Phase Transitions and Structures at 10, 92 and 293 K in Eight Trigonal Double Salts M
                  I[M
                  III(NH3)6](ClO4)2
                  X
                  2

The crystal structures of eight hexaammine-M III double salts have been determined by X-ray diffraction at 293 K, where M I, M III and X are NH4, Co, Cl (I), ammonium hexaamminecobalt(III) diperchlorate dichloride; Cs, Co, Cl (II), caesium hexaamminecobalt(III) diperchlorate dichloride; NH4, Ru, Cl (III), ammonium hexaammineruthenium(III) diperchlorate dichloride; K, Ru, Cl (IV), potassium hexaammineruthenium(III) diperchlorate dichloride; Rb, Ru, Cl (V), rubidium hexaammineruthenium(III) diperchlorate dichloride; Cs, Ru, Cl (VI), caesium hexaammineruthenium(III) diperchlorate dichloride; Cs, Cr, Cl (VII) caesium hexaamminechromium(III) diperchlorate dichloride; Cs, Cr, Br (VIII), caesium hexaamminechromium(III) diperchlorate dibromide. The structures of (I), (IV), (V) and (VI) have also been determined at 92 K and those of (V), (VII) and (VIII) at 10 K. At room temperature all are isomorphous, trigonal R3¯m, Z = 3, with only seven positional parameters for the seven unique non-H atoms. The ammine H atoms are disordered only in the Cs+ and NH_4^+ salts, and the NH_4^+ H atoms in the ammonium salts. At lower temperatures a reversible phase change is observed in all except the K+ member, by the lowering of symmetry to a twinned, but atomically ordered, R3¯ phase. In this R3¯ phase the hexaammine-M III and perchlorate ions have rotated about the threefold axis removing the former mirror plane in the crystal. Displacement parameters, unit cells and observed structures all change smoothly with changes in M I ionic radii and M III—N distances.

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The Isomorphous Structures of Ammonium trans-Diiodobis(ethanedial-dioximato-(1–)-N,N′)cobaltate(III) and Ammonium trans-Diiodobis(ethanedial-dioximato-(1–)-N,N′)rhodate(III): Extended Metaloximate Chains with a Novel ···I–M–I···I–M–I··· Zigzagged Structure

Zeitschrift für Naturforschung B ◽

10.1515/znb-1990-1108 ◽

1990 ◽

Vol 45 (11) ◽

pp. 1508-1512 ◽

Cited By ~ 3

Author(s):

Michel Mégnamisi-Bélombé ◽

Bernhard Nuber

Keyword(s):

Room Temperature ◽

Ammonium Salts ◽

Monoclinic Space Group ◽

Hydroxyl Groups ◽

Coordination Geometry ◽

Crystal Data ◽

X Ray Diffraction ◽

X Ray ◽

Anionic Complexes ◽

Complex Anions

The ammonium salts of the complex anions trans-diiodobis(ethanedial-dioximato)-cobaltate(III), [Col2(GH)2]-, and trans-diiodobis(ethanedial-dioximato)rhodate(III), [RhI2(GH)2]- (GH- = ethanedial dioximate or glyoximate), have been synthesized and their structures determined from single crystal X-ray diffraction data at room temperature. The crystals of the two salts are monoclinic, space group C2/c. NH4[CoI2(GH)2] (I) crystallizes as dark-brown prisms with a greenish reflectance; its crystal data are: C4H10Col2N5O4, Mr = 504.90; a = 8.910(6), b = 11.700(9), c = 11.691(6) Å; β = 93.55(5)°; V = 1216.4 Å3; Z = 4; Dc = 2.78 Mg m-3. NH4[RhI2(GH)2] (II) crystallizes as yellow-brown blocks with crystal data: C4H10I2N5O4Rh, Mr = 548.88; a = 9.038(4), b = 11.949(5), c = 11.770(3) Å; β = 95.54(3)°; V = 1265.16 A3; Z = 4; Dc = 2.87 Mg m-3. The two structures were refined to a final RW = 0.045 for 1209 observed independent reflections and 95 parameters for I, and to a final RW = 0.040 for 1922 observed independent reflections and 87 parameters for II. The coordination geometry around Co or Rh in the anionic complexes is a distorted (4 + 2) octahedron of four equatorial chelating N atoms and two apical iodides. The H atoms of the hydroxyl groups are involved, as usual, in intramolecular O—H—O bridges with uniform Ο···Ο separations of 2.582 Å for I, and 2.713 Å for II. The rectilinear I—Co—I or I—Rh—I triads form “infinite” zigzag chains extending parallel to the ab plane, with a weak I—I contact of 3.988 Å for I, and 4.010 Å for II.

