Crystal Structure and Microstructure of Some La2/3-xLi3xTiO3Oxides:  An Example of the Complementary Use of Electron Diffraction and Microscopy and Synchrotron X-ray Diffraction To Study Complex Materials

2004 ◽  
Vol 126 (11) ◽  
pp. 3587-3596 ◽  
Author(s):  
Susana García-Martín ◽  
Miguel A. Alario-Franco ◽  
Helmut Ehrenberg ◽  
Juan Rodríguez-Carvajal ◽  
Ulises Amador
Keyword(s):  
Crystal Structure ◽  
Electron Diffraction ◽  
Complex Materials ◽  
X Ray Diffraction ◽  
X Ray ◽  
Structure And Microstructure

SU-79: a novel germanate with 3D 10- and 11-ring channels templated by a square-planar nickel complex

2014 ◽  
Vol 1 (3) ◽  
pp. 278-283 ◽  
Author(s):  
Shiliang Huang ◽  
Jie Su ◽  
Kirsten Christensen ◽  
A. Ken Inge ◽  
Jie Liang ◽  
...  
Keyword(s):  
Crystal Structure ◽  
Electron Diffraction ◽  
Single Crystal ◽  
Nickel Complex ◽  
X Ray Diffraction ◽  
X Ray ◽  
Open Framework ◽  
Square Planar

An open-framework germanate SU-79 was synthesized using nickel complex and amine as the templates. The crystal structure was solved by the combination of rotation electron diffraction (RED) and synchrotron single crystal X-ray diffraction.

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.

Crystal Structure of K6Nb44O113 from HREM

1990 ◽  
Vol 48 (1) ◽  
pp. 42-43
Author(s):  
F.H. Li ◽  
C.M. Teng ◽  
J.J. Hu ◽  
F. Nagata ◽  
C. Tsuruta
Keyword(s):  
Crystal Structure ◽  
Electron Diffraction ◽  
Crystal Size ◽  
Fold Axis ◽  
Structure Model ◽  
X Ray Diffraction ◽  
X Ray ◽  
Tetragonal System ◽  
Small Crystal Size ◽  
Different Shapes

Different results about the crystal structure of K6Nb44O113 (KNO) were obtained by X-ray diffraction analysis[1,2]. This might be due to the small crystal size and the impurity of crystalline powders. Such sample are suitable for HREM investigation. Teng et al. studied the crystal by electron diffraction and HREM[3]. They compared the image of KNO with the structure model of Rb3Nb54O146(RNO) proposed by Gatehouse et al.[4]. The latter’s structure which is formed by Nb-O octahedra belongs to the tetragonal system and contains tunnels of different shapes along the four-fold axis(Fig.1). An image of KNO given by Teng et al. shows four-leaf and three-leaf shaped bright dots whose arrangement is in agreement with that of heptagonal and hexagonal tunnels in the structure of RNO respectively. Although Teng et al. proposed that the crystal structure of KNO might also be formed by Nb-O octahedra and contains various tunnels as RNO, they concluded that the symmetry of KNO should be lower than that of RNO. In this abstract it is reported that the crystal structure of KNO is isomorphic to that of RNO as well as that of CsxNb54(O,F)146[5].

scholarly journals The crystal structure of parkinsonite, nominally Pb7MoO9Cl2: a naturally occurring Aurivillius phase

2010 ◽  
Vol 74 (2) ◽  
pp. 269-275 ◽  
Author(s):  
G. O. Lepore ◽  
M. D. Welch
Keyword(s):  
Crystal Structure ◽  
Electron Diffraction ◽  
X Ray Diffraction ◽  
Aurivillius Phase ◽  
X Ray ◽  
Cell Parameters ◽  
Naturally Occurring ◽  
Final Agreement ◽  
Fourfold Axis ◽  
Synthetic Crystal

AbstractThe crystal structure of the sheet oxychloride mineral parkinsonite, nominally Pb7MoO9Cl2, has been determined for synthetic and natural crystals of analysed compositions, (Pb7.28Mo0.72) O8.96Cl1.96 and (Pb7.23Mo0.40V0.37)O8.90Cl1.82, respectively. Parkinsonite is tetragonal, space group I4/mmm. Unit-cell parameters for synthetic and natural crystals are: asynthetic = 3.9773(4) Å, csynthetic = 22.718(4) Å, Vsynthetic = 359.38(5) Å3, and anatural = 3.9570(3) Å, cnatural = 22.634(5) Å, Vnatural = 354.40(5) Å3. Final agreement indices (R1, wR2) for refinements of the two crystals are 0.024, 0.067 (synthetic) and 0.036, 0.078 (natural). Although a superlattice has been identified by electron diffraction for crystals of both samples (Welch et al., 1996), only the substructure could be determined by X-ray diffraction. This X-ray invisibility of the superstructure has also been observed for the closely related sheet oxychlorides asisite and schwartzembergite, for both of which superstructure motifs have been identified by electron diffraction. The Pb(1) site of both parkinsonite crystals is fully occupied by Pb. Refinement of the Pb content of the Pb(2) site for the synthetic and natural crystals gives occupancies of 0.85(1) and 0.70(1) respectively, corresponding to 3.40 and 2.80 Pb(2) a.p.f.u. respectively. The substituent cation Mo (synthetic crystal) and [Mo+V] (natural crystal) was located at a distance of 0.5 Å from Pb(2), being displaced along the fourfold axis. The reduced occupancy of Pb(2) is due to substitution by Mo or [Mo+V]. No evidence for separate Mo and V sites in the substructure of natural parkinsonite was found. Refined occupancies of the Cl site are 0.84(4) and 0.91(5) for the synthetic and natural crystals, respectively, and are consistent with the 9:1 superstructure component identified by electron diffraction.

