scholarly journals Crystal structure of vyacheslavite, U(PO4)(OH), solved from natural nanocrystal: a precession electron diffraction tomography (PEDT) study and DFT calculations

RSC Advances ◽  
2019 ◽  
Vol 9 (34) ◽  
pp. 19657-19661 ◽  
Author(s):  
Gwladys Steciuk ◽  
Seyedayat Ghazisaeed ◽  
Boris Kiefer ◽  
Jakub Plášil
Keyword(s):  
Crystal Structure ◽  
Density Functional Theory ◽  
Electron Diffraction ◽  
Dft Calculations ◽  
Density Functional ◽  
Diffraction Tomography ◽  
Functional Theory ◽  
Phosphate Mineral ◽  
Precession Electron Diffraction ◽  
Nano Crystal

The crystal structure of the U(iv)-phosphate mineral vyacheslavite has been solved from precession electron diffraction tomography (PEDT) data from the natural nano-crystal and further refined using density-functional theory (DFT) calculations.

Synthesis, characterization, crystal structure and density functional theory (DFT) calculations of dioxomolybdenum (VI) complexes of an ONS donor ligand derived from benzoylacetone and S-benzyl dithiocarbazate

Polyhedron ◽  
2013 ◽  
Vol 50 (1) ◽  
pp. 602-611 ◽  
Author(s):  
Manashi Chakraborty ◽  
Sathi Roychowdhury ◽  
Nikhil Ranjan Pramanik ◽  
Tapas Kumar Raychaudhuri ◽  
Tapan Kumar Mondal ◽  
...  
Keyword(s):  
Crystal Structure ◽  
Density Functional Theory ◽  
Dft Calculations ◽  
Density Functional ◽  
Functional Theory ◽  
Donor Ligand

The crystal structure of MoO2(O2)H2O

2018 ◽  
Vol 33 (1) ◽  
pp. 49-54 ◽  
Author(s):  
Joel W. Reid ◽  
James A. Kaduk ◽  
Lidia Matei
Keyword(s):  
Crystal Structure ◽  
Density Functional Theory ◽  
Dft Calculations ◽  
Software Package ◽  
Density Functional ◽  
Powder Diffraction Data ◽  
Functional Theory ◽  
Synchrotron Powder Diffraction ◽  
Monoclinic Lattice ◽  
Strong Agreement

The crystal structure of MoO2(O2)H2O has been solved by analogy with the WO2(O2)H2O structure and refined with synchrotron powder diffraction data obtained from beamline 08B1-1 at the Canadian Light Source. Rietveld refinement, performed with the software package GSAS, yielded monoclinic lattice parameters of a = 12.0417(4) Å, b = 3.87003(14) Å, c = 7.38390(24) Å, and β = 78.0843(11)° (Z = 4, space group P21/n). The structure is composed of double zigzag molybdate chains running parallel to the b-axis. The Rietveld refined structure was compared with density functional theory (DFT) calculations performed with CRYSTAL14, and show strong agreement with the DFT optimized structure.

Natural occurrence of monoclinic Fe3S4 nano-precipitates in pyrrhotite from the Sudbury ore deposit: a Z-contrast imaging and density functional theory study

2015 ◽  
Vol 79 (2) ◽  
pp. 377-385 ◽  
Author(s):  
Huifang Xu ◽  
Zhizhang Shen ◽  
Hiromi Konishi
Keyword(s):  
Crystal Structure ◽  
Density Functional Theory ◽  
Density Functional ◽  
Natural Occurrence ◽  
Contrast Imaging ◽  
Functional Theory ◽  
Ore Deposit ◽  
Monoclinic Form ◽  
Nano Crystal ◽  
Z Contrast

AbstractA monoclinic form of Fe3S4, a polymorph of cubic greigite, occurs as precipitates in a sample of pyrrhotite collected from the Sudbury ore deposit. The nano-crystal precipitates are in a topotaxial relationship with the host pyrrhotite-4C (Fe7S8). The precipitate and the host pyrrhotite have a coherent (001) interface. Half of the octahedral layers in the crystal structure are fully occupied by Fe, while the other half of the octahedral layers are occupied by Fe atoms and vacancies in an ordered manner along the a axis. The crystal structure of the Fe3S4 nano-precipitates has monoclinic symmetry with a space group of I2/m. Its c dimension is 6% smaller than that of the host pyrrhotite due to the large number of vacancies in the structure. Fractional coordinates for S and Fe atoms within the unit cell are determined from Z-contrast images and density functional theory (DFT). The calculated results match the measured values very well. It is proposed that the monoclinic Fe3S4 nano-precipitates formed through ordering of vacancies in pyrrhotite with a low Fe/S ratio (i.e. <0.875) at low temperature.

