Simple concentration-dependent pair interaction model for large-scale simulations of Fe-Cr alloys

TL;DR

This paper introduces a concentration-dependent pair interaction model for Fe-Cr alloys, enabling large-scale simulations that accurately reproduce phase behavior, solubility, and ordering tendencies across temperatures.

Contribution

The work develops a new energetic lattice model based on first-principles calculations with concentration and temperature dependence, validated against experimental phase diagrams.

Findings

Model accurately predicts phase diagram across temperatures.

Cr solubility in Fe is 6-12% below 700 K.

Reproduces ordering, demixing, and spinodal decomposition limits.

Abstract

This work is motivated by the need for large-scale simulations to extract physical information on the iron-chromium system that is a binary model alloy for ferritic steels used or proposed in many nuclear applications. From first-principles calculations and the experimental critical temperature we build a new energetic rigid lattice model based on pair interactions with concentration and temperature dependence. Density functional theory calculations in both norm-conserving and projector augmented-wave approaches have been performed. A thorough comparison of these two different ab initio techniques leads to a robust parametrization of the Fe-Cr Hamiltonian. Mean-field approximations and Monte Carlo calculations are then used to account for temperature effects. The predictions of the model are in agreement with the most recent phase diagram at all temperatures and compositions. The solubility of Cr in Fe below 700 K remains in the range of about 6 to 12%. It reproduces the transition between the ordering and demixing tendency and the spinodal decomposition limits are also in agreement with the values given in the literature.