Wavefunction embedding for molecular polaritons.

Area of Science:

• Quantum chemistry
• Theoretical chemistry
• Chemical physics

Background:

• Polaritonic chemistry utilizes strong light-matter interactions to modify chemical reaction rates within optical cavities.
• Accurate theoretical models are crucial for understanding these light-matter interactions.
• Existing methods like quantum electrodynamics self-consistent field (QED-SCF) are efficient but require accurate functionals, while quantum electrodynamics coupled cluster (QED-CC) methods are accurate but computationally expensive.

Purpose of the Study:

• To develop a computationally efficient and accurate theoretical model for polaritonic chemistry.
• To introduce and validate a novel QED-CC-in-QED-SCF projection-based embedding method.
• To investigate the nature of electron-photon correlation effects in cavity-confined chemical reactions.

Main Methods:

• Development of a projection-based embedding method combining QED-CC and QED-SCF approaches.
• Assessment of the method's performance on prototypical reactions: methyl transfer, proton transfer, and protonation.
• Comparison of results with high-level, computationally intensive QED-CC calculations.

Main Results:

• The new embedding method achieves excellent agreement with more expensive QED-CC results.
• Electron-photon correlation effects in cavity environments are found to be local.
• Only a small region of the system requires treatment at the QED-CC level to capture significant cavity effects.

Conclusions:

• The QED-CC-in-QED-SCF embedding method offers a computationally feasible yet accurate approach for polaritonic chemistry.
• This work provides a guideline for developing future polaritonic embedding models.
• The findings pave the way for advanced theoretical studies in polaritonic quantum chemistry.