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Atomic H interaction with the γ-U (100) surface


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Theoretical analysis of the adsorption of a H atom on the (100) surface of bcc γ-U represented by a 5 layer slab indicates an exothermic reaction with the bridge site as the preferred site with a chemisorption energy of 3.80 eV at the relativistic level of theory with spin–orbit coupling (SOC) included. The ground state magnetic configuration of the U[BOND]H system is found to be nonmagnetic, in agreement with experimental results for UH3. The change in work function of the slab with the addition of the H atom is at a maximum when the adatom is bound to the top site and is 0.61 eV. H bound to the lattice in interstitial regions was also found to be exothermic in nature with the interstitial bridge site being the most stable at 2.13 eV at the nonmagnetic state with SOC included. Two potential wells were found under the surface. The first with a barrier of 0.41 eV and the second with a barrier of 0.71 eV indicating preferred H bonding with the γ-U surface and an aversion to further diffusion into the bulk.