Towards a better parametrisation of Skyrme-like effective forces: A critical study of the SkM force

Abstract

Static nuclear properties associated with a Skyrme-like force in the SkM parametrisation have been extensively studied for both spherical and deformed nuclei through Hartree-Fock plus BCS calculations. These calculations include in particular the determination of the 240Pu fission barrier up to the second saddle point. The validity of some currently used approximations to the Hartree-Fock approach (self-consistent Strutinsky approach, expectation value method and two-step iterative method) has also been assessed. The results of the microscopic calculations have been systematically compared to the corresponding self-consistent results obtained within the extended Thomas-Fermi framework. Such semiclassical calculations also allow a proper characterisation of the SkM force surface properties (in the liquid drop or droplet model sense). Whereas ground-state radii and multipole moments are found in excellent agreement with experimental data, binding energies are systematically too high and fission barriers are significantly too low. These two defects are shown to be correlated through the too low surface tension of the force. A modified parametrisation is discussed which heals both these defects while keeping intact the good reproduction of other properties. This constitutes a first step in the direction of current efforts to determine a better parametrisation of Skyrme-like forces.