We have previously reported the development of the Database for Uranium Oxides (DUOs) using genetic algorithms for structure prediction and density functional theory (DFT). We now present analogous data for uranium fluoride compounds. Uranium fluorides are fuel-cycle relevant materials and thus necessitate the expansion of DUOs into a broader dataset of uranium materials. As in DUOs, uranium cation coordination environments in the uranium fluoride structures have been determined and we present the results of this analysis. Correlations between coordination geometries, relative energies, and other properties of the parent structures have been investigated.<br/><br/>Ultimately, structure prediction requires a determination of the relative stability of related phases. Using DFT requires a large number of calculations on candidate structures and significant computational resources. To this end, the suitability of one potential pre-screening tool, the global instability index (GII), has been assessed, for uranium oxides, fluorides, oxyfluorides, and uranium minerals. With commonly-used parameters for the GII calculations, it is found that the accepted cutoff value for stability of 0.2 cannot be broadly applied to uranium materials and new values are proposed for determining the relative stability of phases.

Assessing the structural stabilities of novel uranium materials with DFT and bond valence calculations

2019 Fall National Meeting

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