Ab initio study of molecular oxygen adsorption on Pu (111) surface

摘要

Using the generalized gradient approximation to density functional theory (DFT), molecular and dissociative oxygen adsorptions on a Pu (111) surface has been studied in detail. Dissociative adsorption with a layer-by-layer alternate spin arrangement of the plutonium layer is found to be energetically more favorable, and adsorption of oxygen does not change this feature. Hor1 (O-2 is parallel to the surface and lattice vectors) approach on the center2 (center of the unit cell, where there is a Pu atom directly below on the third layer) site, both without and with spin polarization, was found to be the preferred chemisorbed site among all cases studied with chemisorption energies of 8.365 and 7.897 eV, respectively. The second-highest chemisorption energy occurs at the Ver (O-2 is vertical to the surface) approach of the bridge site with chemisorption energies of 8.294 eV (non-spin-polarized) and 7.859 eV (spin-polarized), respectively. We find that 5f electrons are more localized in the spin-polarized case than the non-spin-polarized counterparts. Localization of the 5f electrons is higher in the oxygen-adsorbed plutonium layers compared with the bare layers. The ionic part of O-Pu bonding plays a significant role in the chemisorption process, along with Pu 5f-O 2p hybridization. (c) 2005 Wiley Periodicals, Inc.