The kinematic convergent-beam electron diffraction method for nanocrystal structure determination

2009 ◽  
Vol 106 (7) ◽  
pp. 074309 ◽  
Author(s):  
J. T. McKeown ◽  
J. C. H. Spence
Keyword(s):  
Electron Diffraction ◽  
Structure Determination ◽  
Diffraction Method ◽  
Convergent Beam Electron Diffraction ◽  
Beam Electron ◽  
Convergent Beam

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.

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.

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.

Crystal structure determination by convergent-beam electron diffraction

1989 ◽  
Vol 47 ◽  
pp. 476-477
Author(s):  
R. Vincent ◽  
D. J. Exelby
Keyword(s):  
Crystal Structure ◽  
Electron Diffraction ◽  
Structure Determination ◽  
Convergent Beam Electron Diffraction ◽  
Crystal Structure Determination ◽  
Large Set ◽  
Beam Electron ◽  
X Ray ◽  
Structure Factors ◽  
Convergent Beam

In recent years, significant progress has been made towards a solution for the general problem of crystal structure determination by convergent beam electron diffraction (CBED). Even if we consider only perfectly ordered, periodic crystals defined by one of the conventional space groups, diffraction methods based on a focussed sub-micron beam of electrons are applicable to several related sets of structural problems that are not accessible to conventional X-ray or neutron diffraction techniques. We assume here that the space group either is known or has been determined from CBED patterns and that phases and amplitudes for some subset of the structure factors are required. Two limiting cases have been explored in some detail. For crystals where the atomic parameters and Debye-Waller factors are known accurately from high quality X-ray data, information on the charge redistribution for bonding electrons is available from precise measurements of the low order structure factors. Following the original research of Kambe, some recent work has demonstrated that accurate structure amplitudes and three-beam phase invariants can be extracted from the dynamical intensity distribution in CBED reflections. In principle, this approach is completely general but considerable labour would be required to extract sufficient data to solve the structure of an unknown crystal, whereas a large set of kinematic intensities is acquired from a single X-ray pattern.

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

TEM study on laser processed intermetallic phases: Al16Ti6(Fe or Ni)7

1993 ◽  
Vol 8 (3) ◽  
pp. 421-429
Author(s):  
Y. Ma ◽  
J. Gj⊘nnes
Keyword(s):  
Electron Diffraction ◽  
Structure Determination ◽  
Large Angle ◽  
Structure Type ◽  
Convergent Beam Electron Diffraction ◽  
Intermetallic Phases ◽  
Beam Electron ◽  
Convergent Beam

The structures of two laser processed ternary intermetallic phases, Al16Ti6(Fe or Ni)7, have been studied by using electron diffraction and microscopy. A convergent beam electron diffraction (CBED) technique for structure determination is described based upon the principle of kinematic interpretation of large angle systematic reflections in CBED disks. The structure type of phases Al16Ti6(Fe or Ni)7 is characterized as the Mn23Th6(cF116)-type, the same as those of relevant phases Cu16Mg6Si7 and Al50Ti25Fe25 etc., by using the CBED technique. Various errors involved in the analyses are also discussed.

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