Convergent Beam Electron Diffraction Zone Axis Pattern Map of Zirconium

1990 ◽  
Vol 48 (2) ◽  
pp. 496-497
Author(s):  
E. Silva ◽  
R. Scozia
Keyword(s):  
Electron Diffraction ◽  
Convergent Beam Electron Diffraction ◽  
Zone Axis ◽  
Pole Piece ◽  
Small Particles ◽  
Present Communication ◽  
Beam Electron ◽  
Zero Layer ◽  
Set Up ◽  
Convergent Beam

The purpose in obtaining zone axis pattern map (zap map) from a given material is to provide a quick and reliable tool to identify cristaline phases, and crystallographic directions, even in small particles. Bend contours patterns and Kossel lines patterns maps from Zr single crystal in the [0001] direction have been presented previously. In the present communication convergent beam electron diffraction (CBED) zap map of Zr will be shown. CBED patterns were obtained using a Philips microscope model EM300, which was set up to carry out this technique. Convergent objective upper pole piece for STEM and some electronic modifications in the lens circuits were required, furthermore the microscope was carefully cleaned and it was operated at a vacuum eminently good.CBED patterns in the Zr zap map consist of zero layer disks, showing fine details within them which correspond to intersecting set of higher order Laue zone (HOLZ) deficiency lines.

Wavefunction and CBED results of the STEM multislice calculation

1989 ◽  
Vol 47 ◽  
pp. 664-665
Author(s):  
R. F. Loane ◽  
E. J. Kirkland ◽  
J. Silcox
Keyword(s):  
High Resolution ◽  
Electron Diffraction ◽  
Convergent Beam Electron Diffraction ◽  
Zone Axis ◽  
Pole Piece ◽  
Beam Electron ◽  
Stem Image ◽  
Convergent Beam ◽  
Electron Wavefunction ◽  
Insight Into

The multislice algorithm has been used to simulate ADF STEM images. Examination of the evolution of the electron wavefunction as it propagates through the specimen, can provide insight into the sources of contrast in the STEM image. Plots of the wavefunction intensity as a function of position and as a convergent beam electron diffraction (CBED) pattern are two complementary views of the diffraction process. Examples from the large number of these plots that are calculated during the ADF STEM calculations will be presented.The simulated specimen consists of multiples of 47 Å (15 slices) of silicon (111). The slices are 65 Å × 66 Å(512 × 512 pixels) in size, setting the maximum included scattering angle to 95 mrad. The incident probe models a 100 keV VG-HB501 STEM at Scherzer focus with either the low resolution pole piece (Cs=3.3 mm, Δf=1100 Å, αap = 8.2 mrad) or the high resolution pole piece (Cs = 0.7 mm, Δf=510 Å, αap=12.1 mrad). The beam and specimen are aligned exactly along the (111) zone axis (no tilt).

Experimental Studies of Bonding Related Properties in Binary Intermetallics by Convergent Beam Electron Diffraction

2011 ◽  
Vol 1295 ◽  
Author(s):  
X. H. Sang ◽  
A. Kulovits ◽  
J. Wiezorek
Keyword(s):  
Electron Diffraction ◽  
Experimental Studies ◽  
Convergent Beam Electron Diffraction ◽  
Zone Axis ◽  
Order Structure ◽  
Electron Charge Density ◽  
Beam Electron ◽  
Structure Factors ◽  
Different Temperatures ◽  
Convergent Beam

ABSTRACTAccurate Debye-Waller (DW) factors of chemically ordered β-NiAl (B2, cP2, ${\rm{Pm}}\bar 3 {\rm{m}}$) have been measured at different temperatures using an off-zone axis multi-beam convergent beam electron diffraction (CBED) method. We determined a cross over temperature below which the DW factor of Ni becomes smaller than that of Al of ~90K. Additionally, we measured for the first time DW factors and structure factors of chemically ordered γ1-FePd (L10, tP2, P4/mmm) at 120K. We were able to simultaneously determine all four anisotropic DW factors and several low order structure factors using different special off-zone axis multi-beam convergent beam electron diffraction patterns with high precision and accuracy. An electron charge density deformation map was constructed from measured X-ray diffraction structure factors for γ1-FePd.

