Alkaline earth yttrium borates: synthesis, characterization and calculation of unit cell parameters

2016 ◽  
Vol 78 (1) ◽  
pp. 5-9
Author(s):  
G. Çelik Gül ◽  
F. Kurtuluş
Keyword(s):  
Alkaline Earth ◽  
Unit Cell ◽  
Unit Cell Parameters ◽  
Cell Parameters

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.

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.

Sectioned rubisco crystals in TEM

1990 ◽  
Vol 48 (3) ◽  
pp. 664-665
Author(s):  
Gunnel Karlsson ◽  
Jan-Olov Bovin ◽  
Michael Bosma
Keyword(s):  
Plant Cell ◽  
Carbon Fixation ◽  
Unit Cell ◽  
Protein Crystals ◽  
Unit Cell Parameters ◽  
Cell Parameters ◽  
Photosynthetic Carbon Fixation ◽  
Photosynthetic Carbon

RuBisCO (D-ribulose-l,5-biphosphate carboxylase/oxygenase) is the most aboundant enzyme in the plant cell and it catalyses the key carboxylation reaction of photosynthetic carbon fixation, but also the competing oxygenase reaction of photorespiation. In vitro crystallized RuBisCO has been studied earlier but this investigation concerns in vivo existance of RuBisCO crystals in anthers and leaves ofsugarbeets. For the identification of in vivo protein crystals it is important to be able to determinethe unit cell of cytochemically identified crystals in the same image. In order to obtain the best combination of optimal contrast and resolution we have studied different staining and electron accelerating voltages. It is known that embedding and sectioning can cause deformation and obscure the unit cell parameters.

On the accuracy of determining the unit cell parameters of single crystals on modern laboratory diffractometers

2021 ◽  
Vol 62 (5) ◽  
Author(s):  
П.C. Серебренникова ◽  
В.Ю. Комаров ◽  
А.С. Сухих ◽  
С.А. Громилов
Keyword(s):  
Single Crystals ◽  
Unit Cell ◽  
Unit Cell Parameters ◽  
Cell Parameters

scholarly journals Crystal Structure Refinements of Four Monazite Samples from Different Localities

Minerals ◽  
2020 ◽  
Vol 10 (11) ◽  
pp. 1028 ◽  
Author(s):  
M. Mashrur Zaman ◽  
Sytle M. Antao
Keyword(s):  
Crystal Structure ◽  
Electron Probe ◽  
Unit Cell Volume ◽  
Unit Cell ◽  
X Ray Diffraction ◽  
Unit Cell Parameters ◽  
X Ray ◽  
Cell Parameters ◽  
Large Unit Cell ◽  
A Site

This study investigates the crystal chemistry of monazite (APO4, where A = Lanthanides = Ln, as well as Y, Th, U, Ca, and Pb) based on four samples from different localities using single-crystal X-ray diffraction and electron-probe microanalysis. The crystal structure of all four samples are well refined, as indicated by their refinement statistics. Relatively large unit-cell parameters (a = 6.7640(5), b = 6.9850(4), c = 6.4500(3) Å, β = 103.584(2)°, and V = 296.22(3) Å3) are obtained for a detrital monazite-Ce from Cox’s Bazar, Bangladesh. Sm-rich monazite from Gunnison County, Colorado, USA, has smaller unit-cell parameters (a = 6.7010(4), b = 6.9080(4), c = 6.4300(4) Å, β = 103.817(3)°, and V = 289.04(3) Å3). The a, b, and c unit-cell parameters vary linearly with the unit-cell volume, V. The change in the a parameter is large (0.2 Å) and is related to the type of cations occupying the A site. The average <A-O> distances vary linearly with V, whereas the average <P-O> distances are nearly constant because the PO4 group is a rigid tetrahedron.

scholarly journals New crystal structures of adenylate kinase fromStreptococcus pneumoniaeD39 in two conformations

2014 ◽  
Vol 70 (11) ◽  
pp. 1468-1471
Author(s):  
Trung Thanh Thach ◽  
Sangho Lee
Keyword(s):  
Crystal Structures ◽  
Adenylate Kinase ◽  
Bound States ◽  
Critical Role ◽  
Unit Cell ◽  
Unit Cell Parameters ◽  
Space Group ◽  
Cell Parameters ◽  
Ligand Free ◽  
Adenylate Kinases

