研究目的
Investigating the basis set requirements for calculating properties corresponding to removing core electrons by the ΔSCF approach using Hartree-Fock and density functional theory.
研究成果
The study concludes that the pcX-n basis sets provide a systematic way to approach the basis set limit for core-excitation processes such as XPS and XAS calculated by the ΔSCF approach. They offer lower basis set errors than other basis sets of similar size and can be used as local basis sets in combination with energy optimized pcseg-n basis sets for reducing computational costs. The pcX-2 basis set, at the polarized triple zeta level, shows typical basis set errors of ~0.02 eV, suitable for both non-relativistic and relativistic levels of theory when using density functional methods.
研究不足
The study acknowledges the technical challenges in localizing and optimizing the core-hole state, including convergence failure of the SCF procedure and variational collapse to the lowest valence-hole state. Additionally, the ΔSCF method's single-determinant nature and the requirement for separate optimization of each excited state are noted as limitations. The basis set behavior when using response methods for calculating core-excitations may differ, and the findings may be valid only when using the ΔSCF approach.
