scholarly journals Präparative und spektroskopische Untersuchungen zur Dimorphie von CsNiF3.

1976 ◽  
Vol 31 (1) ◽  
pp. 60-65 ◽  
Author(s):  
R. Haegele ◽  
D. Babel ◽  
D. Reinen
Keyword(s):  
Low Temperature ◽  
Perovskite Structure ◽  
Spectral Band ◽  
Ligand Field ◽  
X Ray ◽  
Bond Angles ◽  
Green Colour ◽  
Ligand Field Spectra ◽  
Ray Patterns

While the stable modification of CsNiF3 is of green colour, a yellow phase is obtained by fluorination of CsNiCl3 and decomposition of the product “CsNiF4”, which contains Ni4+ and Ni3+ besides Ni2+. The two modifications have the 2L- and 9L-perovskite-structure, respectively, and are characterized by their X-ray patterns and low-temperature ligand field spectra. The differences in colours and spectral band positions are discussed with respect to the Ni-F-Ni bond angles

The Coordination Chemistry of Phosphoryl Compounds Containing the — N(CH3)2 Group, Part VIII

1972 ◽  
Vol 27 (7) ◽  
pp. 759-763 ◽  
Author(s):  
M. W. G. De Bolster ◽  
W. L. Groeneveld
Keyword(s):  
Coordination Chemistry ◽  
General Formula ◽  
Ligand Field ◽  
Chemical Analyses ◽  
X Ray ◽  
Physical Measurements ◽  
Ligand Field Spectra ◽  
Chloride Adduct ◽  
Ligand Field Parameters ◽  
Group Part

A number of new solvates and adducts containing bisphenyldimethylaminophosphine oxide is reported. The solvates have the general formula M[(C6H5)2P(O)N(CH3)2]42+(anion-)2, in which M = Mg, Ca, Mn, Fe, Co, Ni, Cu, Zn and Cd, and the anions are ClO4- and BF4-. The adducts have the general formula M[(C6H5)2P(O)N(CH3)2]2Cl2, where M stands for the same series of metals.The compounds are characterized and identified by chemical analyses and physical measurements.Ligand-field and vibrational spectra have been investigated; values for the ligand-field parameters are reported. It is concluded that coordination takes place via the oxygen atom of the ligand.X-ray powder patterns were used in combination with ligand-field spectra to deduce the coordination around the metal ions.The interesting behaviour of the nickel (II) chloride adduct upon heating is discussed and it is shown that both a square pyramidal and a tetrahedral modification exists.

Redetermination of the Crystal and Molecular Structure of Cyclohexasulfur, S6 [1]

1978 ◽  
Vol 33 (12) ◽  
pp. 1554-1555 ◽  
Author(s):  
Jürgen Steidel ◽  
Joachim Pickardt ◽  
Ralf Steudel
Keyword(s):  
Molecular Structure ◽  
Structural Analysis ◽  
Low Temperature ◽  
Single Crystals ◽  
Crystal And Molecular Structure ◽  
Torsion Angles ◽  
X Ray ◽  
Bond Angles

A low temperature (-90 °C) X-ray structural analysis of S6 single crystals yielded improved data for the bond distances (206.8 pm), bond angles (102.6°), and torsion angles (73.8°) of the D3d molecule which are in agreement with current theories of homonuclear sulfur bonds.

The determination of composition and thermal history of plagioclase by the X-ray powder method

1955 ◽  
Vol 30 (229) ◽  
pp. 648-656 ◽  
Author(s):  
J. Goodyear ◽  
W. J. Duffin
Keyword(s):  
Chemical Composition ◽  
Low Temperature ◽  
Similar Composition ◽  
X Ray ◽  
Naturally Occurring ◽  
Cell Dimensions ◽  
History Of ◽  
Unit Cell Dimensions ◽  
Ray Patterns

In a recent paper (hereafter referred to as GD) Goodyear and Dufiln (1954) described X-ray powder data for a number of synthetic and chemically analysed plagioclases of composition An0Abl00-Anl00Ab0. Important aspects of this work were a correlation of the X-ray patterns with chemical composition, and a distinction between the pattern of a naturally occurring material of low-temperature origin and that of a synthetic of similar composition. The investigation showed quite clearly that the unit-cell dimensions of a synthetic plagioelase depend but little on composition from An0Abl00 to An70Ab30, whilst they differ from those of the low-temperature modification greatly for albite, to a lessening degree as the composition approaches An70Ab30, and practically not at all in the range An70Ab30-Anl00Ab0.

