The importance of many body interactions in point defect clusters in α Zirconium alloys

Neutron irradiation of commercial Zr alloys containing Sn, Nb and Fe induces the formation of microstructural features, including point defect clusters, dislocation loops and precipitate phases. The distribution and interactions of alloying elements and defects in α‐Zr are crucial for predicting microstructural evolution and mechanical degradation in these alloys. Density functional theory (DFT) simulations are performed to assess interactions among point defect clusters in the HCP Zr lattice. This study examines the energy and configuration of clusters comprising Sn, Nb, Fe and vacancies, considering sizes up to quadruplets of point defects. Both short‐range and long‐range interactions are observed in Sn–Fe and Nb–Fe clusters at different sizes. In addition to binding energies, a many‐body interaction term is determined to quantify the inaccuracies inherent in the defect pair models commonly used in kinetic Monte Carlo simulations, which account for the attractive or repulsive effects introduced by the additional third or fourth defect. Many-body interactions in defect clusters in the HCP lattice are found to be more dependent on the specific atomic configuration of the defects than the quantity of certain defects. Notably, for Nb-dominated clusters, pairwise assumptions show no significant difference from the exact triplet binding energies.