Prediction of pressure-induced new ordered phases in binary uranium-iron alloys.

The potential incorporation of uranium (U) into the Earth's core has been proposed as a significant internal heat source, facilitated by its chemical affinity and possible alloying with iron (Fe) under extreme pressure conditions. However, experimental studies of U under extreme conditions remain challenging, and as a consequence, pressure (P)-induced phase transitions are still underexplored for both U and its compounds. In this work, we investigate the structural behavior and stability of binary uranium-iron (U-Fe) compounds under extreme conditions using high-throughput crystal structure searches based on density functional theory calculations and the particle swarm optimization algorithm. We identify stable compositions across a wide pressure range and evaluate their thermodynamic and dynamical stability up to 250 GPa. Strikingly, we find that the binding strength between U and Fe decreases monotonically with increasing pressure and becomes significantly weaker under Earth's core conditions. These results suggest that pressure-induced weakening of U-Fe interactions may influence the chemical partitioning behavior of uranium relative to iron under deep-Earth conditions, potentially favoring uranium redistribution or enrichment. However, this interpretation remains tentative because finite-temperature and liquid-state effects are not considered. Further studies are needed to assess uranium partitioning and its potential contribution to radiogenic heat production.