Date Published: July 01, 2020
Publisher: International Union of Crystallography
Author(s): Jun-ichi Yoshimura.
Using a recently developed moiré-fringe theory of X-ray diffraction, computer simulations of previous experimental moiré images are presented, for an experimental verification of the moiré-fringe theory and for a theoretical explanation of the peculiar experimental moiré images.
In Part I of this series of theoretical studies of X-ray moiré fringes (Yoshimura, 2015 ▸), we described the basics of the moiré-fringe theory and presented some examples of computed plane-wave moiré images that are considered to represent the basic characteristics of moiré images. In Part II of this series (Yoshimura, 2019a ▸), moiré images obtained through computations under more practical conditions of an incident beam with wider angular spreads were described, and it was shown how they change with such factors as the thicknesses of the specimen bicrystal, the width of an interspacing gap in the bicrystal, the angular width of the incident wave, the curvatures in the bicrystal etc. In this paper, i.e. Part III of the same series, theoretical simulations on the previous experimental moiré images (Yoshimura, 1993 ▸, 1996a ▸,b ▸, 1997a ▸,c ▸) are presented as a further application of this moiré-fringe theory. The experimental moiré images were taken under a quasi-plane-wave condition using an incident beam with a small angulular spread, and with a strained bicrystal used as the specimen. Comparison of simulated moiré images with the experimental images will serve as a check of the correctness of the moiré-fringe theory. On the other hand, this simulation work is an attempt to provide a full theoretical description of the experimental moiré images mentioned above, which have long been unexplained. This theoretical work will help to advance the discussion on the previous moiré-image experiment.
The present paper concludes with the following remarks: