Vibrational strong coupling in liquid water from cavity molecular dynamics

Area of Science:

• Physical Chemistry
• Computational Spectroscopy
• Quantum Dynamics

Background:

• Vibrational polariton spectra are crucial for understanding light-matter interactions in cavities.
• The role of nuclear quantum effects (NQEs) in shaping these spectra remains an active area of research.
• Previous studies suggested NQEs might broaden polariton bands.

Purpose of the Study:

• To evaluate the cavity molecular dynamics (CMD) method for calculating vibrational polariton spectra.
• To clarify the influence of NQEs on polariton band shapes.
• To compare CMD results with simpler theoretical models and experimental data.

Main Methods:

• Cavity molecular dynamics simulations were performed for liquid water.
• Simulated spectra were analyzed for the effects of nuclear quantum effects.
• A harmonic model utilizing cavity-free spectra and cavity geometry was developed and tested.

Main Results:

• Nuclear quantum effects were found to induce anharmonic red shifts, not broadening, in polariton frequencies.
• Simulated cavity spectra were accurately reproduced by a harmonic model using minimal input.
• The harmonic model, combined with experimental spectra, showed good agreement with optical cavity measurements.

Conclusions:

• The cavity molecular dynamics method offers no additional insight into vibrational strong coupling effects on absorption spectra compared to the transfer matrix method.
• A harmonic model provides an accurate and efficient approach for predicting vibrational polariton spectra.
• Established optical methods like the transfer matrix method are sufficient for corroborating experimental cavity results.