Crystal structure model development for soil clay minerals – I. Hydroxy-interlayered smectite (HIS) synthesized from bentonite. A multi-analytical study

Geoderma ◽  
2019 ◽  
Vol 347 ◽  
pp. 135-149 ◽  
Author(s):  
Jan Dietel ◽  
Jens Gröger-Trampe ◽  
Marko Bertmer ◽  
Stephan Kaufhold ◽  
Kristian Ufer ◽  
...  
Keyword(s):  
Crystal Structure ◽  
Clay Minerals ◽  
Analytical Study ◽  
Model Development ◽  
Structure Model ◽  
Soil Clay

scholarly journals Redetermination of the crystal structure of ThI4

IUCrData ◽  
2018 ◽  
Vol 3 (2) ◽  
Author(s):  
H. Lars Deubner ◽  
Florian Kraus
Keyword(s):  
Crystal Structure ◽  
Single Crystals ◽  
Coordination Number ◽  
Coordination Polyhedron ◽  
Lattice Parameters ◽  
Structure Model ◽  
Reliability Factor ◽  
Thorium Dioxide

Single crystals of ThI4, thorium(IV) tetraiodide, were grown from thorium dioxide and aluminium triiodide. In comparison with the structure model reported previously for this compound [Zalkinet al.(1964).Inorg. Chem.3, 639–644], we have determined the lattice parameters and fractional coordinates to a much higher precision, also leading to a better reliability factor (R= 0.029versus0.09). The coordination number of the ThIVatom is eight. Its coordination polyhedron has the shape of an irregular square antiprism. The I atoms each bridge two ThIVatoms, resulting in the formation of infinite layers parallel to (-101) that can be described with the Niggli formula2∞[ThI6/2I2/2].

scholarly journals `Pd20Sn13' revisited: crystal structure of Pd6.69Sn4.31

2015 ◽  
Vol 71 (7) ◽  
pp. 807-809 ◽  
Author(s):  
Wilhelm Klein ◽  
Hanpeng Jin ◽  
Viktor Hlukhyy ◽  
Thomas F. Fässler
Keyword(s):  
Crystal Structure ◽  
Title Compound ◽  
Original Structure ◽  
Site Symmetry ◽  
Structure Model ◽  
Reaction Route ◽  
X Ray ◽  
Anisotropic Displacement Parameters ◽  
Solid State Reaction Route ◽  
Atomic Coordinates

The crystal structure of the title compound was previously reported with composition `Pd20Sn13' [Sarahet al.(1981).Z. Metallkd,72, 517–520]. For the original structure model, as determined from powder X-ray data, atomic coordinates from the isostructural compound Ni13Ga3Ge6were transferred. The present structure determination, resulting in a composition Pd6.69Sn4.31, is based on single crystal X-ray data and includes anisotropic displacement parameters for all atoms as well as standard uncertainties for the atomic coordinates, leading to higher precision and accuracy for the structure model. Single crystals of the title compound were obtainedviaa solid-state reaction route, starting from the elements. The crystal structure can be derived from the AlB2type of structure after removing one eighth of the atoms at the boron positions and shifting adjacent atoms in the same layer in the direction of the voids. One atomic site is partially occupied by both elements with a Pd:Sn ratio of 0.38 (3):0.62 (3). One Sn and three Pd atoms are located on special positions with site symmetry 2. (Wyckoff letter 3aand 3b).

Complete crystal structure of decafluorocyclohex-1-ene at 4.2 K from original neutron diffraction data

2014 ◽  
Vol 70 (2) ◽  
pp. 395-397
Author(s):  
Leonid A. Solovyov ◽  
Alexandr S. Fedorov ◽  
Aleksandr A. Kuzubov
Keyword(s):  
Crystal Structure ◽  
Diffraction Data ◽  
Molecular Orientation ◽  
State Energy ◽  
Structure Model ◽  
Perfect Agreement ◽  
Acta Cryst ◽  
Difference Density ◽  
Density Analysis ◽  
The Difference

The crystal structure model of decafluorocyclohex-1-ene at 4.2 K derived from simulated powder diffraction data and solid-state energy minimization [Smrčoket al.(2013).Acta Cryst.B69, 395–404] is found to be incomplete. In this study it is completed by an additional alternative molecular orientation revealed from the difference density analysis and direct space search. The structure is refined by the derivative difference method in the rigid-body approximation leading to perfect agreement between observed and calculated neutron powder patterns.

scholarly journals Synthesis and crystal structure of Sr2MnGaO5-dFx, layered oxyfluorides

2014 ◽  
Vol 70 (a1) ◽  
pp. C1108-C1108
Author(s):  
Tetsuhiro Katsumta ◽  
Naofumi Takami ◽  
Daisuke Mori ◽  
Yoshiyuki Inaguma
Keyword(s):  
Crystal Structure ◽  
Structure Model ◽  
X Ray Diffraction ◽  
Orthorhombic Distortion ◽  
Fluoride Ions ◽  
Synthesis And Crystal Structure ◽  
Jahn Teller ◽  
Jahn Teller Effect ◽  
Bond Valence Sum ◽  
Distorted Tetrahedral Coordination

