The transformation of groutite (α-MnOOH) into pyrolusite (MnO2)

1964 ◽  
Vol 33 (266) ◽  
pp. 1024-1031 ◽  
Author(s):  
J. Lima-De-Faria ◽  
A. Lopes-Vieira
Keyword(s):  
Single Crystal ◽  
Crystal Surface ◽  
Close Packing ◽  
The Other ◽  
X Ray ◽  
Detailed Interpretation ◽  
Homogeneous Mechanism ◽  
Ray Methods

SummaryThe transformation of groutite (α-MnOOH) by heating has been studied at 300° C in air, by single-crystal and powder X-ray methods. At this temperature groutite transforms topotactically into pyrolusite (MnO2), the a, b, and c axes of groutite becoming respectively the a, b, and c axes of pyrolusite (in pyrolusite b = a). At various stages of the transformation other weak and diffuse spots were observed on X-ray oscillation photographs, which could not be ascribed to pyrolusite. Some of these extra spots fit well to an α-Mn2O3 structure (isostructural with hematite), with c 14·3 and a 4·9 Å; the other few spots could not be identified.The transformation of α-MnOOH into MnO2 is explained by a homogeneous mechanism, with migration of protons and electrons to the crystal surface. A detailed interpretation of this mechanism is presented on the basis of the close-packing characteristics of these two structures.

scholarly journals Die Kristallstruktur des Cyano-Elpasoliths [N(CH3)4]2CsFe(CN)6 / The Crystal Structure of the Cyano Elpasolite [N(CH3)4]2CsFe(CN)6

1982 ◽  
Vol 37 (12) ◽  
pp. 1534-1539 ◽  
Author(s):  
D. Babel
Keyword(s):  
Crystal Structure ◽  
Single Crystal ◽  
The Other ◽  
Methyl Groups ◽  
Orientational Disorder ◽  
Space Group ◽  
X Ray ◽  
Ray Methods ◽  
The Ideal

The crystal structure of the cubic compound [N(CH3)4]2CsFe(CN)6 was determined by X-ray methods: a = 2527.4(6) pm, space group Fd3c, Z = 32, Rg = 0.028 (260 independent single crystal reflections). The resulting distances within the practically undistorted Fe (CN)63- - octahedron are Fe-C = 193.4(6) and C-N = 115.7(7) pm. Compared to the ideal elpasolite structure of space group Fm3m, Z = 4, the octahedra are rotated by 7.4° through their 3 axis. This is discussed as caused by steric requirements of the tetramethylammonium groups (N-C = 148.4(10) and 149.1(38) pm, resp.). Three quarters of them, of which also the hydrogen positions could be located, are well oriented. The remaining quarter shows orientational disorder to approach similar contact distances as the other N(CH3)4+ ion exhibits between the methyl groups and the nitrogen ends of the anions

Crystal Structure of Methyl[tetrakis(pyrazol-1-yl)borato-N,N']mercury(II)

1987 ◽  
Vol 40 (9) ◽  
pp. 1609 ◽  
Author(s):  
AJ Canty ◽  
BW Skelton ◽  
AH White
Keyword(s):  
Crystal Structure ◽  
Single Crystal ◽  
The Other ◽  
X Ray ◽  
Ray Methods

Crystals of methyl[tetrakis(pyrazol-l-yl)borato-N,N']mercury(II) [MeHg(B(pz)4}] are triclinic, Pi, a 12.73(2), b 8.88(1), c 8.10(1) �, α 109.80(8), β 99.16(9), γ 103.05(10)�, Z 2. The structure, determined by single-crystal X-ray methods (R 0.12 for 1598 'observed' reflections), has molecules of MeHg(B(pz)4} with two pz groups coordinated to mercury, giving planar but irregular coordination. The more strongly bound group has Hg-N 2.07(4) A with C-Hg-N 169(2)�, and the other group has Hg-N 2.65(4)� with C-Hg-N 112(1)�.

Studies of the rhenium–oxygen bond. II. The crystal and molecular structure of µ-oxobis(cis-dichloro-cis-di(pyridine)-trans-oxorhenium(V)), ORe(C5H5N)2Cl2ORe(C5H5N)2Cl2O

1978 ◽  
Vol 56 (2) ◽  
pp. 179-188 ◽  
Author(s):  
Colin James Lyne Lock ◽  
Graham Turner
Keyword(s):  
Molecular Structure ◽  
Crystal Structure ◽  
Single Crystal ◽  
Least Squares ◽  
Crystal And Molecular Structure ◽  
The Other ◽  
Full Matrix ◽  
X Ray ◽  
Ray Methods ◽  
Oxygen Bond

