Object Kinetic Monte Carlo calculations of irradiated Fe–Cr dilute alloys: The effect of the interaction radius between substitutional Cr and self-interstitial Fe

Abstract

Keywords: Monte Cario simulations FeCr alloys Radiation effects Fusion materials Fission materialsObject Kinetic Monte Carlo models allow for the study of the evolution of the damage created by irradiation to time scales that are comparable to those achieved experimentally. Therefore, the essential Object Kinetic Monte Carlo parameters can be validated through comparison with experiments. However, this validation is not trivial since a large number of parameters is necessary, including migration energies of point defects and their clusters, binding energies of point defects in clusters, as well as the interaction radii. This is particularly cumbersome when describing an alloy, such as the Fe-Cr system, which is of interest for fusion energy applications. In this work we describe an Object Kinetic Monte Carlo model for Fe-Cr alloys in the dilute limit. The parameters used in the model come either from density functional theory calculations or from empirical interatomic potentials. This model is used to reproduce isochronal resistivity recovery experiments of electron irradiated dilute Fe-Cr alloys performed by Abe and Kuramoto. The comparison between the calculated results and the experiments reveal that an important parameter is the capture radius between substitutional Cr and self-interstitial Fe atoms. A parametric study is presented on the effect of the capture radius on the simulated recovery curves.

Kinetic Monte Carlo Algorithms for Nuclear Materials Applications

“…There are also different ways when dealing with Cr in OKMC codes when modeling FeCr alloys. One option consists of considering Cr as an impurity that can occupy substitutional sites in the lattice (Gámez et al 2011), so it typically diffuses by paring itself with an I or V, until the latter point defect is emitted Martin-Bragado et al (2018). Another way consists of counting the number of both Fe and Cr atoms in each cell (hence allowing the calculation of their concentration in such cells when required), instead of recording individual positions for each Fe and Cr atoms (Dopico et al 2015).…”

“…The interpretation of these curves, and the association of each peak to a particular defect, is not straightforward. The use of combined DFT calculations and KMC simulations has proven to be very useful in the interpretation of these experiments (Fu et al 2005;Gámez et al 2011). Here, an example for pure Fe and FeCr in the dilute limit irradiated with electrons is presented.…”

“…Here, an example for pure Fe and FeCr in the dilute limit irradiated with electrons is presented. For more details of this calculation, see Gámez et al (2011). The resistivity recovery curve can be modeled using information about migration energies of defects from DFT or from empirical potentials (for those clusters too large to study with DFT).…”

“…In this model only those clusters given in Table 2 are included, that is, Cr2I2, I2Cr, and CrI2. For more details on the contribution of these clusters to the recovery stages, see Gámez et al (2011).…”

Kinetic Monte Carlo Simulations of Irradiation Effects

“…KMC studies have shown that solute atoms can confine SIA loop diffusion to short segments (Hudson et al 2004), slow down the loops as proposed in (Chiapetto et al 2015) and change the loop saturation density (Terentyev and Martin-Bragado 2015). It is thus necessary to implement these effects correctly, either by introducing the solutes explicitly in the simulation as in (Hudson et al 2004) (Lee et al 2009) (Gámez et al 2011) (Terentyev and Martin-Bragado 2015) or implicitly by changing the diffusion properties of the loops to reflect the alloying content as in (Chiapetto et al 2015) and (Bonny et al 2018). Another complication with SIA clusters and loops is the fact that the strain they generate in the lattice is not negligible and should be accounted for.…”