Electron-ion coupling effects on simulations of radiation damage in pyrochlore waste forms.

We have performed molecular dynamics simulations of cascade damage in the gadolinium pyrochlore Gd₂Zr₂O₇, comparing results obtained from traditional simulation methodologies that ignore the effect of electron-ion interactions with a 'two-temperature model' in which the electronic subsystem is modeled using a diffusion equation to determine the electronic temperature. We find that the electron-ion interaction friction coefficient γ(p) is a significant parameter in determining the behavior of the system following the formation of the primary knock-on atom (PKA; here, a U³(+) ion). The mean final PKA displacement and the number of defect atoms formed is shown to decrease uniformly with increasing γ(p); however, other properties, such as the final equilibrium temperature and the oxygen-oxygen radial distribution function, show a more complicated dependence on γ(p).