Modulated corrugations in the crystal structure of the superconductor CaAlSi

2006 ◽  
Vol 62 (5) ◽  
pp. 710-718 ◽  
Author(s):  
Karine M. Sparta ◽  
Ralf Müller ◽  
Michael Merz ◽  
Georg Roth ◽  
Peter Adelmann ◽  
...  
Keyword(s):  
Crystal Structure ◽  
Single Crystal ◽  
Thermal History ◽  
Three Dimensional ◽  
X Ray Diffraction ◽  
Modulated Structure ◽  
X Ray ◽  
Modulated Phases ◽  
Modulated Structures ◽  
History Of

We report the crystal structure analyses of CaAlSi from single-crystal and powder X-ray diffraction and the existence of two commensurately modulated phases, a sixfold and a fivefold modulated structure. This polymorphism seems to be correlated to the thermal history of the sample. We describe both modulated structures using a three-dimensional and a (3 + 1)-dimensional formalism.

scholarly journals An investigation of polyhedral deformation in two mixed-metal diarsenates: SrZnAs2O7and BaCuAs2O7

2015 ◽  
Vol 71 (4) ◽  
pp. 330-337 ◽  
Author(s):  
Sabina Kovač ◽  
Ljiljana Karanović ◽  
Tamara Đorđević
Keyword(s):  
Crystal Structure ◽  
Single Crystal ◽  
General Formula ◽  
Three Dimensional ◽  
X Ray Diffraction ◽  
Hydrothermal Conditions ◽  
X Ray ◽  
Open Framework ◽  
Geometrical Characteristics ◽  
Barium Copper

Two isostructural diarsenates, SrZnAs2O7(strontium zinc diarsenate), (I), and BaCuAs2O7[barium copper(II) diarsenate], (II), have been synthesized under hydrothermal conditions and characterized by single-crystal X-ray diffraction. The three-dimensional open-framework crystal structure consists of corner-sharingM2O5(M2 = Zn or Cu) square pyramids and diarsenate (As2O7) groups. Each As2O7group shares its five corners with five differentM2O5square pyramids. The resulting framework delimits two types of tunnels aligned parallel to the [010] and [100] directions where the large divalent nine-coordinatedM1 (M1 = Sr or Ba) cations are located. The geometrical characteristics of theM1O9,M2O5and As2O7groups of known isostructural diarsenates, adopting the general formulaM1IIM2IIAs2O7(M1II= Sr, Ba, Pb;M2II= Mg, Co, Cu, Zn) and crystallizing in the space groupP21/n, are presented and discussed.

scholarly journals X-Ray Single Crystal Structural Analysis of Magnetically Oriented Microcrystals

2014 ◽  
Vol 70 (a1) ◽  
pp. C1138-C1138
Author(s):  
Chiaki Tsuboi ◽  
Kazuki Aburaya ◽  
Shingo Higuchi ◽  
Fumiko Kimura ◽  
Masataka Maeyama ◽  
...  
Keyword(s):  
Molecular Structure ◽  
Crystal Structure ◽  
Single Crystal ◽  
Three Dimensional ◽  
Diffraction Measurement ◽  
X Ray Diffraction ◽  
Data Set ◽  
Uv Curable ◽  
X Ray

We have developed magnetically oriented microcrystal array (MOMA) technique that enables single crystal X-ray diffraction analyses from microcrystalline powder. In this method, microcrystals suspended in a UV-curable monomer matrix are there-dimensionally aligned by special rotating magnetic field, followed by consolidation of the matrix by photopolymerization. From thus achieved MOMAs, we have been succeeded in crystal structure analysis for some substances [1, 2]. Though MOMA method is an effective technique, it has some problems as follows: in a MOMA, the alignment is deteriorated during the consolidation process. In addition, the sample microcrystals cannot be recovered from a MOMA. To overcome these problems, we performed an in-situ X-ray diffraction measurement using a three-dimensional magnetically oriented microcrystal suspension (3D MOMS) of L-alanine. An experimental setting of the in-situ X-ray measurement of MOMS is schematically shown in the figure. L-alanine microcrystal suspension was poured into a glass capillary and placed on the rotating unit equipped with a pair of neodymium magnets. Rotating X-ray chopper with 10°-slits was placed between the collimator and the suspension. By using this chopper, it was possible to expose the X-ray only when the rotating MOMS makes a specific direction with respect to the impinging X-ray. This has the same effect as the omega oscillation in conventional single crystal measurement. A total of 22 XRD images of 10° increments from 0° to 220° were obtained. The data set was processed by using conventional software to obtain three-dimensional molecular structure of L-alanine. The structure is in good agreement with that reported for the single crystal. R1 and wR2 were 6.53 and 17.4 %, respectively. RMSD value between the determined molecular structure and the reported one was 0.0045 Å. From this result, we conclude that this method can be effective and practical to be used widely for crystal structure analyses.

