High-voltage, high-resolution electron microscopy of Au-Cd alloys. I. Hexagonal long-period superstructures near 30 at. % Cd

The crystal structure of Au-Cd (30-32%) alloys has been studied at atomic level with a 1 MV electron microscope. The experimental images can be fitted well with many-beam dynamical calculations for the long-period superstructure (LPS) designated as 7a₀-2H type. The structures with incommensurate periods consist of a number of domains of the 7a₀-2H structure separated by antiphase boundaries which are composed of orthorhombic cells. The result demonstrates the potentiality of high-voltage, high-resolution electron microscopy for direct determination of the atomic arrangements in modulated structures of alloys.