Double hexagonal superstructure of Au–Mg alloy containing 20 at.% Mg studied by high-voltage high-resolution electron microscopy

Abstract
High-resolution observations of Au–20.2 at.% Mg alloy have been carried out by using a 1 MV electron microscope. The many-beam images with the [001] axial illumination are interpreted in terms of the double hexagonal superstructure of 9a 0−4H type. With the aid of computer simulations by the multislice method, it is revealed that two kinds of interpretable image are obtained for different specimen thicknesses at the optimum defocus. The imaging conditions are discussed in comparison with the orthorhombic structure of the D023 type.