High-voltage, high-resolution electron microscopy of Au-Cd alloys. II. Double hexagonal long-period superstructures

Ordered structures of Au₃Cd with a double hexagonal stacking sequence (4H) have been investigated by 1 MV electron microscopy in combination with many-beam dynamical calculations. One- and two-dimensional long-period superstructures (LPS) were observed at atomic level by high-resolution images with [001] incidence. The two-dimensional LPS was determined to be isomorphic with the Au₇₇Mg₂₃ structure. Two-dimensional LPS with stacking sequences 6Hand 9R were also found in the composition range 24-31 at.%Cd.