HRTEM image contrast of short range order in Ni4Mo

Abstract The high resolution transmission electron microscope (HRTEM) imaging of short range order (SRO) in Ni 4 Mo was investigated by means of multi-slice image simulations. The HRTEM images of Ni 4 Mo exhibit locally bright dot patterns corresponding to the [001] projections of the N 2 M 2 -type (chalcopyrite-like) structure. The multi-slice simulations revealed that the N 2 M 2 patterns are rationalized as the projection patterns of the SRO structure which consists of subunit cell clusters of D 1 a , D 0 22 and Pt 2 Mo structures. The N 2 M 2 -type image contrast appears when both the fundamental fcc lattice reflections and the 1 1/2 0 diffuse scattering of SRO contribute enough to imaging. This suggests that a good coincidence in intensity distribution between the Fourier power spectra of HRTEM images and the electron diffraction patterns is one of the conditions for the image contrast of SRO to be interpreted in terms of the projection contrast.