The structure of amorphous and polycrystalline materials using energy-filtered RDF analysis

1992 ◽  
Vol 50 (2) ◽  
pp. 1190-1191
Author(s):  
David Cockayne ◽  
David McKenzie
Keyword(s):  
Electron Diffraction ◽  
Diffraction Pattern ◽  
Density Function ◽  
Electron Diffraction Pattern ◽  
Polycrystalline Materials ◽  
Nearest Neighbour ◽  
X Ray ◽  
Selected Area Electron Diffraction ◽  
Reduced Density ◽  
System F

The technique of Electron Reduced Density Function (RDF) analysis has ben developed into a rapid analytical tool for the analysis of small volumes of amorphous or polycrystalline materials. The energy filtered electron diffraction pattern is collected to high scattering angles (currendy to s = 2 sinθ/λ = 6.5 Å-1) by scanning the selected area electron diffraction pattern across the entrance aperture to a GATAN parallel energy loss spectrometer. The diffraction pattern is then converted to a reduced density function, G(r), using mathematical procedures equivalent to those used in X-ray and neutron diffraction studies.Nearest neighbour distances accurate to 0.01 Å are obtained routinely, and bond distortions of molecules can be determined from the ratio of first to second nearest neighbour distances. The accuracy of coordination number determinations from polycrystalline monatomic materials (eg Pt) is high (5%). In amorphous systems (eg carbon, silicon) it is reasonable (10%), but in multi-element systems there are a number of problems to be overcome; to reduce the diffraction pattern to G(r), the approximation must be made that for all elements i,j in the system, fj(s) = Kji fi,(s) where Kji is independent of s.

scholarly journals High-angle electron diffraction of frozen hydrated collagen

1976 ◽  
Vol 153 (1) ◽  
pp. 139-140 ◽  
Author(s):  
H Chanzy ◽  
J M Franc ◽  
D Herbage
Keyword(s):  
Electron Microscope ◽  
Electron Diffraction ◽  
Diffraction Pattern ◽  
Electron Diffraction Pattern ◽  
Collagen Fibrils ◽  
Diffraction Experiment ◽  
High Angle ◽  
X Ray Diffraction ◽  
X Ray ◽  
Good Agreement

By using the techniques developed by Taylor et al. [(1975) J. Mol. Biol. 92, 165-167] (freezing of the hydrated specimen before its insertion into the electron microscope and keeping it frozen throughout the diffraction experiment), it was possible to obtain a high-angle electron-diffraction pattern from collagen fibrils. This pattern is in good agreement with that obtained by high-angle X-ray diffraction. Electron diffraction will be very useful to study collagen, because the diffraction pattern from a carefully selected area of one fibril is now feasible.

scholarly journals Unit Cell Determination of New Minerals by Using Electron Diffraction

2014 ◽  
Vol 70 (a1) ◽  
pp. C1098-C1098
Author(s):  
Galiya Bekenova
Keyword(s):  
Electron Beam ◽  
Electron Diffraction ◽  
Diffraction Pattern ◽  
Electron Diffraction Pattern ◽  
Reciprocal Lattice ◽  
Fine Powder ◽  
Selected Area Electron Diffraction ◽  
Ewald Sphere ◽  
Type Pattern ◽  
Diffraction Patterns

Many new minerals recently discovered in Kazakhstan had platy (niksergievite), fiber (kazakhstanite) or fine powder (mitryaevaite) structural appearance. In monoclinic minerals with perfect or good (001) cleavage, d100 i d010-spacings in the hk0 zone could be measured on selected area electron-diffraction pattern from monocrystal tilted the way that axis c is parallel to the electron beam direction. This method was used for measuring d-spacings in new minerals such as kazakhstanite, niksergievite as well as in new discovered micas – sokolovaite and orlovite. In minerals with triclinic structure (mitryaevaite) the same method was used to determine d100, d010 as well as γ=1800-γ* (γ* is an angle between reciprocal lattice axes a* and b*). hk0-indices of each ring were defined by comparison of the normal texture (ring type) pattern and selected area pattern. For example, hk0-indices for triclinic cell of mitryaevaite were (010), (100), (-110), (110), (020) etc. When specimen with preferred orientation is tilted under angle φ toward electron beam, an "oblique texture" electron-diffraction pattern is obtained. Arcs of the ellipses on such diffraction pattern are formed by intersection of Ewald sphere with ring nodes. The height of the arc's maximum above the tilt axis is calculated by using the following formula: D=hp+ks+lq, where p, s, q are measured on the diffraction pattern [1-3]. For example, on "oblique texture" electron-diffraction pattern from vanalite with perfect (010) cleavage, arcs are merged with layer lines that intersect the ellipses and D=ks. Allocation of indices on texture electron-diffraction patterns from monoclinic niksergievite, sokolovaite and orlovite with perfect (001) cleavage is more difficult. In these cases, D= hp+lq. Heights of the arcs are situated symmetrical in regards to each lq level. With the help of "oblique texture" diffraction patterns stacking polytypes were indicated for such minerals.

