An X-ray Diffraction Study of the Structure of Vitreous P2O5

1998 ◽  
Vol 53 (3-4) ◽  
pp. 93-104 ◽  
Author(s):  
Uwe Hoppe ◽  
Günter Walter ◽  
Rainer Kranold ◽  
Dörte Stachel
Keyword(s):  
Bond Distance ◽  
Real Space ◽  
Diffraction Peak ◽  
Angle Distribution ◽  
X Ray Diffraction ◽  
X Ray ◽  
Space Resolution ◽  
Structure Factors ◽  
Hole Model ◽  
20 Nm

Abstract Recently, the lengths of the two P-O bonds in the PO4 tetrahedron were obtained by neutron diffraction of high real-space resolution. By use of the present X-ray diffraction experiments, the P-P distance belonging to pairs of corner-linked PO4 units is determined. Using this length of (294 ± 2) pm and taking into account the P-0 bond distance to the bridging oxygen atom of 158 pm, a mean P-O-P angle of 137° ± 3° is calculated. The reverse Monte Carlo simulations fit the neutron and X-ray structure factors. The P-O-P angle distribution obtained this way possesses a mean angle of 141°. An interpretation of the first scattering peaks is presented by analysing the occupancy and the distances of various co-ordination shells by use of model configurations. The low occupancy of the first shells allows the application of the schematic hole model of Dixmier. The first X-ray diffraction peak at 13 nm-1 is related to the P-P2nd shell, the shoulder at 20 nm-1 arises from the P-O2nd shell. The most similar crystalline structure with vitreous P2O5 is the orthorhombic P2O5, form II. But it has more effectively orientated terminal oxygen atoms and, thus, a higher packing than the glass.

scholarly journals High real-space resolution structure of materials by high-energy x-ray diffraction

1999 ◽  
Vol 590 ◽  
Author(s):  
V. Petkov ◽  
S. J. L. Billinge ◽  
J. Heising ◽  
M. G. Kanatzidis ◽  
S. D. Shastri ◽  
...  
Keyword(s):  
Pair Distribution Function ◽  
High Energy ◽  
Real Space ◽  
Function Technique ◽  
X Ray Diffraction ◽  
X Ray ◽  
Space Resolution ◽  
Atomic Pair Distribution Function ◽  
Atomic Pair ◽  
Resolution Structure

ABSTRACTResults of high-energy synchrotron radiation experiments are presented demonstrating the advantages of the high-resolution atomic Pair Distribution Function technique in determining the structure of materials with intrinsic disorder.

scholarly journals High Real-Space Resolution Measurement of the Local Structure ofGa1−xInxAsUsing X-Ray Diffraction

1999 ◽  
Vol 83 (20) ◽  
pp. 4089-4092 ◽  
Author(s):  
V. Petkov ◽  
I-K. Jeong ◽  
J. S. Chung ◽  
M. F. Thorpe ◽  
S. Kycia ◽  
...  
Keyword(s):  
Local Structure ◽  
Real Space ◽  
X Ray Diffraction ◽  
X Ray ◽  
Space Resolution ◽  
Resolution Measurement

Neutron and X-ray Diffraction Study on the Structure of Ultraphosphate Glasses

1997 ◽  
Vol 52 (3) ◽  
pp. 259-269 ◽  
Author(s):  
Uwe Hoppe ◽  
Günter Walter ◽  
Dörte Stachel ◽  
Andrea Barz ◽  
Alex C. Hannon
Keyword(s):  
Crystal Structures ◽  
Coordination Number ◽  
Real Space ◽  
The Other ◽  
Oxide Content ◽  
X Ray Diffraction ◽  
X Ray ◽  
Space Resolution ◽  
Epithermal Neutrons ◽  
The Mean

Abstract The high real-space resolution of neutron diffraction experiments which is provided by use of the epithermal neutrons from spallation sources was exploited in order to differentiate the unlike P-O bonds existing in the PO4 units of phosphate glass networks. The 2 P-O distance peaks, separated by about 12 pm, which were found in the zinc and the calcium ultraphosphate glasses studied are assigned to oxygen sites on bridging (OB) and terminal (OT) positions. The mean P-O distances are nearly invariable versus the growing metal oxide content which results from an elongation of the P-OB and P-OT bonds. The bond lengths which are known from the related crystal structures and from ab initio calculations show almost the same behaviour. The discussion of further details of the crystal structures leads to the conclusion that P-OB rather than P-OT distances should show more details in case of diffraction measurements of even higher real-space resolution. The change of the Zn-O coordination number from 6 to 4 versus increasing ZnO content, which was obtained in previous X-ray diffraction experiments, is confirmed by the recent combination of neutron and X-ray diffraction data. On the other hand, the Ca-O coordination number of about 6 is almost invariable.

