ExASIM: Expanded Atomistic Simulations of Irradiated Materials

Atomistic simulations provide useful insight into the nanoscale properties of materials, but plasma-material interactions are governed by many interacting processes from the near surface to the bulk. To accurately predict the behavior of materials under fusion conditions, simulations must provide results beyond the scope of atomistic simulations quickly enough to reach the timescales relevant to fusion reactors without losing the unique contributions of nanofeatures. The ExASIM formalism has been developed to meet this need. Surfaces are reduced to a collection of basic components that can be modeled atomistically. Fast, binary-collision-approximation-based models are used for simple components, while interfaces and nonuniform components are simulated by molecular dynamics. After accounting for interactions between components, the surface is reassembled to obtain the total outgoing particle flux and surface dynamics. ExASIM can model the behavior of materials under irradiation on the mesoscale, bridging the gap between atomistic simulations and experimental samples. In addition to modeling materials under fusion reactor conditions, many other processes that involve particle irradiation can be simulated to explore plasma-based fabrication techniques for novel materials.