bluuebunny/crossref_metadata_2025_split huggingface dataset:
Colored patterns and the subgroups of their symmetries effecting color permutations
Authors: De Las Peñas Ma. Louise Antonette , Paras Agnes T. 
Published: December 2003

Abstract
In this paper, we study colorings corresponding to the partition of the form

of the symmetry group G of an uncolored pattern where Ji
, H, K are subgroups of G such that K ≤ Ji
≤ H ≤ NG
(K) and

is a complete set of right coset representatives of H in G. In particular, we consider those colorings obtained when Y is partitioned into one set, two sets or singletons and determines the subgroup H* consisting of elements of G effecting color permutations.
Structural topology of potassium uranyl chromates: crystal structures of K8[(UO2)(CrO4)4](NO3)2, K5[(UO2)(CrO4)3](NO3)(H2O)3, K4[(UO2)3(CrO4)5](H2O)8 and K2[(UO2)2(CrO4)3(H2O)2](H2O)4
Authors: Krivovichev Sergey V. , Burns Peter C. 
Published: December 2003

Abstract
Crystals of four potassium uranyl chromates, K8[(UO2)(CrO4)4](NO3)2 (1), K5[(UO2)(CrO4)3](NO3)·(H2O)3 (2), K4[(UO2)3(CrO4)5](H2O)8 (3) and K2[(UO2)2·(CrO4)3(H2O)2](H2O)4 (4), have been synthesized by evaporation of aqueous solutions of (UO2)(NO3)2(H2O)6 and K2CrO4. The structure of (1) (triclinic, P1̅, a = 7.0397(6), b = 9.7341(9), c = 9.7568(9) Å, α = 105.846(2), β = 97.992(2), γ = 93.271(2)°, V = 633.8(1) Å3, Z = 1) was solved by direct methods and refined to R1 = 0.044 (wR2 = 0.098). It is based upon clusters of composition [(UO2)(CrO4)4] that consist of UrO4 square bipyramids (Ur: UO2
2+ uranyl ion) that share corners with four different CrO4 tetrahedra. The clusters are arranged in layers parallel to the (100) plane. K+ cations and NO3
- groups are located between the clusters. The crystal structure of (2) (orthorhombic, P212121, a = 6.1112(11), b = 12.136(2), c = 27.464(4) Å, V = 2036.9(6) Å3, Z = 4) was solved by direct methods and refined to R1 = 0.047 (wR2 = 0.071). it contains chains of composition [(UO2)(CrO4)3] that are parallel to the b axis. The chains consist of UrO5 pentagonal bipyramids that share all equatorial corners with different CrO4 tetrahedra. Planes containing the equatorial ligands of the UrO5 pentagonal bipyramids are approximately parallel to the (100) plane. K+ cations, NO3 groups and H2O groups are between the chains. The crystal structure of (3) (monoclinic, P21/c, a = 8.2336(7), b = 18.8042(17), c = 21.2413(18) Å, β = 89.979(2)°, V = 3288.7(5) Å3, Z = 4) has been solved by direct methods from a crystal twinned on the (001) plane and refined to R1 = 0.060 (wR2 = 0.125). The structure is based upon topologically complex sheets of composition [(UO2)3(CrO4)5] with UrO5 pentagonal bipyramids that share their corners with CrO4 tetrahedra. The sheets are parallel to the (010) plane. K+ cations and H2O groups are located in the interlayer between the sheets. The crystal structure of (4) (monoclinic, P21/c, a = 10.7417(5), b = 14.5290(7), c = 14.1387(6) Å, β = 108.135(1)°, V = 2097.0(2) Å3, Z = 4) was solved by direct methods and refined to R1 = 0.036 (wR2 = 0.067). It is based upon sheets of composition [(UO2)2(CrO4)3(H2O)2] that are parallel to the (010) plane. K+ cations and additional H2O groups are in the interlayer. Nodal representations of uranyl chromate structural units are developed, and a comparison with related structures are presented.
Oriented graphite single-crystal inclusions in diamond
Authors: Glinnemann Jürgen , Kusaka Katsuhiro , Harris Jeffrey W. 
Published: December 2003