The crystal structure of µ-oxobis(cis-dichloro-cis-di(pyridine)-trans-oxorhenium(V)), ORe(C5H5N)2Cl2•O•Re(C5H5N)2Cl2O bas been studied by single crystal X-ray methods. The crystals were orthorhombic with lattice parameters a = 15.367(2), b = 10.283(2), c = 16.685(2) Å. The space group was Pna21 and there were four formula weights per unit cell. A total of 3339 reflections, of which 2990 were observed, were examined, and the structure refined by full matrix least squares (treating the pyridine rings as groups) to an R2 value of 0.0449. The dimer had a roughly rectilinear O—Re—O—Re—O backbone with pairs of chlorine atoms and pyridine molecules arranged cis in each half of the dimer. The two halves of the dimer were arranged such that the pairs of cis atoms in one half were rotated about the Re(1)–Re(2) axis almost 113 ° when compared to the corresponding pair in the other half. Important bond lengths (Re—O(terminal), 1.715(16), 1.764(16); Re—O(bridging), 1.943(16), 1.903(16); Re—Cl, 2.356(5)–2.390(5); Re—N, 2.116(16)–2.180(16)) were close to previously observed values. The molecule was markedly disturbed from the idealized structure and this was caused by intramolecular non-bonded interactions.

scholarly journals Redox-driven atomic-scale changes in mixed catalysts: VOX/WOX/α-TiO2 (110)

RSC Advances ◽  
2014 ◽  
Vol 4 (110) ◽  
pp. 64608-64616 ◽  
Author(s):  
Z. Feng ◽  
M. E. McBriarty ◽  
A. U. Mane ◽  
J. Lu ◽  
P. C. Stair ◽  
...  
Keyword(s):  
Single Crystal ◽  
Crystal Surface ◽  
Oxide Catalysts ◽  
Atomic Scale ◽  
Redox Behavior ◽  
Single Crystal Surface ◽  
Tungsten Oxides ◽  
Mixed Monolayer ◽  
X Ray

X-ray study of vanadium–tungsten mixed-monolayer-oxide catalysts grown on the rutile α-TiO2 (110) single crystal surface shows redox behavior not observed for lone supported vanadium or tungsten oxides.

Molecular tapes in the structure of isoguaninium chloride

2017 ◽  
Vol 74 (1) ◽  
pp. 108-112 ◽  
Author(s):  
Urszula Anna Budniak ◽  
Paulina Maria Dominiak
Keyword(s):  
Crystal Structure ◽  
Single Crystal ◽  
Charge Density ◽  
Interaction Energy ◽  
Electrostatic Interaction ◽  
Electrostatic Interactions ◽  
The Other ◽  
X Ray Diffraction ◽  
X Ray ◽  
Diffraction Structure

Isoguanine, an analogue of guanine, is of intrinsic interest as a noncanonical nucleobase. The crystal structure of isoguaninium chloride (systematic name: 6-amino-2-oxo-1H,7H-purin-3-ium chloride), C5H6N5O+·Cl−, has been determined by single-crystal X-ray diffraction. Structure analysis was supported by electrostatic interaction energy (E es) calculations based on charge density reconstructed with the UBDB databank. In the structure, two kinds of molecular tapes are observed, one parallel to (010) and the other parallel to (50\overline{4}). The tapes are formed by dimers of isoguaninium cations interacting with chloride anions. E es analysis indicates that cations in one kind of tape are oriented so as to minimize repulsive electrostatic interactions.

Crystal Structure of Calcium Picrate Pentahydrate: A New Eight-Coordinate Stereochemistry for [M(bidentate)2(unidentate)4]

1979 ◽  
Vol 32 (2) ◽  
pp. 301 ◽  
Author(s):  
V Diakiw ◽  
TW Hambley ◽  
DL Kepert ◽  
CL Raston ◽  
AH White
Keyword(s):  
Crystal Structure ◽  
Water Molecule ◽  
Single Crystal ◽  
Title Compound ◽  
Lattice Site ◽  
The Other ◽  
Water Molecules ◽  
X Ray Diffraction ◽  
Triangular Face ◽  
X Ray

The crystal structure of the title compound, Ca(C6H2N307)2,5H2O, has been determined by single-crystal X-ray diffraction at 295(1) K and refined by least squares to a residual of 0.049 for 1513 'observed' reflections. Crystals are orthorhombic, Pmab, a 24.169(6), b l0.292(7), c 8.554(2) �, Z 4. The stereochemistry about the calcium has not been observed previously for the system [M(bidentate)2- (unidentate)4]; in the present structure, the calcium is coordinated by a pair of bidentate picrate ligands and the four water molecules in an array in which three of the water molecules occupy a triangular face of a square antiprism, the overall array having m symmetry. The remaining water molecule occupies a lattice site with no close interaction with the other species.

