Quantitative method to predict the energetics of helium-nanocavities interactions in metal systems based on electrophobic interaction

Energetics of helium-nanocavities interactions are crucial for unveiling underlying mechanisms of nanocavity evolution in nuclear materials. Nevertheless, it becomes intractable and even not feasible to obtain these energetics via atomic simulations with increasing nanocavity size and increasing helium content in nanocavities. Herein, a universal scaling law of helium-induced interaction energies in nanocavities in metal systems is proposed based on electrophobic interaction of helium. Based on this scaling law and ab-initio calculations, a predictive method for binding energies of helium and displacement defects to nanocavities of arbitrary sizes and with different helium/vacancy ratios is established for BCC iron as a representative and validated by atomic simulations. This predictive method reveals that the critical helium/vacancy ratio for helium-enhanced vacancy binding to nanocavities increases with increasing nanocavity size, and the helium/vacancy ratio giving the highest stability of nanocavities is about 1.6. The Ostwald ripening of nanocavities is delayed by helium to higher temperatures due to reduced vacancy de-trapping rates from nanocavities. The proposed scaling law can be generalized to many metal systems studied in the nuclear materials community. Being readily coupled into mesoscale models of irradiation damages, this predictive method facilitates clarifying helium role in cavity swelling of metallic nuclear materials.