Practical Post-Kohn-Sham Methods for Time-Reversal Symmetry Breaking References.

Area of Science:

• Computational chemistry
• Quantum mechanics
• Materials science

Background:

• Reduced scaling algorithms are crucial for accurate electronic structure calculations.
• Time-reversal symmetry breaking occurs in systems under magnetic fields or in relativistic open-shell molecules.
• The random phase approximation (RPA) and GW methods are vital for capturing electron correlation effects.

Purpose of the Study:

• To adapt and apply reduced scaling algorithms for correlation energy calculations using RPA and GW methods.
• To enable efficient computation for systems with time-reversal symmetry breaking Kohn-Sham references.
• To assess the accuracy and performance of these updated algorithms.

Main Methods:

• Implementation of reduced scaling algorithms based on auxiliary subspace methods.
• Application to random phase approximation (RPA) and GW correlation energies.
• Utilizing time-reversal symmetry breaking Kohn-Sham references, including those in magnetic fields and for relativistic open-shell molecules.

Main Results:

• Updated algorithms efficiently evaluate RPA and GW quasiparticle energies for systems breaking time-reversal symmetry.
• Computational scaling is reduced by two orders of magnitude with negligible errors.
• GW approximation demonstrates robustness for calculating ionization energies of trivalent lanthanoid ions.
• Combined GW-Bethe-Salpeter equation (BSE) method accurately predicts spectra, including spin-orbit coupling effects.

Conclusions:

• The developed algorithms provide a significant computational advantage for electronic structure calculations.
• The GW-BSE method is effective for studying light-matter interactions in complex molecular systems.
• Accurate prediction of spectra for systems like europium(III) complexes is achievable, incorporating relativistic effects.