Short- and long-range orders in Fe–Cr: A Monte Carlo study

Atomistic kinetic Monte Carlo simulations based on the two-band semiempirical cohesive model for Fe–Cr have revealed a body centered tetragonal Fe14Cr ordered compound at very low temperatures. Density functional theory calculations have shown that this structure is more stable than the Fe15Cr compound reported in literature. The study of short-range order, at higher temperatures, has shown that short-range order is not only characterized by the existence of Fe–Cr correlations in the two first neighbor shells but also by the existence of Cr–Cr correlations in the seventh and eighth neighbor shells corresponding to characteristic lengths of the ordered compound. The comparison of these results to neutron diffuse scattering experiments has shown that these characteristic lengths are observed in the experiments. Nevertheless, it appears that a larger spectrum of correlation lengths must exist in the experimental alloy. A Fourier transform of the atomic configuration has shown that the α phase is short-range ordered in the two-phase region.