Introduction of vacancy drag effect to first-principles-based rate theory model for irradiation-induced grain-boundary phosphorus segregation

Modeling of Phosphorus Transport by Interstitial Dumbbell in α−Iron Using First-Principles-Based Kinetic Monte Carlo

“…The simulation condition was almost the same as in Ref. 7). The calculation region was a one-dimensional region with length L = 1,500 nm.…”

“…Hence, estimations by computer simulations are desired. Thus, several papers report theoretical estimations of irradiation-induced GB P segregation by rate-theory models based on the kinetics of point defects [3][4][5][6][7] . However, the previous estimations are still unsatisfactory.…”

“…So far, we have applied a rate-theory model based on a rst-principles calculation to neutron-irradiation-induced GB P segregation considering the effect of carbon atoms 6) and the V drag effect 7) on the GB P segregation. The model uses the transport coef cient of P atoms for the V mechanism, which is evaluated by kinetic Monte Carlo (kMC) simulation 8) based on the model that is determined by the rst-principles calculation 9) .…”

“…Meanwhile, as for the dumbbell mechanism, its model is also obtained from the rst-principles calculation 5) , but the transport coef cients for the model are obtained from the analytical method 10,11) using several approximations. Because our previous model 7) shows that the transport coefcient of the V mechanism, which is evaluated by the kMC simulation, indicates the V drag effect that the analytical method 10,11) cannot treat, it was suggested that we have to obtain more appropriate coef cients by a kMC simulation based on the rst-principles calculation also in the case of a dumbbell mechanism. Furthermore, our previous rate-theory model does not include the effect of the interstitial P atoms that are generated by self-interstitial atoms (SIAs) kicking out substitutional P atoms and that migrate via octahedral interstitial sites 5) .…”

“…5), and evaluated the diffusion coef cient of both an SIA and a mixed dumbbell composed of an iron (Fe) atom and a P atom. The evaluated diffusion coef cient of the mixed dumbbell was compared with both that of the octahedral P atom, which was calculated analytically using the migration activation energy 5) , and that of the vacancy mechanism, which was evaluated previously 7) . The evaluated diffusion coef cient of SIA was also compared with the analytically evaluated value.…”