Chemical bonding in energetic materials: β-NTO

2001 ◽  
Vol 57 (3) ◽  
pp. 359-365 ◽  
Author(s):  
Elizabeth A. Zhurova ◽  
A. Alan Pinkerton
Keyword(s):  
Dipole Moment ◽  
Low Temperature ◽  
Electron Density ◽  
Chemical Bonding ◽  
Energetic Materials ◽  
Diffraction Experiment ◽  
X Ray Diffraction ◽  
Acta Cryst ◽  
Molecular Dipole ◽  
X Ray

The electron density and related properties of the quasi-stable β form of 5-nitro-2,4-dihydro-3H-1,2,4-triazol-3-one (NTO; space group P21/c) have been determined from a low-temperature [100 (1) K] X-ray diffraction experiment. Intensities were measured with a 2K CCD Bruker diffractometer using Ag Kα radiation. Two detector settings, several φ settings, 0.3° ω scans and 160 s exposure time per frame gave R int = 0.0215 for 68 989 (4080 unique) reflections and (sin θ/λ)max = 1.23 Å−1. The Hansen–Coppens [Acta Cryst. (1978), A34, 909–921] multipole model as implemented in the XD program gave R = 0.0333 (all reflections), which allowed calculation of the electron density, Laplacian and electrostatic potential distributions. The bonding (3,−1) critical points and the molecular dipole moment of 3.2 (1) D were also obtained. Chemical bonding in the molecule is discussed.

Silicate-germanate K2Y[(Si3Ge)O10(OH)] with unusual complex corrugated layer and its correlation to ring silicate gerenite and chain silicate chkalovite

2020 ◽  
Vol 235 (4-5) ◽  
pp. 167-172
Author(s):  
Anastasiia P. Topnikova ◽  
Elena L. Belokoneva ◽  
Olga V. Dimitrova ◽  
Anatoly S. Volkov ◽  
Leokadiya V. Zorina
Keyword(s):  
Low Temperature ◽  
Cross Section ◽  
Complex Anion ◽  
Diffraction Experiment ◽  
X Ray Diffraction ◽  
Unit Cell Parameters ◽  
X Ray ◽  
Cell Parameters ◽  
Chain Silicate ◽  
Novel Complex

AbstractA new silicate-germanate K2Y[(Si3Ge)O10(OH)] was synthesized hydrothermally in a system Y2O3:GeO2:SiO2 = 1:1:2 (T = 280 °C; P = 90–100 atm.); K2CO3 was added to the solution as a mineralizer. Single-crystal X-ray diffraction experiment was carried out at low temperature (150 K). The unit cell parameters are a = 10.4975(4), b = 6.9567(2), c = 15.4001(6) Å, β = 104.894(4)°; V = 1086.86(7) Å3; space group is P 21/c. A novel complex anion is presented by corrugated (Si,Ge) tetrahedral layers connected by couples of YO6 octahedra into the mixed microporous framework with the channels along b and a axes, the maximal size of cross-section is ~5.6 Å. This structure has similarity with the two minerals: ring silicate gerenite (Ca,Na)2(Y,REE)3Si6O18 · 2H2O and chain silicate chkalovite Na2BeSi2O6. Six-member rings with 1̅ symmetry as in gerenite are distinguished in the new layer. They are mutually perpendicular to each other and connected by additional tetrahedra. Straight crossing chains in chkalovite change to zigzag four-link chains in the new silicate-germanate layer.

scholarly journals Topology of the Electron Density and of Its Laplacian from Periodic LCAO Calculations on f-Electron Materials: The Case of Cesium Uranyl Chloride

Molecules ◽  
2021 ◽  
Vol 26 (14) ◽  
pp. 4227
Author(s):  
Alessandro Cossard ◽  
Silvia Casassa ◽  
Carlo Gatti ◽  
Jacques K. Desmarais ◽  
Alessandro Erba
Keyword(s):  
Electron Density ◽  
Chemical Bonding ◽  
Topological Analysis ◽  
Theoretical Description ◽  
Basis Functions ◽  
Quantum Mechanical ◽  
X Ray Diffraction ◽  
X Ray ◽  
Atomic Orbitals ◽  
Uranyl Chloride

The chemistry of f-electrons in lanthanide and actinide materials is yet to be fully rationalized. Quantum-mechanical simulations can provide useful complementary insight to that obtained from experiments. The quantum theory of atoms in molecules and crystals (QTAIMAC), through thorough topological analysis of the electron density (often complemented by that of its Laplacian) constitutes a general and robust theoretical framework to analyze chemical bonding features from a computed wave function. Here, we present the extension of the Topond module (previously limited to work in terms of s-, p- and d-type basis functions only) of the Crystal program to f- and g-type basis functions within the linear combination of atomic orbitals (LCAO) approach. This allows for an effective QTAIMAC analysis of chemical bonding of lanthanide and actinide materials. The new implemented algorithms are applied to the analysis of the spatial distribution of the electron density and its Laplacian of the cesium uranyl chloride, Cs2UO2Cl4, crystal. Discrepancies between the present theoretical description of chemical bonding and that obtained from a previously reconstructed electron density by experimental X-ray diffraction are illustrated and discussed.

