Deuterium trapping and desorption by vacancy clusters in irradiated Mo from object kinetic Monte Carlo simulations

We present a computational study employing Object Kinetic Monte Carlo simulations to investigate the behavior of D in self-irradiated Mo samples. Our simulations reveal that vacancy clusters contributing significantly to D diffusion, trapping, and desorption behavior. It is found that vacancy clusters play an important role in slowing the diffusion of D within the irradiated materials, which can be represented by an effective trapping energy that associated with mobile D atom interacting with the multiple types of vacancy clusters. Furthermore, we analyze the thermal desorption spectrum of D from irradiated Mo samples, demonstrating a saturation effect in D retention at higher damage levels. Notably, the presence of vacancy clusters significantly influences the thermal desorption spectrum, dominating D desorption at temperature higher than 500 K. We also investigate the D desorption behavior under constant temperature storage conditions, revealing a non-exponential desorption rate with a 1/t decrease over time. Our study sheds light on the complex interplay between D and vacancies/vacancy clusters in irradiated materials, highlighting the importance of considering vacancy clusters in modeling D retention and desorption processes.