A two-nearest-neighbor structure model and analysis of low-expansion Fe–Ni alloys

The main goal of the study is to introduce a two-nearest-neighbor structure model for analyzing low-expansion Fe–Ni alloys. A two-shell atomic structure model is proposed to accurately locate the compositions of the alloy. In the presented model, the Cowley parameters of the alloy short-range ordered structure are considered. The selection of the first-nearest-neighbor cluster is determined, and the number and composition ratio of the second-nearest-neighbor atoms are evaluated by means of the spherical periodic oscillation model. The results show that the developed formula can provide a practical procedure for the composition design of low-expansion Fe–Ni alloys.