Adenylate kinases (AdKs; EC 2.7.3.4) play a critical role in intercellular homeostasis by the interconversion of ATP and AMP to two ADP molecules. Crystal structures of adenylate kinase fromStreptococcus pneumoniaeD39 (SpAdK) have recently been determined using ligand-free and inhibitor-bound crystals belonging to space groupsP21andP1, respectively. Here, new crystal structures of SpAdK in ligand-free and inhibitor-bound states determined at 1.96 and 1.65 Å resolution, respectively, are reported. The new ligand-free crystal belonged to space groupC2, with unit-cell parametersa= 73.5,b= 54.3,c= 62.7 Å, β = 118.8°. The new ligand-free structure revealed an open conformation that differed from the previously determined conformation, with an r.m.s.d on Cαatoms of 1.4 Å. The new crystal of the complex with the two-substrate-mimicking inhibitorP1,P5-bis(adenosine-5′-)pentaphosphate (Ap5A) belonged to space groupP1, with unit-cell parametersa= 53.9,b= 62.3,c= 63.0 Å, α = 101.9, β = 112.6, γ = 89.9°. Despite belonging to the same space group as the previously reported crystal, the new Ap5A-bound crystal contains four molecules in the asymmetric unit, compared with two in the previous crystal, and shows slightly different lattice contacts. These results demonstrate that SpAdK can crystallize promiscuously in different forms and that the open structure is flexible in conformation.

Compressibility of β-As4S4: an in situ high-pressure single-crystal X-ray study

2012 ◽  
Vol 76 (4) ◽  
pp. 963-973 ◽  
Author(s):  
G. O. Lepore ◽  
T. Boffa Ballaran ◽  
F. Nestola ◽  
L. Bindi ◽  
D. Pasqual ◽  
...  
Keyword(s):  
Pressure Range ◽  
Substantial Reduction ◽  
Structural Data ◽  
Unit Cell ◽  
Van Der Waals Interactions ◽  
X Ray Diffraction ◽  
Unit Cell Parameters ◽  
X Ray ◽  
Cell Parameters ◽  
Intermolecular Distances

AbstractAmbient temperature X-ray diffraction data were collected at different pressures from two crystals of β-As4S4, which were made by heating realgar under vacuum at 295ºC for 24 h. These data were used to calculate the unit-cell parameters at pressures up to 6.86 GPa. Above 2.86 GPa, it was only possible to make an approximate measurement of the unit-cell parameters. As expected for a crystal structure that contains molecular units held together by weak van der Waals interactions, β-As4S4 has an exceptionally high compressibility. The compressibility data were fitted to a third-order Birch–Murnaghan equation of state with a resulting volume V0 = 808.2(2) Å3, bulk modulus K0 = 10.9(2) GPa and K' = 8.9(3). These values are extremely close to those reported for the low-temperature polymorph of As4S4, realgar, which contains the same As4S4 cage-molecule. Structural analysis showed that the unit-cell contraction is due mainly to the reduction in intermolecular distances, which causes a substantial reduction in the unit-cell volume (∼21% at 6.86 GPa). The cage-like As4S4 molecules are only slightly affected. No phase transitions occur in the pressure range investigated.Micro-Raman spectra, collected across the entire pressure range, show that the peaks associated with As–As stretching have the greatest pressure dependence; the S–As–S bending frequency and the As–S stretching have a much weaker dependence or no variation at all as the pressure increases; this is in excellent agreement with the structural data.

Pseudo-C11b Phase Formation of Titanium Disilicide During the C49 to C54 Transition

1997 ◽  
Vol 481 ◽  
Author(s):  
Patrick L. Smith ◽  
Richard Ortega ◽  
Bill Brennan
Keyword(s):  
Thin Films ◽  
Plane Wave ◽  
Intermediate Phase ◽  
Unit Cell ◽  
Silicon Substrates ◽  
Unit Cell Parameters ◽  
Titanium Disilicide ◽  
Cell Parameters ◽  
Chemical Signatures ◽  
Pseudo Potential

ABSTRACTThe formation of TiSi2 thin films using the SALICIDE process on doped and undoped silicon substrates was studied. XRD TEM, AES, RBS and four probe Rs were used to characterize the material. Unit cell parameters and energetics were determined. Results confirm electrical and chemical signatures consistent with the known C49 conversion to C54. However, XRD indicated a structurally different intermediate phase occurs during the C49 to C54 transformation. Modeling was performed based on C11b structure (14/mmm) type, with the Ti and Si atoms arranged similarly to those in MoSi2. The unit cell was determined to be a = 4.428 Å, b = 4.779 Å, c = 9.078 Å with a Fmmm space group and total pseudo-potential plane wave calculations based on crystallographic simulations of −103.96 ev/Atom.

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