Hydrogen-Bonding in Liquid Water at Multikilobar Pressures

Area of Science:

• Physical Chemistry
• Spectroscopy
• Materials Science

Background:

• Understanding the hydrogen bond (H-bond) network in liquid water is crucial for various scientific disciplines.
• Solvent stress, such as high hydrostatic pressure, significantly alters water's molecular structure and dynamics.
• Terahertz (THz) spectroscopy is a powerful tool for probing intermolecular vibrations in liquids.

Purpose of the Study:

• To investigate the molecular-level changes in the H-bond network of bulk liquid water under high hydrostatic pressure.
• To characterize the pressure-induced alterations in THz spectra and their correlation with structural modifications.
• To explore the role of electronic polarization in THz spectral line shape changes under pressure.

Main Methods:

• Acquisition of high-precision THz spectra of bulk liquid water from ambient conditions up to 10 kbar.
• Performance of ab initio simulations to complement experimental spectroscopic data.
• Analysis of spectral shifts and intensity variations in relation to molecular configurations.

Main Results:

• Observed a 40 cm^-1 blue shift in the intermolecular translational mode at 180 cm^-1 at 10 kbar.
• Detected a blue shift and intensity increase in the relaxation mode under high pressure.
• Correlated spectral changes to a pressure-induced increase in short H-bond configurations.

Conclusions:

• High-pressure THz spectroscopy effectively probes the H-bond network's response to solvent stress.
• Pressure favors shorter H-bonds in water, altering its dynamic and structural properties.
• This technique advances the study of solvation shells and solute-solvent interactions under pressure.