Complex-variable MP2 theory applied to core-vacant states for the computation of Auger spectra

Area of Science:

• Quantum Chemistry
• Atomic and Molecular Physics
• Computational Spectroscopy

Background:

• Auger decay is a fundamental process in atomic and molecular physics.
• Accurate theoretical modeling of Auger spectra is crucial for understanding electronic structure and dynamics.
• Previous methods based on coupled-cluster theory are computationally expensive.

Purpose of the Study:

• To develop a computationally efficient method for modeling Auger spectra.
• To investigate the applicability of second-order Møller-Plesset perturbation (MP2) theory combined with complex scaling for Auger decay.
• To compare the accuracy of the new MP2-based method with coupled-cluster approaches.

Main Methods:

• Modeling Auger spectra using second-order Møller-Plesset perturbation (MP2) theory.
• Employing complex-scaled basis functions to handle resonant states.
• Decomposing complex MP2 energy into decay channel contributions.
• Developing an equation-of-motion (EOM) method for computing final states of Auger decay.

Main Results:

• The MP2-based method achieves computational cost savings compared to coupled-cluster methods.
• Final state energies are obtained with accuracy comparable to EOM coupled-cluster singles and doubles (CCSD) theory.
• Good agreement with EOM-CCSD for K-shell holes in third-row hydrides, with larger deviations for second-row hydrides.
• MP2 yields unphysical results for L1-shell holes but can be corrected with energy denominator shifts.

Conclusions:

• The developed MP2-based EOM method provides a computationally efficient and accurate approach for modeling Auger spectra.
• The method shows promise for studying Auger decay in various molecular systems.
• Further refinements are needed for accurate predictions of L1-shell Auger decay.