ch[SiO4]3 (M = Nd, Sm; Ch = O, S) with apatite-type crystal structure have been synthesized by the reaction of either M2O3 and SiO2 or M2O3, M, S and SiO2 using CsCl as flux in evacuated silica tubes at 850 °C for 7d. The title compounds crystallize hexagonally in the space group P63
/m with two formula units per unit cell. Their crystal structure contains two crystallographically independent lanthanoid cations, of which (M1) is surrounded by nine O ligands in the shape of a tricapped trigonal prism. Additionally, this site is only occupied by 81–84% to assure that the composition is electroneutral. The (M2) cations have an environment of seven O anions in the case of M4.667O[SiO4]3, which form a pentagonal bipyramid. Considering M4.667S[SiO4]3 this polyhedron changes, when one of the apical oxide particles is substituted by two sulfide ligands which then form a “two-legged” pentagonal bipyramid. Both the non-silicon bonded oxygen in the oxide derivative and the sulfur in the sulfide homologue are situated in a channel along [001]. While oxygen prefers a trigonal planar cationic coordination at the Wyckoff position 2a (CN = 3), the sulfur represents the centre of a trigonal antiprism at the Wyckoff position 2b (CN = 6).
On the crystal structure of a new modification of 2-amino-4,6-dichloro-1,3,5-triazine
Authors: Glaser Jochen , Tragl Sonja , Meyer Hans-Jürgen 
Published: February 2005

Abstract
The sublimation of 2-amino-4,6-dichloro-1,3,5-triazine yielded well developed needle-shaped crystals whose X-ray-powder pattern did not match with that of the known orthorhombic compound with the space group P212121 [1]. The investigation of a needle-shaped single crystal revealed a new monoclinic modification, which crystallizes in the space group P21/c. At T = 220 K the following lattice parameters were refined: a = 8.403(1) Å, b = 12.152(1) Å, c = 13.898(2) Å and β = 123.01(1)°. The unit cell volume amounts to 1190(1) Å3 for 8 formula units.
In-situinvestigation of oxygen diffusion in Sr, Mg-doped LaGaO3superionic conductors with a simultaneously applied electric field
Authors: Günter Marco Maria , Boysen Hans , Corte Carsten , Lerch Martin , Suard Emanuelle 
Published: February 2005

AbstractIn-situneutron powder diffraction investiägations of the oxygen super-ionic conductors La0.9Sr0.1Ga0.8Mg0.2O2.85and La0.8Sr0.2Ga0.8Mg0.2O2.80were performed at 1460 K with and without an applied electric field (U= 3 V DC) resulting in lasting ionic currents of 180–270 mA. At this temperature both samples adopt the cubic perovskite structure (Pm-3m). Field-induced structural changes are evidenced by anharmonic terms in the Debye-Waller factors of oxygen only for the first sample. The corresponding probability density function maps indicate curved diffusion pathways around the Ga atoms shifted further into the direction of an octahedral void with applied field. In addition, double maxima appear in the direction of the Ga—O bond which are more prominent in the second sample. A tentative explanation of the observed phenomena is given in terms of long range ordering of the corresponding potential minima and residual short range order clusters persisting at high temperatures.
High-pressure phase transition of the oxonitridosilicate chloride Ce4[Si4O3+xN7–x]Cl1–xOx with x = 0.12 and 0.18
Authors: Friedrich Alexandra , Knorr Karsten , Lieb Alexandra , Rath Stephanie , Hanfland Michael , Winkler Björn , Schnick Wolfgang 
Published: February 2005

