Subsystem-Based GW/Bethe-Salpeter Equation.

Area of Science:

• Computational Chemistry
• Quantum Chemistry
• Theoretical Chemistry

Background:

• Subsystem Density-Functional Theory (DFT) and Time-Dependent DFT (TDDFT) are effective for ground and excited states.
• Fragmentation approaches are crucial for large molecular systems.

Purpose of the Study:

• Extend subsystem DFT to GW and Bethe-Salpeter Equation (BSE) methods for excited states.
• Develop a parameter-free approach for subsystem GW/BSE calculations.
• Assess the accuracy and efficiency for complex chemical environments.

Main Methods:

• Derivation of working equations for subsystem-based GW/BSE.
• Partitioning of screened-Coulomb interaction for multiple subsystems.
• Development of approximations to include environmental screening.

Main Results:

• Successful application of subsystem GW/BSE for quasi-particle and excitation energies.
• Comparison with supermolecular calculations validates the approach.
• Demonstrated computational efficiency and utility for photoinduced processes.

Conclusions:

• Subsystem GW/BSE offers an accurate and efficient fragmentation method for excited-state calculations.
• The approach effectively incorporates environmental screening effects.
• This method is valuable for studying complex systems and photoinduced phenomena.