Atomistic study of irradiation-induced plastic and lattice strain in tungsten

Accurate plasticity models, that faithfully depict the behavior of intricate movement and interaction of dislocation lines within complex three-dimensional networks under conditions of high dose irradiation, are still lacking. Here we demonstrate a practical way to perform decomposition of the elasto-plastic deformation directly from atomistic simulation snapshots. Through molecular dynamics simulations on a large single crystal, we elucidate the intricate process of converting plastic strain, lattice strain, and rigid rotation during irradiation. Our study highlights how prismatic dislocation loops act as initiators of plastic strain effects in heavily irradiated metals, resulting in experimentally measurable alterations in lattice strain. We show the onset of plastic strain starts to emerge at high dose, leading to the spontaneous emergence of dislocation slip and irradiation-induced excess lattice site formation. This phenomenon arises from the agglomeration of dislocation loops into a dislocation network, changing the apparent number of atomic lattice planes in the simulation cell. Furthermore, our numerical framework enables us to categorize the plastic transformation into two distinct types: pure slip events, associated with no change in lattice sites, and swelling, accompanied by excess lattice sites formation. The latter type is particularly responsible for the observed divergence in interstitial and vacancy counts, and also impacts the behavior of dislocations, potentially activating non-conventional slip systems.