TEM of twinning in alpha and beta phase plutonium

1990 ◽  
Vol 48 (4) ◽  
pp. 1014-1015
Author(s):  
T. G. Zocco ◽  
R. I. Sheldon ◽  
H. F. Rizzo
Keyword(s):  
Crystal Structure ◽  
Beta Phase ◽  
Alpha Phase ◽  
Unit Cell ◽  
Phase Identification ◽  
Orientation Relationships ◽  
Monoclinic Crystal ◽  
Space Group ◽  
Monoclinic Crystal Structure ◽  
Β Phase

Twinning in α and β phase Pu has been studied by Transmission Electron Microscopy (TEM) to experimentally determine active twinning systems in this complex metal. Twinning in alpha phase Pu was studied in 2 specimens including a triode sputter deposited film, and a partially transformed (α+δ phase) Pu nominally lwt% Ga alloy. A thick film of metastable beta phase was also obtained by triode sputter deposition. Phase identification of all samples was determined from x-ray diffraction patterns. Alpha phase has a monoclinic crystal structure with 16 atoms per unit cell and a P21/m space group. Beta phase has a body-centered monoclinic crystal structure with 34 atoms per unit cell and an I2/m space group.Parent/twin orientation relationships were determined by electron diffraction pattern analysis, stereographic projection analysis and fundamental crystallographic calculations.A computer program was also developed to search for all possible twinning systems in α Pu.

Electron density, disorder and polymorphism: high-resolution diffraction studies of the highly polymorphic neuralgic drug carbamazepine

2016 ◽  
Vol 72 (1) ◽  
pp. 39-50 ◽  
Author(s):  
Ioana Sovago ◽  
Matthias J. Gutmann ◽  
Hans Martin Senn ◽  
Lynne H. Thomas ◽  
Chick C. Wilson ◽  
...  
Keyword(s):  
Crystal Structure ◽  
High Resolution ◽  
Diffraction Data ◽  
Structural Formula ◽  
Orthorhombic Crystal ◽  
Monoclinic Crystal ◽  
Orthorhombic Crystal Structure ◽  
Space Group ◽  
X Ray ◽  
Monoclinic Crystal Structure

Analysis of neutron and high-resolution X-ray diffraction data on form (III) of carbamazepine at 100 K using the atoms in molecules (AIM) topological approach afforded excellent agreement between the experimental results and theoretical densities from the optimized gas-phase structure and from multipole modelling of static theoretical structure factors. The charge density analysis provides experimental confirmation of the partially localized π-bonding suggested by the conventional structural formula, but the evidence for any significant C—N π bonding is not strong. Hirshfeld atom refinement (HAR) gives H atom positional and anisotropic displacement parameters that agree very well with the neutron parameters. X-ray and neutron diffraction data on the dihydrate of carbemazepine strongly indicate a disordered orthorhombic crystal structure in the space groupCmca, rather than a monoclinic crystal structure in space groupP21/c. This disorder in the dihydrate structure has implications for both experimental and theoretical studies of polymorphism.

Crystal structure of Cu3(AsO4)2

1968 ◽  
Vol 46 (6) ◽  
pp. 917-927 ◽  
Author(s):  
Sandra J. Poulsen ◽  
C. Calvo
Keyword(s):  
Crystal Structure ◽  
Oxygen Atom ◽  
Bond Distance ◽  
Unit Cell ◽  
Monoclinic Crystal ◽  
Space Group ◽  
Bond Lengths ◽  
Oxygen Distance ◽  
Atom Bond ◽  
Oxygen Atoms

Cu3(AsO4)2 forms a monoclinic crystal with lattice parameters a = 6.327(5) Å, b = 8.642(5) Å, c = 11.313(5) Å, β = 92.04(4)°, and Z = 4. The space group is P21/c. The two orthoarsenate anions in the unit cell have average AsO bond lengths of 1.68 Å and 1.70 Å with mean deviations of 0.02 Å and 0.01 Å respectively. The three cations are fivefold coordinated to oxygen atoms with mean cation oxygen atom bond lengths of 2.005 Å, 2.053 Å, and 2.017 Å for the three independent cations. The range of bond distances extends from 1.892 Å to 2.362 Å. Only one additional cation oxygen distance of less than 3 Å occurs and this lies at 2.76 Å. The cation polyhedra form sheets parallel to the ab plane by corner and edge sharing of common oxygen atoms. Adjacent sheets are bonded through the long Cu—O bond distance cited above and by the AsO43− anions. Each of the arsenic atoms shares three oxygen atoms with one sheet and one with the adjacent one.

scholarly journals The luminescence properties of yttria based phosphors and study of YBO3 formation via H3BO3 addition

