First-Principles Modeling of ThO$_{2}$ Solid Solutions with Oxides of Trivalent Cations

Solid solutions formed by doping ThO$_{2}$ with oxides of trivalent cations, such as Y$_{2}$O$_{3}$ and La$_{2}$O$_{3}$, are suitable for solid electrolyte applications, similar to doped zirconia and ceria. ThO$_{2}$ has also been gaining much attention as an alternative to UO$_{2}$ in nuclear energy applications, the aforementioned trivalent cations being important fission products. In both cases the mixing energetics and short-range ordering/clustering are key to understanding structural and transport properties. Using first-principles atomistic calculations, we address intra- and intersublattice interactions for both cation and anion sublattices in ThO$_{2}$-based fluorite-type solid solutions and compare the results with similar modeling studies for related trivalent-doped zirconia systems.