Abstract
The high-pressure behaviour of the oxonitridosilicate chlorides Ce4[Si4O3+xN7–x]Cl1–xOx, x = 0.12 and 0.18, is investigated by in situ powder synchrotron X-ray diffraction. Pressures up to 28 GPa are generated using the diamond-anvil cell technique. A reversible phase transition of first order occurs at pressures between 8 and 10 GPa. Within this pressure range the high- and the low-pressure phases are observed concomitantly. At the phase transition the unit cell volume is reduced by about 5%, and the cubic symmetry (space group P213) is reduced to orthorhombic (space group P212121) following a translationengleiche group-subgroup relationship of index 3. A fit of a third-order Birch-Murnaghan equation of state to the p–V data results in a bulk modulus B
0 = 124(5) GPa with its pressure derivative B′ = 5(1) at V
0 = 1134.3(4) Å3 for the low-pressure phase and in B
0 = 153(10) GPa with B′ = 3.0(6) at V
0 = 1071(3) Å3 for the high-pressure phase. The orthorhombic phase shows an anisotropic axial compression with the a axis (which is the shortest axis) being more compressible (k(a) = 0.0143(4) 1/GPa) than the b and c axes (k(b) = 0.0045(2), k(c) = 0.0058(2) 1/GPa). The experimental results confirm an earlier prediction of the pressure-induced instability of isotypic Ce4[Si4O4N6]O, and also show that the bulk modulus was predicted reasonably well.
Noncentrosymmetric coordination networks based on nitrate and acetylenedicarboxylate anions
Authors: Schuy Andrea , Billetter Heinrich , Hohn Frauke , Pantenburg Ingo , Ruschewitz Uwe 
Published: February 2005

Abstract
Single crystals of Ba2(ADC)(NO3)2 · 4 H2O (1), Ba7(ADC)6(NO3)2 · 14 H2O (2), and Ba3(ADC)2Cl(NO3) × 5 H2O (3) were prepared by crystallisation at the phase boundary of a two phase system (ADC = C2(COO)2). They crystallize in noncentrosymmetric space groups (1: C2221, Z = 4; 2: I2, Z = 2; 3: P2212, Z = 2). For 1 a SHG signal of approx. 0.29 KDP (1 KDP = SHG of KH2PO4) was determined. All hitherto known compounds of the almost linear dianion of acetylenedicarboxylic acid crystallize in centrosymmetric space groups, but by inserting trigonal planar nitrate anions into the crystal structure a symmetry breaking seems to occur, which leads to noncentrosymmetric crystal structures. Several examples from the literature show that this observation might be also valid for other compounds.
The crystal structure of γ-P4, a low temperature modification of white phosphorus
Authors: Okudera Hiroki , Dinnebier Robert E. , Simon Arndt 
Published: February 2005

Abstract
The crystal structure of γ-P4, one of three modifications hitherto reported on white phosphorus, was determined from X-ray powder diffraction data collected at T = 123 K on a Guinier-Simon camera equipped with a cold gas blower and an image plate detector. Crystallographic data at T = 123 K are: space group C2/m, a = 9.1709(5) Å, b = 8.3385(5) Å, c = 5.4336(2) Å, and β = 90.311(3)°, V = 415.51(6) Å3, Z = 4. The crystal structure of γ-P4 was solved by the method of simulated annealing. The subsequent Rietveld refinement in the range 12° < 2θ < 92° employing rigid-body constraints on the P4 molecule converged at Rp
= 3.8, wRp
= 5.0, and RF

2 = 14.0%. The asymmetric unit of γ-P4 contains three P atoms; two P atoms in a molecule are related by a mirror plane which bisects the molecule. The centers of gravity of these P4 molecules show a distorted body-centered cubic arrangement. The four apices of the P4 tetrahedron point to the largest possible voids formed by neighbor molecules. The difference to the crystal structures of SiF4 and GeF4 with an exact bcc arrangement of tetrahedral molecules is discussed as well as, in terms of layer stackings, the similarity of the structures of γ- and β-P4.
Phosphorus-rich phosphorus selenides P14+xSe (x = 1, 5)
Authors: Ruck Michael , Hoppe Diana , Simon Paul 
Published: February 2005