A search-match program for materials identification in the Transmission Electron Microscope using electron diffraction pattern analysis

1990 ◽  
Vol 48 (4) ◽  
pp. 432-433
Author(s):  
S.H. Vale
Keyword(s):  
Electron Diffraction ◽  
Diffraction Pattern ◽  
Electron Diffraction Pattern ◽  
Pattern Analysis ◽  
Chemical Information ◽  
Large Database ◽  
X Ray ◽  
Colour Image ◽  
Transmission Electron ◽  
Combining Data

A program has been written for an energy dispersive x-ray microanalysis system computer to identify a sample by combining data from an electron diffraction pattern collected in a TEM with chemical information from the sample. The combined information is compared with a large database held on the computer to find a suitable set of matching compounds.The program was written for a Link Analytical AN10000 microanalysis system which is based on a computer with a 16 bit word length, 20 MHz CPU with 512 kbyte of memory for programs and data, 40 Mbyte hard disk and a 512 × 512 pixel colour image display with its own memory. The database used was the NBS/SANDIA/ICDD electron diffraction database adapted for the AN 10000 computer. This database contains about 70000 compound entries and occupies 9 Mbyte of disk space.

Bimolecular and Monomolecular Lipid Films: Selected Area Electron Diffraction

1969 ◽  
Vol 27 ◽  
pp. 338-339
Author(s):  
Robert M. Glaeser ◽  
David W. Deamer
Keyword(s):  
Electron Diffraction ◽  
Membrane Structure ◽  
Molecular Organization ◽  
Membrane Material ◽  
X Ray Diffraction ◽  
Membrane Systems ◽  
X Ray ◽  
Selected Area Electron Diffraction ◽  
Lipid Films ◽  
Ultimate Objective

In the investigation of the molecular organization of cell membranes it is often supposed that lipid molecules are arranged in a bimolecular film. X-ray diffraction data obtained in a direction perpendicular to the plane of suitably layered membrane systems have generally been interpreted in accord with such a model of the membrane structure. The present studies were begun in order to determine whether selected area electron diffraction would provide a tool of sufficient sensitivity to permit investigation of the degree of intermolecular order within lipid films. The ultimate objective would then be to apply the method to single fragments of cell membrane material in order to obtain data complementary to the transverse data obtainable by x-ray diffraction.

Electron diffraction studies of amorphous and polycrystalline thin films

1990 ◽  
Vol 48 (4) ◽  
pp. 118-119
Author(s):  
D J H Cockayne ◽  
D R McKenzie
Keyword(s):  
Thin Films ◽  
Electron Diffraction ◽  
Polycrystalline Materials ◽  
Good Resolution ◽  
Scattered Intensity ◽  
Radial Density ◽  
X Ray ◽  
Polycrystalline Thin Films ◽  
Nitrogen Ion ◽  
Diffraction Patterns

The study of amorphous and polycrystalline materials by obtaining radial density functions G(r) from X-ray or neutron diffraction patterns is a well-developed technique. We have developed a method for carrying out the same technique using electron diffraction in a standard TEM. It has the advantage that studies can be made of thin films, and on regions of specimen too small for X-ray and neutron studies. As well, it can be used to obtain nearest neighbour distances and coordination numbers from the same region of specimen from which HREM, EDS and EELS data is obtained.The reduction of the scattered intensity I(s) (s = 2sinθ/λ ) to the radial density function, G(r), assumes single and elastic scattering. For good resolution in r, data must be collected to high s. Previous work in this field includes pioneering experiments by Grigson and by Graczyk and Moss. In our work, the electron diffraction pattern from an amorphous or polycrystalline thin film is scanned across the entrance aperture to a PEELS fitted to a conventional TEM, using a ramp applied to the post specimen scan coils. The elastically scattered intensity I(s) is obtained by selecting the elastically scattered electrons with the PEELS, and collecting directly into the MCA. Figure 1 shows examples of I(s) collected from two thin ZrN films, one polycrystalline and one amorphous, prepared by evaporation while under nitrogen ion bombardment.

Photographical Record of the Dispersion Surface in Rotating Crystal Electron Diffraction Pattern

1968 ◽  
Vol 23 (4) ◽  
pp. 544-549 ◽  
Author(s):  
G. Lehmpfuhl ◽  
A. Reissland
Keyword(s):  
Dynamical System ◽  
Electron Diffraction ◽  
Diffraction Pattern ◽  
Electron Diffraction Pattern ◽  
Plane Waves ◽  
Zone Axis ◽  
System Of Equations ◽  
Wave Fields ◽  
Dispersion Surface ◽  
Crystal Electron

Strong interacting wave fields in a wedge-shaped crystal are separated into different plane waves when leaving the crystal and reveal points on the dispersion surface. By rotating the crystal while moving the film one obtains a photographical record of a section through the dispersion surface which may be compared with theory. An experiment with a macroscopic MgO wedge is reported. The 002 interference with excitation error nearly zero was recorded near the [I10] zone axis while rotating the crystal about the [001] axis. The diagrams are compared with dynamical 17-beam calculations. The results show that a reduction of the infinite dynamical system of equations to 17 equations is correct under these special geometrical conditions.

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