Point defect dynamics in bcc metals

Abstract

We present an analysis of the time evolution of self-interstitial atom and vacancy (point defect) populations in pure bcc metals under constant irradiation flux conditions. Mean-field rate equations are developed in parallel to a kinetic Monte Carlo (kMC) model. When only considering the elementary processes of defect production, defect migration, recombination and absorption at sinks, the kMC model and rate equations are shown to be equivalent and the time evolution of the point defect populations is analyzed using simple scaling arguments. We show that the typically large mismatch of the rates of interstitial and vacancy migration in bcc metals can lead to a vacancy population that grows as the square root of time. The vacancy cluster size distribution under both irreversible and reversible attachment can be described by a simple exponential function. We also consider the effect of highly mobile interstitial clusters and apply the model with parameters appropriate for vanadium and α−iron.

Cascade damage evolution: rate theory versus kinetic Monte Carlo simulations

“…without spatial correlations. Results showed that in that case, kMC and RT results almost overlap, as it was observed by Rottler et al [20] in similar conditions. With these initial conditions, both kMC and RT models show a peak at T = 264 K with the same intensity and none of them show peak at 231 K. Thus, peak III A seen at T = 231 K in the kMC calculations is due to the recombination of correlated V-I n≥3 arrangements that form in the cascade during irradiation, whereas the one observed at T = 264 K in the RT model is due to uncorrelated recombinations between V and I n≥3 .…”

“…Different research teams [11,14,18,23,26] have used this approach to study the nucleation and growth of defects in various materials over the years. Recently, Rottler et al [20] used the RT formalism to investigate point defect dynamics in metals and showed that, when defects are homogeneously distributed, kMC and RT models are in near perfect agreement. However, when complex mechanisms have to be considered, results obtained by RT models can deviate from those obtained by kMC.…”

Method to account for arbitrary strains in kinetic Monte Carlo simulations

“…work by Stoller et al 47 or Rottler et al 48 ) that the point defect absorption rate of sinks, such as dislocations, is spatially homogeneous, with the spatial heterogeneity being subsumed into model parameters. Using the methodology outlined and validated above, it is now possible to compute more accurate values of point defect absorption rates by sinks without resorting to parameters.…”

Modeling of long-term defect evolution in heavy-ion irradiated 3C-SiC: Mechanism for thermal annealing and influences of spatial correlation

“…In fact, it has been shown that when defects are uniformly distributed, KMC and MFRT models are in reasonable agreement. 74 In this section, defects in the form of cascades and isolated defects were annealed isochronally with the temperature and time steps adopted in Section III(B). Fig.…”