Point Group and Space Group Identification by Convergent Beam Electron Diffraction

The rare earth hexaborides are known for their tendency towards very high crystal perfection. They can be grown into large single crystals of very high purity by inert gas arc floating zone refinement. The authors have found that single-crystal cerium hexaboride grown in this manner contains a significant number of inclusions of an impurity phase that interrupts the otherwise single crystallinity of this prominent cathode material. An iterative approach is used to unequivocally determine the space group and the lattice parameters of the impurity phase based on geometries of convergent-beam electron diffraction (CBED) patterns and the symmetry elements that they possess in their intensity distributions. It is found that the impurity phase has a tetragonal unit cell with space group P4/mbm and lattice parameters a = b = 7.23 ± 0.03 and c = 4.09 ± 0.02 Å. These agree very well with those of a known material, CeB4. Confirmation that this is indeed the identity of the impurity phase is provided by quantitative CBED (QCBED) where the very close match between experimental and calculated CBED patterns has confirmed the atomic structure. Further confirmation is provided by a density functional theory calculation and also by high-angle annular dark-field scanning transmission electron microscopy.

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Space Group Determination of Decagonal Quasicrystals of an Al70Ni15Fe15Alloy Using Convergent-Beam Electron Diffraction

Japanese Journal of Applied Physics ◽

10.1143/jjap.31.l109 ◽

1992 ◽

Vol 31 (Part 2, No. 2A) ◽

pp. L109-L112 ◽

Cited By ~ 38

Author(s):

Masakazu Saito ◽

Michiyoshi Tanaka ◽

An Pang Tsai ◽

Akihisa Inoue ◽

Tsuyoshi Masumoto

Keyword(s):

Electron Diffraction ◽

Convergent Beam Electron Diffraction ◽

Beam Electron ◽

Space Group ◽

Decagonal Quasicrystals ◽

Convergent Beam

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Space-group determination by dynamic extinction in convergent-beam electron diffraction: errata

Acta Crystallographica Section A Foundations of Crystallography ◽

10.1107/s0108767384001495 ◽

1984 ◽

Vol 40 (6) ◽

pp. 721-721 ◽

Cited By ~ 1

Author(s):

M. Tanaka ◽

H. Sekii ◽

T. Nagasawa

Keyword(s):

Electron Diffraction ◽

Convergent Beam Electron Diffraction ◽

Beam Electron ◽

Space Group ◽

Convergent Beam

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SPACE GROUP DETERMINATION OF Li2O·3Nb2O5 BY CONVERGENT BEAM ELECTRON DIFFRACTION

Acta Physica Sinica ◽

10.7498/aps.33.1586 ◽

1984 ◽

Vol 33 (11) ◽

pp. 1586

Author(s):

YANG CUI-YING ◽

FENG GUO-GANG ◽

ZHOU YU-QING ◽

TANG DI-SHENG

Keyword(s):

Electron Diffraction ◽

Convergent Beam Electron Diffraction ◽

Beam Electron ◽

Space Group ◽

Convergent Beam

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Thickness dependence of the intensities of the 200 forbidden reflections in the TiBe2 diamond type structure

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100106193 ◽

1988 ◽

Vol 46 ◽

pp. 826-827

Author(s):

Dang-Rong Liu ◽

D. B. Williams

Keyword(s):

Electron Diffraction ◽

Diffraction Pattern ◽

Convergent Beam Electron Diffraction ◽

Type Structure ◽

Beam Electron ◽

Space Group ◽

X Ray ◽

Electron Diffraction Technique ◽

Convergent Beam ◽

Diamond Type

It is interesting to note that for the diamond type structure of Si, Ge and diamond, the forbidden {200} reflections in the exact <100> orientation diffraction pattern cannot be seen. In contrast, we also note a standing controversy over the structure of the MgAl2O4, spinel. Its structure was determined long ago by x-ray powder method as Fd3m (the diamond type). However, its electron diffraction pattern taken in the <100> orientation shows weak {200} reflections, which are taken as evidence that the spinel should have the space group F43m (the blende type), rather than Fd3m. Others speculate that these {200} reflections result from the high order Laue zone (HOLZ) reflections, and the spinel should be Fd3m. Nevertheless, still others think that these analyses are not conclusive. We have carefully studied the space group of TiBe2 using the convergent beam electron diffraction technique, and unambiguously demonstrated that its space group must be Fd3m.

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