An implementation of nuclear time-dependent density-functional theory and its application to the nuclear isovector electric dipole resonance

Abstract

Background Time-dependent density-functional theory (TDDFT) continues to be useful in describing a multitude of lowenergy static and dynamic properties. In particular, with recent advances of computing capabilities, large-scale TDDFT simulations are possible for fission dynamics as well as isovector dipole (IVD) resonances.Purpose Following a previous paper [Y. Shi, Phys. Rev. C 98, 014329(2018)], we present an extension of the density-functional theory to allow for dynamic calculations based on the obtained static Hartree-Fock results. We perform extensive benchmark calculations, by comparing the calculated results with that of an existing code Sky3D. To perform linearresponse calculations using the TDDFT method, comparisons have been made with the finite-amplitude quasiparticle random-phase approximation (FAM-QRPA) method. We plan to apply the TDDFT method to a systematic description of the IVD resonances in the Zr, Mo, and Ru isotopes.Methods The strengths of IVD resonances are calculated using two complementary methods: TDDFT and FAM-QRPA methods. For the TDDFT results, additional benchmark calculations have been performed using the well-tested code Sky3D. In these three models, the important ingredients which have major influence on the results, such as time-odd potentials, boundary conditions, smoothing procedures, spurious peaks etc., have been carefully examined. ResultsThe current TDDFT and the Sky3D codes yield almost identical response functions once both codes use the same time-odd mean fields and absorbing boundary conditions. The strengths of the IVD resonances calculated using the TDDFT and FAM-QRPA methods agree reasonably well with the same position of the giant dipole resonance. Upon seeing a reasonable accuracy offered by the implemented code, we perform systematic TDDFT calculations for spherical Zr and Mo isotopes near N = 50, where experimental data exist. For neutron-rich Zr, Mo, and Ru isotopes where shape evolution exist we predict the photoabsorption cross sections based on oblate and triaxial minima. ConclusionsThe TDDFT code provides reasonable description for IVD resonances. Applying it to the spherical Zr and Mo nuclei, a reasonable agreement with experimental data has been achieved. For neutron-rich Zr isotopes, the photoabsorption cross section based on the two coexisting minima reflects the feature of the deformation of the minima.