Polysulfonylamine, CIII [1] Ein Hydroxylamin mit bemerkenswert kurzer O-N-B Bindung: Kristall- und Molekülstruktur von MeO-N(SO2Me)2 / Polysulfonylamines, C III [1] A Hydroxylamine with a Remarkably Short O-N Bond: Crystal and Molecular Structure of MeO-N(SO2Me)2

1998 ◽  
Vol 53 (5-6) ◽  
pp. 634-636 ◽  
Author(s):  
Martina Näveke ◽  
Armand Blaschette ◽  
Peter G. Jones
Keyword(s):  
Molecular Structure ◽  
Crystal Structure ◽  
Low Temperature ◽  
Title Compound ◽  
Crystal And Molecular Structure ◽  
X Ray Diffraction ◽  
Orthorhombic Space Group ◽  
Space Group ◽  
X Ray ◽  
Bond Angles

Abstract The crystal structure of the known title compound was determined by low-temperature X-ray diffraction (orthorhombic, space group Pbcn, Z = 4). The molecule displays an unusually short O-N bond, a relatively long C-O bond and a moderately pyramidal O-NS2 skeleton (O-N 133.1, C-O 148.5 pm, sum of bond angles at N: 347.4°).

Alteration of Uranium-Rich Microlite

2000 ◽  
Vol 663 ◽  
Author(s):  
R. Gieré ◽  
E. C. Buck ◽  
R. Guggenheim ◽  
D. Mathys ◽  
E. Reusser ◽  
...  
Keyword(s):  
Electron Diffraction ◽  
Low Temperature ◽  
Nuclear Waste ◽  
X Ray ◽  
Geologic Time ◽  
Pyrochlore Group ◽  
Tropical Conditions ◽  
Natural Analogues ◽  
Growth Zoning ◽  
Ray Patterns

ABSTRACTMicrolite, a Ta-rich member of the pyrochlore group, occurs in 440 Ma old lithium pegmatites in Mozambique and exhibits a pronounced growth zoning, with a U-free core surrounded by a U-rich rim (UO2≤ 17 wt%). Subsequent to the uplift of the host rock, microlite was subjected to intense low-temperature alteration during which Na, Ca and F were leached from the microlite crystals. This alteration, resulting from exposure to tropical conditions, also led to localized redistribution of radiogenic Pb (formation of plumbomicrolite) and to hydration of microlite, but U remained immobile. The low-temperature alteration effects are only observed in the U-rich rim, which is characterized by abundant microfractures. As demonstrated by electron diffraction images and powder X-ray patterns, the U-rich rim is largely metamict. Our investigation illustrates the importance of natural analogues in evaluating the durability of pyrochlore-based nuclear waste-form materials over geologic time.

scholarly journals Complex Formation Between Imidazole and Nickel(II) Salts

1974 ◽  
Vol 29 (7-8) ◽  
pp. 527-531 ◽  
Author(s):  
J. C. Jansen ◽  
J. Reedijk
Keyword(s):  
Complex Formation ◽  
Infrared Spectra ◽  
Coordination Compounds ◽  
Tetragonal Symmetry ◽  
Ligand Field ◽  
X Ray ◽  
Square Planar ◽  
Ligand Field Spectra ◽  
Crystal Field Parameters ◽  
Imidazole Compounds