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Reversible phase transitions in Na2S under pressure: a comparison with the cation array in Na2SO4

Acta Crystallographica Section B Structural Science ◽

10.1107/s0108768100016621 ◽

2001 ◽

Vol 57 (2) ◽

pp. 151-156 ◽

Cited By ~ 69

Author(s):

A. Vegas ◽

A. Grzechnik ◽

K. Syassen ◽

I. Loa ◽

M. Hanfland ◽

...

Keyword(s):

Room Temperature ◽

Diamond Anvil Cell ◽

Lattice Parameters ◽

X Ray Diffraction ◽

Rietveld Refinements ◽

X Ray ◽

Diamond Anvil ◽

Binary Compounds ◽

Reversible Phase

The structural behavior of the antifluorite Na2S, disodium sulfide, has been studied under pressure up to 22 GPa by in situ synchrotron X-ray diffraction experiments in a diamond anvil cell at room temperature. At approximately 7 GPa, Na2S undergoes a first phase transition to the orthorhombic anticotunnite (PbCl2) structure (Pnma, Z = 4). The lattice parameters at 8.2 GPa are a = 6.707 (5), b = 4.120 (3), c = 8.025 (4) Å. At approximately 16 GPa, Na2S undergoes a second transition adopting the structure of the Ni2In-type (P63/mmc, Z = 2). The lattice parameters at 16.6 GPa are a = 4.376 (18), c = 5.856 (9) Å. Both pressure-induced phases have been confirmed by full Rietveld refinements. An inspection of the cation array of Na2SO4 reveals that its Na2S subarray is also of the Ni2In-type. This feature represents a new example of how the cation arrangements in ternary oxides correspond to the topology of the respective binary compounds. We discuss analogies between the insertion of oxygen and the application of pressure.

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Structural and Raman spectroscopic studies of the two M0.50SbFe(PO4)3 (M = Mg, Ni) NASICON phases

Powder Diffraction ◽

10.1017/s0885715617000331 ◽

2017 ◽

Vol 32 (S1) ◽

pp. S40-S51

Author(s):

Abderrahim Aatiq ◽

Asmaa Marchoud ◽

Hajar Bellefqih ◽

My Rachid Tigha

Keyword(s):

Room Temperature ◽

Structural Information ◽

Rietveld Analysis ◽

Spectroscopic Studies ◽

X Ray Diffraction ◽

X Ray ◽

Raman Spectroscopic ◽

Raman Spectroscopic Study ◽

Unit Cells ◽

Xrd Patterns

Structures of the two M0.50SbFe(PO4)3 (M = Mg, Ni) phases, abbreviated as [Mg0.50] and [Ni0.50], were determined at room temperature from X-ray diffraction (XRD) powder data using the Rietveld analysis. Both compounds belong to the NASICON structural family. XRD patterns of [Mg0.50] and [Ni0.50] phases were easily indexed with a primitive hexagonal unit cell [P$\overline 3 $ space group, Z = 6] similar to that already obtained for La0.33Zr2(PO4)3. Obtained unit cells parameters are [a = 8.3443(1) Å, c = 22.3629(1) Å], and [a = 8.3384(1), c = 22.3456(1) Å], respectively, for [Mg0.50] and [Ni0.50] phosphates. In both samples, the [Sb(Fe)(PO4)3]− NASICON framework is preserved and a partially-ordered distribution of Sb5+ and Fe3+ ions is observed. Raman spectroscopic study was used to obtain further structural information about the nature of bonding in [Mg0.50] and [Ni0.50] phases.

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The influence of next nearest neighbours on cation radii in spinels: the example of the Co3O4-CoCr2O4solid solution

Mineralogical Magazine ◽

10.1180/0026461036730116 ◽

2003 ◽

Vol 67 (3) ◽

pp. 547-554 ◽

Cited By ~ 5

Author(s):

H. St. C. O’Neill

Keyword(s):

Room Temperature ◽

Nearest Neighbour ◽

X Ray Diffraction ◽

Ionic Radii ◽

Cation Site ◽

X Ray ◽

Nearest Neighbours ◽

Neighbour Effects ◽

Oxide Spinels ◽

Octahedral Cations

AbstractLattice parameters and crystal structures of the synthetic spinels Co3O4, CoCr2O4, and solid solutions in the binary join Co3O4-CoCr2O4, have been determined by powder X-ray diffraction structural refinements. In all these spinels the cation distribution is completely normal at room temperature, and the tetrahedrally coordinated cation site is occupied only by Co2+. The ionic radius of Co2+(tet) increases from 0.556(3) in Co3O4to 0.599(4) in CoCr2O4. In the spinel structure, the interatomic distance between the tetrahedral cations and oxygen are geometrically independent of those between the octahedral cations and oxygen; thus the variation in effective ionic radii is ascribed to next-nearest neighbour effects, induced by covalent tendencies in the low-spin Co3+-O bond. The results demonstrate that the assumption of constant ionic radii even within an isomorphic group such as the oxide spinels needs to be made with caution.

