Sodalite, Na4Si3Al3O12Cl: structure and ionic mobility at high temperatures by neutron diffraction

1996 ◽  
Vol 52 (4) ◽  
pp. 616-627 ◽  
Author(s):  
R. K. McMullan ◽  
S. Ghose ◽  
N. Haga ◽  
V. Schomaker
Keyword(s):  
Neutron Diffraction ◽  
Translational Motion ◽  
Site Occupancy ◽  
Ionic Mobility ◽  
Lattice Parameter ◽  
K Value ◽  
Bond Lengths ◽  
Librational Motion ◽  
Diffusion Paths ◽  
The Difference

Crystal data: Na4Si3Al3O12Cl, cubic, space group P43n, Z = 2, F(000) = 233.06 fm, μ n = 0.06 cm−1, lattice parameter ao  (Å) [T] (K) at eight temperatures: 8.882 (1) [295]; 8.902 (2) [500]; 8.912 (1) [600]; 8.923 (1) [700] 8.951 (2) [800]; 8.971(1) [900]; 8.988 (1) [1000]; 9.037 (1) [1200]. The crystal structure has been determined at six temperatures (295 ≤ T ≤ 1200 K) based on neutron diffraction data with (sin θ/λ) < 0.80 Å−1. Besides conventional parameters, the least-squares refinement model included thermal tensor parameters up to fourth-order for sodium and chlorine (295 ≤ T ≤ 1200 K) and up to third-order for oxygen (T ≥ 700 K), together with the 1:1 coupled site occupancy factors of sodium and chlorine (T = 1200 K). The indices-of-fit, wR(F 2), are in the range 0.015–0.028 with observation-to-parameter ratios from 7.0 to 8.6. Bond lengths and angles in the aluminosilicate framework have average e.s.d.'s less than 0.002 Å and 0.08°. Between 295 and 1200 K, the observed Si—O (Al—O) bond lengths differ by −0.015 Å (−0.012 Å); corrections for librating rigid SiO4 (AlO4) groups change the difference to +0.004 Å (+0.006 Å), compared with the 295 K value of 1.620 Å (1.741 Å). The unique Si—O—Al angle increases from 138.24° (295 K) to 146.87° (1200 K), while the Si and Al valence angles are virtually unchanged. Between 295 and 1200 K the [Na4Cl] clusters expand with increases in the Na—Cl bond lengths of 0.200 Å, with simultaneous increases in Na—O bond lengths of 0.145 Å and decreases in the shortest Na...O contact distances of 0.126 Å. The thermal expansion of sodalite is attributed to the increasing amplitudes of coupled translational motion of the Na+ ions and the librational motion of the [Al/ SiO4] tetrahedra, leading to the untwisting of the aluminosilicate framework. Maps of the probability density functions for Na+ and Cl− indicate ionic diffusion paths along (111) directions. There is a finite probability of finding the Na+ ion within the plane of the next-nearest O atoms, suggesting that Na+ jumps from an occupied to an unoccupied site in the next-nearest cage through the six-membered ring of [Al/SiO4] tetrahedra.

Structural, electrical characterization and oxygen-diffusion paths in LaSrGa1-xMgxO4-δ (x=0.0-0.2) layered perovskites: an impedance spectroscopy and neutron diffraction study

2021 ◽  
Author(s):  
Carlos Marino ◽  
Juan Basbus ◽  
Ana L. Larralde ◽  
Jose Antonio Alonso ◽  
Maria Teresa Fernandez-Diaz ◽  
...  
Keyword(s):  
Impedance Spectroscopy ◽  
Neutron Diffraction ◽  
Structural Characterization ◽  
Oxygen Diffusion ◽  
Electrical Characterization ◽  
Neutron Diffraction Study ◽  
Oxygen Ions ◽  
Diffusion Paths ◽  
Layered Perovskites

This work presents the results of the structural characterization of LaSrGa1-xMgxO4-δ oxides with x=0.0-0.2 (LSGM'); these oxides with layered K2NiF4-type structure are potential electrolytes of oxygen ions with applications in...

