Density functional study of O2 adsorption on (100) surface of γ-uranium

Chemisorption of the oxygen molecule on the (100) surface of gamma-uranium was investigated using the generalized gradient approximation to Density Functional Theory. Dissociative adsorptions of O-2 are found to be significantly favored compared to molecular adsorptions. Interstitial adsorptions of molecular oxygen are less probable, as no bound states are found in this case. Only after dissociation of O-2 is atomic oxygen diffusion through the surface possible. The O 2p orbitals are found to hybridize with U 5f bands, and some of the U 5f electrons become more localized. A significant charge transfer from the first layer of the uranium surface to the oxygen atoms is found to occur, making the bonding partly ionic. For the most favored site, the dissociative chemisorption energy is similar to9.5 eV, which indicates a strong reaction of uranium surface with oxygen. Spin polarization does not have a significant effect on the chemisorption process. For most of the sites and approaches, chemisorption configurations are almost same for both spin-polarized and non-spin-polarized cases. For the most favored chemisorption sites of oxygen on uranium, paramagnetic adsorption is slightly stronger, by 0.304 eV, compared to magnetic adsorption. (C) 2004 Wiley Periodicals, Inc. Int J Quantum Chem 102: 98 -105, 2005.