Enantiomorph identification of crystals belonging to the point groups 321 and 312 by convergent-beam electron diffraction

2007 ◽  
Vol 40 (2) ◽  
pp. 241-249 ◽  
Author(s):  
Haruyuki Inui ◽  
Akihiro Fujii ◽  
Hiroki Sakamoto ◽  
Satoshi Fujio ◽  
Katsushi Tanaka
Keyword(s):  
Electron Diffraction ◽  
Diffraction Method ◽  
Convergent Beam Electron Diffraction ◽  
Zone Axis ◽  
The Other ◽  
Zeroth Order ◽  
Beam Electron ◽  
First Order ◽  
Point Groups ◽  
Convergent Beam

The recently proposed CBED (convergent-beam electron diffraction) method for enantiomorph identification has been successfully applied to crystals belonging to the point groups 321 and 312. The intensity asymmetry of zeroth-order Laue zone and/or first-order Laue zone reflections of Bijvoet pairs is easily recognized in CBED patterns with the incidence along appropriate zone-axis orientations for each member of the enantiomorphic pair. The intensity asymmetry with respect to the symmetry line is reversed upon changing the space group (handedness) from one to the other. Thus, enantiomorph identification can be easily performed in principle for all crystals belonging to the point groups 321 and 312.

Appropriate zone-axis orientations for the determination of crystal polarity by convergent-beam electron diffraction

2015 ◽  
Vol 48 (3) ◽  
pp. 736-746 ◽  
Author(s):  
Katsushi Tanaka ◽  
Norihiko L. Okamoto ◽  
Satoshi Fujio ◽  
Hiroki Sakamoto ◽  
Haruyuki Inui
Keyword(s):  
Electron Diffraction ◽  
Rotation Axis ◽  
Convergent Beam Electron Diffraction ◽  
Zone Axis ◽  
Mirror Plane ◽  
Axis Orientation ◽  
Beam Electron ◽  
Polarity Determination ◽  
Point Groups ◽  
Convergent Beam

A convergent-beam electron diffraction (CBED) method is proposed for polarity determination, in which polarity is determined from the intensity asymmetry of any of thehkl–\overline h\overline k\overline l Friedel pairs appearing in a zone-axis CBED pattern with a symmetric arrangement of Bijvoet pairs of reflections. The intensity asymmetry occurs as a result of multiple scattering among Bijvoet pairs of reflections in the CBED pattern. The appropriate zone-axis orientations for polarity determination are deduced for 19 of the 25 polar point groups from symmetry considerations so as to observe Bijvoet pairs of reflections symmetrically in a single CBED pattern. These appropriate zone-axis orientations deduced for the 19 polar point groups coincide with nonpolar directions. This is because the nonpolar directions for these point groups are perpendicular to an even-fold rotation axis, which guarantees the symmetric arrangement of Bijvoet pairs of reflections with respect to the symmetry (m–m′) line in a CBED pattern taken along any of the appropriate zone-axis orientations. Them–m′ line in the CBED pattern is proved to be perpendicular to the trace of the even-fold rotation axis. On the other hand, if the nonpolar direction is either perpendicular to a mirror plane or parallel to a roto-inversion axis as in the four point groupsm, 3m1, 31m, \overline 6, the nonpolar direction cannot be used as the appropriate zone-axis orientation for polarity determination because the Bijvoet pairs of reflections are not arranged symmetrically in the CBED pattern. The validity of the CBED method is confirmed both by experiment and by calculation of CBED patterns.