Problems Associated with Kα Doublet in Residual Stress Measurements

1979 ◽  
Vol 23 ◽  
pp. 333-339
Author(s):  
S. K. Gupta ◽  
B. D. Cullity
Keyword(s):  
Residual Stress ◽  
Silicon Powder ◽  
Lattice Parameter ◽  
Diffraction Peak ◽  
Parameter Determination ◽  
X Ray Diffraction ◽  
X Ray ◽  
Analysis Techniques ◽  
The Difference ◽  
Similar Accuracy

Since the measurement of residual stress by X-ray diffraction techniques is dependent on the difference in angle of a diffraction peak maximum when the sample is examined consecutively with its surface at two different angles to the diffracting planes, it is important that these diffraction angles be obtained precisely, preferably with an accuracy of ± 0.01 deg. 2θ. Similar accuracy is desired in precise lattice parameter determination. In such measurements, it is imperative that the diffractometer be well-aligned. It is in the context of diffractometer alignment with the aid of a silicon powder standard free of residual stress that the diffraction peak analysis techniques described here have been developed, preparatory to residual stress determinations.

Molecular orbital structures of sulfones

1982 ◽  
Vol 60 (6) ◽  
pp. 730-734 ◽  
Author(s):  
Russell J. Boyd ◽  
Jeffrey P. Szabo
Keyword(s):  
Crystal Structure ◽  
Gas Phase ◽  
Molecular Orbital ◽  
Geometry Optimization ◽  
Membered Ring ◽  
Molecular Orbital Calculations ◽  
Bond Lengths ◽  
Comparison With Experiment ◽  
The Difference

Abinitio molecular orbital calculations are reported for several cyclic and acyclic sulfones. The geometries of XSO2Y, where X, Y = H, F, or CH3 are optimized at the STO-3G* level. Similar calculations are reported for the smallest cyclic sulfone, thiirane-1,1 -dioxide, as well as the corresponding sulfoxide, thiirane-1-oxide, and the parent sulfide, thiirane. Where comparison with experiment is possible, the agreement is satisfactory. In order to consider the possibility of substantial differences between axial and equatorial S—O bonds in the gas phase, as observed in the crystal structure of 5H,8H-dibenzo[d,f][1,2]-dithiocin-1,1-dioxide, STO-3G* calculations are reported for a six-membered ring, thiane-1,1-dioxide, and a model eight-membered ring. Limited geometry optimization of the axial and equatorial S—O bonds in the chair conformations of the six- and eight-membered rings leads to bond lengths of 1.46 Å with the difference being less than 0.01 Å.

Neutron Scattering from Small Lead Particles

1974 ◽  
Vol 52 (8) ◽  
pp. 748-752 ◽  
Author(s):  
V. Novotny ◽  
T. M. Holden ◽  
G. Dolling
Keyword(s):  
Neutron Diffraction ◽  
Neutron Scattering ◽  
Coherence Length ◽  
Crystalline State ◽  
Lattice Parameter ◽  
Small Particles ◽  
Average Amplitude ◽  
Vycor Glass ◽  
Diffraction Peaks

Neutron diffraction experiments on small particles of lead in the pores of Vycor glass are described. The small particles have a coherence length of (107 ± 20) Å; there is only a slight increase in the lattice parameter as compared with bulk lead, but an analysis of the intensity of the diffraction peaks reveals that there is an increase in the average amplitude of vibration of 28%. At least 80% of the lead in the glass is present in the crystalline state and contributes to the coherent diffraction.

scholarly journals Hydrogen Diffusion Coefficient, Hydrogen Solution Coefficient and Hydrogen Permeability of Nb-TiNi Eutectic Alloy

2010 ◽  
Vol 638-642 ◽  
pp. 1131-1136
Author(s):  
Wei Liang Wang ◽  
Kazuhiro Ishikawa ◽  
Kiyoshi Aoki
Keyword(s):  
Diffusion Coefficient ◽  
Hydrogen Absorption ◽  
Hydrogen Diffusion ◽  
Hydrogen Permeability ◽  
K Value ◽  
Hydrogen Flow ◽  
Hydrogen Diffusion Coefficient ◽  
High K ◽  
Pressure Region ◽  
The Difference

In general, hydrogen permeabilityΦ of the alloy membrane is expressed as the product of the hydrogen diffusion coefficient D and the hydrogen solution coefficient K. Therefore, to improve the hydrogen permeability efficiently, the values of K and D should be separately considered. In the present study, hydrogen absorption and permeation behaviors of the Nb19Ti40Ni41 alloy consisting of the eutectic phase are investigated by measuring pressure-composition-isotherm (PCI) and by the hydrogen flow method and compared with those of palladium. The hydrogen absorption in the Nb19Ti40Ni41 alloy does not obey the Sieverts’ law in the pressure region of 0-1.0MPa at 523K, but it shows linear relationship between the difference in the square root of hydrogen pressure and hydrogen content between 0.1 and 0.4MPa. Although the value of D for the Nb19Ti40Ni41 alloy is considerably lower than that of palladium, its high K value enhances the hydrogen permeability Φ. It is suggested that the enhancement of D by microstructural control for Nb19Ti40Ni41 alloy is effective for improvement of Φ.

