scholarly journals Crystal structure of Ni-sorbed synthetic vernadite: a powder X-ray diffraction study

2008 ◽  
Vol 72 (6) ◽  
pp. 1279-1291 ◽  
Author(s):  
S. Grangeon ◽  
B. Lanson ◽  
M. Lanson ◽  
A. Manceau
Keyword(s):  
Crystal Structure ◽  
Coherent Scattering ◽  
Layer Charge ◽  
Layer Plane ◽  
X Ray Diffraction ◽  
X Ray ◽  
Octahedral Sites ◽  
Ph Values ◽  
Oceanic Sediments ◽  
Ni Uptake

AbstractVernadite is a nanocrystalline turbostratic phyllomanganate containing Ni, and is widespread in surface environments and oceanic sediments. To improve our understanding of Ni uptake in this mineral, two series of analogues of vernadite (δ-MnO2) were prepared with Ni/Mn atomic ratios of 0.002—0.105 at pH4 and 0.002—0.177 at pH 7. Their structures were characterized using X-ray powder diffraction (XRD). The δ-MnO2 nano-crystals are essentially monolayers with coherent scattering domains sizes of ∼10 Å perpendicular to the layering and ∼55 Å within the layer plane. For Ni/Mn < 0.01, the layer charge deficit is apparently balanced entirely by interlayer Mn, Na and protons. At higher Ni/Mn, Ni occupies the same site as interlayer Mn above and below vacant sites within the MnO2 layer and at sites along the edges of the layer. However, the layer charge is balanced differently at the two pH values. At pH 4, Ni uptake is accompanied by a reduction in structural Na and protons, whereas interlayer Mn remains strongly bound to the layers. At pH 7, interlayer Mn is less strongly bound and is partially replaced by Ni. The results of this study also suggest that the number of vacant octahedral sites and multi-valent charge-copmpensating interlayer species are underestimated by the currently used structure models of δ-MnO2.

Crystal-structure refinement of a Zn-rich kupletskite from Mont Saint-Hilaire, Quebec, with contributions to the geochemistry of zinc in peralkaline environments

2006 ◽  
Vol 70 (5) ◽  
pp. 565-578 ◽  
Author(s):  
P. C. Piilonen ◽  
I. V. Pekov ◽  
M. Back ◽  
T. Steede ◽  
R. A. Gault
Keyword(s):  
Crystal Structure ◽  
Low Temperature ◽  
Structure Refinement ◽  
Crystal Structure Refinement ◽  
X Ray Diffraction ◽  
X Ray ◽  
Octahedral Sites ◽  
Mixed Ligands ◽  
High Alkalinity ◽  
Ligand Species

AbstractThe chemistry and crystal structure of a unique Zn-rich kupletskite: (K1.55Na0 .21Rb0.09Sr0.01)Σ1.86(Na0.82Ca0.18)Σ1.00(Mn4.72Zn1.66Na0.41Mg0.12)Σ7.00 (Ti1.85Nb0.11Hf0.03)Σ1.99(Si7.99Al0.12)Σ8.11O26 (OH)4(F0.77OH0.23)Σ1.00, from analkalin e pegmatite at Mont Saint-Hilaire, Quebec, Canada has been determined. Zn-rich kupletskite is triclinic, , a = 5.3765(4), b = 11.8893(11), c = 11.6997(10), α = 113.070(3), β = 94.775(2), γ = 103.089(3), R1 = 0.0570 for 3757 observed reflections with Fo > 4σ(Fo). From the single-crystal X-ray diffraction refinement, it is clear that Zn2+ shows a preference for the smaller, trans M(4) site (69%), yet is distributed amongst all three octahedral sites coordinated by 4 O2− and 2 OH− [M(2) 58% and M(3) 60%]. Of note is the lack of Zn in M(1), the larger and least-distorted of the four crystallographic sites, with an asymmetric anionic arrangement of 5 O2− and 1 OH−. The preference of Zn for octahedral sites coordinated by mixed ligands (O and OH) is characteristic of its behaviour in alkaline systems, in contrast to granitic systems where Zn tends to favour [4]-coordinated, OH− and H2O-free sites with only one ligand species (O, S, Cl, B, I). In alkaline systems, [4]Zn is only present in early sphalerite or in late-stage zeolite-like minerals. The bulk of Zn in alkaline systems is present as discrete [6]Zn phases such as members of the astrophyllite, labuntsovite, milarite and nordite groups, a result of the formation of network-forming complexes inthe low-temperature, low-fS2, high-alkalinity and highly oxidizing systems.

