  First principles linear combinations of Gaussian type orbitals-fitting
function (LCGTO-FF) electronic structure calculations are used to study
thickness dependencies in the surface energies and work functions of ultra-thin
(111) films of fcc delta-Pu, up to five layers thick. The calculations are
carried out at both scalar- and fully-relativistic (with and without spin-orbit
coupling) levels of approximation. The surface energy is shown to be rapidly
convergent, while the work function exhibits a strong quantum size effect for
all thicknesses considered. The surface energy and work function of the
semi-infinite solid are predicted to be 1.12 J/m^2 and 2.85(+ or -0.20) eV,
respectively, for the fully-relativistic case. These results are in substantial
disagreement with results from previous electronic structure calculations. The
present predictions are in fair agreement with the most recent experimental
data for polycrystalline delta-Pu, namely 0.91 J/m^2 and 3.1-3.3 eV, for the
surface energy and work function, respectively.