Coordination compounds of formula Ni(Iz)nX2(H2O)m, in which Iz=imidazole, n = 1, 2, 4, 6, m = 0-4, and X = Cl-, Br-, I- and NCS-, are described. The anhydrous compounds are prepared from ethanolic solutions of Iz and nickel(II) salts in stoichiometric amounts in the presence of the dehydrating agent triethylorthoformate. Without this dehydrating agent hydrates are isolated for n = 2,4 and 6 with X = Cl, Br.The compounds were identified by means of infrared spectra (4000-25 cm-1), ligand-field spectra (35000-4000 cm-1) and X-ray powder diagrams. Compounds of formula [Ni(Iz)6]X2 all contain octahedrally coordinated Ni2+, for which the spectrochemical parameters were obtained. Tetragonal Ni2+ ions occur in [Ni(Iz)4X2] in which X = Cl and NCS, and in [Ni(Iz)4(H2O)2]X2 in which X = Cl and Br. These compounds are paramagnetic and the crystal-field parameters for tetragonal symmetry have been calculated. In [Ni(Iz)4]X2 with X = I and Br, the Ni2+ ions are square-planar coordinated with anions in the second coordination sphere, resulting in orange-coloured diamagnetic compounds.Anion-bridged distorted octahedrally coordinated Ni2+ ions probably occur in the compounds of formula Ni(Iz)2X2, in which Iz takes the axial positions. Similar structures are suggested for the mono-imidazole compounds, NiIzX2.

Die Kristallstruktur von Phosphortrichlorid bei –110 °C / The Crystal Structure of Phosphorus Trichloride at –110 °C

1979 ◽  
Vol 34 (7) ◽  
pp. 1035-1036 ◽  
Author(s):  
Hans Hartl ◽  
Michael Rama
Keyword(s):  
Crystal Structure ◽  
Structural Analysis ◽  
Low Temperature ◽  
Van Der Waals ◽  
Phosphorus Trichloride ◽  
X Ray ◽  
Bond Angles ◽  
Intermolecular Contacts ◽  
Van Der Waals Radii

Abstract A low temperature (-110°C) X-ray structural analysis of PCI3 yielded the bond distances P-Cl = 203.43(12) and 201.86(23) pm and bond angles Cl-P-Cl = 100.04(7)° and 100.19(7)°. The shortest intermolecular contacts P ··· Cl and Cl ···C1 are in the range of the sum of van der Waals-radii

Spektroskopische Untersuchungen zum Jahn-Teller-Effekt des Cu2+-Ions in Verbindungen vom Typ A2 CuL6, I / Spectroscopic Ivestigations with Respect to the Jahn-Teller-Effect of Cu(II) in Compounds of the Type A2CuL6, I

1974 ◽  
Vol 29 (5-6) ◽  
pp. 295-303 ◽  
Author(s):  
Claus Friebel
Keyword(s):  
Esr Spectra ◽  
Ligand Field ◽  
X Ray ◽  
Octahedral Sites ◽  
Structural Differences ◽  
Structure Determinations ◽  
Jahn Teller ◽  
Jahn Teller Effect ◽  
Ligand Field Spectra ◽  
Atomic Parameters

Structural relations between perovskite-related lattices of the type A2CuL6 and the perovskite compounds A2(12) [BCu](6)L6 (1: 1 order in the octahedral sites, elpasolite type) are demonstrated by two examples, the compounds A,Cu(OH)6 [A = Ba, Sr] and Ba2CuF6. From the ESR spectra a coupling of Jahn-Teller-distorted Cu-ligand-octahedra in these compounds corresponding to a “disturbed” type of antiferrodistortive order can be deduced. This result is in agreement with recent X-ray structure determinations. The ligand field spectra of the hydroxocuprates(II) indicate tetragonally elongated CuO6-octahedra with very long axial distances. From the ESR investigations further conclusions can be drawn concerning structural differences between the Ba- and the Sr-compound [Sr2Cu(OH6)], the atomic parameters of which are still unknown.

scholarly journals Influence of mechanical activation on synthesis of zinc metatitanate