Sr2MnGaO5 brownmillerite has an interesting structure. In this compound, MnO6 octahedra and GaO4 tetrahedra are ordered along c-axis. The MnO6 octahedra are deformed due to Jahn-Teller effect with four short equatorial Mn-O distances and two long apical one. Oxygen vacancies in the GaO layer provide distorted tetrahedral coordination for the Ga cation. The oxide and/or fluoride ions are introduced into the vacancies in GaO layer. The synthesis of Sr2MnGaO4.78F1.22 using XeF2 as a fluorinating agent is reported, while the small amount SrF2 impurity is contained[1]. On the other hand, low temperature fluorination using polyvinylidenefluoride (PVDF) is powerful method for the synthesis of oxyfluoides from brownmillerite[2]. In this study, we synthesize the Sr2MnGaO5-dFx (x=0.5, 1.0, 1.5, 2.0) using PVDF and investigate the variation of crystal structure with x. Sr2MnGaO5 brownmillerites were prepared sold state reaction method. Starting materials were SrCO3, Mn2O3 and Ga2O3. The mixture was heated twice in Ar at 13000C for 72h. For the preparation of Sr2MnGaO5-dFx (x=0.5, 1.0, 1.5, 2.0), stoichiometric amounts of Sr2MnGaO5 brownmillerite and PVDF were ground and the mixture were heated in N2 at 4000C for 8h. And then, the as prepared materials were subsequently heated in O2 at 4000C for 8h. The Sr2MnGaO5-dFx were obtained without impurities. As shown in Fig., the orthorhombic distortion reduced with the increase in x. The X-ray diffraction data of Sr2MnGaO5-dF1.0 could be refined on the structure model belonging the space group Icmm. the bond valence sum of Ga3+ calculated from Ga-O bond length indicates that the fluoride ions are introduced into GaO layer preferentially. The measurements of magnetic properties for Sr2MnGaO5-dFx are in progress.

New Structure Model for Lithium Nickel Batteries

2000 ◽  
Vol 623 ◽  
Author(s):  
M.A. Monge ◽  
E. Gutiérrez-Puebla ◽  
I. Rasines ◽  
J.A. Campa
Keyword(s):  
Crystal Structure ◽  
Single Crystals ◽  
Structural Type ◽  
Close Packing ◽  
The Other ◽  
Structure Model ◽  
Magnetization Measurements ◽  
Mixed Layers

AbstractAfter growing black colored single crystals of LixNi1−xO (x = 0.27) and solving its crystal structure, a model is proposed as an alternative to the structural type admitted for LixNi1−xO. The new rhombohedral cell consists of a cubic close packing of oxygens in which the alternation of two kind of mixed layers containing Li and Ni in different ratios can be detected along the c direction. This model implies a Li order incompatible with the alternation of Ni layers, one of them pure and the other containing some Li. The results of magnetization measurements look consistent with the new structural type, and reveal that LixNi1−xO behaves as mictomagnetic.

A simple approach to quasicrystal structure and phason defect formulation

1990 ◽  
Vol 46 (2) ◽  
pp. 142-149 ◽  
Author(s):  
F. H. Li ◽  
Y. F. Cheng
Keyword(s):  
Crystal Structure ◽  
Dimensional Space ◽  
Physical Space ◽  
Simple Approach ◽  
High Dimensional ◽  
Periodic Lattice ◽  
Structure Model ◽  
Continuous Rotation ◽  
Geometrical Relationship ◽  
Quasicrystal Structure

The advantages of the cut or section method in describing quasicrystal structures and phason defects are given. The real and reciprocal quasilattice formulation is derived straightforwardly. It is shown that the linear phason strain which leads to the quasilattice distortion is equivalent to a rotation of physical space relative to the high-dimensional space. A continuous rotation of the physical space will make the quasilattice deviate from its idealized form and turn gradually into a periodic lattice. The derivation of a geometrical relationship between the icosahedral quasilattice and the corresponding b.c.c. lattice becomes simple and clear. This will be beneficial to the construction of a quasicrystal structure model by reference to the corresponding b.c.c. crystal structure.

Accuracy of XRPD QPA using the combined Rietveld–RIR method

2000 ◽  
Vol 33 (2) ◽  
pp. 267-278 ◽  
Author(s):  
Alessandro F. Gualtieri
Keyword(s):  
Crystal Structure ◽  
Phase Composition ◽  
Incoherent Scattering ◽  
Quantitative Phase Analysis ◽  
Polycrystalline Materials ◽  
Structure Model ◽  
Thermal Displacement ◽  
Model Assumption ◽  
Pyroclastic Rocks ◽  
X Ray

QPA (quantitative phase analysis) of polycrystalline materials using XRPD (X-ray powder diffraction) can be performed using the combined Rietveld and reference intensity ratio (RIR) methods, providing an estimate of both the crystalline and the amorphous phase in a mixture. Although the accuracy of estimates of the phase composition of simple ternary or quaternary mixtures is generally very good, uncertainties remain and bias the accuracy of phase determinations in complex systems such as pyroclastic rocks, which may contain two or more zeolite species, a number of other phases (generally up to four or five), and glass. The contribution of the incoherent scattering, biasing accuracy, in the glass determination has been discussed in an earlier work on the modal analysis of pyroclastic rocks [Gualtieri (1996).Powder Diffr.11, 97–106]. In this work, the assumption of the crystal structure, the influence of the spike addition, background and atomic (thermal) displacement parameters are discussed. It is shown that the structure-model assumption no longer holds for systems containing complex phases such as zeolites, as the accuracy is degraded and, as far as the influence of the added spike is concerned, there is an underestimation of the glass content with increasing amounts of added spike.

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