The Modulated Structure of SrAuSn2

2004 ◽  
Vol 59 (11-12) ◽  
pp. 1451-1457 ◽  
Author(s):  
Saeid Esmailzadeh ◽  
Rolf-Dieter Hoffmann ◽  
Rainer Pöttgen
Keyword(s):  
Three Dimensional ◽  
Group Symmetry ◽  
Induction Melting ◽  
Single Crystal Diffraction ◽  
Small Deviations ◽  
Modulated Structure ◽  
Cell Dimensions ◽  
Sample Chamber ◽  
Unit Cell Dimensions ◽  
Modulation Wave Vector

The ternary stannide SrAuSn2 was synthesized by induction melting of the elements under an argon atmosphere in a sealed niobium ampoule in a water-cooled sample chamber of a high-frequency furnace. The structure of SrAuSn2 was investigated by X-ray powder and single crystal diffraction. It was found to be favourable to describe as a commensurately modulated structure. The 3+1 dimensional superspace group symmetry P : Cmcm(α, 0, 0) : 0s0 with the unit cell dimensions a = 460.20(14), b = 2038.8(8), c = 460.34(19) pm and the modulation wave vector q =¼ [100]*. The Sn1 atoms were those with the strongest modulation while the rest of the atoms showed rather small deviations from the average structure. The SrAuSn2 structure is closely related to the CeNiSi2 type. Geometrically these structures are built up from distorted ThCr2Si2 and AlB2 slabs. The gold atoms are located in the ThCr2Si2 slab. They have a distorted square pyramidal tin coordination at Au-Sn distances ranging from 266 to 294 pm. These pyramids are condensed via common edges forming two-dimensional layers. The latter are condensed via the Sn1 atoms within the AlB2 slabs that form one-dimensional zigzag chains with Sn1-Sn1 distances ranging from 282 to 288 pm. These chains show the strong modulations. Together, the gold and tin atoms build up a three-dimensional [AuSn2] network, in which the strontium atoms fill distorted hexagonal channels.

Molecular packing in crystals of the aromatic hydrocarbons

1965 ◽  
Vol 286 (1404) ◽  
pp. 98-116 ◽  
Keyword(s):  
Van Der Waals ◽  
Equilibrium Structure ◽  
Group Symmetry ◽  
Structural Variations ◽  
Angular Variation ◽  
Coupling Energy ◽  
Quadrupole Interactions ◽  
Quadrupole Coupling ◽  
Cell Dimensions ◽  
Unit Cell Dimensions

The van der Waals energy, quadrupole-quadrupole coupling energy, and hydrogen-hydrogen repulsions have been calculated for the equilibrium structure of crystalline naphthalene and for several displaced structures. The displacements are small rotations of the molecules about their symmetry axes, phased so that the space-group symmetry and unit-cell dimensions are preserved. For structural variations of this type the hydrogen-hydrogen repulsions have a strong minimum within a few degrees angular variation from equilibrium, indicating that these repulsions are dominant and determine the crystal structure for this class of displacement. The attractive van der Waals and quadrupole interactions on the other hand are not minimized at the equilibrium structure; they vary slowly (by a few wavenumbers per degree rotation) and approximately linearly.

scholarly journals Synthesis and Characterization of [2-CH3CH2C6H4NH3]6P6O18⋅4H2O

2011 ◽  
Vol 2011 ◽  
pp. 1-6 ◽  
Author(s):  
Houda Marouani ◽  
Salem Slayyem Al-Deyab ◽  
Mohamed Rzaigui
Keyword(s):  
Hydrogen Bonds ◽  
Electrostatic Interactions ◽  
Three Dimensional ◽  
Spectroscopic Studies ◽  
Monoclinic System ◽  
Dimensional Network ◽  
Cell Dimensions ◽  
Unit Cell Dimensions ◽  
Ir Spectroscopic