Abstract
A crystallographic study of 13 specimens of diamonds with euhedral single-crystalline graphite inclusions in their centres is presented. All inclusions belong to the hexagonal graphite modification (space group P63/mmc; a
0 ≈ 2.46 Å, c
0 ≈ 6.70 Å) and are up to 300 μm in diameter. Comparison of the measured c-lattice parameters of the graphite crystals with lattice parameters of graphite at elevated isostatic pressures indicates remnant pressures of up to 2.6 GPa acting on the inclusions. All samples exhibit distinct orientation relations between graphite and diamond. In 12 samples the direction [001] of graphite (G[001]) approximately parallels one of the directions 〈111〉 of cubic diamond (D〈111〉). The largest deviation is about 4°. A further division of these 12 samples is: (a) The three G〈100〉 directions have angles of about 4° with three D〈110〉 directions. This orientation relation is observed in five samples. (b) The angle between the same directions is about 34° in six samples. (c) In one sample this angle is about 16°. In a 13th specimen G[001] approximately parallels one of the three D〈100〉. The deviation is of about 6°, and one of the G〈100〉 directions nearly parallels one of the D〈110〉. These orientation relations are analysed with a simplified application of the “coincidence site lattice (CSL)” concept. A 14th specimen is different to all others, as it exhibits a large (about 300 μm edge length) region with a sharp hexagonal borderline filled with a “patchwork” of tiny graphite “islands”. Several parallel lamellae of up to 5 μm thickness result in a hexagonal pyramidal form. This graphite inclusion is suggested to be protogenetic with respect to the diamond.
Compositional and structural variations in the ternary system Li – Al – Si
Authors: Spina Laurent , Jia Yong Zhong , Ducourant Bernard , Tillard Monique , Belin Claude 
Published: December 2003

Abstract
The Li–Al–Si ternary system has been investigated and four ternary phases characterized using both powder and single crystal X-ray diffraction data. LiAlSi and Li7Al3Si4 crystallize in the F4̅3m, cubic system, Li18Al2Si6 in tetragonal I41/amd and Li15Al3Si6 in hexagonal P63/m space group. The structure of LiAlSi (a = 5.94 Å), previously reported from powder data, has been confirmed. The new compound Li7Al3Si4 has been identified and, due to a higher lithium content, its cell parameter is slightly larger (a = 6.115 Å). The tetragonal cell (a = 6.179(1) Å, c = 12.199(4) Å) of Li18Al2Si6 may be considered as a (1 × 1 × 2) supercell of the cubic one. Structural variations are strongly correlated to compositional fluctuations and atomic substitutions, in every case the SI–Al network displays some covalent character. In the Li15Al3Si6 hexagonal cell, bonding is more covalent leading to a heterographite-like SI–Al network.
Crystal structures of 2,2′-bipyridine adducts of two cadmium O-alkyl dithiocarbonates: rationalisation of disparate coordination geometries based on different crystal packing environments
Authors: Chen Daulin , Lai Chian Sing , Tiekink Edward R. T. 
Published: December 2003

Abstract
Two distinct coordination geometries are found in the structures of Cd(S2COR)2(2,2′-bipyridine). For R = CH2CH2OCH3 (1) a N2S2 donor set defines a distorted tetrahedral geometry for cadmium as the xanthate ligands adopt a monodentate coordination mode. By contrast, a N2S3 donor set is found in the structure where R is butyl (2) as one of the xanthate ligands is chelating. An analysis of the crystal structures shows that both lattices feature extensive C–H...π interactions and that in (1) there are C–H...O interactions that are not present in (2). In (2) there are π...π interactions that are absent in (1). A qualitative argument based on crystal packing considerations is proposed to explain the differences in molecular structures.
The first crystal structure of a free neutral form of a nicotine derivative
Authors: Evain Michel , Felpin François-Xavier , Laurence Christian , Lebreton Jacques , Le Questel Jean-Yves 
Published: December 2003

