M. Lavrentiev (Sp), D. Nguyen-Manh, S.L. Dudarev, UKAEA, Abingdon (UK)
We present vacancy-mediated kinetic and exchange Monte Carlo simulations of the binary Fe-Cr alloy in the
region of small (up to 20%) chromium concentrations. The energy of the system was calculated using DFT-based
cluster approximation [1]. DFT calculations were also used to estimate the activation energy of vacancy jumps.
For Cr concentrations below 10% chromium atoms are well separated from each other; at higher concentrations
the clustering of Cr atoms begins. We study the size distribution of Cr clusters as a function of temperature and
concentration and the formation of clusters from initial random distribution of chromium atoms via vacancy
migration. At low temperatures, only a few large clusters are formed with Cr-Fe interfaces parallel to the [110]
planes. At higher temperatures, the number of clusters increases and their shape becomes less well defined. We
find that the complex clustering and ordering processes occurring in Fe-Cr may be described using a few
concentration-independent cluster expansion coefficients and activation energies. Diffusion coefficients for Cr and
Fe atoms are evaluated as a function of temperature and concentration. We also study local order and local
concentration in the vicinity of a vacancy.
1. M.Yu. Lavrentiev, R. Drautz, D. Nguyen-Manh, T.P.C. Klaver, S.L. Dudarev. Phys. Rev. B 75, 014208 (2007).