Can GW handle multireference systems?

Area of Science:

• Quantum Chemistry
• Computational Physics
• Electronic Structure Theory

Background:

• The GW approximation is successful for weakly correlated systems due to infinite bubble diagram summation.
• Its performance in multireference systems with strong electron correlation is largely unexplored.
• Understanding GW in these challenging systems is crucial for accurate electronic structure calculations.

Purpose of the Study:

• To investigate the efficacy of the GW approximation for closed-shell, singlet ground-state multireference molecular systems.
• To evaluate GW performance across diverse scenarios exhibiting strong electron correlation.
• To identify factors influencing GW accuracy in the presence of strong correlation.

Main Methods:

• Examined the potential energy curve of BeH2 during Be insertion into H2.
• Computed electron detachment/attachment energies for LiF, BeO, BN, C2, B2, and O3.
• Studied a triangular H6 cluster for spin frustration and HF dissociation for single bond breaking.

Main Results:

• GW performance in multireference systems is sensitive to the level of self-consistency and initial guess.
• Spin-symmetry breaking at the Hartree-Fock level significantly impacts GW results.
• The study provides a detailed analysis of GW's capabilities and limitations in strong correlation regimes.

Conclusions:

• The GW approximation shows a nuanced performance in strongly correlated multireference systems.
• Accuracy depends critically on computational parameters like self-consistency and initial guess.
• Further development or careful application is needed for reliable GW calculations in complex molecular systems.