scholarly journals Crystal Chemistry of Chlormagaluminite, Mg4Al2(OH)12Cl2(H2O)2, a Natural Layered Double Hydroxide

Minerals ◽  
2019 ◽  
Vol 9 (4) ◽  
pp. 221 ◽  
Author(s):  
Elena S. Zhitova ◽  
Sergey V. Krivovichev ◽  
Igor V. Pekov ◽  
Vasiliy O. Yapaskurt
Keyword(s):  
Crystal Structure ◽  
Crystal Structure Data ◽  
Three Dimensional ◽  
Formula Unit ◽  
X Ray Diffraction ◽  
Average Chemical Composition ◽  
X Ray ◽  
Octahedral Sites ◽  
Double Hydroxide ◽  
Oh Content

Chlormagaluminite is the only Cl-dominated hydrotalcite-supergroup mineral species with M2+:M3+ = 2:1. The holotype sample of chlormagaluminite from the Kapaevskaya volcanic pipe (Irkutsk Oblast, Siberia, Russia) has been chemically and structurally characterized. The average chemical composition of the mineral is (electron microprobe, OH content is calculated by stoichiometry and H2O from the crystal-structure data, wt. %): MgO 33.85, FeO 1.09, Al2O3 22.07, Cl 14.72, H2Otot 30.96, Cl=O −3.39, total 99.30. The empirical formula based on Mg + Al + Fe = 6 atoms per formula unit (apfu) is [Mg3.91Fe2+0.07Al2.02(OH)12]Cl2.02(H2O)2.0(2). The crystal structure has been solved from single-crystal X-ray diffraction data in the space group P63/mcm, a = 5.268(3), c = 15.297(8) Å and V = 367.6(4) Å3. The refinement converged to R1 = 0.083 on the basis of 152 unique reflections with I > 2σ(I) collected at room conditions. The powder pattern contains standard reflections of a 2H polytype and two additional reflections [(010), d010 = 4.574 Å; (110), d110 = 2.647 Å] indicative of Mg and Al ordering according to the superstructure. The structure is based upon brucite-type octahedral layers with an ordered distribution of Mg and Al over octahedral sites. The Cl− anions and H2O molecules reside in the interlayer, providing a three-dimensional integrity of the structure.

In-plane crystalline anisotropy of bulk β-Ga2O3

2021 ◽  
Vol 54 (4) ◽  
Author(s):  
Xiaocui Ma ◽  
Rui Xu ◽  
Jianfang Xu ◽  
Leiying Ying ◽  
Yang Mei ◽  
...  
Keyword(s):  
Crystal Structure ◽  
Grain Boundaries ◽  
Bulk Material ◽  
Stacking Faults ◽  
Coherent Scattering ◽  
Limiting Factors ◽  
X Ray Diffraction ◽  
Limited Size ◽  
X Ray ◽  
Crystalline Anisotropy

The anisotropy of X-ray diffraction scanning of (201) β-Ga2O3 bulk material has been investigated. Symmetric rocking curves (RCs) exhibit distinctly different broadening along different azimuths, with a maximum along [102] and a minimum along a direction rotated by 30° from [010]. Williamson–Hall analysis was applied to study possible factors causing the broadening in these RCs, including instrumental factors, mosaic tilt and coherent scattering. It was found that the RC broadening is determined by both isotropic mosaic tilt and anisotropy in the length over which the crystal structure is not disrupted by limiting factors such as grain boundaries or stacking faults, which we term the `lateral limited size'. In this case, the lateral limited size is governed by {200} stacking faults along the [102] direction and grain boundaries along the [010] direction. The result presents a new anisotropy characteristic of (201) β-Ga2O3.