AbstractThe single crystal X-ray diffraction analysis of a racemic form of a nicotine derivative, 5-(2-hydroxy-2-methylbut-3-ynyl)-3-(1-methyl-2-pyrrolidinyl)pyridine (2), provides structural information on molecular geometry and intermolecular interactions that could be relevant for the transport and docking of nicotine ligands to nicotinic acetylcholine receptors (nAChRs), since it is the first crystal structure of a free neutral form of a nicotine derivative. Each enantiomer of the two independent molecules of the asymmetric unit is characterized by (i) anantiorientation of the N2 methyl substituent with respect to the pyridine ring (ii) an envelope form of the pyrrolidine ring (iii) an orientation roughly perpendicular of the pyridine and pyrrolidine rings. The crystal packing is characterized by the formation of OH...N1 hydrogen-bond cyclic dimers that are packed through van der Waals interactions. This selectivity of hydrogen-bonding site in favor of the N1 pyridine nitrogen found in the solid state for (2) agrees with the greater hydrogen-bond acceptor strength of the N1 pyridine nitrogen compared to the N2 pyrrolidine one previously found in solution for nicotine (1).
Reversible crystal-to-crystal phase transition in dibromobis(4-vinylpyridine)zinc
Authors: Hu Chunhua , Huster Jürgen , Englert Ullrich 
Published: December 2003

Abstract
In the solid state the mononuclear tetrahedral complex dibromobis(4-vinylpyridine)zinc shows a reversible crystal-to-crystal phase transition which was studied by temperature dependent single crystal X-ray diffraction experiments. At low temperatures the compound crystallizes in space group P1̅ with one ordered complex molecule in general position. Results derived from an intensity data set collected at 120 K are reported. Above the phase transition at 207 K both the cell metric and the symmetry of the diffraction pattern allow the transformation to a centered monoclinic unit cell in space group C2/c. In this high temperature phase the molecule is located on a twofold crystallographic axis and shows disorder with respect to the orientation of the vinyl substituent. The crystal and molecular structure based on a data collection at 293 K is described.
Intermetallic compounds with ordered U3Si2 or Zr3Al2 type structure – crystal chemistry, chemical bonding and physical properties
Authors: Lukachuk Mar'yana , Pöttgen Rainer 
Published: December 2003

Abstract
The crystal chemistry of binary and ternary intermetallic compounds with tetragonal U3Si2 or Zr3Al2 type structure is reviewed. Besides the preparation techniques and crystal chemistry, we especially focus on the structure–property relations and chemical bonding peculiarities.
Structural studies on the Fresnoite type compound Ba2VSi2O8
Authors: Höche Thomas , Esmaeilzadeh Saeid , Withers Ray L. , Schirmer Henning 
Published: December 2003

Abstract
Single crystals of Ba2VSi2O8 have successfully been grown from a high-temperature solution and single crystal X-ray diffraction used to refine its fresnoite type average crystal structure. In contrast to other recently investigated representatives of the fresnoite family of compounds, Ba2VSi2O8 did not at first appear to be incommensurately modulated. Neither single crystal X-ray diffraction nor powder neutron diffraction gave any indication for the existence of satellite reflections in addition to the strong average structure Bragg reflections. A careful electron diffraction study, however, has revealed the existence of weak incommensurate satellite reflections characterized by the primitive primary modulation wave-vectors q
1 = 0.297 [110]* ½c* and q
2 = 0.297 [11̅0]* + ½c*. The reciprocal space positioning of these incommensurate primary modulation wave-vectors, the overall (3 + 2)-d superspace group symmetry, as well as the shapes of the refined displacement ellipsoids determined from the single crystal XRD refinement are all consistent with their arising from condensed Rigid Unit Mode (RUM) modes of distortion of the Ba2VSi2O8 parent structure. The weakness of the satellite reflections in Ba2VSi2O8 relative to, for example, Ba2TiGe2O8 or Sr2TiSi2O8 arises from the significantly smaller amplitude of the condensed RUM mode as is clear from the magnitudes of the refined average structure anistropic displacement ellipsoids.
Rare earth disilicates R
2Si2O7 (R = Gd, Tb, Dy, Ho): type B
Authors: Fleet Michael E. , Liu Xiaoyang 
Published: December 2003

