Generating interstitial water within the persisting tetrahedral H-bond network explains density increase upon...

Area of Science:

• Physical Chemistry
• Condensed Matter Physics
• Materials Science

Background:

• The atomic structure of liquid water remains a subject of scientific debate, despite water's prevalence.
• Understanding water's structure is crucial for various scientific disciplines.

Purpose of the Study:

• To investigate the local atomic and electronic structure of water under high pressure.
• To elucidate the structural changes and hydrogen-bonding dynamics in compressed liquid water.

Main Methods:

• Utilized X-ray Raman scattering spectroscopy for experimental analysis.
• Employed ab initio and path integral molecular dynamics simulations for computational modeling.
• Analyzed oxygen K-edge excitation spectra to identify structural fingerprints.

Main Results:

• Observed increasing evidence of non-hydrogen-bonded H2O molecules in the first hydration shell.
• Identified a compaction mechanism involving the continuous collapse of the second hydration shell.
• Detected the generation of interstitial water within locally tetrahedral hydrogen-bonding environments.

Conclusions:

• High pressure induces significant changes in the local atomic and electronic structure of liquid water.
• The study provides evidence for a transition towards a more compact water structure under pressure.
• Findings contribute to resolving long-standing controversies regarding liquid water's atomic arrangement.