Adaptive kinetic Monte Carlo analysis of healing mechanisms in radiation damaged pyrochlore Gd2Ti2O7.

Disposal of high-level radioactive waste has been a long-standing problem requiring methods for evaluating the level and type of damage as well as linking the level of crystal damage to leaching of radionuclides from the matrix and dissolution of the matrix itself. Numerous Molecular Dynamics (MD) simulations have been undertaken to link the damage created by a recoil event to the suitability of a given material to act as a storage matrix. In this context, we have employed adaptive kinetic Monte Carlo to provide new insights over an extended time frame up to seconds into the healing of Gd2Ti2O7 after a simulated cascade and the complex diffusion of anions and cations. Comparison of the present results with previously published data demonstrates that MD simulations covering up to nanoseconds are not capable of accounting for relevant rare events with high-barrier ionic diffusion, which limits the reach of the insights into radiation damage in materials derived from short (ns-scale) MD simulations alone.