Crystal structure of KCaF3 determined by the Rietveld profile method

1997 ◽  
Vol 12 (2) ◽  
pp. 70-75 ◽  
Author(s):  
Alicja Ratuszna ◽  
Michel Rousseau ◽  
Philippe Daniel
Keyword(s):  
Crystal Structure ◽  
Room Temperature ◽  
Lattice Parameters ◽  
Profile Method ◽  
Anisotropic Temperature ◽  
Monoclinic Distortion ◽  
Refinement Procedure ◽  
Watson Statistic ◽  
Temperature Factors ◽  
Atomic Coordinates

Using the Rietveld profile method, the atomic coordinates and anisotropic temperature factors of KCaF3 were refined. At room temperature, KCaF3 crystallizes in monoclinic B21/m symmetry, with the lattice parameters: a=8.754(2) Å, b=8.765(4) Å, c=8.760(5) Å, β=90.48(3)°, V=672.1(3) Å3, Z=8. The refinement procedure was stopped when RB=0.05 and the Durbin–Watson statistic factor=0.85 had been reached. The structure determined is related to the tilting of CaF6 octahedra of the a−b+c− type, which are responsible for the monoclinic distortion in perovskite crystals.

scholarly journals Crystal structure of K[Hg(SCN)3] – a redetermination

2014 ◽  
Vol 70 (9) ◽  
pp. i46-i46 ◽  
Author(s):  
Matthias Weil ◽  
Thomas Häusler
Keyword(s):  
Crystal Structure ◽  
Room Temperature ◽  
Three Dimensional ◽  
Lattice Parameters ◽  
Bond Lengths ◽  
Dimensional Network ◽  
Anisotropic Displacement Parameters ◽  
Precision And Accuracy ◽  
Standard Deviations ◽  
Atomic Coordinates

The crystal structure of the room-temperature modification of K[Hg(SCN)3], potassium trithiocyanatomercurate(II), was redetermined based on modern CCD data. In comparison with the previous report [Zhdanov & Sanadze (1952).Zh. Fiz. Khim.26, 469–478], reliability factors, standard deviations of lattice parameters and atomic coordinates, as well as anisotropic displacement parameters, were revealed for all atoms. The higher precision and accuracy of the model is, for example, reflected by the Hg—S bond lengths of 2.3954 (11), 2.4481 (8) and 2.7653 (6) Å in comparison with values of 2.24, 2.43 and 2.77 Å. All atoms in the crystal structure are located on mirror planes. The Hg2+cation is surrounded by four S atoms in a seesaw shape [S—Hg—S angles range from 94.65 (2) to 154.06 (3)°]. The HgS4polyhedra share a common S atom, building up chains extending parallel to [010]. All S atoms of the resulting1∞[HgS2/1S2/2] chains are also part of SCN−anions that link these chains with the K+cations into a three-dimensional network. The K—N bond lengths of the distorted KN7polyhedra lie between 2.926 (2) and 3.051 (3) Å.

Die Kristallstruktur des Trichlorphons C4H8O4PCl3

1969 ◽  
Vol 24 (9) ◽  
pp. 1071-1074 ◽  
Author(s):  
E. Höhne ◽  
Kh. Lohs
Keyword(s):  
Crystal Structure ◽  
Least Squares ◽  
Least Squares Method ◽  
Unit Cell ◽  
Fourier Methods ◽  
Space Group ◽  
R Factor ◽  
Anisotropic Temperature ◽  
Temperature Factors ◽  
Atomic Coordinates

The crystal structure of trichlorphon [O,O-Dimethyl- (1-hydroxy-2,2,2-trichlor-äthyl) -phosphonat] has been determined by PATTERSON and FOURIER methods. Space group P212121 with 4 molecules in a unit cell of dimensions α = 8,96 ± 0,03 A, b= 18,60 ± 0,05 Å, c = 5,80 ± 0,02 A were determined. Atomic coordinates and anisotropic temperature factors have been refined by the least squares method. The final R-factor is R (hkl) =0,102.

The crystal structure of diamminesilver dinitroargentate, [Ag(NH3)2]Ag(NO2)2*

1977 ◽  
Vol 146 (4-6) ◽  
Author(s):  
H. M. Maurer ◽  
Alarich Weiss
Keyword(s):  
Crystal Structure ◽  
Least Squares ◽  
Heavy Atom ◽  
Anisotropic Temperature ◽  
Light Atoms ◽  
Difference Fourier ◽  
Temperature Factors ◽  
Heavy Atom Method ◽  
Silver Atoms ◽  
Block Diagonal

AbstractThe crystal structure of diamminesilver dinitroargentate, [Ag(NHThe point positions of the silver atoms were obtained by the heavy-atom method whereas those of the light atoms were found by difference Fourier syntheses. Coordinates and anisotropic temperature factors were refined by block-diagonal least-squares methods with the result