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HRTEM Study of a Modulated Structure in Homologous Compounds In2O3(ZnO)m

Microscopy and Microanalysis ◽

10.1017/s1431927600010497 ◽

1997 ◽

Vol 3 (S2) ◽

pp. 721-722

Author(s):

Yoshio Bando ◽

Chunfei Li ◽

Masaki Nakamura ◽

Noboru Kimizuka

Keyword(s):

Room Temperature ◽

Structural Changes ◽

X Ray Diffraction ◽

Ionic Radii ◽

Modulated Structure ◽

Sinusoidal Modulation ◽

X Ray ◽

Metal Atoms ◽

Homologous Compounds ◽

Random Fashion

The structure of the homologous compounds InMO3(ZnO)m (M=In, Fe, Ga, and Al, m=integer) is considered to be a layered structure, consisting of InO21− layer (In-O) ) interleaved with MZnmOm+11+ layers (M/Zn-O) along the c-axis. In the M/Zn-O layers, the distribution of two kinds of metal atoms is considered to be random fashion from X-ray diffraction analysis. However, in the previous HRTEM study of InFeO3(ZnO)m with m larger than 6, we found a modulated structure, where the image contrast showed a sinusoidal modulation curve present only in the Fe/Zn-O layers. Elemental analysis by EDS clarified that the modulated structure was caused by the ordering of Fe atoms within the Fe/Zn-O layers. In the present study, we try to observe In2O3(ZnO)m compounds, where Fe3+ atoms are replaced by In3+ atoms which have larger ionic radii. We are interested in whether the replacement of Fe3+ by In3+ atoms may cause any structural changes between In2O3(ZnO)m and InFeO3(ZnO)m.The samples were prepared by heating powders of In2O3 and ZnO sealed in Pt tube at 1350 °C for about 3 days and then rapidly cooled down to room temperature. The electron microscope observation was performed by using JEM-2000EX, operated at an accelerating voltage of 200 kV.

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Electron Microscopy of Human Gallstones

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100065523 ◽

1971 ◽

Vol 29 ◽

pp. 296-297

Author(s):

C. Wolpers ◽

R. Blaschke

Keyword(s):

Electron Microscopy ◽

Room Temperature ◽

Bile Pigment ◽

X Ray Diffraction ◽

Triclinic Crystal System ◽

X Ray ◽

Follow Up Study ◽

Infra Red ◽

Main Components

Scanning microscopy was used to study the surface of human gallstones and the surface of fractures. The specimens were obtained by operation, washed with water, dried at room temperature and shadowcasted with carbon and aluminum. Most of the specimens belong to patients from a series of X-ray follow-up study, examined during the last twenty years. So it was possible to evaluate approximately the age of these gallstones and to get information on the intensity of growing and solving.Cholesterol, a group of bile pigment substances and different salts of calcium, are the main components of human gallstones. By X-ray diffraction technique, infra-red spectroscopy and by chemical analysis it was demonstrated that all three components can be found in any gallstone. In the presence of water cholesterol crystallizes in pane-like plates of the triclinic crystal system.

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Electron Microscope study of commensurate-incommensurate phase transition in BaZnGeO4

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100173996 ◽

1990 ◽

Vol 48 (4) ◽

pp. 172-173

Author(s):

Naoki Yamamoto ◽

Makoto Kikuchi ◽

Tooru Atake ◽

Akihiro Hamano ◽

Yasutoshi Saito

Keyword(s):

Phase Transition ◽

Electron Microscope Study ◽

Room Temperature ◽

Hexagonal Lattice ◽

Ferroelectric Materials ◽

Temperature Phase ◽

X Ray Diffraction ◽

X Ray ◽

Periodic Arrays ◽

Modulation Wave Vector

BaZnGeO4 undergoes many phase transitions from I to V phase. The highest temperature phase I has a BaAl2O4 type structure with a hexagonal lattice. Recent X-ray diffraction study showed that the incommensurate (IC) lattice modulation appears along the c axis in the III and IV phases with a period of about 4c, and a commensurate (C) phase with a modulated period of 4c exists between the III and IV phases in the narrow temperature region (—58°C to —47°C on cooling), called the III' phase. The modulations in the IC phases are considered displacive type, but the detailed structures have not been studied. It is also not clear whether the modulation changes into periodic arrays of discommensurations (DC’s) near the III-III' and IV-V phase transition temperature as found in the ferroelectric materials such as Rb2ZnCl4.At room temperature (III phase) satellite reflections were seen around the fundamental reflections in a diffraction pattern (Fig.1) and they aligned along a certain direction deviated from the c* direction, which indicates that the modulation wave vector q tilts from the c* axis. The tilt angle is about 2 degree at room temperature and depends on temperature.

