Slater transition methods for core-level electron binding energies.

Area of Science:

• Computational Chemistry
• Quantum Mechanics
• Spectroscopy

Background:

• Accurate computation of core-level ionization energies is crucial for understanding electronic structure and chemical bonding.
• Existing methods like the full core hole (ΔSCF) approach can be computationally intensive.
• Alternative methods based on fractional-occupancy self-consistent field (SCF) calculations offer potential efficiencies.

Purpose of the Study:

• To evaluate and benchmark different computational methods for determining core-level ionization energies.
• To compare the accuracy and efficiency of Slater-type transition state methods against the ΔSCF approach.
• To assess the utility of these methods for simulating spectroscopic experiments, such as X-ray emission spectroscopy.

Main Methods:

• Benchmarking of the full core hole (ΔSCF) method.
• Evaluation of Slater's transition state concept using fractional-occupancy SCF calculations.
• Development and testing of a generalized Slater-type method with two fractional-occupancy calculations.
• Application of an empirical shifting procedure to improve accuracy.
• Modeling of X-ray emission spectroscopy using Slater-type methods.

Main Results:

• Slater-type methods achieve mean errors of 0.3-0.4 eV for K-shell ionization energies, comparable to advanced many-body techniques.
• An empirical shifting procedure reduces the average error to below 0.2 eV.
• The shifted Slater transition method provides a practical and computationally efficient alternative to ΔSCF.
• The method is suitable for simulating transient X-ray experiments probing excited electronic states.

Conclusions:

• The shifted Slater transition method is a simple, practical, and accurate approach for computing core-level binding energies.
• This method requires only initial-state Kohn-Sham eigenvalues and comparable computational effort to ΔSCF.
• It offers significant advantages for simulating complex spectroscopic experiments, particularly those involving excited states.