Low-temperature unit-cell parameters of La1−x Pr x CaBaCu3O7 compounds

1993 ◽  
Vol 28 (12) ◽  
pp. 3303-3306
Author(s):  
A. M. Shamah ◽  
S. Ahmed ◽  
M. K. El-Mously
Keyword(s):  
Low Temperature ◽  
Unit Cell ◽  
Unit Cell Parameters ◽  
Cell Parameters

scholarly journals Lithium oxide: a quantum-corrected and classical Monte Carlo study

2019 ◽  
Vol 21 (27) ◽  
pp. 14964-14972 ◽  
Author(s):  
M. Yu. Lavrentiev ◽  
N. L. Allan ◽  
C. Wragg
Keyword(s):  
Monte Carlo ◽  
Low Temperature ◽  
Monte Carlo Study ◽  
Unit Cell ◽  
Lithium Oxide ◽  
Quantum Corrections ◽  
Unit Cell Parameters ◽  
Cell Parameters ◽  
Theory And Experiment

Quantum corrections to unit cell parameters provide correct low-temperature limits and must be allowed for when comparing theory and experiment.

Über die Reaktion von KPPh2 mit Fe(CO)5 und Fe(CO)4CS; Molekülstruktur von [(CO)4FePPh2]- / On the Reaction of KPPh*, with Fe(CO)5 and Fe(CO)4CS; Molecular Structure of [(CO)4FePPh2]-

1996 ◽  
Vol 51 (5) ◽  
pp. 715-721 ◽  
Author(s):  
Wolfgang Petz ◽  
Frank Weller
Keyword(s):  
Molecular Structure ◽  
Elevated Temperature ◽  
Nmr Spectroscopy ◽  
Low Temperature ◽  
Unit Cell ◽  
Radical Mechanism ◽  
Unit Cell Parameters ◽  
Triclinic Space Group ◽  
Space Group ◽  
Cell Parameters

Fe(CO)5 reacts with [PPh2]- in THF at -78 °C to give the adduct [(CO)4FeCOPPh2]- (3) which decomposes at elevated temperature to give [(CO)4FePPh2]- (1), [Fe2(CO)8]2- (2) and (Ph2P)2 probably via a radical mechanism. Attempts to transfer 3 with the electrophiles MeSO3CF3 or Me3SnCl into the corresponding carbenes have failed and Fe(CO)5 along with Ph2PMe and Me3SnPPh2, respectively, are formed. 1 adds one equivalent of CS2 to generate [(CO)4FePPh2CS2]- (4). The [K-18-Krone-6] salt of 1 crystallizes in the triclinic space group P 1̄ with the unit cell parameters a = 929.5(2), b = 1112 .1(2), c = 2017.9(4) pm, α = 100.29(3)°; β = 94.07(3) °; γ = 114.58(3) °. The existence of 3 is established by low temperature 31P NMR spectroscopy.

Flexibility Of The Zeolite Rho Framework: The Redistribution Of Extra Framework Cations As A Function Of Temperature.

1991 ◽  
Vol 233 ◽  
Author(s):  
John B. Parise ◽  
Xing Liu ◽  
David R. Corbin ◽  
Glover A. Jones
Keyword(s):  
Low Temperature ◽  
Cell Expansion ◽  
Unit Cell ◽  
X Ray Diffraction ◽  
Unit Cell Parameters ◽  
X Ray ◽  
Cell Parameters ◽  
Abrupt Changes ◽  
Zeolite Rho ◽  
Diffraction Patterns

ABSTRACTUpon heating Ba2+, Sr2+ and Cd2+-exchanged zeolite RHO, abrupt changes have been observed in the cubic unit cell parameters [1–3]. Calculations of the powder x-ray diffraction patterns indicate these changes result from relocation of the extra-framework cations. For Ba2+ and Sr2+-exchanged RHO, a shift from the single 8-ring (S8R) to the double 8-ring (D8R)-site is accompanied by contraction of the unit cell. However, for the Cd2+-exchanged material relocation from the S8R to the single 6-ring (S6R)-site coincides with cell expansion. Further, with relocation of Cd2+ the low temperature acentric (A) form is transformed to a centric (C) structure above 300°C. The shift of Cd2+ ion occurs over a distance of 5.7Å, the largest observed in a zeolite.

Structural irregularities and peculiarities of low-temperature thermal properties of Sn24P19.4Br8 clathrate

2017 ◽  
Vol 46 (28) ◽  
pp. 9110-9117 ◽  
Author(s):  
V. V. Novikov ◽  
A. V. Matovnikov ◽  
N. V. Mitroshenkov ◽  
B. I. Kornev ◽  
K. S. Pilipenko ◽  
...  
Keyword(s):  
Heat Capacity ◽  
Thermal Properties ◽  
Low Temperature ◽  
Unit Cell ◽  
Unit Cell Parameters ◽  
Temperature Changes ◽  
Cell Parameters ◽  
Temperature Range ◽  
Structural Irregularities

Temperature changes of the heat capacity and unit cell parameters of Sn24P19Br8 clathrate were experimentally determined in the temperature range of 2 to 300 K.

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

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 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.

Sign in / Sign up

Export Citation Format

Share Document