Abstract
New phosphorus-rich phosphorus selenides P14+xSe (x = 1, 5) were synthesized by reaction of amorphous red phosphorus and SeO2. The crystal structures of P15Se and P19Se were solved from single-crystal X-ray data (space group Pnma (No. 62); P15Se: a = 9.963(2) Å, b = 3.231(1) Å, c = 13.412(3) Å; P19Se: a = 9.917(2) Å, b = 3.230(1) Å, c = 13.410(3) Å). The structures consist of pentagonal tubes packed collaterally with two-dimensional disorder, which was confirmed by TEM investigations.
Crystal structure and optical properties of the new 8O polytype of Ca2Ta2O7
Authors: Ebbinghaus Stefan G. , Kalytta Andreas , Kopf Jürgen , Weidenkaff Anke , Reller Armin 
Published: February 2005

Abstract
Single crystals of the new 8O modification of Ca2Ta2O7 were grown by optical floating zone melting and their structure was solved by X-ray diffraction. 8O Ca2Ta2O7 crystallizes in space group C2221 with a = 7.3690(2) Å, b = 12.7296(3) Å, c = 48.263(1) Å. The structure is related to the weberite structure type and can be described as a stacking of 8 basic building units per unit cell. Each building unit consists of one Ta3Ca and one Ca3Ta layer with a cubic close packed arrangement. Transmission measurements in the UV-Vis and IR region reveal a high transparency in a wide energy range from 0.2–3.5 eV. Dielectric measurements yield a high ɛ′ value of 60 at room temperature.
Photoluminescence of ZnGa2S4 : Eu2+
Authors: Wickleder Claudia , Zhang Shuang , Haeuseler Hartmut 
Published: February 2005

Abstract
ZnGa2S4:Eu2+ shows a light green emission at room as well as at low temperatures. The maximum of the band of the 4f65d1 → 4f7 emission is located at about 536 nm (18657 cm–1) and depends slightly on the excitation energy. The respective excitation band has a maximum at 470 nm (21277 cm–1). These results lead to the assumption that the Eu2+ ions are substituted at octahedral voids of the host lattice rather than at cationic sites. This is to be expected also because of the different ionic radii of the cations. Further emission and excitation bands are detected at higher energies in ZnGa2S4:Eu2+ as well as in undoped ZnGa2S4 which depend strongly on the respective excitation and emission energies and can, thus, be assigned to host lattice bands.
In situ bulk structural study on solid-state dynamics and catalytic activity correlations of a H4[PNbMo11O40] partial oxidation catalyst
Authors: Ressler Thorsten , Timpe Olaf , Girgsdies Frank 
Published: February 2005

Abstract
We report on the preparation and characterization of a niobium containing Keggin type heteropolyoxomolybdate (HPOM), H4[PNbMo11O40] · 13 H2O, with Nb substituting Mo in the Keggin ion. H4[PNbMo11O40] · 13 H2O exhibits a long-range order structure similar to that of H3[PMo12O40] · 13 H2O. The structural evolution of H4[PNbMo11O40] · 13 2O was studied under reducing (propene) and partial oxidation reaction conditions (propene and oxygen) by in situ X-ray diffraction and X-ray absorption spectroscopy combined with mass spectrometry and corroborated by thermogravimetric analysis. Following the loss of crystal water in the temperature range from 373 K to 573 K, a partial decomposition and reduction of the molybdenum and the formation of a characteristic cubic HPOM is observed at 573 K, similar to the structural evolution of H3[PMo12O40] · 13 H2O and H4[PVMo11O40] · 13 H2O during treatment in propene. However, in contrast to H3[PMo12O40] · 13 H2O and H4[PVMo11O40] · 13 H2O, the cubic HPOM decomposes rapidly and the MoO3 formed is subsequently reduced to MoO2. Nb centers in the Keggin ion considerably destabilize the HPOM and accelerate the decomposition towards MoO3. A similar structural evolution is observed under propene and oxygen. The formation of the cubic HPOM with Mo centers on extra-Keggin framework positions coincides with the onset of catalytic activity. However, at about 673 K the active phase further decomposes to a mixture of MoO3 and a more stable cubic HPOM resulting in a pronounced decrease of the catalytic activity. Evidently, preparation and structure-activity relationships for Nb containing mixed metal oxide catalysts need to take into account the particular structure directing properties of Nb during thermal activation.