Interpretation of the Nano-Electron-Diffraction Patterns along the Five-Fold Axis of Decahedral Gold Nanoparticles

2011 ◽  
Vol 17 (2) ◽  
pp. 279-283 ◽  
Author(s):  
L.D. Romeu ◽  
J. Reyes-Gasga
Keyword(s):  
Gold Nanoparticles ◽  
Electron Beam ◽  
Electron Diffraction ◽  
Diffraction Pattern ◽  
Rotational Symmetry ◽  
Fold Axis ◽  
Double Refraction ◽  
Dynamical Diffraction ◽  
Refraction Effect ◽  
Diffraction Patterns

AbstractThe transition from 10-fold to 5-fold symmetry was observed during the analysis of nanodiffraction patterns of a gold decahedral multiple twinned nanoparticle of 15 nm in diameter. The analysis shows that as the convergence of the beam is increased, the rotational symmetry of the diffraction pattern shifts from 10- to 5-fold. The 10-fold symmetry predicted by Friedel's law is lost by the asymmetric shift of the diffraction spots, an effect that becomes more noticeable as the electron beam convergence increases. Dynamical and kinematical diffraction calculations indicate this decrease in symmetry is the result of a double refraction effect coupled with the variation of the dynamical diffraction conditions arising from a varying electron beam convergence.

Contrast of Kossel Patterns in Electron Diffraction

1974 ◽  
Vol 29 (12) ◽  
pp. 1929-1930b ◽  
Author(s):  
F. Fujimoto ◽  
G. Lehmpfuhl
Keyword(s):  
Electron Beam ◽  
Electron Diffraction ◽  
Diffraction Pattern ◽  
Hollow Cone ◽  
Angular Aperture ◽  
Kossel Pattern ◽  
Diffraction Patterns ◽  
Convergent Beam

Electron diffraction patterns from a Si crystal taken with a convergent beam of large angular aperture (Kossel pattern) are compared with the diffraction pattern taken with a hollow cone convergent electron beam. For thin crystals the patterns are complementary. This behaviour is discussed.

scholarly journals Particle size and convergent electron diffraction patterns of triangular prismatic gold nanoparticles

2021 ◽  
Vol 67 (4 Jul-Aug) ◽  
Author(s):  
Clemente Fernando-Marquez ◽  
Gilberto Mondragón-Galicia ◽  
Lourdes Bazán-Díaz ◽  
José Reyes-Gasga
Keyword(s):  
Particle Size ◽  
Gold Nanoparticles ◽  
Electron Diffraction ◽  
Diffraction Pattern ◽  
Stacking Faults ◽  
Au Nanoparticle ◽  
Diffraction Patterns ◽  
Convergent Beam ◽  
Beam Diffraction ◽  
Fcc Structure

Convergent beam diffraction (CBED) patterns of nanoparticles are possible. CBED of triangular prismatic shaped Au nanoparticle with focus on diffraction pattern symmetry and forbidden reflections observed along [111] and [112] zone axes are reported in this work. It is well known that the CBED patterns of nanoparticles of 30 nm or less in size only show bright kinematical discs. The dynamic contrast with Kikuchi and sharp HOLZ lines within the bright discs, as observed in CBED of volumetric materials, is well observed in particles larger of 500 nm in size. In addition, it is shown that the 1/3[422] and 1/2[311] weak forbidden reflections observed in the [111] and [112] electron diffraction patterns of these particles do not modify the symmetry of the CBED patterns, but they disappear as the size of the particle increases. The symmetry of the CBED patterns are always observed in concordance with the space group Fm3m (No. 225) of the Au unit cell. The possible explanations for observing forbidden reflections are the incomplete ABC stacking due to surface termination and the stacking faults in the fcc structure.

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.

Determination of hydrogen ordering within the β-RH2+xphase (R= Ho, Y) using electron diffraction techniques

2000 ◽  
Vol 33 (5) ◽  
pp. 1246-1252 ◽  
Author(s):  
Elizabeth J. Grier ◽  
Amanda K. Petford-Long ◽  
Roger C. C. Ward
Keyword(s):  
Electron Diffraction ◽  
Neutron Scattering ◽  
Diffraction Pattern ◽  
Computer Simulations ◽  
Fluorite Structure ◽  
Long Range Order ◽  
Hydrogen Atoms ◽  
Ordered Structures ◽  
Diffraction Patterns

Computer simulations of the electron diffraction patterns along the [\bar{1}10] zone axes of four ordered structures within the β-RH2+xphase, withR= Ho or Y, and 0 ≤x≤ 0.25, have been performed to establish whether or not the hydrogen ordering could be detected using electron diffraction techniques. Ordered structures within otherRH2+x(R= Ce, Tb) systems have been characterized with neutron scattering experiments; however, for HoH(D)2+x, neutron scattering failed to characterize the superstructure, possibly because of the lowxconcentration or lack of long-range order within the crystal. This paper aims to show that electron diffraction could overcome both of these problems. The structures considered were the stoichiometric face-centred cubic (f.c.c.) fluorite structure (x= 0), theD1 structure (x= 0.125), theD1astructure (x= 0.2) and theD022structure (x= 0.25). In the stoichiometric structure, with all hydrogen atoms located on the tetrahedral (t) sites, only the diffraction pattern from the f.c.c. metal lattice was seen; however, for the superstoichiometric structures, with the excess hydrogen atoms ordered on the octahedral (o) sites, extra reflections were visible. All the superstoichiometric structures showed extra reflections at the (001)f.c.c.and (110)f.c.c.type positions, with structureD1 also showing extra peaks at (½ ½ ½)f.c.c.. These reflections are not seen in the simulations at similar hydrogen concentrations with the hydrogen atoms randomly occupying theovacancies.

