From aqueous speciation to supramolecular assembly in alkaline earth-uranyl polyoxometalates

2017 ◽  
Vol 53 (69) ◽  
pp. 9550-9553 ◽  
Author(s):  
Clément Falaise ◽  
Sarah M. Hickam ◽  
Peter C. Burns ◽  
May Nyman
Keyword(s):  
Alkaline Earth ◽  
Supramolecular Assembly ◽  
Unit Cell ◽  
Ionic Lattice

Macrocation and macroanion Sr-uranyl hybrid capsules self-assemble into an ionic lattice, presenting the fourth largest inorganic unit cell reported.

A supramolecular assembly of a multifunctional calix[4]arene with alkali and alkaline earth cations in solution and in the solid state

1996 ◽  
Vol 7 (3) ◽  
pp. 215-222 ◽  
Author(s):  
Francoise Arnaud-neu ◽  
Geraldine Barrett ◽  
George Ferguson ◽  
John F. Gallagher ◽  
M. Anthony McKervey ◽  
...  
Keyword(s):  
Solid State ◽  
Alkaline Earth ◽  
Supramolecular Assembly ◽  
Alkaline Earth Cations

Crystallographic changes in (CaxSr1−x)n+1 TinO3n+1 layer perovskites: XPS and XAES investigations

1992 ◽  
Vol 7 (2) ◽  
pp. 482-489 ◽  
Author(s):  
S. Myhra ◽  
J.C. Rivière ◽  
K. Hawkins ◽  
T.J. White
Keyword(s):  
Kinetic Energy ◽  
Alkaline Earth ◽  
Unit Cell ◽  
Structural Transitions ◽  
Constituent Species ◽  
Cell Volumes ◽  
Layered Perovskites

Layered perovskites (Ruddlesden–Popper phases), (CaxSr1−x)n+1 TinO3n+1 with n = 3, ∞ and x ranging from 0 to 1, have been investigated by XPS and XAES. The structural transitions, identified in other studies, have been correlated with changes in the chemical environments of the constituent species. In particular, the tetragonal to orthorhombic transition at x = 0.65 ± 0.1 appears to generate nonequivalent cation environments for the alkaline earth species in (Ca, Sr)O12 coordination. Other binding and kinetic energy shifts can be correlated with changes in and distortions of unit cell volumes.

Über Oxocuprate, XX Ein Erdalkalioxocuprat(II) mit geschlossenen Baugruppen: BaCuO2 / About Oxocuprates, XX Alkaline-earth Oxocuprate(II) with Closed Structural Groups : BaCuO2

1977 ◽  
Vol 32 (2) ◽  
pp. 121-123 ◽  
Author(s):  
R. Kipka ◽  
Hk. Müller-Buschbaum
Keyword(s):  
Single Crystal ◽  
Coordination Number ◽  
Lattice Constant ◽  
Alkaline Earth ◽  
Unit Cell ◽  
Space Group ◽  
X Ray ◽  
Ray Methods

The new alkaline-earth oxocuprate(II) BaCuO2 was prepared and investigated by single crystal X-ray methods. (Space group : Oh9-Im 3 m, lattice constant: a = 1827 pm.) The distribution of 360 atoms per unit cell leads to a complicated polyhedral framework with Cu2+ in well known square coordination. One of the Ba2+ positions has the extraordinary coordination number 24.

scholarly journals Synthesis and crystal structure of a mixed alkaline-earth powellite, Ca0.84Sr0.16MoO4

2020 ◽  
Vol 76 (2) ◽  
pp. 121-124
Author(s):  
Ryan M. Kissinger ◽  
Saehwa Chong ◽  
Brian J. Riley ◽  
Jarrod V. Crum
Keyword(s):  
Crystal Structure ◽  
Alkaline Earth ◽  
Unit Cell ◽  
X Ray Diffraction ◽  
Unit Cell Parameters ◽  
Synthesis And Crystal Structure ◽  
Xrd Pattern ◽  
X Ray ◽  
Cell Parameters ◽  
Good Agreement

A mixed alkaline-earth powellite, Ca0.84Sr0.16MoO4 (calcium strontium molybdate), was synthesized by a flux method and its crystal structure was solved using single-crystal X-ray diffraction (SC-XRD) data. The compound crystallized in the I41/a space group as with a typical CaMoO4 powellite, but with larger unit-cell parameters and unit-cell volume as a result of the partial incorporation of larger Sr cations into the Ca sites within the crystal. The unit cell and volume were well fitted with the trendline calculated from literature values, and the powder X-ray diffraction (P-XRD) pattern of the ground crystal is in good agreement with the calculated pattern from the solved structure.

