Adsorption and dissociation of molecular oxygen on $\alpha $-Pu (020) surface: A density functional study*

Molecular and dissociative oxygen adsorption on the (020) surface of $\alpha $-Pu have been studied using the full-potential linearized augmented-plane-wave plus local orbitals (FP-LAPW+lo) basis method. Four adsorption sites and three approaches of O$_{2}$ molecule have been considered. Adsorption energies have been optimized according to the distance of the adsorbates from the Pu surface as well as the oxygen dimer bond length. Dissociative adsorption is found for two horizontal approaches (O$_{2}$ is parallel to the surface and parallel/perpendicular to a lattice vector) and to be more energetically favorable at the scalar and ``fully'' relativistic (NSOC vs. SOC) levels of theory. Hor2 approach on the top site was the preferred adsorption site among all cases studied here. Molecular adsorption occurs at the Vert (O$_{2}$ is vertical to the surface) approach. The work functions, net spin magnetic moments, and charge transfer are also calculated.