Single crystals of [2-CH3CH2C6H4NH3]6P6O18⋅4H2O are synthesized in aqueous solution by the interaction of cyclohexaphosphoric acid and 2-ethylaniline. This compound crystallizes in the monoclinic system with P21/c space group the unit cell dimensions are: a=16.220(4) Å, b=10.220(5) Å, c=20.328(4) Å, β=113.24(3)∘, Z=2, and V=3096.5(18) Å3. The atomic arrangement can be described by layers formed by cyclohexaphosphate anions P6O186− and water molecules connected by hydrogen bonds O–H⋯O. These inorganic layers are developed around bc planes at x=1/2 and are interconnected by the H-bonds created by ammonium groups of organic cations. All the hydrogen bonds, the van der Waals contacts and electrostatic interactions between the different entities give rise to a three-dimensional network in the structure and add stability to this compound. The thermal behaviour and the IR spectroscopic studies of this new cyclohexaphosphate are discussed.

Electrostatic lattice energy in ionic crystals: optimization of the convergence of Ewald series

1978 ◽  
Vol 34 (6) ◽  
pp. 974-979 ◽  
Author(s):  
M. Catti
Keyword(s):  
Lattice Energy ◽  
Rates Of Convergence ◽  
Unit Cell ◽  
Group Symmetry ◽  
Cube Root ◽  
Cell Dimensions ◽  
Madelung Energy ◽  
Direct Lattice ◽  
Unit Cell Dimensions ◽  
Theoretical Results

Ewald's method is reconsidered to express the dependence of Madelung energy on the ionic charges explicitly, also taking into account the space-group symmetry of the structure. Upper bounds for the residues of the two partial series have been calculated by integral approximation; that relative to the direct-lattice series is shown to depend on the cube root of the unit-cell volume. The optimum value of the parameter A, which equalizes the rates of convergence of the two sums and minimizes the total number of terms, has been determined numerically for a given termination error and for a range of unit-cell dimensions. Theoretical results are tested by calculations on some specific crystal structures.

Analysis of unit cell dimensions in terms of frameworks and elemental atomic diameters

1983 ◽  
Vol 163 (3-4) ◽  
Author(s):  
E. Hellner ◽  
W. B. Pearson
Keyword(s):  
Three Dimensional ◽  
Unit Cell ◽  
Structural Description ◽  
Cell Dimensions ◽  
Unit Cell Dimensions

AbstractStructural description in terms of frameworks – three-dimensional periodic arrangements of points which are occupied by atoms – is used as the basis of analysing the cell dimensions of phases with the MgCu

Three isostructural solvates of a tetrahydrofurochromenone derivative

2017 ◽  
Vol 73 (5) ◽  
pp. 407-413 ◽  
Author(s):  
Balasubramanian Sridhar ◽  
Jagadeesh Babu Nanubolu ◽  
Krishnan Ravikumar ◽  
Govindaraju Karthik ◽  
Basi Venkata Subba Reddy
Keyword(s):  
Three Dimensional ◽  
Unit Cell ◽  
Multicomponent Systems ◽  
Two Dimensional ◽  
The Core ◽  
Cell Dimensions ◽  
Similarity Indices ◽  
Unit Cell Dimensions ◽  
Similar Unit ◽  
Crystal Packings

Isostructurality is more likely to occur in multicomponent systems. In this context, three closely related solvates were crystallized, namely, benzene (C27H21BrO6·C6H6), toluene (C27H21BrO6·C7H8) and xylene (C27H21BrO6·C8H10) with methyl 3a-acetyl-3-(4-bromophenyl)-4-oxo-1-phenyl-3,3a,4,9b-tetrahydro-1H-furo[3,4-c]chromene-1-carboxylate, and their crystal structures determined. All three structures belong to the same space group (P\overline{1}) and display similar unit-cell dimensions and conformations, as well as isostructural crystal packings. The isostructurality is confirmed by unit-cell and isostructural similarity indices. In each solvate, weak C—H...O and C—H...π interactions extend the molecules into two-dimensional networks, which are further linked by C—H...Br and Br...Br interactions into three-dimensional networks. The conformation of the core molecule is predominantly responsible for governing the isostructurality.

