Optimized basis of covariant density functional theory: point coupling functionals and excited states

Abstract

The present investigation focuses on the improvement of the accuracy of the description of physical observables of interest in moderately sized fermionic basis within the framework of covariant density functional theory. It extends previous study of Ref. [1] to point coupling (PC) covariant energy density functionals (CEDFs) and to excited states. Using as a benchmark the solutions corresponding either to infinite fermionic basis or those extrapolated to such a basis it is shown that the optimization of oscillator frequency $\hbarω_0$ of the harmonic oscillator (HO) basis leads to a substantial improvement in the description of different physical observables in the fermionic basis truncated at $N_F$. Globally optimized scaling factors $f_{opt}(A)$ of the oscillator frequency and the sizes $N_F^{\varepsilon}$ of the HO bases providing the required accuracy $\varepsilon$ in the calculations of the binding energies are generated for the PC functionals. The optimization of the basis also significantly improves the accuracy of the description of potential energy curves, defining the fission barriers and fission isomers in actinides and superheavy nuclei, provided that the size of the basis is at least equal to $N_F=20$. The optimization of the HO basis improves the accuracy of the description of the energies of bound single-particle states: the only exceptions are weakly bound neutron states with low orbital momenta $l=0$, 1 and 2. It is demonstrated for the first time that the halo densities of neutron halo nuclei generated in the coordinate space calculations are well reproduced in the calculations with very large fermionic HO bases.