Redetermination of Co4Nb2O9 by single-crystal X-ray methods

2006 ◽  
Vol 62 (5) ◽  
pp. i117-i119 ◽  
Author(s):  
María A. Castellanos R. ◽  
Sylvain Bernès ◽  
Marina Vega-González
Keyword(s):  
Single Crystal ◽  
High Precision ◽  
Cation Distribution ◽  
Crystal Data ◽  
Space Group ◽  
X Ray ◽  
Ray Methods

A high-precision structure of tetracobalt diniobium nonaoxide, Co4Nb2O9, is presented, based on X-ray single-crystal data. The space group and cation distribution previously obtained from powder data [Bertaut, Corliss, Forrat, Aleonard & Pauthenet (1961). J. Phys. Chem. Solids, 21, 234–251] are confirmed.

Notizen: Die Kristallstruktur von Rb2Ca(N3)4 · 4 H2O / The Crystal Structure of RB2Ca(N3)4 · 4 H2O

1988 ◽  
Vol 43 (4) ◽  
pp. 497-498
Author(s):  
Franz A. Mautner ◽  
Harald Krischner ◽  
Christoph Kratky
Keyword(s):  
Crystal Structure ◽  
Single Crystal ◽  
Orthorhombic Space Group ◽  
Space Group ◽  
X Ray ◽  
Ray Methods

Abstract The crystal structure of Rb2Ca(N3)4 · 4H2O has been determined by single crystal X-ray methods. The compound is isotypic with K2Ca(N3)4 · 4 H2O and crystallizes in the orthorhombic space group Ccca, Z = 4, a = 1949.1(12) pm, b = 1099.5(3) pm, c - 622.2(1) pm.

Synthesis and Structure of and Cation Distribution in the Zirconium Cluster Rb[(Zr6C)Cl15]

2008 ◽  
Vol 63 (5) ◽  
pp. 507-512 ◽  
Author(s):  
Henning W. Rohm ◽  
Martin Köckerling
Keyword(s):  
Crystal Structure ◽  
Single Crystal ◽  
Cation Distribution ◽  
Type Structure ◽  
The Other ◽  
X Ray Diffraction ◽  
X Ray ◽  
Coulombic Interactions ◽  
Cluster Network ◽  
Zirconium Cluster

Rb[(Zr6C)Cl15] was prepared by heating ZrCl4, Zr powder, RbCl and Al4C3 at 850 °C for 21 days. The crystal structure was determined by single crystal X-ray diffraction (space group Pmma, a = 18.484(3), b = 18.962(2), c = 9.708(1) Å, V = 2505.4(6) Å3, and Z = 4). Rb[(Zr6C)Cl15] crystallises in the Cs[Nb6Cl15]-type structure. It is built up from two interconnected types of cluster chains, one with linear Zr−Cla−a-Zr bridges, the other one with bent bridges. The rubidium cations are spread over three different sites within the cluster network which differs significantly from the cation distribution in the comparable potassium and caesium phases. The cation distribution can be rationalised considering the size of the cavities and the Coulombic interactions.

Crystal structure of coalingite

1971 ◽  
Vol 38 (295) ◽  
pp. 286-294 ◽  
Author(s):  
J. Pastor-Rodriguez ◽  
H. F. W. Taylor
Keyword(s):  
Crystal Structure ◽  
Single Crystal ◽  
Water Molecules ◽  
Structural Elements ◽  
Structural Element ◽  
X Ray ◽  
Octahedral Sites ◽  
Carbonate Ions ◽  
Disordered Layer ◽  
Ray Methods

SummaryThe crystal structure of coalingite (Mg10Fe2(OH)24(CO3)·2H2O) has been determined using single-crystal X-ray methods. The mineral is trigonal, with space group Rm, aH = 3·12, cH = 37·4 Å, Z = ½, and (0001) cleavage. The structure is of a layer type, and is based on a structural element about 12·5 Å thick in the c-direction and consisting of two brucite-like layers and one disordered layer containing carbonate ions and water molecules and resembling those in sjögrenite and pyroaurite. The unit cell comprises three of these structural elements stacked together in the c-direction. The Mg2+ and Fe3+ ions are randomly distributed among all the octahedral sites of the brucite-like layers. The structure closely resembles those of sjögrenite and pyroaurite, but has two brucite-like layers between each CO32−−H2O layer where these have one. There is a tendency to random interstratification, and the crystals appear to contain intergrown regions of brucite and of sjögrenite or pyroaurite. Coalingite-K probably has a similar structure, but with three brucite-like layers between each -H2O layer; its idealized formula is probably Mg16Fe2(OH)36(CO3).2H2O.

Sign in / Sign up

Export Citation Format

Share Document