Real-Space Pseudopotential Method for the Calculation of 1 s Core-Level Binding Energies.

We systematically studied a real-space pesudopotential method for the calculation of 1 s core-electron binding energies of second-row elements B, C, N, and O within the framework of Kohn-Sham density functional theory (KS-DFT). With Dirichlet boundary conditions, pseudopotential calculations can provide accurate core-electron binding energies for molecular systems, when compared with the results from all-electron calculations and experiments. Furthermore, we report that with one simple additional nonself-consistent calculation as a refinement step using a hybrid exchange-correlation functional, we can generally improve the accuracy of binding energy shifts, promising a strategy for improving accuracy at a much lower computational cost. The specializations in the present approach, combined with our efficient real-space KS-DFT implementation, provide key advantages for calculating accurate core-electron binding energies of large-scale systems.