Accuracy of the Faddeev Random Phase Approximation for Light Atoms

TL;DR

This paper evaluates the Faddeev random phase approximation (FRPA) for light atoms, showing it provides accurate total and ionization energies and improves with larger atomic numbers compared to other methods.

Contribution

It demonstrates the effectiveness of FRPA in calculating energies of light atoms and compares its accuracy with CCSD, ADC(3), and experimental data.

Findings

FRPA yields satisfactory results for two-electron systems.

FRPA improves with larger atomic numbers, adding about 5 mH correlation energy.

Ionization potential corrections reduce discrepancies with experimental values.

Abstract

The accuracy of the Faddeev random phase approximation (FRPA) method is tested by calculating the total and ionization energies of a set of light atoms up to Ar. Comparisons are made with the results of coupled-cluster singles and doubles (CCSD), third-order algebraic diagrammatic construction [ADC(3)], and with the experiment. It is seen that even for two-electron systems, He and Be-2+, the inclusion of RPA effects leads to satisfactory results and therefore it does not over-correlate the ground state. The FRPA becomes progressively better for larger atomic numbers where it gives about 5 mH more correlation energy and it shifts ionization potentials by 2-10 mH, with respect to its sister method ADC(3). The corrections for ionization potentials consistently reduce the discrepancies with the experiment.