A Morophological and Crystal Structure Analysis of Particulate Rare Earth III Fluorides

1972 ◽  
Vol 30 ◽  
pp. 542-543
Author(s):  
Coy R. Morris
Keyword(s):  
Crystal Structure ◽  
Rare Earth ◽  
Structural Analysis ◽  
Electron Diffraction ◽  
Crystal Structure Analysis ◽  
X Ray Diffraction ◽  
Structural Units ◽  
X Ray ◽  
Lower Chamber ◽  
Rare Earth Trifluorides

Previous work in this area (oftedal-1929, Zalkin and Templeton-1952 ) using X-ray diffraction techniques assigned primitive structural units to the rare earth trifluorides of Lanthanum, Cerium, Praseodymium, Neodymium, Ytterbium and Samarium.The work of greatest interest in this investigation is that of Zalkin and Templeton. In their investigation they found that the 4f trifluorides from La to Nd are hexagonal while those from Sm to Lu are orthorhombic with SmF3 exhibiting a dual structure of both units, depending on the temperature of formation.Continuing the recent work of Barr, the structures of LaF3, NdF3, PrF3, SmF3 and YbF3 were investigated using lower chamber diffraction (LCD) which produced results appearing to conflict with the X-ray work of Zalkin and Templeton. To these authors knowledge there are no known publications dealing with the structural analysis of these five rare earth trifluorides other than the two papers cited. In addition, these works deal with X-ray determinations which, although complementary to electron diffraction, lack the microanalysis and limited innerplanar spacing analysis characteristic to ED.

scholarly journals The First Covalent Organic Framework solved by Rotation Electron Diffraction

2014 ◽  
Vol 70 (a1) ◽  
pp. C191-C191
Author(s):  
Jie Su ◽  
Yue-Biao Zhang ◽  
Yifeng Yun ◽  
Hiroyasu Furukawa ◽  
Felipe Gándara ◽  
...  
Keyword(s):  
Crystal Structure ◽  
Electron Diffraction ◽  
Single Crystal ◽  
Structure Determination ◽  
Software Package ◽  
Single Crystal Structure ◽  
X Ray Diffraction ◽  
X Ray ◽  
Molecular Arrangement

Covalent organic frameworks (COFs) represent an exciting new type of porous organic materials, which are constructed with organic building units via strong covalent bonds.[1] The structure determination of COFs is challenging, due to the difficulty in growing sufficiently large crystals suitable for single crystal X-ray diffraction, and low resolution and peak broadening for powder X-ray diffraction. Crystal structures of COFs are typically determined by modelling building with the aid of geometry principles in reticular chemistry and powder X-ray diffraction data. Here, we report the single-crystal structure of a new COF (COF-320) determined by 3D rotation electron diffraction (RED),[2] a technique applied in this context for the first time. The RED method can collect an almost complete three-dimensional electron diffraction dataset, and is a useful technique for structure determination of micron- and nanosized single crystals. To minimize electron beam damage, the RED dataset was collected at 89 K. 3D reciprocal lattice of COF-320 was reconstructed from the ED frames using the RED – data processing software[2]. As the resolution of the RED data only reached 1.6 Å, the simulated annealing parallel tempering algorithm in the FOX software package [3] was used to find a starting molecular arrangement from the 3D RED data. Finally, the crystal structure of COF-320 was solved in the space group of I-42d and refined using the SHELXL software package. The single-crystal structure of COF-320 exhibits a 3D extended framework by linking the tetrahedral organic building blocks and biphenyl linkers through imine-bonds forming a highly porous 9-fold interwoven diamond net.