Incommensurately modulated phase of Rb2CoBr4 at 295 and 200 K

2000 ◽  
Vol 56 (1) ◽  
pp. 17-21 ◽  
Author(s):  
K. Friese ◽  
G. Madariaga ◽  
T. Breczewski
Keyword(s):  
Crystal Structure ◽  
Close Relationships ◽  
Room Temperature ◽  
Lattice Parameters ◽  
Modulated Structure ◽  
Space Group ◽  
Average Structure ◽  
First Order ◽  
Modulation Function ◽  
Modulated Phase

The crystal structure of Rb_2CoBr_4 at 295 and 200 K has been determined. At these temperatures Rb_2CoBr_4 exhibits an incommensurately modulated structure with wavevector {\bf q} = (1/3+\delta){\bf a}^*. At room temperature only the average structure was refined. Lattice parameters are a = 9.732 (3), b = 13.328 (4), c = 7.654 (3) Å, space group Pnam. The R(F) value was 0.0414 for 286 observed reflections (0.0778 for all 477 reflections). At 200 K the lattice parameters are a = 9.691 (4), b = 13.278 (5), c = 7.630 (6) Å, superspace group P:Pnam:\overline{1}ss. Main reflections and satellite reflections of first order were measured. The refinement converged at R(F) = 0.052 for 309 observed reflections (255 main reflections and 54 satellites) and 0.2971 for all reflections (1849; 695 main reflections and 1154 satellites). Amplitudes and phases of the modulation function as well as bond distances show close relationships to those observed in the incommensurately modulated phase of Rb_2ZnBr_4.

The crystal and electron structure of O-(2-chloroethyl)-O-isobutyl-O-(2-phenyl-4-methylthio-3-oxo-2H-pyridazine-5-yl) thiophosphate

1987 ◽  
Vol 52 (3) ◽  
pp. 696-706 ◽  
Author(s):  
Viktor Vrábel ◽  
František Pavelčík ◽  
Eleonóra Kellö ◽  
Stanislav Miertuš ◽  
Václav Konečný ◽  
...  
Keyword(s):  
Crystal Structure ◽  
Structure Refinement ◽  
Bond Distance ◽  
Direct Methods ◽  
Electron Structure ◽  
Anisotropic Temperature ◽  
Wiberg Index ◽  
Trigonal Pyramid ◽  
Net Charges ◽  
Temperature Factors

The crystal structure of the title fungicide was solved by direct methods, using Σ2 relationship and tangent formula. The structure refinement was made by full-matrix least-squares with anisotropic temperature factors to the final R = 0.096 for 1 486 significant reflexions. The compound crystallizes in the orthorhombic system, the space group Pccn. The lattice parameters are a = 1.8719(9), b = 3.0426(33), c = 0.7616(2) nm and Z = 8. The intermolecular interactions of types C-H···Cl and C-H···O are observed between the centrosymmetrically related molecules in the crystal structure. The coordination polyhedron around phosphorus is between trigonal pyramid and tetrahedron. The planes of the phenyl and pyridazine rings are rotated through 70° each other. The electron structure was calculated by semiempirical CNDO/2 method. The calculations revealed the most negative net charges on S(2) and O(1). The value of Wiberg index Iw = 1.08 and the bond distance 0.149 nm show that the bond N(1)-C(5) is simple and is not involved in the conjugation.

Zur Kenntnis des Argyrodit-Strukturtyps: Die Kristallstruktur von Ag8SiS6 / The Argyrodite Structure Type : The Crystal Structure of Ag8SiS6

1977 ◽  
Vol 32 (4) ◽  
pp. 373-379 ◽  
Author(s):  
Bernt Krebs ◽  
Jürgen Mandt
Keyword(s):  
Crystal Structure ◽  
High Temperature ◽  
Room Temperature ◽  
Structure Type ◽  
Orthorhombic Space Group ◽  
X Ray ◽  
Temperature Modification ◽  
Face Centered ◽  
Temperature Factors ◽  
High Temperature Modification

The room temperature modification of Ag8SiS6 is orthorhombic, space group Pna21, with α = 15.024, b = 7.428, c = 10.533 Å, Z = 4. A complete single crystal X-ray structure analysis shows the structure to contain tetrahedral SiS4(4-) units (Si-S 2.094(12) ... 2.130(12) Å) besides isolated sulfide groups coordinated by Ag; the compound may thus be formulated as Ag8(SiS4)(S)2. The coordination of the Ag atoms by sulfur is distorted tetrahedral (Ag-S 2.557...2.757 A), approximately trigonal planar (Ag-S 2.386...2.775 A, with one additional weakly bonded axial S at 2.991 ... 3.330 Å), or linear (Ag-S 2.414... 2.443 Å). Within the (ordered) Ag sublattice the temperature factors are significantly higher than for Si and S, indicating a certain mobility of the Ag atoms. The arrangement of the thiosilicate -sulfide part of the structure is pseudocubic face-centered, showing the close structural relationship to the disordered cubic high temperature modification of Ag8GeTe6.