scholarly journals Crystal structure determination of karibibite, an Fe3+ arsenite, using electron diffraction tomography

2017 ◽  
Vol 81 (5) ◽  
pp. 1191-1202 ◽  
Author(s):  
Fernando Colombo ◽  
Enrico Mugnaioli ◽  
Oriol Vallcorba ◽  
Alberto García ◽  
Alejandro R. Goñi ◽  
...  
Keyword(s):  
Crystal Structure ◽  
Electron Diffraction ◽  
Dft Calculations ◽  
Density Functional ◽  
Weak Interactions ◽  
Diffraction Tomography ◽  
X Ray Diffraction ◽  
Orthorhombic Space Group ◽  
X Ray ◽  
Cell Parameters

AbstractThe crystal structure of karibibite, Fe33+(As3+O2)4(As23+O5)(OH), from the Urucum mine (Minas Gerais, Brazil), was solved and refined from electron diffraction tomography data [R1 = 18.8% for F > 4σ(F)] and further confirmed by synchrotron X-ray diffraction and density functional theory (DFT) calculations. The mineral is orthorhombic, space group Pnma and unit-cell parameters (synchrotron X-ray diffraction) are a = 7.2558(3), b = 27.992(1), c = 6.5243 (3) Å, V = 1325.10(8) Å3, Z = 4. The crystal structure of karibibbite consists of bands of Fe3+O6 octahedra running along a framed by two chains of AsO3 trigonal pyramids at each side, and along c by As2O5 dimers above and below. Each band is composed of ribbons of three edge-sharing Fe3+O6 octahedra, apex-connected with other ribbons in order to form a kinked band running along a. The atoms As(2) and As(3), each showing trigonal pyramidal coordination by O, share the O(4) atom to form a dimer. In turn, dimers are connected by the O(3) atoms, defining a zig-zag chain of overall (As3+O2)n-n stoichiometry. Each ribbon of (Fe3+O6) octahedra is flanked on both edges by the (As3+O2)n-n chains. The simultaneous presence of arsenite chains and dimers is previously unknown in compounds with As3+. The lone-electron pairs (4s2) of the As(2) and As(3) atoms project into the interlayer located at y = 0 and y = ½, yielding probable weak interactions with the O atoms of the facing (AsO2) chain.The DFT calculations show that the Fe atoms have maximum spin polarization, consistent with the Fe3+ state.

scholarly journals Substituent Effects in 3,3’ Bipyrazole Derivatives. X-ray Crystal Structures, Molecular Properties and DFT Analysis

2021 ◽  
Vol 68 (3) ◽  
pp. 718-727
Author(s):  
Ibrahim Bouabdallah ◽  
Tarik Harit ◽  
Mahmoud Rahal ◽  
Fouad Malek ◽  
Monique Tillard ◽  
...  
Keyword(s):  
Crystal Structure ◽  
Density Functional Theory ◽  
Solid State ◽  
Dft Calculations ◽  
Single Crystal ◽  
Crystal Structures ◽  
Density Functional ◽  
Substituent Effects ◽  
Functional Theory ◽  
X Ray

The single crystal X-ray structure of new 1,1’-bis(2-nitrophenyl)-5,5’-diisopropyl-3,3’-bipyrazole, 1, is triclinic P I–, a = 7.7113(8), b = 12.3926(14), c = 12.9886(12) Å, α = 92.008(8), β = 102.251(8), γ = 99.655(9)°. The structural arrangement is compared to that of 5,5’-diisopropyl-3,3’-bipyrazole, 5, whose single crystal structure is found tetragonal I41/a, a = b = 11.684(1), c = 19.158(1) Å. The comparison is also extended to the structures previously determined for 1,1’-bis(2-nitrophenyl)-5,5’-propyl-3,3’-bipyrazole, 2, 1,1’-bis(4-nitrophenyl)-5,5’-diisopropyl-3,3’-bipyrazole, 3, and 1,1’-bis(benzyl)-5,5’-diisopropyl-3,3’-bipyrazole, 4. Density Functional Theory (DFT) calculations are used to investigate the molecular geometries and to determine the global reactivity parameters. The geometry of isolated molecules and the molecular arrangements in the solid state are analyzed according to the nature of the groups connected to the bipyrazole core.

