Ab Initio Study of Molecular Oxygen Adsorption on Pu (111) Surface M. N. HUDA, A. K. RAY Department of Physics, P. O. Box 19059, University of Texas at Arlington, Arlington, Texas 76019 Received 30 March 2005; accepted 4 May 2005 Published online 5 July 2005 in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/qua.20701 ABSTRACT: 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 OOPu bonding plays a significant role in the chemisorption process, along with Pu 5fOO2p hybridization. © 2005 Wiley Periodicals, Inc. Int J Quantum Chem 105: 280 –291, 2005 Key words: density functional theory; adsorption; plutonium; oxygen; actinides Introduction I n recent years, advances in theoretical and com- putational formalisms have increased research significantly in high-Z strongly correlated materials and heavy fermion systems. In this area, actinides play a central role, yet surface chemistry and phys- ics of the actinides remain a largely unexplored territory. One of the many motivations to study the actinide surfaces is a desire to understand the sig- nature role of 5f electrons in bonding and localiza- tion, as well as the mechanisms that lead to surface corrosion in the presence of environmental gases. This problem is not only scientifically and techno- logically challenging, but also environmentally im- portant. As is known, the actinides are character- ized by a gradual filling of the 5f-electron shell, as the degree of localization increases with the atomic Correspondence to: A. K. Ray; e-mail: akr@uta.edu Contract grant sponsor: U. S. Department of Energy (Chem- ical Sciences, Geosciences and Biosciences Division, Office of Basic Energy Sciences, Office of Science). Contract grant number: DE-FG02-03ER15409. Contract grant sponsor: Welch Foundation (Houston, TX). Contract grant number: Y-1525 International Journal of Quantum Chemistry, Vol 105, 280 –291 (2005) © 2005 Wiley Periodicals, Inc.