Multipole electron densities and atomic displacement parameters in urea from accurate powder X-ray diffraction

2019 ◽  
Vol 75 (4) ◽  
pp. 600-609 ◽  
Author(s):  
Bjarke Svane ◽  
Kasper Tolborg ◽  
Lasse Rabøl Jørgensen ◽  
Martin Roelsgaard ◽  
Mads Ry Vogel Jørgensen ◽  
...  
Keyword(s):  
Electron Density ◽  
Molecular System ◽  
Atomic Displacement ◽  
High Symmetry ◽  
X Ray Diffraction ◽  
High Quality ◽  
Acta Cryst ◽  
X Ray ◽  
Density Determination ◽  
Structure Factors

Electron density determination based on structure factors obtained through powder X-ray diffraction has so far been limited to high-symmetry inorganic solids. This limit is challenged by determining high-quality structure factors for crystalline urea using a bespoke vacuum diffractometer with imaging plates. This allows the collection of data of sufficient quality to model the electron density of a molecular system using the multipole method. The structure factors, refined parameters as well as chemical bonding features are compared with results from the high-quality synchrotron single-crystal study by Birkedalet al.[Acta Cryst.(2004), A60, 371–381] demonstrating that powder X-ray diffraction potentially provides a viable alternative for electron density determination in simple molecular crystals where high-quality single crystals are not available.

Charge Densities and Electrostatic Potentials for Energetic Materials

1995 ◽  
Vol 418 ◽  
Author(s):  
A. A. Pinkerton ◽  
A. Martin
Keyword(s):  
High Resolution ◽  
Low Temperature ◽  
Diffraction Data ◽  
Energetic Materials ◽  
X Ray Diffraction ◽  
X Ray ◽  
Charge Densities ◽  
Contour Maps ◽  
Deformation Density ◽  
Dinitramide Salts

AbstractHigh resolution (sinθ/λ < 1.34 Å−1), low temperature (85 K) X-ray diffraction data has been used to map the deformation density and the derived electrostatic potential for three dinitramide salts. The traditional presentation of contour maps has been replaced with 3D views of the molecule. A comparison of the dinitramide ions from each salt is presented.

scholarly journals In situlaser irradiation setup for a Bruker three-circle goniometer

2017 ◽  
Vol 50 (5) ◽  
pp. 1556-1558
Author(s):  
Dmitry S. Yufit
Keyword(s):  
Low Temperature ◽  
Single Crystals ◽  
Laser Irradiation ◽  
Diffraction Experiment ◽  
X Ray Diffraction ◽  
X Ray

A new design of a setup forin situlaser irradiation of single crystals during an X-ray diffraction experiment is presented. The system is designed for use with a Bruker three-circle goniometer in combination with a Helix ultra-low-temperature cryostat and consists of a laser mount and a set of three adjustable mirrors. The main advantages of the presented system include a stationary laser mount, the ability to irradiate a sample inside the Be nozzle and no impediments to the goniometer movements.

On the errors in molecular dipole moments derived from accurate diffraction data

1999 ◽  
Vol 55 (5) ◽  
pp. 965-967 ◽  
Author(s):  
Philip Coppens ◽  
Anatoliy Volkov ◽  
Yuriy Abramov ◽  
Tibor Koritsanszky
Keyword(s):  
Dipole Moment ◽  
Diffraction Data ◽  
Dipole Moments ◽  
Molecular Ions ◽  
X Ray Diffraction ◽  
Molecular Dipole ◽  
X Ray ◽  
Molecular Dipole Moment ◽  
Error Treatment ◽  
Additional Constraints

The error in the molecular dipole moment as derived from accurate X-ray diffraction data is shown to be origin dependent in the general case. It is independent of the choice of origin if an electroneutrality constraint is introduced, even when additional constraints are applied to the monopole populations. If a constraint is not applied to individual moieties, as is appropriate for multicomponent crystals or crystals containing molecular ions, the geometric center of the entity considered is a suitable choice of origin for the error treatment.

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