Ab-initio studies of impurity diffusion and segregation in iron

Tsuru, Tomohito   ; Kaji, Yoshiyuki  

Since the solute impurities have an effect on the embrittlement through segregation under irradiation, the solute stability of impurity elements is of considerable importance. In addition, the influence of irradiation on the diffusion characteristics of impurities becomes prominent due to the several acceleration effects of high irradiance circumstances. In the present study, the diffusion characteristic of large-radius impurities in iron are investigated by first principles calculations. The vacancy formation energy and binding energy between impurity and vacancy were obtained by first principles density functional theory (DFT) calculations. And the migration energy was calculated by nudged elastic band method collaborated with DFT. Finally, the entropic contributions to all free energies and jump frequency are evaluated by considering vibrational phonon frequencies based on frozen phonon employing the harmonic approximation for the lattice dynamics.