Abstract
The type B structure of the single rare earth element disilicates has been revised using room temperature and pressure single-crystal X-ray diffraction measurements on Gd2Si2O7, Tb2Si2O7 and Ho2Si2O7 synthesized at 2–2.5 GPa, 1400–1500 °C in a piston-cylinder apparatus and Dy2Si2O7 synthesized hydrothermally at 0.1 GPa. Crystal data are: triclinic, space group P1̅, Z = 4; Gd2Si2O7 – a = 6.6609(2), b = 6.7081(2), c = 12.1390(4) Å, α = 94.277(1), β = 90.577(1), γ = 91.441(1)°, R = 0.033, and Dx
= 5.929 g/cm3; Tb2Si2O7 – a = 6.6331(3), b = 6.6799(2), c = 12.0967(2) Å, α = 94.128(1), β = 90.609(2), γ = 91.541(1)°, R = 0.038, and Dx
= 6.041 g/cm3; Dy2Si2O7 – a = 6.6158(2), b = 6.6604(2), c = 12.0551(4) Å, α = 94.373(2), β = 90.836(2), γ = 91.512(2)°, R = 0.031, and Dx
= 6.156 g/cm3; and Ho2Si2O7 – a = 6.5960(2), b = 6.6328(3), c = 12.0214(6) Å, α = 94.479(1), β = 90.856(1), γ = 91.749(2)°, R = 0.034, and Dx
= 6.313 g/cm3. Substitution of Gd3+, Tb3+, Dy3+, and Ho3+ cations into the type B structure results in proportional linear decrease in size of the REEOn polyhedra and unit-cell parameters, and leaves the silicate stereochemistry essentially unchanged.
Synthesis of 4-(3-coumarinyl)-3-benzyl-4-thiazolin-2-one 4-methylbenzylidenehydrazone and determination of the isomeric structure by X-ray analysis
Authors: Özbey Süheyla , Karalı Nilgün , Gürsoy Aysel 
Published: December 2003

Abstract
In this study 4-(3-coumarinyl)-3-benzyl-4-thi azolin-2-one 4-methylbenzylidenehydrazone 3 was synthesised. An independent proof of the thiazolylhydrazone structure of 3 was achieved by single crystal X-ray diffraction analysis. Elemental analyses and spectral data (IR, 1H-NMR, 13C-NMR and EIMS) of 3 was also determined. The coumarin ring system and the thiazole ring are almost planar, the dihedral angle between them is 62.93(5)°. The phenyl groups make dihedral angles of 86.09(7) and 31.67(7)° with the thiazole ring plane. The crystal structure is stabilised by intra-, intermolecular hydrogen contacts and C–H...π type interactions.
Small-angle neutron scattering and phase separation in alloys
Authors: Kostorz G. 
Published: December 2003

Abstract
The basic principles of small-angle neutron scattering and the two-phase model, frequently used for the interpretation of scattering data, are presented. Some studies on phase separation in alloy single crystals serve to illustrate the possibilities of the method. Small-angle neutron scattering of Ni-rich Ni—Ti studied during ageing at elevated temperatures indicates a complex sequence of phases during decomposition, involving two stages of metastable coherent precipitation preceding the formation of the stable hexagonal phase.
Disorder in decagonal quasicrystals
Authors: Frey F. , Weidner E. 
Published: December 2003