2018 ◽  
Vol 12 (3) ◽  
pp. 262-267 ◽  
Author(s):  
Seyed Rafiaei
Keyword(s):  
Crystal Structure ◽  
Solid State ◽  
Boric Acid ◽  
Luminescence Properties ◽  
Monoclinic Crystal ◽  
Solid State Method ◽  
Space Group ◽  
Monoclinic Crystal Structure ◽  
State Method ◽  
Nano Phosphor

In this paper, Y2O3:Eu3+ nano-phosphor was synthesized through the facile solid-state method and influence of H3BO3 addition to the prepared Y2O3:Eu3+ powder was investigated. The consumption of boric acid resulted in the formation of YBO3 by changing the crystal structure from cubic to hexagonal. Noteworthy, through the use of specific quantities of H3BO3 (medium amount), Y3BO6 impurity with the monoclinic crystal structure and the space group C2/m was formed. FESEM observations showed that the addition of H3BO3 leads to the coarsening of the synthesized particles; changing from approximately 80 nm to 1 ?m. Also, it was concluded that the transformation of the crystal structure causes a dramatic change of phosphor emission colours from reddish to orange.

scholarly journals Luminescent properties of Eu-doped magnetic Na3FeF6

RSC Advances ◽  
2018 ◽  
Vol 8 (67) ◽  
pp. 38410-38415 ◽  
Author(s):  
Hong Jia ◽  
Yiping Zhou ◽  
Xiaoyan Wang ◽  
Weiying Zhang ◽  
Xun Feng ◽  
...  
Keyword(s):  
Crystal Structure ◽  
Luminescent Properties ◽  
Monoclinic Crystal ◽  
Space Group ◽  
Iron Fluoride ◽  
Structure Space ◽  
Monoclinic Crystal Structure

Sodium iron fluoride (Na3FeF6) is a colorless ferromagnetic fluoride with a monoclinic crystal structure (space group P21/c), and it is expected to be an ideal platform for exploring magneto-optical interactions.

Diaquaiodidotetrasarcosinepotassium: an overview of sarcosine metal halogenide structures

2012 ◽  
Vol 69 (1) ◽  
pp. 11-16 ◽  
Author(s):  
Michel Fleck ◽  
Vahram V. Ghazaryan ◽  
Aram M. Petrosyan
Keyword(s):  
Crystal Structure ◽  
Water Molecule ◽  
Potassium Iodide ◽  
Monoclinic Crystal ◽  
Space Group ◽  
Short Overview ◽  
Monoclinic Crystal Structure

The monoclinic crystal structure of tetrasarcosine potassium iodide dihydrate {orcatena-poly[[potassium-tetra-μ-sarcosine-κ4O:O′;κ4O:O] iodide dihydrate]}, {[K(C3H7NO2)4]I·2H2O}nor Sar4·KI·2H2O (space groupC2/c), comprises two crystallographically different sarcosine molecules and one water molecule on general positions, and one K+cation and one I−anion located on twofold axes. The irregular eight-coordinated K+polyhedra are connected into infinite chains along [001]viasarcosine molecules. This compound is the first sarcosine metal halogenide salt with a 4:1 ratio. A short overview of other sarcosine metal halogenide salts is presented and relationships to similar glycine salts are discussed.

scholarly journals Crystal Structures of New Ivermectin Pseudopolymorphs

Crystals ◽  
2021 ◽  
Vol 11 (2) ◽  
pp. 172
Author(s):  
Kirill Shubin ◽  
Agris Bērziņš ◽  
Sergey Belyakov
Keyword(s):  
Crystal Structure ◽  
Molecular Conformation ◽  
Methyl Tert Butyl Ether ◽  
Minor Role ◽  
Scanning Calorimetry ◽  
Orthorhombic Crystal ◽  
Monoclinic Crystal ◽  
Orthorhombic Crystal Structure ◽  
Space Group ◽  
Structure Space

New pseudopolymorphs of ivermectin (IVM), a potential anti-COVID-19 drug, were prepared. The crystal structure for three pseudopolymorphic crystalline forms of IVM has been determined using single-crystal X-ray crystallographic analysis. The molecular conformation of IVM in crystals has been compared with the conformation of isolated molecules modeled by DFT calculations. In a solvent with relatively small molecules (ethanol), IVM forms monoclinic crystal structure (space group I2), which contains two types of voids. When crystallized from solvents with larger molecules, like γ-valerolactone (GVL) and methyl tert-butyl ether (MTBE), IVM forms orthorhombic crystal structure (space group P212121). Calculations of the lattice energy indicate that interactions between IVM and solvents play a minor role; the main contribution to energy is made by the interactions between the molecules of IVM itself, which form a framework in the crystal structure. Interactions between IVM and molecules of solvents were evaluated using Hirshfeld surface analysis. Thermal analysis of the new pseudopolymorphs of IVM was performed by differential scanning calorimetry and thermogravimetric analysis.

