The dissociation of H₂O on theγ-U (110) and (100) surfaces: anab initiostudy

The dissociation of H₂O onγ-U (110) andγ-U (100) surfaces has been studied by usingab initiomolecular dynamics simulations at an elevated temperature of 800 K. The simulation results show the dissociation of H₂O into the OH group and H atom, which are finally adsorbed on the uranium surface. The dissociation results from electronic interactions between surface uranium 6d/5 f states and the s orbitals of H and the 2p orbitals of O. Additionally, the hybridization between the 6d orbital of surface uranium and the 2p orbital of oxygen plays a dominant role in dissociative adsorption. A significant charge transfer from the uranium surface to the O and H atoms is observed, indicating the formation of U-O and U-H chemical bonds. Specifically, forγ-U (110) surface, the most preferred site for OH is the 3-fold hollow site and H occupies the bridge site or the 3-fold hollow site. On the other hand, forγ-U (100) surface, OH prefers to adsorb on the bridge site and H occupies the 3-fold hollow site or the bridge site. Furthermore, when H₂O is placed on the TOP site, its initial dissociation on theγ-U (110) surface is easier compared to theγ-U (100) surface.