Towards a Thomas-Fermi mass formula for extrapolation to the neutron-drip line

For an analysis of the r-process of stellar nucleosynthesis, binding energies of the unknown nuclei close to the neutron drip line are required. The way to get these energies is to use the nuclear mass formula to extrapolate from the known nuclei to the unknown nuclei close to the neutron-drip line. It is observed that the mass formulas based on existing forms of the droplet model (DM) extrapolate very badly out to the neutron-drip line, but a mass formula based on the Extended Thomas-Fermi (ETF) method with Skyrme-type force extrapolates out to the neutron-drip line almost as well as the Hartree-Fock (HF) method and is computationally much faster than HF method. (M.G.B.)