Spatially resolved stochastic cluster dynamics for radiation damage evolution in nanostructured metals

A spatially resolved stochastic cluster dynamics (SRSCD) model is introduced to describe radiation-induced defect evolution in metals. The stochastic nature of the method allows SRSCD to model more chemical species and more mobile defects than rate theory methods without loss of computational efficiency, while reaching larger timescales and simulating larger volumes than object-oriented kinetic Monte Carlo (OKMC) methods. To comprehend the capabilities of the method and access new understanding of defect evolution, SRSCD is used in three scenarios. In the first, the results of Frenkel pair implantation are found to match those of rate theory in both spatially homogeneous and spatially resolved media. Next, to study spatial resolution effects and correspondence to OKMC, the results of 20 keV cascade implantation into copper is simulated and an acceptable match with OKMC is found. Finally the method is used to study the problem of helium desorption in thin iron foils. The model is compared with available experimental measures and is found to be in good agreement. The ability of SRSCD to include many mobile species of defects allows a detailed analysis of the mechanisms of helium release from the free surface of the iron foils. As a result new dominant mechanisms of helium release are discussed as well as their operating regimes.