The Structure of Amorphous Hydrogenated Silicon:Carbon Alloys Using X-Ray and Neutron Scattering and Computer Simulation - The Effect of Hydrogen Dilution

1992 ◽  
Vol 270 ◽  
Author(s):  
T. M. Burke ◽  
P. J. R. Honeybone ◽  
D. W. Huxley ◽  
R. J. Newport ◽  
Th. Frauenheim ◽  
...  
Keyword(s):  
Computer Simulation ◽  
Diffraction Data ◽  
Density Functional ◽  
Real Space ◽  
X Ray Diffraction ◽  
X Ray ◽  
Space Resolution ◽  
Silicon Carbon ◽  
Two Samples ◽  
Silane Precursor

ABSTRACTNeutron and X-ray diffraction techniques have been applied to the study of two samples of a-Si:C:H. Both samples were prepared using conventional glow discharge methods, but the hydrocarbon/silane precursor gas was diluted with hydrogen in one case. Analysis of the X-ray diffraction data gives a clear picture of the silicon network, since the scattering profile is dominated by the Si-Si correlations. The high real-space resolution neutron diffraction data, however allows one to comment on the effect of this dilution on the silicon-carbon bonding morphology, and in particular on the degree to which the additional hydrogen enhances hetero-coordination. In addition we present the results of a preliminary computer simulation study of the structure of a-C:H and a-Si:H using an approximate molecular dynamic density functional theory, and discuss its viability in the study of the more complex a-Si:C:H ternary alloy.

scholarly journals Evidence for charge localization in the ferromagnetic phase ofLa1−xCaxMnO3from high real-space-resolution x-ray diffraction

2000 ◽  
Vol 62 (2) ◽  
pp. 1203-1211 ◽  
Author(s):  
S. J. L. Billinge ◽  
Th. Proffen ◽  
V. Petkov ◽  
J. L. Sarrao ◽  
S. Kycia
Keyword(s):  
Real Space ◽  
Ferromagnetic Phase ◽  
X Ray Diffraction ◽  
X Ray ◽  
Space Resolution ◽  
Charge Localization

scholarly journals The boson peak and the first sharp diffraction peak in (As2S3)x(GeS2)1–x glasses

2021 ◽  
Vol 24 (3) ◽  
pp. 312-318
Author(s):  
A.V. Stronski ◽  
◽  
T.S. Kavetskyy ◽  
L.O. Revutska ◽  
I. Kaban ◽  
...  
Keyword(s):  
Raman Spectroscopy ◽  
High Resolution ◽  
High Energy ◽  
Boson Peak ◽  
Diffraction Peak ◽  
X Ray Diffraction ◽  
Partial Structure ◽  
X Ray ◽  
Structure Factors ◽  
Direct Proportionality

The parameters of the boson peak (BP) and the first sharp diffraction peak (FSDP) in (As2S3)x(GeS2)1x glasses measured using high-resolution Raman spectroscopy and high-energy synchrotron X-ray diffraction measurements are examined as a function of x. It has been found that there is no correlation between the positions of BP and FSDP. The BP position shows a nonlinear composition behavior with a maximum at about x = 0.4, whereas the FSDP position changes virtually linearly with x. The intensities of both BP and FSDP show nonlinear composition dependences with the slope changes at x = 0.4, although there is no direct proportionality. Analysis of the partial structure factors for the glasses with x = 0.2, 0.4 and 0.6 obtained in another study has shown that the cation-cation atomic pairs of Ge–Ge, Ge–As and As–As make the largest contribution to FSDP, where the Ge–Ge and Ge–As pairs are dominant.

Isomorphous replacement in electron diffraction of wet crystals of rat hemoglobin

1983 ◽  
Vol 41 ◽  
pp. 446-447
Author(s):  
William F. Tivol ◽  
Murray Vernon King ◽  
D. F. Parsons
Keyword(s):  
Electron Diffraction ◽  
Heavy Atom ◽  
Isomorphous Substitution ◽  
X Ray Diffraction ◽  
Salt Solutions ◽  
X Ray ◽  
Isomorphous Replacement ◽  
Structure Factors ◽  
Diffraction Structure ◽  
The Mean

Feasibility of isomorphous substitution in electron diffraction is supported by a calculation of the mean alteration of the electron-diffraction structure factors for hemoglobin crystals caused by substituting two mercury atoms per molecule, following Green, Ingram & Perutz, but with allowance for the proportionality of f to Z3/4 for electron diffraction. This yields a mean net change in F of 12.5%, as contrasted with 22.8% for x-ray diffraction.Use of the hydration chamber in electron diffraction opens prospects for examining many proteins that yield only very thin crystals not suitable for x-ray diffraction. Examination in the wet state avoids treatments that could cause translocation of the heavy-atom labels or distortion of the crystal. Combined with low-fluence techniques, it enables study of the protein in a state as close to native as possible.We have undertaken a study of crystals of rat hemoglobin by electron diffraction in the wet state. Rat hemoglobin offers a certain advantage for hydration-chamber work over other hemoglobins in that it can be crystallized from distilled water instead of salt solutions.

Highlights in the history of X-ray topography1

1995 ◽  
Vol 210 (6) ◽  
Author(s):  
A. R. Lang
Keyword(s):  
Magnetic Domain ◽  
Diffraction Theory ◽  
Dislocation Loops ◽  
X Ray Diffraction ◽  
X Ray ◽  
Domain Structures ◽  
Structure Factors ◽  
History Of ◽  
Dislocation Sources ◽  
Non Destructive

AbstractX-ray topography provides a non-destructive method of mapping point-by-point variations in orientation and reflecting power within crystals. The discovery, made by several workers independently, that in nearly perfect crystals it was possible to detect individual dislocations by X-ray diffraction contrast started an epoch of rapid exploitation of X-ray topography as a new, general method for assessing crystal perfection. Another discovery, that of X-ray Pendellösung, led to important theoretical developments in X-ray diffraction theory and to a new and precise method for measuring structure factors on an absolute scale. Other highlights picked out for mention are studies of Frank-Read dislocation sources, the discovery of long dislocation helices and lines of coaxial dislocation loops in aluminium, of internal magnetic domain structures in Fe-3 wt.% Si, and of stacking faults in silicon and natural diamonds.

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.

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