NQR and Crystal Structure of 4,5-Dichloroimidazole, C3H2N2Cl2

1992 ◽  
Vol 47 (1-2) ◽  
pp. 177-181 ◽  
Author(s):  
Shi-Qi Dou ◽  
Alarich Weiss
Keyword(s):  
Crystal Structure ◽  
Phase Transition ◽  
Temperature Dependence ◽  
Room Temperature ◽  
Unit Cell ◽  
Space Group ◽  
Temperature Range ◽  
Temperature Coefficients ◽  
Group D

AbstractThe two line 35Cl NQR spectrum of 4,5-dichloroimidazole was measured in the temperature range 77≦ T/K ≦ 389. The temperature dependence of the NQR frequencies conforms with the Bayer model and no phase transition is indicated in the curves v ( 35Cl)= f(T). Also the temperature coefficients of the 35Cl NQR frequencies are "normal". At 77 K the 35Cl NQR frequencies are 37.409 MHz and 36.172 MHz and at 389 K 35.758 MHz and 34.565 MHz. The compound crystallizes at room temperature with the tetragonal space group D44-P41212, Z = 8 molecules per unit cell; at 295 K : a = 684.2(5) pm, c = 2414.0(20) pm. The relations between the crystal structure and the NQR spectrum are discussed.

Primäre und sekundäre Ethyl-und i-Propylsulfoniumsalze sowie Kristallstruktur von i-C3H7SH2+SbF6- [1]

1996 ◽  
Vol 51 (2) ◽  
pp. 277-285
Author(s):  
Rolf Minkwitz ◽  
Ulrike Lohmann ◽  
Hans Preut
Keyword(s):  
Crystal Structure ◽  
Structure Analysis ◽  
Bond Distance ◽  
Crystal Structure Analysis ◽  
Unit Cell ◽  
Monoclinic Space Group ◽  
Spectroscopic Methods ◽  
Sulfonium Salt ◽  
Space Group

Abstract The synthesis of salts of the type RnSH3-n+MF6- (R = C2H5, i-C3H7; n = 1, 2; M = As, Sb) by protonation of the corresponding thiols and sulfides in the superacid systems HF/MF5 is reported. The salts have been characterized by vibrational and NMR spectroscopic methods. Isopropylsulfonium hexafluoroantimonate is the first known example of a sulfonium salt, for which a SH bond distance has been determined by a crystal structure analysis, i-C3H7SH2+SbF6- crystallizes in the monoclinic space group P21/m with a = 568.0(4), b = 801.1(6), c = 1019.7(8) pm, β = 82.63(6) °, with two formula units per unit cell.

Methansulfinylchlorid-Lewissäure-Addukte CH3S(Cl)OMF5 (M = As, Sb) und Kristallstruktur von CH3S(Cl)OSbCl5 [1] / Methanesulfinylchloride Lewis Acid Adducts CH3S(Cl)OMF5 (M = As, Sb) and Crystal Structure of CH3S(Cl)OSbCl5 [1]

1996 ◽  
Vol 51 (1) ◽  
pp. 133-138 ◽  
Author(s):  
Rolf Minkwitz ◽  
Ulrike Lohmann ◽  
Hans Preut
Keyword(s):  
Crystal Structure ◽  
Nmr Spectroscopy ◽  
Lewis Acid ◽  
Unit Cell ◽  
Monoclinic Space Group ◽  
Space Group ◽  
New Compounds ◽  
Lewis Acid Adducts

Abstract CH3S(0)C1 reacts in HF as solvent with MF5 (M = As, Sb) to give products CH3S(Cl)OMF5 (M = As, Sb). The new compounds are stable below 253 K and were charac­ terized by Raman and NMR spectroscopy.In addition, the crystal structure of CH3S(Cl)OSbCl5 has been determinated. The complex crystallizes in the monoclinic space group P21/n with a = 644.3(5), b = 1905.9(14), c = 900.0(7) pm, β = 99.27(6)° with four formula units per unit cell.

Über die Kristallstruktur von KSc2 F7 / The Crystal Structure of KSc2 F7

1985 ◽  
Vol 40 (6) ◽  
pp. 726-729 ◽  
Author(s):  
Klaus Güde ◽  
Christoph Hebecker
Keyword(s):  
Crystal Structure ◽  
Single Crystals ◽  
Unit Cell ◽  
Space Group ◽  
X Ray ◽  
Monoclinic Unit Cell ◽  
R Value ◽  
Ray Methods

Abstract Single crystals of KSc2F7 have been prepared from a mixture of KF and ScF3 . The samples were investigated by X-ray methods. KSc2F7 crystallizes orthorhombically with a = 10.643(2), b = 6.540(1), c = 4.030(1) Å. These data indicate a close crystallographic connection to the monoclinic unit cell of KIn2F7 [1], But in contrast to KIn2F7 , KSc2 F7 crystallizes in space group No. 65. Cmmm - D192h. The R-value for 341 observed independent reflections is 0.060.

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