Nihon Kessho Gakkaishi

Electron Microscope Studies of Phase Transitions and Incommensurate Structures in Dielectrics

Naoki YAMAMOTO

1992Volume 34Issue 1 Pages 1-10
Published: February 25, 1992
Released on J-STAGE: September 30, 2010

DOIhttps://doi.org/10.5940/jcrsj.34.1

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The article reviews the electron microscope studies of incommensurate phases in dielectrics. General structural properties of the incommensurate phase such as the formation of discommensuration (DC) array near the Lock-in transition point are described. Superspacegroup is used for analyzing the continuously modulated structure, being applied to the analyses of the incommensurate structures of Sr₂Nb₂O₇ and Bi₂Sr₂CaCu₂O₈. A DC array corresponds to an array of domain walls in the commensurate phase, which forms a characteristic domain structure, such as a so-called ‘stripple’. The domain configuration around the stripple in the IC phase of Rb₂ ZnCl₄ is identified from the diffraction contrasts of DCs in the electron microscope images.

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Space-group Determination of Incommensurately-modulated Structures by Convergent-beam Electron Diffraction

Michiyoshi TANAKA, Masami TERAUCHI

1992Volume 34Issue 1 Pages 11-18
Published: February 25, 1992
Released on J-STAGE: December 10, 2010

DOIhttps://doi.org/10.5940/jcrsj.34.11

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The interrelation between the symmetries of CBED patterns and symmetry symbols for incommensurately-modulated structures given by de Wolff, Jannsen and Janner are clarified. 1) Point groups; The symmetry symbol 1 shows no symmetry in CBED patterns. The symbols other than 1 show the symmetries of the corresponding symbols for the average structure. 2) Space groups; The four dimensional glide planes and screw axes give dynamical extinction in the kinematically forbidden reflections due to the symmetry elements. Dynamical extinction rules in CBED patterns were tabulated for one example of the four dimensional space groups.

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Study of Moiré Fringes using Synchrotron X-rays

Jun-ichi YOSHIMURA

1992Volume 34Issue 1 Pages 19-26
Published: February 25, 1992
Released on J-STAGE: September 30, 2010

DOIhttps://doi.org/10.5940/jcrsj.34.19

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It has recently been shown that X-ray moire fringes are not exactly the projection of the intensity distribution of the wave field on the exit surface of the crystal, but do oscillate along the beam path behind the crystal. Such nonprojectiveness of moire fringes is inexplicable by the conventional understanding of moiré fringes, and therefore is of interest from a fundamental viewpoint as well as practical one. In this paper the phenomena of the nonprojectiveness are described on the basis of the latest experimental data obtained by synchrotron radiation.

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Crystallographic Refinement by Simulated Annealing using Molecular Dynamics

Kazuo NAKAMURA

1992Volume 34Issue 1 Pages 27-30
Published: February 25, 1992
Released on J-STAGE: September 30, 2010

DOIhttps://doi.org/10.5940/jcrsj.34.27

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How to use PROLSQ

Arno PÄHLER

1992Volume 34Issue 1 Pages 31-40
Published: February 25, 1992
Released on J-STAGE: September 30, 2010

DOIhttps://doi.org/10.5940/jcrsj.34.31

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ATOMS, a Program for Drawing Crystal Structures

Fujio IZUMI

1992Volume 34Issue 1 Pages 41-43
Published: February 25, 1992
Released on J-STAGE: September 30, 2010

DOIhttps://doi.org/10.5940/jcrsj.34.41

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