O₂, CO₂, and H₂O Chemisorption on UN(001) Surface: Density Functional Theory Study

We performed density functional theory calculations of O₂, CO₂, and H₂O chemisorption on the UN(001) surface using the generalized gradient approximation and PW91 exchange-correlation functional at non-spin polarized level with the periodic slab model. Chemisorp-tion energies vs. molecular distance from UN(001) surface were optimized for four sym-metrical chemisorption sites. The results showed that the bridge parallel, hollow parallel and bridge hydrogen-up adsorption sites were the most stable site for O₂, CO₂, and H₂O molecular with chemisorption energies of 14.48, 4.492, and 5.85 kJ/mol, respectively. From the point of adsorbent (the UN(001) surface), interaction of O₂ with the UN(001) surface was of the maximum magnitude, then CO₂ and H₂O, indicating that these interactions were associated with structures of the adsorbate. O2 chemisorption caused N atoms on the surface to migrate into the bulk, however CO₂ and H₂O had a moderate and negligible effect on the surface, respectively. Calculated electronic density of states demonstrated the electronic charge transfer between s, p orbital in chemisorption molecular and U6d, U5f orbital.