A density functional study of molecular oxygen adsorption and reaction barrier on Pu (100) surface

TL;DR

This study uses density functional theory to analyze how oxygen molecules adsorb and react on a plutonium (100) surface, revealing the energetically favored dissociative adsorption modes and the influence of spin polarization.

Contribution

It provides detailed insights into the adsorption energies, preferred sites, and electronic structure changes of oxygen on Pu (100), highlighting the role of spin polarization and 5f electron localization.

Findings

Dissociative adsorption is more favorable than molecular adsorption.

Spin polarization significantly affects chemisorption energies.

Oxygen adsorption alters the electronic structure and work function of Pu (100).

Abstract

Oxygen molecule adsorptions on a Pu (100) surface have been studied in detail, using the generalized gradient approximation to density functional theory. Dissociative adsorption with a layer by layer alternate spin arrangement of the plutonium layer is found to be energetically more favorable compared to molecular adsorption. Hor2 approach on a bridge site without spin polarization was found to the highest chemisorbed site with energy of 8.787 eV among all the cases studied. The second highest chemisorption energy of 8.236 eV, is the spin-polarized Hor2 or Ver approach at center site. Inclusion of spin polarization affects the chemisorption processes significantly, non-spin-polarized chemisorption energies being typically higher than the spin-polarized energies. We also find that the 5f electrons to be more localized in spin-polarized cases compared to the non-spin-polarized counterparts. The ionic part of O-Pu bonding plays a significant role, while the Pu 5f-O 2p hybridization was found to be rather week. Also, adsorptions of oxygen push the top of 5f band deeper away from the Fermi level, indicating further bonding by the 5f orbitals might be less probable. Except for the interstitial sites, the work functions increase due to adsorptions of oxygen.