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.

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.

scholarly journals Heat capacity and thermal expansion of yttrium tantalate

2019 ◽  
Vol 484 (2) ◽  
pp. 181-183
Author(s):  
A. V. Khoroshilov ◽  
A. A. Ashmarin ◽  
V. N. Guskov ◽  
E. G. Sazonov ◽  
K. S. Gavrichev ◽  
...  
Keyword(s):  
Differential Scanning Calorimetry ◽  
Heat Capacity ◽  
Thermal Expansion ◽  
Heat Capacities ◽  
Unit Cell ◽  
Unit Cell Parameters ◽  
Scanning Calorimetry ◽  
Crystal Lattices ◽  
Cell Parameters ◽  
The Difference

The isobaric heat capacities of two monoclinic (M' and M) modifications of yttrium orthotantalate at temperatures 5–1300 K have been measured by the adiabatic and differential scanning calorimetry methods. It has been demonstrated that the difference in structure between the crystal lattices of M' and M has small effect in the heat capacity, and the difference between the heat capacities of these phases Cp(M)-Cp(M') is small, always positive, and increases in the range of the lowest temperatures. The unit cell parameters of M-YTaO4 have been determined as a function of temperature in the range 300–1173 K.

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

Thermal expansion of cancrinite

1996 ◽  
Vol 60 (403) ◽  
pp. 949-956 ◽  
Author(s):  
Ishmael Hassan
Keyword(s):  
Thermal Expansion ◽  
Room Temperature ◽  
Unit Cell ◽  
Unit Cell Parameters ◽  
Cell Parameters ◽  
Temperature Range ◽  
Thermal Expansion Coefficients ◽  
Expansion Mechanism ◽  
Expansion Coefficients ◽  
Cell Volumes

AbstractThermal expansion coefficients were measured for a cancrinite from Bancroft, Ontario, Canada. Measurements of cell parameters and unit-cell volumes were obtained at room temperature and at heating intervals of 50°C over the temperature range from 50 to 1400°C. The unit-cell parameters for cancrinite increase non-linearly with temperature up to 1200°C and shortly thereafter, the mineral melted. The c parameter increases more rapidly than the a parameter, and the c/a ratio increases linearly with temperature. A plausible thermal expansion mechanism for cancrinite, which is based on the framework expansion that occurs as a function of cavity content, is presented. In the thermal expansion of cancrinite, the short Na-H2O in the H2O-Na—H2O chain expands to form equal distances to the two H2O molecules in the chain. This causes the Na atoms to move towards the plane of the six-membered rings and forces the tetrahedra to rotate and the rings become more planar. The Na atoms then form bonds to all six (O1 and O2) oxygen atoms in a ring; the Na-O1 bonds become shorter and the Na-O2 bonds become longer. These effects cause an increase in both a and c, and thus an increase in the c/a ratio. A similar thermal expansion mechanism operates in the sodalite-group minerals where the six-membered rings and Na-Cl bond are involved.

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.

scholarly journals Теплопроводность твердых растворов Cu-=SUB=-2-=/SUB=-ZnGe-=SUB=-1-x-=/SUB=-Sn-=SUB=-x-=/SUB=-Se-=SUB=-4-=/SUB=-

2020 ◽  
Vol 54 (2) ◽  
pp. 113
Author(s):  
И.В. Боднарь
Keyword(s):  
Thermal Conductivity ◽  
Medium Composition ◽  
Unit Cell ◽  
Tetragonal Structure ◽  
Composition Parameter ◽  
Unit Cell Parameters ◽  
Cell Parameters ◽  
Temperature Range ◽  
Composition And Structure ◽  
Vegard’S Law

Abstract Cu_2ZnGeSe_4 and Cu_2ZnSnSe_4 and Cu_2ZnGe_1 –_ x Sn_ x Se_4-alloy crystals are grown by the Bridgman method (vertical variant). The composition and structure of the crystals are determined. It is established that both the initial compounds and their alloys crystalize with the formation of tetragonal structure. The unit-cell parameters a and c of the crystals are calculated, and the dependences of these parameters on the composition of the alloys are constructed. It is shown that, under variations in the composition parameter x , the parameters a and c vary in accordance with Vegard’s law. The thermal conductivity of the Cu_2ZnGeSe_4 and Cu_2ZnSnSe_4 compounds and Cu_2ZnGe_1 –_ x Sn_ x Se_4 alloys is measured in the temperature range 300–600 K. It is found that the thermal conductivity varies with x , with a minimum for the medium composition.

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
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