ETUDE DU POUVOIR NUTRITIF EN PHOSPHORE DE CERTAINS SOLS DU QUEBEC A L'AIDE DU 32P

1976 ◽  
Vol 56 (3) ◽  
pp. 285-291
Author(s):  
B. TOUATI ◽  
C. PLENCHETTE ◽  
M. TABI
Keyword(s):  
Soil Phosphorus ◽  
Phosphate Fertilizer ◽  
Soil Types ◽  
K Value ◽  
Type Experiment ◽  
A Value ◽  
The Difference ◽  
The Way

In a pot-type experiment with ryegrass, 32P was used to label isotopically exchangeable soil phosphorus as well as a phosphate fertilizer. The tagging of both forms of phosphorus enable us to determine the pool (L) for soil reserves and the A value which is the availability of these reserves in the presence of fertilizer. The authors establish correlations between the ratio K = L/A and the assimilable phosphorus as determined by the Bray II method, and also between K and the "extra" phosphorus. The authors state that the latter was the difference between the plant phosphorus with and without fertilizer. From this study it is concluded: (1) that the K value seems to be a better criterion than the amount of assimilable phosphorus to estimate the phosphorus fertility of a soil; (2) that the study of the variation of the K value according to the soil types informs us about the reserves behavior and about the way of nutrition for the plant. The calculation of the K value is aimed toward a more adequate fertilization for given types of soil.

scholarly journals Comparison of Ocular Biometry between Primary Open Angle Glaucoma Patients and Normal subjects

2021 ◽  
Vol 13 (2) ◽  
pp. 62-68
Author(s):  
Nisha Manandhar ◽  
Chandni Pradhan ◽  
Purushottam Joshi ◽  
Prabha Subedi ◽  
Pranav Shrestha
Keyword(s):  
Anterior Chamber ◽  
Axial Length ◽  
Primary Open Angle Glaucoma ◽  
Open Angle Glaucoma ◽  
Anterior Chamber Depth ◽  
Control Group ◽  
Open Angle ◽  
K Value ◽  
The Difference ◽  
Glaucoma Group

Introduction: Glaucoma is one of the major causes of irreversible blindness. In Nepal, the most common type of Glaucoma seen is Primary Open Angle Glaucoma. There are many risk factors associated with Primary Open Angle Glaucoma. The main objective of the study was to compare ocular biometric parameters in patients diagnosed with Primary Open Angle Glaucoma and age matched controls. Material and methods: This is a hospital based cross sectional study done at Mechi Eye Hospital. The study included 137 cases of Primary Open Angle Glaucoma and 75 normal individuals as control.  Axial length (AL), anterior chamber depth (ACD), Keratometry ‘K’ value and Central Corneal Thickness (CCT) were measured. Mann – Whitney U test was used for statistical analysis. Results: Mean age in Primary Open Angle Glaucoma group was (55.25 ± 10.16 years) and in the control group was (60.96 ± 10.91 years). Axial length  in the Primary Open Angle Glaucoma group (23.16 ±1.19 mm) was deeper as compared to the control group (22.69 ±0.89 mm), the difference was statistically significant (p<0.001). Anterior chamber depth (ACD) was statistically deeper in the Primary Open Angle Glaucoma group (3.05 ±0.51 mm) as compared to the control group (2.86 ±0.46 mm), (p<0.01). Central corneal thickness (CCT) was thinner in the Primary Open Angle Glaucoma group (519.5 ±36.25 um) as compared to the control group (525.40 ±37.77 um) but the difference was not found to be statistically significant (p<0.19). K value in Primary Open Angle Glaucoma (7.54 ±0.41mm) was higher than age-matched controls (7.58 ± 0.33mm) but the difference was not statistically significant (p<0.79). Conclusion: Patients with Primary Open Angle Glaucoma had longer Axial length (AL) and deeper Anterior chamber depth (ACD) as compared to normal individuals.

