Using Koopmans' theorem for constructing basis sets: approaching high Rydberg excited states of lithium with a compact Gaussian basis

0574593 - FZÚ 2024 RIV GB eng J - Journal Article
Šmydke, Jan
Using Koopmans' theorem for constructing basis sets: approaching high Rydberg excited states of lithium with a compact Gaussian basis.
Physical Chemistry Chemical Physics. Roč. 25, č. 30 (2023), s. 20250-20258. ISSN 1463-9076. E-ISSN 1463-9084
R&D Projects: GA ČR(CZ) GA20-21179S
Institutional support: RVO:68378271
Keywords : Rydberg states * Gaussian basis sets * lithium * Koopmans' theorem * electronic structure
OECD category: Atomic, molecular and chemical physics (physics of atoms and molecules including collision, interaction with radiation, magnetic resonances, Mössbauer effect)
Impact factor: 3.3, year: 2022
Method of publishing: Open access

For accurate ab initio description of Rydberg excited states, this study suggests generating appropriate diffuse basis functions by cheap variational optimization of virtual orbitals of the corresponding ion core. By following this approach, dozens of converged correlated lithium Rydberg states, namely, all the states up to 24S, 25P, 14D, 16F and 16G, not yet achieved via other ab initio approaches, could be obtained at the EOM-CCSD level of theory with compact and mostly state-selective contracted Gaussian basis sets. Despite its small size and Gaussian character, the optimized basis leads to highly accurate excitation energies that differ merely in the order of meV from the reference state-of-the-art explicitly correlated Gaussian method and even surpass Full-CI results on the Slater basis by an order of magnitude.
Permanent Link: https://hdl.handle.net/11104/0345698