Static nuclear properties and the parametrisation of Skyrme forces

We present a systematic study of the dependence of static nuclear properties on the parameters of the effective interaction used in the Hartree-Fock (HF) and extended-Thomas-Fermi (ETF) models. For this purpose, a set of trial Skyrme forces, which are constrained by a fit to nuclear radii and binding energies, is developed. This leaves six free parameters: the spin-orbit strength, the nuclear-matter compression modulus, the isoscalar and isovector contributions to the effective masses, the value of the exchange parameter x3 (governing the surface-symmetry properties) and the coefficient of the 'gradient-symmetry' term vertical strokenablarhosub(n)-nablarhosub(p)vertical stroke2 in the energy-density functional. The influence of these parameters on various properties is studied: droplet-model parameters, quality of the fit to experimental masses, extrapolation of masses, fit to charge radii, charge distributions and neutron-skin thicknesses, semiclassical fission barriers, and Landau parameters. Indications are given of the directions which could be followed in order to improve the fit to experimental data. Several correlations remaining in the results suggest that a larger number of degrees of freedom obtained by additional terms could be useful. (orig.)