Influencing factors of atomic order in the binary sigma phase

The atomic order (i.e. atomic constituent distribution or site occupancy preference on inequivalent sites of a crystal structure) of the sigma phase is driven by both size and electronic (the number of valence electrons and the total number of electron shells) factors. By classifying the binary sigma systems into different categories according to the size and electron configuration of the two constituent elements, the site occupancy regularity of the sigma phase can be observed and analyzed.204