Abstract
Complementary neutron and x-ray diffuse scattering may provide insight into structural super-ordering and disordering of decagonal quasicrystals (d-phases), and, in consequence, into the formation and stability of aperiodically ordered alloys. Neutron diffraction makes a contrasting almost isoelectronic atomic species possible, as well as a separation of elastic and inelastic diffuse intensity contributions. Experimental work at high temperatures is comparatively unproblematic. The method suffers, however, from the difficulty in obtaining sufficiently sized mono-grain samples and a lack of dedicated neutron diffraction instruments. Recent results, with a main focus on high-temperature (<1000°C) investigations of disordered decagonal Al—Ni—Co phases are reported and some tentative models are discussed.
Crystal structures and crystal chemical relationships of kröhnkite- and collinsite-type compounds Na2
Me
2+(XO4)2 · 2 H2O (X = S, Me = Mn, Cd; and X = Se, Me = Mn, Co, Ni, Zn, Cd) and K2Co(SeO4)2 · 2 H2O
Authors: Wildner M. , Stoilova D. 
Published: December 2003

Abstract
The crystal structures of eight compounds with compositions A
2
Me
2+(XO4)2 · 2H2O (A = Na, X = S, Me
2+ = Mn, Cd; A = Na, X = Se, Me
2+ = Mn, Co, Ni, Zn, Cd; and A = K, X = Se, Me
2+ = Co) were investigated using single crystal X-ray CCD diffraction data. The Mn- and Cd-compounds crystallize in the monoclinic kröhnkite structure type [Na2Cu(SO4)2 · 2 H2O, space group P21/c], the Co-, Ni-, and Zn-selenates in the closely related triclinic structure type of collinsite [Ca2Mg(PO4)2 · 2 H2O, space group P1̅]. Both types are built up from infinite Me(XO4)2(H2O)2 chains, composed of MeO4(H2O)2 octahedra alternating with each two XO4 tetrahedra by sharing corners. A—O bonds and hydrogen bonds link the chains to layers and further on to the three-dimensional structures. The influence of the ionic radii of the various A, Me, and X cations on the distances between these structural units is discussed. Special attention is paid to polyhedral distortions as well as to individual peculiarities of the alkaline coordinations and the hydrogen bonding systems. Thus, the crystal chemical relationships between the two structure types as well as to isotypic copper compounds, which are characterized by the strong octahedral Jahn-Teller distortions, are elucidated.
Solution of the structure and disorder of Ln13Br18B3(Ln = Gd, Tb)
Authors: Oeckler O. , Kienle L. , Mattausch Hj. , Jarchow O. , Simon A. 
Published: December 2003

AbstractThe average structures (Immm) of Gd13Br18B3(A= 3.9923(2) Å,B= 17.0462(12) Å,C= 28.3039(19) Å) and Tb13Br18B3(A= 3.9637(3) Å,B= 16.9063(13) Å,C= 28.1068(18) Å) were solved taking into account Bragg intensities only. The average structure contains an ordered honeycomb arrangement of chains formed from trans edge sharing Tb6B octahedra and disordered and partly occupied chains of double octahedra in the channels. Pronounced diffuse scattering which is elongated in [001]* indicates a 2D order of the structure. High resolution electron microscopy (HRTEM) gives insight into the nature of the ordering and leads to a model of discrete Tb10B2clusters in the channels which are perfectly ordered in layers in a 2 × 2 × 2 supercell. These layers are randomly stacked with well defined translation values to each other along [100].
Structural distortion of theα,β, andγpolymorphs of glycine on cooling
Authors: Boldyreva E. V. , Drebushchak T. N. , Shutova E. S. 
Published: December 2003