Structure of Feroxyhite as Determined by Simulation of X-Ray Diffraction Curves

Clay Minerals ◽  
1993 ◽  
Vol 28 (2) ◽  
pp. 209-222 ◽  
Author(s):  
V. A. Drits ◽  
B. A. Sakharov ◽  
A. Manceau
Keyword(s):  
Structural Parameters ◽  
Stacking Faults ◽  
Site Occupancy ◽  
Volume Ratio ◽  
Coherent Scattering ◽  
Close Packing ◽  
X Ray Diffraction ◽  
X Ray ◽  
Octahedral Sites ◽  
Atomic Coordinates

AbstractPowder X-ray diffraction (XRD) curves were calculated for the different structural models so far proposed for feroxyhite (δFeOOH). The influence on XRD features of different structural parameters, including site occupancy of Fe atoms, atomic coordinates, content and distribution of stacking faults, and dimension of coherent scattering domains, were considered. On the basis of agreement between experimental and simulated curves it is shown that δFeOOH is a mixture of feroxyhite proper and ultradispersed hematite in the 9 : 1 volume ratio. Feroxyhite proper consists of hexagonal close packing of anions containing 5% stacking faults. Iron atoms occupy only octahedral sites and are distributed in such a way that face-sharing filled octahedral pairs regularly alternate with vacant octahedral pairs along the c axis. This distribution of Fe atoms is quite similar to that established by Patrat et al. (1983), but in each pair, Fe atoms are displaced by the same value of 0.3 Å in opposite directions away from the centre of their octahedron. Nearest Fe-Fe distances calculated for the model proposed (2.88, 3.01, 3-39 and 3-73 Å) practically coincide with those found by EXAFS spectroscopy for the same sample (2-91, 3.04, 3.41 and 3.7-3.8 Å).

X-Ray Crystal Structure of [Rh(OH2)6](ClO4)3.3H2O

1989 ◽  
Vol 42 (11) ◽  
pp. 2051 ◽  
Author(s):  
GD Fallon ◽  
L Spiccia
Keyword(s):  
Crystal Structure ◽  
Single Crystal ◽  
Unit Cell ◽  
X Ray Diffraction ◽  
Space Group ◽  
X Ray ◽  
Octahedral Sites ◽  
Cell Dimensions ◽  
Unit Cell Dimensions

The crystal structure of [Rh(OH2)6](ClO4)3.3H2O has been determined by single-crystal X-ray diffraction and found to be isomorphous with that of M(ClO4)2.6H2O (M= Fe, Zn, Mn, Co, Ni) and LiClO4.3H2O. Crystal: are hexagonal, space group P63mc with unit cell dimensions a 7.817(2) and c 5.208(1) �. The lattice consists of a uniform arrangement of H2O and ClO4- groups with the RhIII centre occupying 1/3 of the octahedral sites formed by the H2O groups. The RhIII is not situated at the centre of the octahedron. However, the two Rh-O distances [2.128(6) and 2.136(6) �] may be considered identical, i.e. within the errors.

Crystal structure of an inclusion complex between chiral monoaza-15-crown-5 and S(–)-1-phenyl-ethyl ammonium percholorate

2003 ◽  
Vol 218 (5) ◽  
Author(s):  
Süheyla Özbey ◽  
F. B. Kaynak ◽  
M. Toğrul ◽  
N. Demirel ◽  
H. Hoşgören
Keyword(s):  
Crystal Structure ◽  
Inclusion Complex ◽  
Single Crystal ◽  
X Ray Diffraction ◽  
Space Group ◽  
X Ray ◽  
New Type

AbstractA new type of inclusion complex, S(–)-1 phenyl ethyl ammonium percholorate complex of R-(–)-2-ethyl - N - benzyl - 4, 7, 10, 13 - tetraoxa -1- azacyclopentadecane, has been prepared and studied by NMR, IR and single crystal X-ray diffraction techniques. The compound crystallizes in space group

