The interaction of oxygen with theα-U(001) surface: anab initiostudy

Abstract

First-principles calculations based on density functional theory have been performed to investigate the adsorption, dissociation and diffusion of oxygen on the α-Uranium(001) surface. The results showed that O 2 tends to dissociate followed by the occupation of the two adjacent three-fold hollow sites. The weak molecular adsorption was found for O 2 adsorbed perpendicularly at the top of a uranium (U) atom. The investigation of the dissociation for O 2 from the top site with the O atoms falling into the two adjacent hollow sites indicated the spontaneous dissociation of O 2 . The surface diffusion of atomic oxygen between two adjacent hollow sites encountered an activation barrier of 0.55 eV, indicating the slow motion for O on the α-U(001) surface.

Elucidating the Initial Steps in α-Uranium Hydriding Using First-Principles Calculations

“…This indicates that there are only two preferred adsorption sites on the (001) surface for a single hydrogen adsorption: hollow1 and hollow2. Similar results are observed in nitrogen–uranium and oxygen–uranium systems. In addition, all functionals used here indicate that the hollow2 site is slightly more energetically favorable (∼0.06 eV) compared to hollow1.…”

First-principles study of oxygen adsorption and diffusion on the UN(001) surface

“…The energy profile for this surface diffusion is illustrated in figure 3(b). The curve has shown that the surface diffusion barrier for oxygen on UN(001) surface is ∼0.5 eV, which is similar to 0.55 eV that we found for oxygen diffusing on α-U(001) surface in previous work [27]. These results have shown that the introduction of nitrogen to the uranium surface may not increase the diffusing probability of dissociated oxygen either to the near surface or on the surface.…”