The modulated structure of the calcium aluminate Ca6(AlO2)12·Bi2O3

2010 ◽  
Vol 66 (6) ◽  
pp. 585-593 ◽  
Author(s):  
O. Pérez ◽  
S. Malo ◽  
M. Hervieu
Keyword(s):  
Single Crystal ◽  
Calcium Aluminate ◽  
Three Dimensional ◽  
X Ray Diffraction ◽  
Electron Pairs ◽  
Modulated Structure ◽  
X Ray ◽  
Trigonal Bipyramidal ◽  
Superspace Formalism ◽  
Single Crystal Analysis

Bismuth calcium aluminate, Bi2Ca6Al12O27, has been prepared as a ceramic and a single crystal. Analysis of reciprocal space using both electron and X-ray diffraction show an R-centred hexagonal unit cell: a = b = 17.3892 (4), c = 6.986 (1) Å. Additional weak reflections are observed; they require the introduction of a modulation wavevector q = 0.0453 (2)c* for indexing. The modulated structure has been solved using the superspace formalism [superspace group X\overline{3}(00\gamma)0]. A framework of corner-sharing AlO4 tetrahedra forms corrugated sixfold rings and uncommon triple rings. The Ca2+ cations exhibit an eightfold coordination sphere; edge-sharing CaO8 polyhedra form intertwinned zigzagging rows along c creating a three-dimensional net. Bi atoms are located in large hexagonal tunnels parallel to c and form Bi2O3 pairs, which adopt a trigonal bipyramidal configuration. The 6s 2 lone-electron pairs (Lp) point along c, in the opposite direction to the three Bi—O strong bonds to form two BiO3Lp tetrahedra with a common base. Different orientations of the Bi2O3Lp2 pairs, rotated by 60° around c, are observed. Their stacking modes in each of the hexagonal tunnels are described. The sequence of the stacking varies along c in each of the tunnels.

A Three-Dimensional Silver(I) Framework Assembled from Nitrilotriacetate

2005 ◽  
Vol 58 (2) ◽  
pp. 115 ◽  
Author(s):  
Chun-Long Chen ◽  
Qian Zhang ◽  
Ji-Jun Jiang ◽  
Qin Wang ◽  
Cheng-Yong Su
Keyword(s):  
Crystal Structure ◽  
Ir Spectroscopy ◽  
Coordination Polymer ◽  
Single Crystal ◽  
Elemental Analysis ◽  
Three Dimensional ◽  
Single Crystal Structure ◽  
X Ray Diffraction ◽  
X Ray ◽  
Coordination Numbers

The reaction of AgCF3CO2 with nitrilotriacetate (NTA) yields the three-dimensional silver(i) coordination polymer {Ag3[N(CH2COO)3]}n 1 which was characterized by means of elemental analysis and IR spectroscopy as well as X-ray diffraction. The single crystal structure shows that the NTA3– anions act as unusual heptadentate 13-coordination agents and the silver(i) atoms exhibit various coordination numbers in the range 3–6.