Structure-unit cell-based approach on three-dimensional representative braided preforms from four-step braiding: Experimental determination of effects of structure-process parameters on predetermined yarn path

2011 ◽  
Vol 82 (3) ◽  
pp. 220-241 ◽  
Author(s):  
Kadir Bilisik ◽  
Nesrin Sahbaz
Keyword(s):  
Cell Structure ◽  
Three Dimensional ◽  
Unit Cell ◽  
Number Of Layers ◽  
Cell Structures ◽  
Cell Dimensions ◽  
Unit Cell Dimensions ◽  
Surface Angle ◽  
Unit Cell Structure

The aim of this study was to understand the effects of braid pattern and the number of layers on three-dimensional (3D) braided unit cell structures. Various unit cell-based representative 3D braided preforms were developed. Data generated from these structures included unit cell dimensions, yarn angle, and yarn length in the unit cell structures. It was shown that braid patterns affected the 3D braided unit cell structures. The 1 × 1 braid pattern made fully interconnected integral 3D braided unit cell structures, whereas the 2 × 1 braid pattern created disconnected braid layers that were connected to the structures edges. When the number of layers increased, 3D braided unit cell thickness also increased. Braid pattern slightly affected the braider yarn angle, whereas the number of layers did not influence it. It was observed that the number of layers considerably affected the yarn length in the unit cell structure. Increasing the layer number from five to 10 layers created a yarn path in the unit cell edge regions called the ‘multilayer yarn length’. This yarn path was not observed below five-layer 3D braided unit cell structures. In jamming conditions, minimum jamming decreased the width of the unit cell structure, but maximum jamming increased its width. On the other hand, minimum jamming decreased the surface angle of the unit cell structure, whereas maximum jamming increased the surface angle. In addition, it was realized that jamming conditions influenced the density of the unit cell but did not affect the yarn length in the unit cell structures.

scholarly journals Preparation and Characterization of 2-Phenoxyethyl(thiophen-2-yl)tellane (C4H3S)TeCH2CH2OC6H5

2006 ◽  
Vol 61 (1) ◽  
pp. 61-64
Author(s):  
Ludmila Vigo ◽  
Raija Oilunkaniemi ◽  
Risto S. Laitinen
Keyword(s):  
Three Dimensional ◽  
Monoclinic Crystal ◽  
X Ray ◽  
Compound C ◽  
Dimensional Network ◽  
Cell Dimensions ◽  
Weak Hydrogen Bonds ◽  
Intermolecular Contacts ◽  
Unit Cell Dimensions

The synthesis and structure of (C4H3S)TeCH2CH2OC6H5 (1) (C4H3S = thiophen-2-yl) are reported and compared to those of the analogous selenium compound (C4H3S)SeCH2CH2OC6H5 previously synthesized by our group. The compound was characterized by 1H, 13C{1H}-, and 125Te- NMR spectroscopy as well as by X-ray single crystal crystallography. 1 crystallizes in the monoclinic crystal system, space group P21, with Z = 2, and unit cell dimensions a = 10.618(2) Å , b = 5.357(1) Å , c = 10.684(2) Å , β = 96.57(3)°. The lattice is composed of discrete molecules that are joined together by weak hydrogen bonds into a three-dimensional network. The thiophen-2-yl ring is disordered and shows two alternative orientations with the site occupation factors of 0.70(1) and 0.30(1). All bond parameters are quite normal. The comparison of the lattices in 1 and in its selenium anologue shows that while the closest intermolecular contacts are similar, the packing of the molecules is different.

Selective contrast in images of crystalline cytochrome oxidase dimers

1983 ◽  
Vol 41 ◽  
pp. 442-443
Author(s):  
T. G. Frey ◽  
M. J. Costello ◽  
J. E. Reardon ◽  
P. A. Frey
Keyword(s):  
Cytochrome Oxidase ◽  
Three Dimensional ◽  
Phospholipid Bilayer ◽  
Specimen Preparation ◽  
Inner Mitochondrial Membrane ◽  
Entire Structure ◽  
Beef Heart Mitochondria ◽  
Cell Dimensions ◽  
Plane Group ◽  
Unit Cell Dimensions

