Skyrme-Hartree-Fock-Bogoliubov mass models on a 3D mesh: V. The N2LO extension of the Skyrme EDF

TL;DR

This paper introduces BSkG5, a nuclear structure model based on N2LO Skyrme EDF, achieving high accuracy in nuclear mass, radii, and fission barriers while maintaining a consistent neutron matter equation of state.

Contribution

The paper develops the first large-scale N2LO Skyrme EDF model, improving accuracy and reducing parameters compared to previous models.

Findings

Achieves RMS deviation of 0.649 MeV for nuclear masses

Matches accuracy for charge radii and fission barriers

Demonstrates feasibility of complex N2LO EDF calculations

Abstract

We present BSkG5, the latest entry in the Brussels-Skyrme-on-a-Grid (BSkG) series and the first large-scale nuclear structure model based on next-to-next-to-leading order (N2LO) Skyrme energy density functional (EDF). By extending the traditional Skyrme EDF ansatz with central terms containing up to four gradients, we are able to combine an excellent global description of nuclear ground state properties with a stiff equation of state for pure neutron matter that is consistent with all astronomical observations of neutron stars. More precisely, the new model matches the accuracy of earlier BSkG models but with two parameters less: we achieve root-mean-square deviations of 0.649 MeV for 2457 atomic masses, 0.0267 fm for 810 charge radii, and 0.43 MeV for 45 primary fission barriers of actinide nuclei. We demonstrate that the complexities of N2LO EDFs are not insurmountable, even for demanding many-body calculations.