Computationally-efficient stochastic cluster dynamics method for modeling damage accumulation in irradiated materials

TL;DR

This paper introduces an improved stochastic cluster dynamics method that efficiently models defect accumulation in irradiated materials, overcoming computational challenges of traditional approaches for high-dose nuclear applications.

Contribution

The paper presents novel algorithmic enhancements to the stochastic cluster dynamics method, enabling accurate and efficient simulations of complex defect populations in irradiated materials.

Findings

Successfully modeled defect cluster accumulation in iron films under triple ion-beam irradiation.

Achieved significant speed-up over traditional rate theory and kinetic Monte Carlo methods.

Maintained high accuracy in defect statistics despite computational optimizations.

Abstract

An improved version of a recently developed stochastic cluster dynamics (SCD) method {[}Marian, J. and Bulatov, V. V., {\it J. Nucl. Mater.} \textbf{415} (2014) 84-95{]} is introduced as an alternative to rate theory (RT) methods for solving coupled ordinary differential equation (ODE) systems for irradiation damage simulations. SCD circumvents by design the curse of dimensionality of the variable space that renders traditional ODE-based RT approaches inefficient when handling complex defect population comprised of multiple (more than two) defect species. Several improvements introduced here enable efficient and accurate simulations of irradiated materials up to realistic (high) damage doses characteristic of next-generation nuclear systems. The first improvement is a procedure for efficiently updating the defect reaction-network and event selection in the context of a dynamically expanding reaction-network. Next is a novel implementation of the $\tau$-leaping method that speeds up SCD simulations by advancing the state of the reaction network in large time increments when appropriate. Lastly, a volume rescaling procedure is introduced to control the computational complexity of the expanding reaction-network through occasional reductions of the defect population while maintaining accurate statistics. The enhanced SCD method is then applied to model defect cluster accumulation in iron thin films subjected to triple ion-beam ($\text{Fe}^{3+}$, $\text{He}^{+}$ and $ $$\text{H\ensuremath{{}^{+}}}$$ $) irradiations, for which standard RT or spatially-resolved kinetic Monte Carlo simulations are prohibitively expensive.