scholarly journals Gently does it for submicron crystals

eLife ◽  
2013 ◽  
Vol 2 ◽  
Author(s):  
Oliver B Zeldin ◽  
Axel T Brunger
Keyword(s):  
Electron Beam ◽  
Protein Structure ◽  
Electron Diffraction ◽  
Diffraction Data ◽  
Three Dimensional ◽  
Electron Diffraction Data ◽  
Large Numbers ◽  
Diffraction Patterns ◽  
Weak Electron

A protein structure has been refined with electron diffraction data obtained by using a very weak electron beam to collect large numbers of diffraction patterns from a few sub-micron-sized three-dimensional crystals.

scholarly journals A novel nondestructive diagnostic method for mega-electron-volt ultrafast electron diffraction

2019 ◽  
Vol 9 (1) ◽  
Author(s):  
Xi Yang ◽  
Junjie Li ◽  
Mikhail Fedurin ◽  
Victor Smaluk ◽  
Lihua Yu ◽  
...  
Keyword(s):  
Electron Beam ◽  
Electron Diffraction ◽  
Diffraction Pattern ◽  
Real Time ◽  
Beam Energy ◽  
Energy Spread ◽  
Radial Mode ◽  
Electron Beam Energy ◽  
Ultrafast Electron Diffraction ◽  
Electron Volt

AbstractA real-time, nondestructive, Bragg-diffracted electron beam energy, energy-spread and spatial-pointing jitter monitor is experimentally verified by encoding the electron beam energy and spatial-pointing jitter information into the mega-electron-volt ultrafast electron diffraction pattern. The shot-to-shot fluctuation of the diffraction pattern is then decomposed to two basic modes, i.e., the distance between the Bragg peaks as well as its variation (radial mode) and the overall lateral shift of the whole pattern (drift mode). Since these two modes are completely decoupled, the Bragg-diffraction method can simultaneously measure the shot-to-shot energy fluctuation from the radial mode with 2·10−4 precision and spatial-pointing jitter from the drift mode having wide measurement span covering energy jitter range from 10−4 to 10−1. The key advantage of this method is that it allows us to extract the electron beam energy spread concurrently with the ongoing experiment and enables online optimization of the electron beam especially for future high charge single-shot ultrafast electron diffraction (UED) and ultrafast electron microscopy (UEM) experiments. Furthermore, real-time energy measurement enables the filtering process to remove off-energy shots, improving the resolution of time-resolved UED. As a result, this method can be applied to the entire UED user community, beyond the traditional electron beam diagnostics of accelerators used by accelerator physicists.

Small-Spot Illumination For High-Resolution Electron Microscopy of Beam-Sensitive Specimens

1985 ◽  
Vol 43 ◽  
pp. 320-321
Author(s):  
Kenneth H. Downing ◽  
Robert M. Glaeser
Keyword(s):  
Electron Microscopy ◽  
Electron Beam ◽  
High Resolution ◽  
Electron Diffraction ◽  
High Resolution Electron Microscopy ◽  
Photographic Emulsion ◽  
Lateral Motion ◽  
Small Spot ◽  
Resolution Electron ◽  
Diffraction Patterns

The contrast observed in images of beam-sensitive, crystalline specimens is found to be significantly less than one would predict based on observations of electron diffraction patterns of the specimens. Factors such as finite coherence, inelastic scattering, and the limited MTF of the photographic emulsion account for some decrease in contrast. It appears, however, that most of the loss in signal is caused by motion of the specimen during exposure to the electron beam. The introduction of point and other defects in the crystal, resulting from radiation damage, causes bending and lateral motion, which degrade the contrast in the image. We have therefore sought to determine whether the beam-induced specimen motion can be reduced by reducing the area of the specimen which is illuminated at any one time.

Automatic Computer Measurement of Selected Area Electron Diffraction Patterns from Asbestos Minerals

1988 ◽  
Vol 32 ◽  
pp. 593-600
Author(s):  
J. C. Russ ◽  
T. Taguchi ◽  
P. M. Peters ◽  
E. Chatfield ◽  
J. C. Russ ◽  
...  
Keyword(s):  
Electron Diffraction ◽  
Diffraction Pattern ◽  
Diffraction Data ◽  
Automatic Method ◽  
Automatic Computer ◽  
Selected Area Electron Diffraction ◽  
Computer Measurement ◽  
Integrated Intensity ◽  
Diffraction Patterns ◽  
True Center

Conventional selected area diffraction patterns as obtained in the TEM present difficulties for identification of materials such as asbestifonn minerals, although diffraction data is considered to be one of the preferred methods for making this identification. The preferred orientation of the fibers in each field of measurement, and the spotty patterns that are obtained, do not readily lend themselves to measurement of the integrated intensity values for each dspacing, and even the d-spacings may be hard to determine precisely because the true center location for the broken rings requires estimation. To overcome these problems, we have implemented an automatic method for diffraction pattern measurement. It automatically locates the center of patterns with high precision, measures the radius of each ring of spots in the pattern, and integrates the density of spots in that ring.

Sign in / Sign up

Export Citation Format

Share Document