2005 ◽  
Vol 37 (2) ◽  
pp. 115-122 ◽  
Author(s):  
Nebojsa Labus ◽  
Nina Obradovic ◽  
Tatjana Sreckovic ◽  
V. Mitic ◽  
Momcilo Ristic
Keyword(s):  
Electron Microscopy ◽  
Scanning Electron Microscopy ◽  
Low Temperature ◽  
Specific Surface ◽  
Mechanical Activation ◽  
Surface Area ◽  
Perovskite Structure ◽  
Mechanical Treatment ◽  
X Ray ◽  
Scanning Electron

Investigations of a ZnO-TiO2 binary oxide mixture during mechanical treatment were mainly focused on obtaining orthotitanate Zn2TiO4 with a spinel structure. Due to the specific way of energy transfer during mechanical treatment using a high-energy ball mill, the system passes through low temperature ZnTiO3 metatitanate phase formation. Mechanical activation was performed on an equimolar ratio mixture of ZnO and TiO2. The anatase phase was previously submitted to heat treatment for achieving a starting mixture rich in a rutile phase. Milling conditions were preset for observing the formation of a low temperature ZnTiO3 phase with a perovskite structure. The powder microstructure was characterized using scanning electron microscopy. A nitrogen gas sorption analyzer with the BET method was used to determine the specific surface area and porosity, indicating changes of powder sample properties during mechanical activation. Also, X ray powder diffractometry was applied to obtain the phase composition. Powders were then pressed into pellets and their compressibility was observed through density changes. According to microstructures obtained by scanning electron microscopy analysis, the system underwent a primary and secondary agglomeration process. Specific surface area measurements supported that conclusion. Compressibility investigations established the difference between compressibility of the non-activated mixture and activated powders. X-ray diffraction analysis revealed that a perovskite structure forms simultaneously with a spinel phase during the process of mechanical activation.

X-Ray Studies of Low-Temperature Polybutadiene and Butadiene-Styrene Copolymers

1949 ◽  
Vol 22 (2) ◽  
pp. 356-369 ◽  
Author(s):  
Karl E. Beu ◽  
W. B. Reynolds ◽  
C. F. Fryling ◽  
H. L. McMurry
Keyword(s):  
Molecular Weight ◽  
Low Temperature ◽  
Polymer Chains ◽  
Polymerization Temperature ◽  
X Ray ◽  
Styrene Copolymers ◽  
Emulsion Polymerizations ◽  
Diffraction Patterns ◽  
Ray Patterns ◽  
Butadiene Styrene

Abstract Although it is now generally recognized that the temperature of polymerization affects profoundly the properties of emulsion elastomers, there is very little evidence available pertaining to the cause of the variations of properties. It is felt by some that the improved properties of low-temperature elastomers can be related to variations in molecular weight and molecular-weight distribution. In this laboratory, however, the opinion has prevailed that the lower emulsion polymerization temperatures appreciably alter the fine structure of the molecules with an increase in the regularity of the polymer chains. If there were actually less branching and cross-linking in low-temperature polymers, and less 1,2-addition to monomer components, the increased order should be evident from x-ray diffraction patterns. To provide information on the above questions, x-ray studies were made with four purposes in view: (1) to determine the effect of polymerization temperature on the crystallization properties of unstretched and stretched polybutadienes; (2) to determine the influence of styrene content on the crystallization of butadiene-styrene copolymers; (3) to study some effects of compounding and vulcanization on crystallizable polybutadiene; and (4) to use the preferred orientation patterns obtained from some of these polymers for structural evaluations. To accomplish these objectives, x-ray patterns were obtained at several temperatures of some unstretched and stretched polybutadiene polymers, butadiene-styrene copolymers, and a vulcanized and compounded polybutadiene. The polybutadienes were prepared by emulsion polymerizations at 55°, 40°, 30°, 20°, 5°, −10° and −20° C. Since the −20° C polybutadiene showed the most marked crystallization patterns, the effects of compounding and of styrene addition were studied, using polymers prepared at this temperature for comparison. Three butadiene-styrene copolymers containing, respectively, 10, 20, and 30 per cent styrene in the monomer charge and one vulcanized polybutadiene compounded with Wyex carbon black were studied.

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