Short-range order, thermal vibration and expansion, and other properties of pseudosymmetric and mixed crystals of small organic molecules - Mixed crystals of phenzaine and n -oxyphenazine: refinement of crystal structures

1970 ◽  
Vol 266 (1180) ◽  
pp. 593-622 ◽  
Keyword(s):  
Unit Cell ◽  
Mixed Crystals ◽  
X Ray Diffraction ◽  
Small Organic Molecules ◽  
Anisotropic Temperature ◽  
Cell Dimensions ◽  
Average Unit ◽  
Unit Cell Dimensions ◽  
Temperature Factors ◽  
Atomic Coordinates

Compositions (accurate to about 1%) of mixed crystals of phenazine (P) and N -oxyphenazine (NOP) were determined from their u.v. absorption spectra. Densities, habit and unit-cell dimensions were found at 20 °C for crystals containing respectively 0, 8, 52, 81 and 100 mole % NOP relative to P; and X-ray diffraction data (F obs ) were obtained for all these and also at — 90 °C for NOP. All are isostructural (NOP being pseudocentrosymmetric) in P2 1 / a with two molecules per average unit cell. Atomic coordinates, bond lengths and anisotropic temperature factors are listed, site-occupation factors for the oxygen atoms being used for the 8, 52 and 81 mole % compositions. A qualitative explanation, in terms of structure, is offered for the anisotropic thermal expansion of NOP.

Crystal structure of praseodymium sulphate octahydrate

1981 ◽  
Vol 155 (3-4) ◽  
Author(s):  
I. S. Ahmed Farag ◽  
M. A. El-Kordy ◽  
N. A. Ahmed
Keyword(s):  
Crystal Structure ◽  
Least Squares Method ◽  
Three Dimensional ◽  
The Other ◽  
Water Molecules ◽  
X Ray Diffraction ◽  
Bridging Ligand ◽  
Dimensional Network ◽  
Anisotropic Temperature ◽  
Temperature Factors

AbstractThe crystals of PrThe crystal structure has been determined from three-dimensional single-crystal X-ray diffraction data and refined by the least-squares method, using anisotropic temperature factors, to a discrepancy index ofThe molecules are arranged in layers forming a three-dimensional network. Each Pr atom is coordinated with eight oxygen atoms, four of which are related to sulphate groups, the other four are to water molecules. The sulphate ion, located at the twofold axis, behaves as a bidentate bridging ligand connecting two Pr atoms. The other sulphate ion acts as a threefold bridging ligand between three neighbouring Pr atoms.

The crystal structure of BiTel

1993 ◽  
Vol 204 (1) ◽  
Author(s):  
K. G. Keramidas ◽  
G. P. Voutsas ◽  
A. Papazoglou ◽  
P. I. Rentzeperis
Keyword(s):  
Crystal Structure ◽  
Single Crystal ◽  
Least Squares ◽  
Three Dimensional ◽  
Full Matrix ◽  
Anisotropic Temperature ◽  
Equilateral Triangles ◽  
Computer Controlled ◽  
Temperature Factors ◽  
Isosceles Triangles

AbstractThe crystal structure of BiTeI has been redetermined with 1924 independent reflections, using three-dimensional intensities measured on a computer controlled Philips PW 1100 single crystal diffractometer. The structure belongs to the rhombohedral space groupThe positional and thermal parameters, with anisotropic temperature factors, were refined by full-matrix least-squares calculations to a finalEach Bi atom is six-coordinated by three Te and three I atoms at distances 3.88(5) Å and 3.05(2) Å respectively thus forming a distorted octahedron. The faces of the octahedron are two equilateral triangles (Te-Te-Te, I-I-I) with sides 4.336 Å and six isosceles triangles (three I-Te-I and three Te-I-Te) with sides I–Te 3.29(3) Å and I–I or Te–Te 4.336 Å.The octahedra are linked to each other by a common Te–I edge along the

scholarly journals Rerefinement of the crystal structure of trichloridosulfonium(IV) hexachloridouranate(V), (SCl3)[UCl6]

IUCrData ◽  
2020 ◽  
Vol 5 (7) ◽  
Author(s):  
Holger Lars Deubner ◽  
Sergei I. Ivlev ◽  
Florian Kraus
Keyword(s):  
Crystal Structure ◽  
Single Crystal ◽  
Single Crystals ◽  
Lattice Parameters ◽  
Structure Model ◽  
X Ray Diffraction ◽  
X Ray ◽  
Ionic Compound ◽  
Distorted Octahedral ◽  
Atomic Coordinates

Single crystals of trichloridosulfonium(IV) hexachloridouranate(V) were obtained from the reaction of uranium(IV) chloride with an excess of disulfur dichloride and studied by single-crystal X-ray diffraction. In comparison with the structure model reported previously [Sawodny et al. (1983). Z. Anorg. Allg. Chem. 499, 81–88.], the lattice parameters and fractional atomic coordinates were determined to a much higher precision, leading overall to an improved structure model. The ionic compound contains trigonal–pyramidal (SCl3)+ cations and slightly distorted octahedral [UCl6]− anions. The structure was refined as an inversion twin with a twin ratio of 4.4:1.

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