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Xenon Trioxide Adducts of O-Donor Ligands; [(CH3)2CO]3XeO3, [(CH3)2SO]3(XeO3)2, (C5H5NO)3(XeO3)2, and [(C6H5)3PO]2XeO3

10.26434/chemrxiv.7092263.v1 ◽

2018 ◽

Author(s):

Katherine Marczenko ◽

James Goettel ◽

Gary Schrobilgen

Keyword(s):

Room Temperature ◽

Triphenylphosphine Oxide ◽

Donor Ligands ◽

Mechanical Shock ◽

X Ray Diffraction ◽

X Ray ◽

Oxygen Coordination ◽

Xenon Trioxide ◽

Distorted Octahedra ◽

Coordination Spheres

Oxygen coordination to the Xe(VI) atom of XeO3 was observed in its adducts with triphenylphosphine oxide, dimethylsulfoxide, pyridine-N-oxide, and acetone. The crystalline adducts were characterized by low-temperature, single-crystal X-ray diffraction and Raman spectroscopy. Unlike solid XeO3, which detonates when mechanically or thermally shocked, the solid [(C6H5)3PO]2XeO3, [(CH3)2SO]3(XeO3)2, and (C5H5NO)3(XeO3)2 adducts are insensitive to mechanical shock, but undergo rapid deflagration when ignited by a flame. Both [(C6H5)3PO]2XeO3 and (C5H5NO)3(XeO3)2 are air-stable whereas [(CH3)2SO]3(XeO3)2 slowly decomposes over several days and [(CH3)2CO]3XeO3 undergoes adduct dissociation at room temperature. The xenon coordination sphere of [(C6H5)3PO]2XeO3 is a distorted square pyramid which provides the first example of a five-coordinate XeO3 adduct. The xenon coordination spheres of the remaining adducts are distorted octahedra comprised of three Xe---O secondary contacts that are approximately trans to the primary Xe–O bonds of XeO3. Quantum-chemical calculations were used to assess the Xe---O adduct bonds, which are predominantly electrostatic σ-hole bonds between the nucleophilic oxygen atoms of the bases and the σ-holes of the xenon atoms.

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Effect of trytophan as dopant on potassium acid phthalate single crystals

10.31221/osf.io/cn28k ◽

2019 ◽

Author(s):

Chem Int

Keyword(s):

Single Crystals ◽

Room Temperature ◽

Visible Region ◽

X Ray Diffraction ◽

X Ray ◽

Slow Evaporation Technique ◽

Absorption Studies ◽

Evaporation Technique ◽

Potassium Acid Phthalate ◽

Acid Phthalate

Optically transparent single crystals of potassium acid phthalate (KAP, 0.5 g) 0.05 g and 0.1 g (1 and 2 mol %) trytophan were grown in aqueous solution by slow evaporation technique at room temperature. Single crystal X- ray diffraction analysis confirmed the changes in the lattice parameters of the doped crystals. The presence of functional groups in the crystal lattice has been determined qualitatively by FTIR analysis. Optical absorption studies revealed that the doped crystals possess very low absorption in the entire visible region. The dielectric constant has been studied as a function of frequency for the doped crystals. The thermal stability was evaluated by TG-DSC analysis.

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Structural and Enhanced Optical Properties of Stabilized γ‒Bi2O3 Nanoparticles: Effect of Oxygen Ion Vacancies

Nanomaterials ◽

10.3390/nano10061023 ◽

2020 ◽

Vol 10 (6) ◽

pp. 1023 ◽

Cited By ~ 2

Author(s):

Ashish Chhaganlal Gandhi ◽

Chia-Liang Cheng ◽

Sheng Yun Wu

Keyword(s):

Room Temperature ◽

Excess Oxygen ◽

Ambient Atmosphere ◽

Photoluminescence Spectra ◽

X Ray Diffraction ◽

X Ray ◽

Band Emission ◽

Oxygen Ion ◽

Integrated Intensity ◽

Effect Of Oxygen

We report the synthesis of room temperature (RT) stabilized γ–Bi2O3 nanoparticles (NPs) at the expense of metallic Bi NPs through annealing in an ambient atmosphere. RT stability of the metastable γ–Bi2O3 NPs is confirmed using synchrotron radiation powder X-ray diffraction and Raman spectroscopy. γ–Bi2O3 NPs exhibited a strong red-band emission peaking at ~701 nm, covering 81% integrated intensity of photoluminescence spectra. Our findings suggest that the RT stabilization and enhanced red-band emission of γ‒Bi2O3 is mediated by excess oxygen ion vacancies generated at the octahedral O(2) sites during the annealing process.

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