Polarizable Embedding for Excited-State Reactions: Dynamically Weighted Polarizable QM/MM

Area of Science:

• Computational Chemistry
• Quantum Mechanics
• Spectroscopy

Background:

• Polarizable embedding methods are increasingly used for electronic excited states.
• Existing methods primarily focus on optical absorption and emission spectra.
• Their applicability to excited-state chemical reactions remains less explored.

Purpose of the Study:

• To assess the suitability of polarizable embedding methods for excited-state reactions.
• To develop an improved polarizable embedding method for describing electronic crossings.

Main Methods:

• Construction of a model system (LiFBe) featuring electronic crossing coupled to a polarizable species.
• Evaluation of current polarizable Quantum Mechanics/Molecular Mechanics (QM/MM) methods.
• Development of a novel dynamically weighted polarizable QM/MM method.

Main Results:

• Current polarizable QM/MM methods show inadequacy in describing potential energy surfaces near electronic crossings.
• The newly developed dynamically weighted polarizable QM/MM method demonstrates high accuracy.
• The new method closely reproduces potential energy surfaces from high-level multireference configuration interaction calculations.

Conclusions:

• Polarizable embedding methods require refinement for accurate modeling of excited-state reactions.
• The dynamically weighted polarizable QM/MM method offers a promising advancement for studying such systems.
• This new method achieves near-quantitative accuracy in reproducing complex potential energy surfaces.