Enantiomorph identification of crystals belonging to the point groups of 622 and 6 by convergent-beam electron diffraction method

2007 ◽  
Vol 15 (2) ◽  
pp. 154-167 ◽  
Author(s):  
Akihiro Fujii ◽  
Hiroki Sakamoto ◽  
Satoshi Fujio ◽  
Katsushi Tanaka ◽  
Haruyuki Inui
Keyword(s):  
Electron Diffraction ◽  
Diffraction Method ◽  
Convergent Beam Electron Diffraction ◽  
Beam Electron ◽  
Point Groups ◽  
Convergent Beam

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.

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.

Three-phase structure invariants and structure factors determined with the quantitative convergent-beam electron diffraction method

1999 ◽  
Vol 55 (2) ◽  
pp. 188-196 ◽  
Author(s):  
R. Høier ◽  
C. R. Birkeland ◽  
R. Holmestad ◽  
K Marthinsen
Keyword(s):  
Electron Diffraction ◽  
Phase Structure ◽  
Diffraction Method ◽  
Convergent Beam Electron Diffraction ◽  
Beam Electron ◽  
Structure Factors ◽  
Refinement Method ◽  
Three Phase ◽  
Phase Sensitive ◽  
Convergent Beam

Quantitative convergent-beam electron diffraction is used to determine structure factors and three-phase structure invariants. The refinements are based on centre-disc intensities only. An algorithm for parameter-sensitive pixel sampling of experimental intensities is implemented in the refinement procedure to increase sensitivity and computer speed. Typical three-beam effects are illustrated for the centrosymmetric case. The modified refinement method is applied to determine amplitudes and three-phase structure invariants in noncentrosymmetric InP. The accuracy of the results is shown to depend on the choice of the initial parameters in the refinement. Even unrealistic starting assumptions and incorrect temperature factor lead to stable results for the structure invariant. The examples show that the accuracy varies from 1 to 10° in the electron three-phase invariants determined and from 0.5 to 5% for the amplitudes. Individual phases could not be determined in the present case owing to spatial intensity correlations between phase-sensitive pixels. However, for the three-phase structure invariant, stable solutions were found.

Convergent-beam electron diffraction studies of domains in tetragonal phase of lead zirconate titanate ceramics

1987 ◽  
Vol 45 ◽  
pp. 26-27
Author(s):  
M.L.A. Dass
Keyword(s):  
Electron Diffraction ◽  
Lead Zirconate Titanate ◽  
Tetragonal Phase ◽  
Diffraction Method ◽  
Rhombohedral Phase ◽  
Lead Zirconate ◽  
Convergent Beam Electron Diffraction ◽  
Beam Electron ◽  
Zirconate Titanate ◽  
Convergent Beam

Lead zirconate titanate Pb(ZrxTi(1-x))O3 (PZT) ceramics are ferroelectrics formed as solid solutions between PbTiO3 and PbZrO3. Among the different phases in the ferroelectric state, the primary ones are the Ti+4 rich tetragonal phase and the Zr+4 rich rhombohedral phase. The coexistence of both T and R phases at the boundary composition has been reported using the convergent beam electron diffraction method. In an attempt to characterize the ferroelectric domains in the different phases, a study on the tetragonal phase is reported here, as such an analysis is useful in identifying the phases at the phase boundary.The ceramic used in this study was prepared by conventional ceramic processing and the composition of the sample examined was Pb(Zr0.55Ti0.45)O3. The structure has been found to be tetragonal with lattice parameters a=4.0155Å and c=4.1033Å using X-ray diffraction studies of powder samples.

Symmetry determination on Pb-free piezoceramic 0.5Ba(Zr0.2Ti0.8)O3-0.5(Ba0.7Ca0.3)TiO3 using convergent beam electron diffraction method

2014 ◽  
Vol 115 (5) ◽  
pp. 054108 ◽  
Author(s):  
Jinghui Gao ◽  
Lixue Zhang ◽  
Dezhen Xue ◽  
Takayoshi Kimoto ◽  
Minghui Song ◽  
...  
Keyword(s):  
Electron Diffraction ◽  
Diffraction Method ◽  
Convergent Beam Electron Diffraction ◽  
Beam Electron ◽  
Convergent Beam

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.

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