From Many-Body Ab Initio to Effective Excitonic Models: A Versatile Mapping Approach Including Environmental...

Area of Science:

• Computational chemistry
• Theoretical physics
• Quantum mechanics

Background:

• Accurate modeling of electronic excitations is crucial in chemistry and physics.
• Existing methods face challenges in describing both molecular and charge-transfer excitons, especially with environmental interactions.
• Bridging the gap between high-level ab initio calculations and effective models is an ongoing challenge.

Purpose of the Study:

• To introduce a novel multistate projective diabatization scheme.
• To enable systematic mapping of many-body ab initio calculations onto effective excitonic models.
• To incorporate environmental effects within a quantum mechanics/molecular mechanics (QM/MM) framework.

Main Methods:

• Utilizing Green's function formalisms for a multistate projective diabatization.
• Employing the Bethe-Salpeter equation framework to describe excitonic states.
• Integrating QM/MM for environmental effect modeling.

Main Results:

• The developed method successfully maps ab initio data to effective excitonic models.
• It accurately describes both Frenkel molecular excitons and intermolecular charge-transfer states.
• Incorporation of QM/MM effects is shown to be critical for parameter accuracy and transferability in condensed phases.

Conclusions:

• The presented diabatization scheme offers a robust and consistent approach for modeling excitonic systems.
• The method's ability to handle diverse exciton types and environmental interactions enhances its applicability.
• This work provides a crucial tool for accurate simulations of electronic excitations in condensed-phase and extended systems.