Quantitative Zone-Axis Convergent Beam Electron Diffraction: Current Status and Future Prospects

2003 ◽  
Vol 9 (5) ◽  
pp. 411-418 ◽  
Author(s):  
Martin Saunders
Keyword(s):  
Electron Diffraction ◽  
Charge Density ◽  
Convergent Beam Electron Diffraction ◽  
Zone Axis ◽  
Current Status ◽  
Crystalline Materials ◽  
Beam Electron ◽  
Structure Factors ◽  
Bond Charge ◽  
Convergent Beam

Quantitative zone-axis convergent beam electron diffraction (CBED) is now an established technique. Over the past decade it has been developed into a tested method for the accurate refinement of structure factors, allowing the details of the charge density and bonding effects to be studied in crystalline materials. Strategies for obtaining the most accurate results have evolved, and the most important influences on the accuracy have been determined. Initial applications of the technique to bond charge density determination have led to the extension of the method to the refinement of other important parameters influencing the experimental data, such as Debye–Waller factors and the absorption potential. The development and current status of quantitative zone-axis CBED are discussed. Prospects for the future development and application of the technique are also considered.

Identification of the Chirality and Polarity of Intermetallic Compounds with the Point Groups of 23, 432, 422, and 321 by Electron Diffraction

2007 ◽  
Vol 539-543 ◽  
pp. 1457-1462 ◽  
Author(s):  
Haruyuki Inui ◽  
Katsushi Tanaka ◽  
Kyosuke Kishida ◽  
Satoshi Fujio
Keyword(s):  
Electron Diffraction ◽  
Intermetallic Compounds ◽  
Diffraction Method ◽  
Convergent Beam Electron Diffraction ◽  
Zone Axis ◽  
The Other ◽  
Beam Electron ◽  
Symmetry Line ◽  
Point Groups ◽  
Convergent Beam

A CBED (convergent-beam electron diffraction) method proposed by the present authors for chiral identification of enantiomorphic crystals has been successfully applied to intermetallic compounds with the point groups of 23, 422, 432 and 321. The intensity asymmetry of ZOLZ and/or FOLZ reflections of the Bijvoet pairs is easily recognized in CBED patterns with the incidence along the appropriate zone-axis orientations for each of the two members of the enantiomorphic pair and the intensity asymmetry with respect to the symmetry line is reversed upon changing the space group (handedness) from one to the other. Thus, the generality of the proposed method in identifying the chirality for all crystallographycally possible enantiomorphic crystals is verified.

Observation of Dynamic Extinction Lines in the (420) Diffraction Disks of the MgAl2O4 Spinel CBED Pattern

1990 ◽  
Vol 48 (2) ◽  
pp. 506-507
Author(s):  
Dangrong R. Liu
Keyword(s):  
Electron Diffraction ◽  
Convergent Beam Electron Diffraction ◽  
Zone Axis ◽  
Beam Electron ◽  
Space Group ◽  
Mgal2o4 Spinel ◽  
Principal Axes ◽  
Diffraction Patterns ◽  
Convergent Beam ◽  
Dynamic Scattering

Many people have observed dynamic extinction lines in the {200} diffraction disks of the <100> zone axis CBED (convergent beam electron diffraction) patterns of the MgAl2O4 spinel. These dark lines are manifestation of the space group of the material and can easily be explained with the Gjønnes-Moodie theory. However, in addition to the extinction lines in the {200} disks, We have also been able to observe dynamic extinction lines present in the {420} diffraction disks in the same CBED pattern.The CBED work in this work was carried out with a JEOL-2000FX microscope operated at 100.15 kV. One <100> zone axis CBED pattern is shown in Fig. 1. The dark lines are clearly shown in the {420} disks running through the two perpendicular non-principal axes, in exactly same way as the dark lines in {200} disks.One can easily explain the dynamic extinction lines in the {200} disks with the Gjønnes-Moodie theory by drawing dynamic scattering pairs oG-Ga and oH-Ha, oK-Ka and oL-La etc. in the diagram (Fig. 2).

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