Occupation-number-based energy functional for nuclear masses

Theoretical understanding of nuclear bulk properties (masses and radii) are fundamental parts of Q-Vlaue and astrophysical calculations. To this end we show the development of an energy functional for mass calculations across the nuclear chart with orbital occupational numbers as the relevant degrees of freedom. The functional is based on Hohenberg-Kohn theory. Motivation for its form comes from both phenomenology and relevant microscopic systems. The resulting shell-model based functional achieves a least-squares error of the order of chi=1.31 MeV with 17 fit coefficients. We also find good agreement in the ability of the functional to calculate nuclear radii in an harmonic oscillator basis and present a novel method for the systematic growth of future nuclear energy functionals.