High-resolution structure determination by ALCHEMI

1983 ◽  
Vol 41 ◽  
pp. 178-181 ◽  
Author(s):  
Peter G. Self ◽  
Peter R. Buseck
Keyword(s):  
Site Occupancy ◽  
Real Space ◽  
Unit Cell ◽  
Bragg Angle ◽  
Electron Current ◽  
High Resolution Structure ◽  
Beam Incident ◽  
Crystallographic Planes ◽  
Electron Beam Incident ◽  
Resolution Structure

ALCHEMI (Atom Location by CHanneling Enhanced Microanalysis) enables the site occupancy of atoms in single crystals to be determined. In this article the fundamentals of the method for both EDS and EELS will be discussed. Unlike HRTEM, ALCHEMI does not place stringent resolution requirements on the microscope and, because EDS clearly distinguishes between elements of similar atomic number, it can offer some advantages over HRTEM. It does however, place certain constraints on the crystal. These constraints are: a) the sites of interest must lie on alternate crystallographic planes, b) the projected charge density on the alternate planes must be significantly different, and c) there must be at least one atomic species that lies solely on one of the planes.An electron beam incident on a crystal undergoes elastic scattering; in reciprocal space this is seen as a diffraction pattern and in real space this is a modulation of the electron current across the unit cell. When diffraction is strong (i.e., when the crystal is oriented near to the Bragg angle of a low-order reflection) the electron current at one point in the unit cell will differ significantly from that at another point.

The External Shape of Human γ GI Immunoglobulin from Crystal Sections

1971 ◽  
Vol 29 ◽  
pp. 428-429
Author(s):  
L. W. Labaw
Keyword(s):  
Molecular Weight ◽  
Sodium Phosphate ◽  
Osmium Tetroxide ◽  
Unit Cell ◽  
Monoclinic Space Group ◽  
X Ray ◽  
Large Molecular Weight ◽  
Cell Dimensions ◽  
Unit Cell Dimensions ◽  
Crystallographic Axes

Crystals of a human γGl immunoglobulin have the external morphology of diamond shaped prisms. X-ray studies have shown them to be monoclinic, space group C2, with 2 molecules per unit cell. The unit cell dimensions are a = 194.1, b = 91.7, c = 51.6Å, 8 = 102°. The relatively large molecular weight of 151,000 and these unit cell dimensions made this a promising crystal to study in the EM.Crystals similar to those used in the x-ray studies were fixed at 5°C for three weeks in a solution of mother liquor containing 5 x 10-5M sodium phosphate, pH 7.0, and 0.03% glutaraldehyde. They were postfixed with 1% osmium tetroxide for 15 min. and embedded in Maraglas the usual way. Sections were cut perpendicular to the three crystallographic axes. Such a section cut with its plane perpendicular to the z direction is shown in Fig. 1.This projection of the crystal in the z direction shows periodicities in at least four different directions but these are only seen clearly by sighting obliquely along the micrograph.

The orientation of sickle hemoglobin fibers within fascicles

1988 ◽  
Vol 46 ◽  
pp. 400-401
Author(s):  
Christopher A. Miller ◽  
Bridget Carragher ◽  
William A. McDade ◽  
Robert Josephs
Keyword(s):  
Sickle Cell ◽  
Sickle Cell Anemia ◽  
Relative Orientation ◽  
Unit Cell ◽  
Red Cell ◽  
High Ph ◽  
Sickle Hemoglobin ◽  
Polar Crystal ◽  
Helical Configuration

Highly ordered bundles of deoxyhemoglobin S (HbS) fibers, termed fascicles, are intermediates in the high pH crystallization pathway of HbS. These fibers consist of 7 Wishner-Love double strands in a helical configuration. Since each double strand has a polarity, the odd number of double strands in the fiber imparts a net polarity to the structure. HbS crystals have a unit cell containing two double strands, one of each polarity, resulting in a net polarity of zero. Therefore a rearrangement of the double strands must occur to form a non-polar crystal from the polar fibers. To determine the role of fascicles as an intermediate in the crystallization pathway it is important to understand the relative orientation of fibers within fascicles. Furthermore, an understanding of fascicle structure may have implications for the design of potential sickling inhibitors, since it is bundles of fibers which cause the red cell distortion responsible for the vaso-occlusive complications characteristic of sickle cell anemia.

Kinematical and Dynamical CBED Pattern Models: Increasing the Accuracy of the Unit-Cell Parameter Measurements Based on CBED Patterns

1990 ◽  
Vol 48 (2) ◽  
pp. 540-541
Author(s):  
I.N. Yadhikov ◽  
S.K. Maksimov
Keyword(s):  
Reciprocal Lattice ◽  
Unit Cell ◽  
Reciprocal Lattice Vector ◽  
Unit Cell Parameters ◽  
Lattice Vector ◽  
Cell Parameters ◽  
Accuracy Of Measurements ◽  
The Difference ◽  
Image Position ◽  
Convergent Beam

Convergent beam electron diffraction (CBED) is widely used as a microanalysis tool. By the relative position of HOLZ-lines (Higher Order Laue Zone) in CBED-patterns one can determine the unit cell parameters with a high accuracy up to 0.1%. For this purpose, maps of HOLZ-lines are simulated with the help of a computer so that the best matching of maps with experimental CBED-pattern should be reached. In maps, HOLZ-lines are approximated, as a rule, by straight lines. The actual HOLZ-lines, however, are different from the straights. If we decrease accelerating voltage, the difference is increased and, thus, the accuracy of the unit cell parameters determination by the method becomes lower.To improve the accuracy of measurements it is necessary to give up the HOLZ-lines substitution by the straights. According to the kinematical theory a HOLZ-line is merely a fragment of ellipse arc described by the parametric equationwith arc corresponding to change of β parameter from -90° to +90°, wherevector, h - the distance between Laue zones, g - the value of the reciprocal lattice vector, g‖ - the value of the reciprocal lattice vector projection on zero Laue zone.

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