Structural analysis of metastable pharmaceutical loratadine form II, by 3D electron diffraction and DFT+D energy minimisation

CrystEngComm ◽  
2020 ◽  
Vol 22 (43) ◽  
pp. 7490-7499
Author(s):  
Grahame R. Woollam ◽  
Partha P. Das ◽  
Enrico Mugnaioli ◽  
Iryna Andrusenko ◽  
Athanassios S. Galanis ◽  
...  
Keyword(s):  
Crystal Structure ◽  
Density Functional Theory ◽  
Structural Analysis ◽  
Electron Diffraction ◽  
Density Functional ◽  
Ambient Conditions ◽  
Functional Theory ◽  
Energy Minimisation ◽  
3D Electron

Coupling 3D electron diffraction and density functional theory provided the metastable pharmaceutical crystal structure within nanometre range, under ambient conditions.

XRD Multi-Temperatures Study of N,N'-bis(2-Hydroxyethyl)Benzene-1,4-Dicarboxamide

2010 ◽  
Vol 163 ◽  
pp. 256-259
Author(s):  
Gabriela Bednarek ◽  
Maria Nowak ◽  
Joachim Kusz ◽  
Jerzy Ossowski
Keyword(s):  
Crystal Structure ◽  
Density Functional Theory ◽  
Dft Calculations ◽  
Chemical Reactions ◽  
Title Compound ◽  
Density Functional ◽  
Temperature Analysis ◽  
Functional Theory ◽  
X Ray ◽  
The Stability

N,N’ – bis – (2– hydroxy – ethylene) – terephthalamide (BHETA) has been obtained by aminolysis of polyethylene terephthalate (PET) using excess of monoethanoloamine and it has been physicochemically characterized [1]. In this paper there are shown the results of the multi-temperature X-ray measurement which were performed to provide information about the stability of the structure. Detailed temperature analysis of the crystal structure allows us to determine properties of the compound which is very important product of recycling PET wastes in order to use it for further chemical reactions. The structure of the title compound was also modelled by density functional theory (DFT) calculations.

scholarly journals Incorporation of Iron(II) and (III) in Hydroxyapatite—A Theoretical Study

Crystals ◽  
2021 ◽  
Vol 11 (10) ◽  
pp. 1219
Author(s):  
Olga Nikolaevna Makshakova ◽  
Daria Vladimirovna Shurtakova ◽  
Alexey Vladimirovich Vakhin ◽  
Peter Olegovich Grishin ◽  
Marat Revgerovich Gafurov
Keyword(s):  
Crystal Structure ◽  
Density Functional Theory ◽  
Dft Calculations ◽  
Potential Application ◽  
Density Functional ◽  
Theoretical Study ◽  
Charge Compensation ◽  
Comprehensive Analysis ◽  
Functional Theory ◽  
Experimental Works

Hydroxyapatite (Ca10(PO4)6(OH)2, HAp) doped with various transition metals has generated great interest in view of its potential application in a wide variety of fields, including in catalysis as a support with a series of attractive properties. Despite a large number of experimental works devoted to the synthesis and application of iron-substituted hydroxyapatites, problems concerning the location, introduced defects, and charge compensation schemes for Fe2+ and/or Fe3+ cations in the crystal structure of HAp remain unclear. This paper is devoted to the comprehensive analysis of iron (II) and (III) introduction into the HAp lattice by density functional theory (DFT) calculations. We show that the inclusion of Fe2+ in the Ca(1) and Ca(2) positions of HAp is energetically comparable. For the Fe3+, there is a clear preference to be included in the Ca(2) position. The inclusion of iron results in cell contraction, which is more pronounced in the case of Fe3+. In addition, Fe3+ may form a shorter linkage to oxygen atoms. The incorporation of both Fe2+ and Fe3+ leads to notable local reorganization in the HAp cell.

A revisit to the structure of Au20(SCH2CH2Ph)16: a cubic nanocrystal-like gold kernel

Nanoscale ◽  
2018 ◽  
Vol 10 (22) ◽  
pp. 10357-10364 ◽  
Author(s):  
Pu Wang ◽  
Xiangxiang Sun ◽  
Xia Liu ◽  
Lin Xiong ◽  
Zhongyun Ma ◽  
...  
Keyword(s):  
Crystal Structure ◽  
Density Functional Theory ◽  
Dft Calculations ◽  
Density Functional ◽  
Structural Form ◽  
Functional Theory ◽  
The Density Functional Theory ◽  
Total Energies

A new stable structural form of Au20(SR)16 cluster is theoretically predicted. The density functional theory (DFT) calculations with the inclusion of dispersion corrections indicated the nanocrystal-like isomer (Au20-Iso1) has comparable and even lower total energies compared to the non-fcc crystal structure of Au20(SPh-tBu)16.

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