Relaxation of the (111) Surface of $\delta $-Pu and Effects of Atomic Adsorption: An \textit{Ab Initio} Study

The full-potential all-electron linearized augmented plane wave plus local orbitals (FP-L/APW+lo) method has been employed to study the relaxation of the $\delta $-Pu (111) surface and the consequent effects for atomic adsorption of C, N and O atoms on this surface. The surface was modeled by a 5-layer slab with a (2$\times $2) surface unit cell. Upon relaxation of the slab, the interlayer separation between the surface and the subsurface layers expanded by 7.1{\%} with respect to the bulk interlayer separation while the separation between the subsurface and central layers expanded by 0.4{\%}. The hollow fcc adsorption site was found to be the most stable site for C and N with chemisorption energies of 6.420 eV and 6.549 eV respectively, while the hollow hcp adsorption site was found to be the most stable site for O with a chemisorption energy of 7.858 eV. The adsorbate-induced changes in the surface properties, namely the Pu magnetic moments, work function, and electronic structure will be discussed.