Crystal Forms of Semisynthetic Ergot Alkaloid Terguride

2002 ◽  
Vol 67 (4) ◽  
pp. 479-489 ◽  
Author(s):  
Michal Hušák ◽  
Bohumil Kratochvíl ◽  
Ivana Císařová ◽  
Ladislav Cvak ◽  
Alexandr Jegorov ◽  
...  
Keyword(s):  
Crystal Structure ◽  
Ergot Alkaloid ◽  
Simplified Model ◽  
Quantum Mechanical ◽  
Quantum Mechanical Calculations ◽  
X Ray Diffraction ◽  
Torsion Angles ◽  
Crystal Forms ◽  
X Ray ◽  
Independent Molecules

Two new structures of semisynthetic ergot alkaloid terguride created by unusual number of symmetry-independent molecules were determined by X-ray diffraction methods at 150 K. Form A (monoclinic, P212121, Z = 12) contains three symmetry-independent terguride molecules and two molecules of water in the asymmetric part of the unit cell. The form CA (monoclinic, P21, Z = 8) is an anhydrate remarkable by the presence of four symmetry-independent molecules in the crystal structure. Conformations of twelve symmetry-independent molecules that were found in four already described terguride structures are compared with torsion angles obtained by ab initio quantum-mechanical calculations for the simplified model of N-cyclohexyl-N'-diethylurea.

scholarly journals High-pressure synthesis and crystal structure of the mixed-cation borate Ga4In4B15O33(OH)3

2019 ◽  
Vol 74 (4) ◽  
pp. 357-363
Author(s):  
Daniela Vitzthum ◽  
Hubert Huppertz
Keyword(s):  
Crystal Structure ◽  
High Pressure ◽  
High Temperature ◽  
Diffraction Data ◽  
X Ray Diffraction ◽  
Synthesis And Crystal Structure ◽  
X Ray ◽  
Mixed Cation ◽  
High Pressure High Temperature ◽  
Pressure Synthesis

AbstractThe mixed cation triel borate Ga4In4B15O33(OH)3 was synthesized in a Walker-type multianvil apparatus at high-pressure/high-temperature conditions of 12.5 GPa and 1300°C. Although the product could not be reproduced in further experiments, its crystal structure could be reliably determined via single-crystal X-ray diffraction data. Ga4In4B15O33(OH)3 crystallizes in the tetragonal space group I41/a (origin choice 2) with the lattice parameters a = 11.382(2), c = 15.244(2) Å, and V = 1974.9(4) Å3. The structure of the quaternary triel borate consists of a complex network of BO4 tetrahedra, edge-sharing InO6 octahedra in dinuclear units, and very dense edge-sharing GaO6 octahedra in tetranuclear units.

Crystal structure determination of the conformation of two bicyclo[3.3.1]nonan-ones

1985 ◽  
Vol 63 (6) ◽  
pp. 1166-1169 ◽  
Author(s):  
John F. Richardson ◽  
Ted S. Sorensen
Keyword(s):  
Crystal Structure ◽  
Direct Methods ◽  
Chair Conformation ◽  
Molecular Structures ◽  
Boat Conformation ◽  
X Ray Diffraction ◽  
Space Group ◽  
X Ray ◽  
Final Agreement

The molecular structures of exo-7-methylbicyclo[3.3.1]nonan-3-one, 3, and the endo-7-methyl isomer, 4, have been determined using X-ray-diffraction techniques. Compound 3 crystallizes in the space group [Formula: see text] with a = 15.115(1), c = 7.677(2) Å, and Z = 8 while 4 crystallizes in the space group P21 with a = 6.446(1), b = 7.831(1), c = 8.414(2) Å, β = 94.42(2)°, and Z = 2. The structures were solved by direct methods and refined to final agreement factors of R = 0.041 and R = 0.034 for 3 and 4 respectively. Compound 3 exists in a chair–chair conformation and there is no significant flattening of the chair rings. However, in 4, the non-ketone ring is forced into a boat conformation. These results are significant in interpreting what conformations may be present in the related sp2-hybridized carbocations.

Sign in / Sign up

Export Citation Format

Share Document