First-principle Calculation on O₂ Adsorption on UC(001) Surface

Based on density function theory, the adsorption of O₂ molecules on UC(001) surface was calculated by GGA+U method. The results show that the GGA+U method with U_eff=1.5 eV is consistent well with the experimental results such as the lattice constant and cohesive energy of UC bulk. The top two atom layers will decompose into two sub-layers after relaxation. The adsorption sites and orientation of O₂ pose a significant influence on adsorption process with adsorption energy varying from 2.21 eV to 8.55 eV. By the analysis of Bader charge, differential charge density and partial density of states, the mechanism of dissociation activation is that 5f and 6d electrons of U transfer to π2p and π*2p molecular orbitals of O₂.