Incommensurately modulated ordering of tetrahedral chains in Ca2Fe2O5 at elevated temperatures

2005 ◽  
Vol 61 (6) ◽  
pp. 656-662 ◽  
Author(s):  
Hannes Krüger ◽  
Volker Kahlenberg
Keyword(s):  
High Temperature ◽  
Single Crystal ◽  
Elevated Temperatures ◽  
Three Dimensional ◽  
Ambient Conditions ◽  
X Ray Diffraction ◽  
Modulated Structure ◽  
X Ray ◽  
Left Handed ◽  
Lattice Periodicity

The basic building units of brownmillerite-type A 2 B 2O5 structures are perovskite-like layers of corner-sharing BO6 octahedra and zweier single chains of BO4 tetrahedra. A three-dimensional framework is formed by alternate stacking of octahedral layers and sheets of tetrahedral chains. The compound Ca2Fe2O5 is known to have Pnma symmetry at ambient conditions. The space group Imma was reported to be evident above 963 K. New high-temperature single-crystal X-ray diffraction experiments at 1100 K revealed that Ca2Fe2O5 forms an incommensurately modulated structure adopting the superspace group Imma(00γ)s00, with γ = 0.588 (2). The modulation affects the sequence of the enantiomorphic (right- and left-handed) oriented tetrahedral chains within the layer, breaking the lattice periodicity along c. This ordering can be modelled with crenel occupation modulation functions for the tetrahedrally coordinated Fe, as well as for the O atom interconnecting the tetrahedra.

The crystal structure of galeite, Na15(SO4)5F4Cl

1975 ◽  
Vol 40 (312) ◽  
pp. 357-361 ◽  
Author(s):  
L. Fanfani ◽  
A. Nunzi ◽  
P. F. Zanazzi ◽  
A. R. Zanzari
Keyword(s):  
Crystal Structure ◽  
Single Crystal ◽  
Least Squares ◽  
Diffraction Data ◽  
Three Dimensional ◽  
Thermal Parameters ◽  
X Ray Diffraction ◽  
Cell Content ◽  
X Ray ◽  
Structure Factors

SummaryThe crystal structure of galeite from Searles Lake (California) has been determined by means of X-ray diffraction data on a single crystal. A possible structure was derived from that of schairerite on the basis of chemical and lattice analogies and was confirmed by comparison of the observed diffractometric structure factors with the calculated ones. The refinement was performed by least-squares methods employing isotropic thermal parameters and assuming that atoms related by translational pseudosymmetry exhibit equal thermal parameters. The final R value is 0·09. The cell content is 3[Na15(SO4)5F4Cl]; the space group is P31m The lattice dimensions are a 12·197(4)Å, c 13·955(10) Å The marked subcell has P3m1 symmetry and a 7·042Å, c 13·955 Å. The crystal structure of galeite consists of a three-dimensional framework, formed by coordination octahedra around Na+ ions, including tetrahedral holes with sulphur atoms at the centres. The three-dimensional framework can be considered built up by five octahedral sheets (seven sheets can be recognized in schairerite and six in sulphohalite). The very close analogies occurring in the structures of galeite and schairerite are discussed.

Structure of KNbOB2O5 – a commensurately modulated structure

2005 ◽  
Vol 61 (4) ◽  
pp. 361-366 ◽  
Author(s):  
Siegbert Schmid ◽  
Trixie Wagner
Keyword(s):  
Single Crystal ◽  
Diffraction Data ◽  
Group Symmetry ◽  
X Ray Diffraction ◽  
Modulated Structure ◽  
Space Group ◽  
X Ray ◽  
Average Structure ◽  
Modulated Structures ◽  
First Time

Members of the AMOB2O5 (A = K, Rb, Cs, Tl; M = Nb, Ta) family of compounds can be described as modulated structures with a single superspace group and very similar modulation functions. Single-crystal X-ray diffraction data (Mo Kα radiation) are used to solve and refine the structure of KNbOB2O5 in these terms for the first time. The average structure is solved and refined in the space group Pmn21. Subsequently, the atomic modulation functions are determined using JANA2000 and superspace-group symmetry Pmn21(0,0.375,0)s. The commensurately modulated structure is finally refined as a superstructure in the space group Pbn21 using SHELXS97 converging to R 1 = 0.024.

scholarly journals Synthesis, crystal structure and study of the crystal packing in the complex bis(4-aminopyridine-κN 1)dichloridocobalt(II)