scholarly journals DEVELOPMENT OF THE CONDITIONS FOR STORING THALLIUM AMALGAM

2021 ◽  
Vol 447 (3) ◽  
pp. 65-70
Author(s):  
А.S. Mussina ◽  
G.U. Baitasheva ◽  
N.О. Myrzakhmetova ◽  
Zh.A. Tagabergenova ◽  
E.P. Gorbulicheva
Keyword(s):  
Reaction Rate ◽  
Decomposition Reaction ◽  
Metal Loss ◽  
Distilled Water ◽  
K Value ◽  
Long Term Storage ◽  
Rate Of Dissolution ◽  
Protective Medium ◽  
Zero Order Reaction ◽  
The Difference

It has been established that lNH2SO4 solution and distilled water can be used as a protective medium for a long-term storage (30-40 days) of thallium amalgam of eutectic composition (8.6 mas.%), without sliming of its surface and an insignificant change of its concentration. An inverse dependence between the decomposition reaction rate and the ratio of the solution volume per unit of the contact surface (V:S), which corresponds to the height of the liquid layer (h) above the amalgam, is observed. At h ~ 2.5 cm and higher, the reaction rate becomes stabilized. The value of metal loss during its storage for 10-15 days does not exceed 0.5-1.0 mas.% of the initial thallium content in the amalgam. It has been shown that the rate of dissolution of thallium from amalgam is rather low, and in sulfuric acid solution it is only slightly higher than that in water with all S:V ratios. A similar picture is observed upon thallium amalgam decomposition in the same media in an open vessel; the difference consists only in a higher K value (Table 4). Thus, with S:V = 1:2.5, in an open vessel K in lNH2SO4 makes up 10,5.1011 mol/cm2.sec, and in H2O – 7.3.1011 mol/cm2.sec, whereas in a closed vessel K in lNH2SO4 makes up 1,9.1011 mol/cm2. sec, and in H2O – 1.5.1011 mol/cm2.sec. For 40 days of thallium amalgam (8.54 mas.%) storage in 1NH2SO4 the loss of thallium has been 1.3 mas.%, and in the distilled water - 1 mas.%. The quantity of the dissolved metal increases in proportion to the experiment duration, which is characteristic for a zero-order reaction, and this dependence is observed for all S:V ratios from 1:1 to 1:7. Besides, a possibility to use some saturated hydrocarbons, wherein no sliming of thallium amalgam occurs, as a protective wash liquid has been shown.

A Brief Introduction to Alloy Phase Chemistry Determination under EPMA/SEM-EDS Conditions and its Applications

2012 ◽  
Vol 706-709 ◽  
pp. 2450-2455 ◽  
Author(s):  
Zhi Fang Peng ◽  
Li Sheng Cai ◽  
Ying Ying Dang ◽  
Lei Zhao ◽  
Fang Fang Peng ◽  
...  
Keyword(s):  
Site Occupancy ◽  
Lattice Parameter ◽  
Structure Property ◽  
Heat Resistant Steel ◽  
Surrounding Matrix ◽  
Structure Property Relationships ◽  
Precipitated Phases ◽  
Phase Chemistry ◽  
Physical Quantities ◽  
Accurate Quantification

A so called multiphase separation method (MPSM) is proposed to quantitatively separate precipitated phases from their surrounding matrix phase in chemistry for bulk alloy/steel samples under EPMA/SEM-EDS measurement conditions. Applied examples to comparisons of the results through the MPSM with the values either cited or obtained via other analytical means relevant are indicative of the feasibility, accuracy as well as applicability of the MPSM, which deal with chemistry, amount, lattice parameter, elemental partitioning, atomic-site occupancy and stability of precipitated phases of either superalloy or heat-resistant steel samples analyzed. Successful applications of the MPSM not only show a significant improvement for difficulties in accurate quantification in phase chemistry under the EPMA/SEM-EDS measurement conditions but also provide with a useful and helpful tool to determine some other important physical quantities in alloys and steels, which make it possible to quantitatively and more widely evaluate structure-property relationships of the materials investigated through analyzing their bulk samples under EPMA/SEM-EDS measurement conditions.

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