Vesicle crystals of cytochrome oxidase dimers embedded in the phospholipid bilayer of a collapsed vesicle are produced when beef heart mitochondria are treated with Triton detergents. The crystals have the symmetry of plane group p22121 with unit cell dimensions of a=95 A, b=125 A, and c=210 A. The molecules protrude 60 A beyond the lipid bilayer on the inside of the vesicle, but very little beyond the bilayer on the outside. Decoration of crys- stals with subunit-specific antibodies identified the outside surface of the vesicle crystals as corresponding to the M-side (matrix) of the inner mitochondrial membrane and the inside surface as the C-side (cytoplasmic).We have used various methods of specimen preparation to selectively image different regions of the dimer crystals in order to correlate the structure of dimers with that of 'Y'-shaped monomers. Electron micrographs of negatively stained specimens (Fig. 1a, 2a) give a two-dimensional projection of the three-dimensional stain replica of the entire structure.

Syntheses and crystal structures of Li(Ta0.89Ti0.11)O2.945 and (Li0.977Eu0.023)(Ta0.89Ti0.11)O2.968

2013 ◽  
Vol 28 (3) ◽  
pp. 178-183 ◽  
Author(s):  
Tomohiro Uchida ◽  
Shiho Suehiro ◽  
Toru Asaka ◽  
Hiromi Nakano ◽  
Koichiro Fukuda
Keyword(s):  
Crystal Structures ◽  
Maximum Entropy Method ◽  
Rietveld Method ◽  
Three Dimensional ◽  
Structural Models ◽  
Entropy Method ◽  
Density Distributions ◽  
Cell Dimensions ◽  
Conventional Structure ◽  
Unit Cell Dimensions

Crystal structures of Li(Ta0.89Ti0.11)O2.945 and (Li0.977Eu0.023)(Ta0.89Ti0.11)O2.968 were investigated by laboratory X-ray powder diffraction. Both title compounds were trigonal with space group R3c and Z = 6. The hexagonal unit-cell dimensions were a = 0.514 82 9(2) nm, c = 1.377 61 2(4) nm, and V = 0.316 21 6(2) nm3 for the former compound and a = 0.517 71 2(2) nm, c = 1.373 50 0(6) nm, and V = 0.318 81 2(3) nm3 for the latter. The initial structural models, being isostructural with LiTaO3, were refined by the Rietveld method. The maximum-entropy method-based pattern fitting (MPF) method was subsequently used to confirm the validity of the structural models, in which conventional structure bias caused by assuming intensity partitioning was minimized. Atomic arrangements of the final structural models were in excellent agreement with the three-dimensional electron-density distributions determined by MPF.

Reaktion von 1.4-Dienen mit Metallkomplexen, I Darstellung und Röntgenstrukturanalyse eines π-enyl-Komplexes der Zusammensetzung (C8H13PdCl)2/ Reaction of 1,4-Dienes with Metal Complexes, I Synthesis and X-ray Structure Determination of a π-enyl Complex of Composition (C8H18PdCl)2

1976 ◽  
Vol 31 (4) ◽  
pp. 455-462 ◽  
Author(s):  
Peter Feldhaus ◽  
Richard Ratka ◽  
Hermann Schmid ◽  
Manfred L. Ziegler
Keyword(s):  
Metal Complexes ◽  
Structure Determination ◽  
Three Dimensional ◽  
Fourier Methods ◽  
X Ray ◽  
H Nmr ◽  
Nmr Data ◽  
Cell Dimensions ◽  
Unit Cell Dimensions

Reaction of (C6H5CN)2PdCl2 and 1,3-dimethylenecyclohexane led to an exocyclic π-enyl complex of formula (C8H13PdCl)2-bis(η3-2-methylene-6-methylcyclohexyl)(di-µ-chloro)-dipalladium. IR and 1H NMR data are in agreement with this formulation.The compound is monoclinic, with unit cell dimensions α = 499.97 ± 0.08, b =1342.26 ± 0.19, c =1379.60 ± 0.20 pm, β = 99.43 ± 0.02°, space group C5h2-P21/C, Ζ = 2, dX-ray = 1.83 g/cm3.The structure was determined from three-dimensional X-ray data by Patterson and Fourier methods. Least squares refinement by use of 1045 independent reflections has reached R1 = 5.6%.

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