High-resolution electron microscopy on incommensurate long-period superstructures of hexagonal-close-packed Cu-Sb alloy

Hexagonal incommensurate long-period superstructures of the Cu-Sb alloys containing 18-20 at.% Sb have been investigated by means of superstructure imaging using a high-resolution electron microscope. Honeycomb-type distributions of hexagonal domains consisting of the commensurate superstructure of type 7a₀-2H are observed. The incommensurabilities of superstructure can be interpreted well with a hexagonal model composed of the 7a₀-2H domains surrounded by domain walls which contain higher Sb content than the domain interior. The observed image contrast is reproduced well with multislice computer simulations based on the structure models proposed for the 7a₀-2H domain and the domain wall.