Hydrogen adsorption on δ-Pu (1 0 0) and (1 1 1) surfaces using the generalized gradient approximation of the density functional theory with Perdew and Wang functionals have been studied at both the spin-polarized level and the non-spin-polarized level. For the (1 0 0) surface at the non-spin-polarized level, we find that the center position of the (1 0 0) surface is the most favorable site with a chemisorption energy of 2.762eV and an optimum distance of the hydrogen adatom to the Pu surface of 1.07A. For the spin-polarized (100) surface, the center site is again the preferred site with a chemisorption energy of 3.467eV and an optimum hydrogen distance of 1.13A. For the non-spin-polarized (1 1 1) surface, the center position is also the preferred site, but with slightly lower chemisorption energy, namely 2.756eV and a higher hydrogen distance, 1.40A, compared to the (1 0 0) center site. The center site is also the preferred site for the spin-polarized (1 1 1) surface, with a chemisorption energy of 3.450eV and a hydrogen distance of 1.42A. Also, for the spin-polarized calculations, the over all net magnetic moments of the (1 1 1) surface changed significantly due to the hydrogen adsorption. The 5f orbitals are delocalized, especially as one approaches the Fermi level. However, the degree of localization decreases for spin-polarized calculations. The coordination numbers have a significant role in the chemical bonding process. Mulliken charge distribution analysis indicates that the interaction of Pu with H mainly takes place in the first layer and that the other two layers are only slightly affected. Work functions, in general, tend to increase due to the presence of a hydrogen adatom. © 2004 Elsevier B.V. All rights reserved.
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