AbstractThe effect of cooling down to 150 K on the structures ofα- (s.g.P21/n),β- (s.g.P21), andγ- (s.g.P31) polymorphs of glycine was studied by X-ray single-crystal diffraction. No polymorphic transformations were detected. Relative volume changes and the anisotropy of structural distortion of the three polymorphs of glycine were compared. Maximum contraction of structures was measured in theb-direction for theα- andβ-polymorphs, and in thea-direction for theγ-polymorph. Minimum contraction in theγ-polymorph was measured inc-direction. The structures of theα- and theβ-polymorphs slightly expanded on cooling in the directions close toc. The directions of maximum and minimum lattice strain were related to the directions of weak and strong hydrogen bonds in the structures. Crystal structures for the three polymorphs were refined at 294 K and at 150 K. The effects of cooling on the intramolecular geometry of glycine molecules and on the intermolecular hydrogen bonds in all the three polymorphs were compared. Structural distortion on cooling was compared with that on increasing hydrostatic pressure.
Structural investigation of dichlorobis(benzimidazole)Zn(II) complex
Authors: Sahin E. , İde S. , Kurt M. , Yurdakul S. 
Published: December 2003

Abstract
The molecular structure of the title complex [ZnCl2(C7H6N2)2] was investigated by X-ray diffraction and IR spectroscopy. The Zn(II) complex crystallizes triclinically (P1̅ (no 2); a = 7.440(2) Å, b = 7.734(2) Å, c = 13.3127(4) Å, α = 85.91(2)°, β = 85.97(2)°, γ = 83.05(5)°, Z = 3; V = 757.3(3) Å3). In the molecular structure, the Zn atom is coordinated tetrahedrally by two Cl– anions and two benzimidazole ligands.
Stable Al—Ni—Rh decagonal phase
Authors: Grushko B. , Mi S. 
Published: December 2003

Abstract
Decagonal (D) phase was found to be stable at 1100 °C in a small compositional range around Al70.5Ni15.5Rh14 which overlaps with the overall range of the D-phase in Al—Ni—Co. The Al—Ni—Rh D-phase exhibits the “basic” tenfold diffraction pattern and the basic periodicity of about 0.4 nm with diffuse diffraction layers corresponding to the double periodicity. At 1100°C it coexists with the ternary extensions of binary “Al3Rh” and C—Al5Rh2 and with the liquid, at 1000°C no D-phase was observed.
Electron crystallography of zeolites. 2. Mordenite and the role of secondary scattering on structure determination
Authors: Dorset Douglas L. 
Published: December 2003

Abstract
Electron diffraction intensity data from the zeolite, mordenite, were used in experimental tests of direct phase determinations for crystal structure analysis. Measurement of patterns from platy and acicular microcrystals yields orthorhombic cell dimensions: a = 18.11, b = 20.17, c = 7.50 Å, consistent with the known x-ray structure. The major perturbation to the intensity data is secondary scattering (also known as ´double diffraction′), an incoherent multiple scattering phenomenon, producing strong reflections where weak ones should be found. Although the phase determination itself is not severely compromised, the error in the observed structure factor amplitudes leads to a distortion of the initial potential maps so that only a partial structure can be determined (e.g. one class of T-sites). It is possible to apply an approximate correction to the observed intensity data for secondary scattering, based on the weighted self-convolution of the partial model intensities. With the improved observed structure factor magnitudes all T-sites are found in the Fourier refinement at an overall mean deviation of 0.24 Å from their ideal positions.
Crystal structure determination of systematically intergrown compounds: Li5(OH)2Br3 and Li2(OH)Br
Authors: Friese K. , Hönnerscheid A. , Jansen Martin 
Published: December 2003

Abstract
We carried out a structure refinement of a crystal which was composed of two phases. Phase I was up to now unknown and corresponds to Li5(OH)2Br3 with lattice parameters a = 4.02335(1), c = 21.5638(1) Å, space group I4̅m2. Phase II is Li2(OH)Br with lattice parameters a = 4.04594(3) Å and space group Pm3̅m. The two phases have the a, b-plane in common and consequently part of the reflections overlap systematically. We performed a joint structure refinement of the two phases taking into account all reflections. The structure of Li5(OH)2Br3 is characterized by anti-perovskite like double layers of composition 2 × Li2(OH)Br, which alternate with rock-salt like layers of composition LiBr. Results for Li2(OH)Br are in good agreement with literature and confirm the correctness of the underlying model and the usefulness of the method employed in structure refinement.