The gas-phase mechanisms of UF4 and UF5 conversion into UF6 at different electronic states have been investigated using density functional theory (DFT) calculations, including relativistic effects and without the frozen core approximation. New geometries and electronic states of the isolated molecules were obtained, and their reactions were predicted to occur without a potential energy barrier. Our calculations show that UF4+F2 collision will most likely produce UF5+F in the gas phase. Relevant surface crossings between different electronic states are also obtained and their roles in collision dynamics are discussed.
Keywords: DFT; Gas-phase reactions; Uranium hexafluoride.