Crystal structure and microstructure of synthetic hexagonal magnesium–cobalt cordierite solid solutions (Mg2−2xCo2xAl4Si5O18)

2013 ◽  
Vol 69 (2) ◽  
pp. 110-121 ◽  
Author(s):  
Francisco Javier Serrano ◽  
Noemí Montoya ◽  
José Luis Pizarro ◽  
María Mercedes Reventós ◽  
Marek Andrzej Kojdecki ◽  
...  
Keyword(s):  
Crystal Structure ◽  
Electron Microscopy ◽  
Scanning Electron Microscopy ◽  
Size Distribution ◽  
Solid Solutions ◽  
X Ray Diffraction ◽  
X Ray ◽  
Structure And Microstructure ◽  
Crystalline Microstructure ◽  
Scanning Electron

Co2+-containing cordierite glasses, of nominal compositions (Mg1−xCox)2Al4Si5O18(withx= 0, 0.2, 0.4, 0.6, 0.8 and 1), were prepared by melting colloidal gel precursors. After isothermal heating at 1273 K for around 28 h, a single-phase α-cordierite (high-temperature hexagonal polymorph) was synthesized. All materials were investigated using X-ray powder diffraction and field-emission scanning electron microscopy. The crystal structure and microstructure were determined from X-ray diffraction patterns. Rietveld refinement confirmed the formation of magnesium–cobalt cordierite solid solutions. The unit-cell volume increased with the increase of cobalt content in the starting glass. The crystalline microstructure of the cordierites was interpreted using a mathematical model of a polycrystalline material and characterized by prevalent crystallite shape, volume-weighted crystallite size distribution and second-order crystalline lattice-strain distribution. Hexagonal prismatic was the prevalent shape of α-cordierite crystallites. Bimodality in the size distribution was observed and interpreted as a consequence of two paths of the crystallization: the nucleation from glass of μ-cordierite, which transformed into α-cordierite with annealing, or the nucleation of α-cordierite directly from glass at high temperatures. Scanning electron microscopy images agreed well with crystalline microstructure characteristics determined from the X-ray diffraction line-profile analysis.

Effects of Ho-Doping on Crystal Structure and Microstructure of La0.7Sr0.3MnO3 Ceramics

2013 ◽  
Vol 745-746 ◽  
pp. 96-101 ◽  
Author(s):  
Ben Zhe Sun ◽  
Si Lang Zhou ◽  
Tie Shen
Keyword(s):  
Crystal Structure ◽  
Electron Microscopy ◽  
Perovskite Structure ◽  
Volume Fraction ◽  
Partial Substitution ◽  
X Ray Diffraction ◽  
Doping Amount ◽  
X Ray ◽  
Transmission Electron ◽  
Structure And Microstructure

Crystal structure and microstructure of La0.7-xHoxSr0.3MnO3 (x=0.2,0.6) prepared by usual ceramic techniques and grinding procedure were investigated using X-ray diffraction (XRD) and transmission electron microscopy (TEM). When doping amount x equals to 0.2, incorporation of Ho atoms contributed to phase separation and coexistence of rhombohedral (La0.7Sr0.3MnO3) and hexagonal (HoMnO3) phases. La0.7Sr0.3MnO3 phase is of typical perovskite structure, whereas, HoMnO3 phase is non-perovskite structure. As x reaches 0.6, the volume fraction of HoMnO3 phase was significantly increasing. Meanwhile, an orthorhombic lattice with perovskite structure and space group Pnma can be observed. It prevented from partial substitution of La 3+ or Sr2+ by Ho3+ and the distortion of Mn-O octahedra.

scholarly journals Reticular design and crystal structure determination of covalent organic frameworks

2021 ◽  
Author(s):  
Ha L. Nguyen
Keyword(s):  
Crystal Structure ◽  
Electron Diffraction ◽  
Structure Determination ◽  
Rational Design ◽  
Crystal Structure Determination ◽  
Conceptual Basis ◽  
X Ray Diffraction ◽  
Topological Approach ◽  
X Ray

This article describes the conceptual basis of rational design in COF chemistry and comprehensively discusses the crystal structure determination of COFs using the topological approach, X-ray diffraction, and 3D electron diffraction.

Accuracy of linear polymer crystal structures determined from electron diffraction intensities: Problems with zonal data

1983 ◽  
Vol 41 ◽  
pp. 22-23
Author(s):  
Douglas L. Dorset
Keyword(s):  
Crystal Structure ◽  
Electron Diffraction ◽  
Structural Information ◽  
Structure Refinement ◽  
Diffraction Theory ◽  
X Ray Diffraction ◽  
X Ray ◽  
Multidimensional Parameter ◽  
Unknown Structure ◽  
Refinement Process

In contrast to analyses based on X-ray and neutron diffraction intensity data, electron crystal structure determination for organic materials is only a crudely-developed procedure. Although the pioneering work of Vainshtein and co-workers has been very important for realization of the technique's advantages, self-consistent procedures based on earlier-derived diffraction theory have only recently emerged, enabling a reasonable estimate of what structural information might be obtained from a given microcrystalline organic specimen and how this might be best achieved. Problems which are unresolved include the optimal refinement procedure for an unknown structure and also the adequate identification of the correct crystal structure during this refinement process.The behavior of the crystallographic residual(R) during structure refinement is manifested by various minima in a multidimensional parameter space. The description of this space is more complicated for electron diffraction than for X-ray diffraction, although both cases include atomic position, atomic thermal vibration, atomic occupancy, “extinction”, and crystal distortion.

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