Vibrational spectral diffusion and hydrogen bond dynamics in heavy water from first principles

Area of Science:

• Physical Chemistry
• Computational Chemistry
• Spectroscopy

Background:

• Understanding hydrogen bond dynamics is crucial for liquid water properties.
• Vibrational spectral diffusion provides insights into ultrafast molecular motions.
• Heavy water (deuterated water) offers a unique system to study these phenomena.

Purpose of the Study:

• To theoretically investigate vibrational spectral diffusion and hydrogen bond dynamics in heavy water.
• To establish relationships between OD bond instantaneous frequencies and hydrogen bond distances.
• To elucidate the time scales governing spectral diffusion and hydrogen bond lifetimes.

Main Methods:

• First-principles theoretical study using ab initio molecular dynamics simulations.
• Wavelet method for time series analysis and frequency calculations.
• Frequency-time correlation and spectral hole dynamics calculations.

Main Results:

• Averaged correlation found between OD bond frequency and hydrogen bond distance, though not one-to-one instantaneously.
• Identified short-time (approx. 100 fs) and long-time (approx. 2 ps) decay components in spectral diffusion.
• Fast hydrogen bond making dynamics (approx. 100 fs) contribute to short-time spectral diffusion.
• Observed damped oscillations (150-200 fs) attributed to intermolecular vibrations.

Conclusions:

• Hydrogen bond dynamics significantly influence vibrational spectral diffusion in heavy water.
• The study provides a detailed microscopic picture of spectral diffusion and hydrogen bond lifetimes.
• Results are validated by power spectra and hydrogen bond kinetics calculations.