Short range order in Ni4Mo and its high resolution electron microscope images

Abstract The short range ordered (SRO) structure in Ni 4 Mo has been investigated by means of high resolution transmission electron microscopy with digital image processing and Monte Carlo simulation. High resolution transmission electron microscope (HRTEM) images were recorded with an Imaging Plate (IP) system. Conventionally printed images of the SRO state exhibit locally dot patterns corresponding to N 2 M 2 -type (chalcopyrite-like) structure. However, the dot patterns transform into those of subunit cell clusters of D 1 a , D 0 22 and Pt 2 Mo structures, when the image is output with a different gray scale. The Monte Carlo simulation with appropriate interaction parameters of atoms has explained successfully the HRTEM images. It is concluded that the SRO state in Ni 4 Mo involves subunit cell clusters of D 1 a , D 0 22 and Pt 2 Mo structures in the atomistic level of microstructure. The concept of 〈1 1/2 0〉* static concentration waves corresponding to the N 2 M 2 pattern is rationalized as a mesoscopically averaging view of the SRO state.