Predictive Phase Stability of Actinide-Bearing Hollandite Waste Forms from First-Principles Calculations

In this work, we investigated the stability trends of actinide-bearing hollandites using density functional theory calculations. Incorporating actinides generally decreased the stability of cesium end-members relative to their barium equivalents. Among the actinides, neptunium-containing structures were consistently the least stable. Curium was the most stable actinide in the +3 oxidation state, followed by americium, plutonium, uranium, and neptunium. Conversely, in the +4 state, uranium-bearing hollandites were the most stable. An inverse correlation between actinide content and stability was consistently observed.