2017 ◽  
Vol 73 (5) ◽  
pp. 399-406 ◽  
Author(s):  
Olga Carolina Sanchez Montilva ◽  
Federico Movilla ◽  
Maricel Gabriela Rodriguez ◽  
Florencia Di Salvo
Keyword(s):  
Crystal Structure ◽  
Single Crystal ◽  
Crystal Packing ◽  
Three Dimensional ◽  
Spectroscopic Techniques ◽  
X Ray Diffraction ◽  
X Ray ◽  
Π Interactions ◽  
Structures And Properties ◽  
Statistical Studies

Despite the large number of reported crystalline structures of coordination complexes bearing pyridines as ligands, the relevance of π–π interactions among these hereroaromatic systems in the stabilization of their supramolecular structures and properties is not very well documented in the recent literature. The title compound, [CoCl2(C5H6N2)2], was obtained as bright-blue crystals suitable for single-crystal X-ray diffraction analysis from the reaction of 4-aminopyridine with cobalt(II) chloride in ethanol. The new complex was fully characterized by a variety of spectroscopic techniques and single-crystal X-ray diffraction. The crystal structure showed a tetrahedral complex stabilized mainly by bidimensional motifs constructed by π–π interactions with large horizontal displacements between the 4-aminopyridine units, and N—H...Cl hydrogen bonds. Other short contacts, such as C—H...Cl interactions, complete the three-dimensional arrangement. The supramolecular investigation was extended by statistical studies using the Cambridge Structural Database and a Hirshfeld surface analysis.

Crystal Structure of the Pyridinium Salt of the Polymeric Tris(thiocyanato)dicuprate(I) Anion

1979 ◽  
Vol 32 (12) ◽  
pp. 2757 ◽  
Author(s):  
CL Raston ◽  
B Walter ◽  
AH White
Keyword(s):  
Crystal Structure ◽  
Nitrogen Atom ◽  
Single Crystal ◽  
Title Compound ◽  
Three Dimensional ◽  
Pyridinium Salt ◽  
The Other ◽  
X Ray Diffraction ◽  
X Ray ◽  
Dimensional Network

The title compound, [C5H6N]+ [Cu2(SCN)3]-, has been prepared and its crystal structure determined by single-crystal X-ray diffraction at 295(1) K. Crystals are monoclinic, Cc, a 11.238(7), b 11.644(4), c 10.020(4)Ǻ, β 102.67(3)°, Z 4, the structure being refined to a residual of 0.037 for the 960 'observed' reflections. The structure comprises a three-dimensional network of copper(I) atoms linked by bridging thiocyanate groups, the pyridinium counterions occupying sites in the network cavities. Both copper atoms are four-coordinate, one having an environment of one nitrogen atom [Cu-N, 1.926(9)Ǻ] and three sulfur atoms [Cu-S, 2.319(3), 2.421(3), 2.448(3)Ǻ], while the other is coordinated by two atoms of each type [Cu-N, 1.935(9), 1.947(10); Cu-S, 2.430(3), 2.493(4) Ǻ].

scholarly journals A New Supramolecular Assembly Obtained by Reaction Between Thiosaccharin and Hexamethylenediamine

2007 ◽  
Vol 62 (12) ◽  
pp. 1530-1534
Author(s):  
Enrique J. Baran ◽  
Oscar E. Piro ◽  
Juan Zinczuk
Keyword(s):  
Crystal Structure ◽  
Single Crystal ◽  
Ionic Crystal ◽  
Functional Group ◽  
Three Dimensional ◽  
Supramolecular Assembly ◽  
Monoclinic Space Group ◽  
X Ray Diffraction ◽  
X Ray ◽  
Anions And Cations

The crystal structure of hexamethylenediammonium bis(thiosaccharinate) dihydrate, [H3N-(CH2)6-NH3](tsac)2 · 2H2O (tsac=C7H4NO2S2, the anion of thiosaccharin), was determined by single-crystal X-ray diffraction. It crystallizes in the monoclinic space group P21/a with Z = 4. The thiosaccharinate moiety is planar and shows small but significant modifications in the bonding of the thioamide functional group as compared with the protonated neutral molecule. The ionic crystal is further stabilized by an extensive H-bonding network, which links the anions and cations into an infinite three-dimensional supramolecular assembly. The FTIR spectrum of the compound is briefly discussed in comparison with those of the neutral constituent molecules.

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