Water: two liquids divided by a common hydrogen bond

Area of Science:

• Physical Chemistry
• Materials Science
• Chemical Physics

Background:

• Water exhibits a unique, disordered network structure due to directional hydrogen bonds, differing from simpler liquids.
• The atomic coordination number in water is typically 4-5, contrasting with the order of 12 in simpler liquids.
• Ongoing controversy surrounds the precise structural model of water.

Purpose of the Study:

• To propose an accurate structural model for water.
• To explain the pressure and temperature dependence of water's structure and thermodynamic properties.
• To provide a simple explanation for spectroscopic evidence suggesting water is a mixture of two components.

Main Methods:

• Representing water structure as a mixture of two identical, interpenetrating molecular species.
• Analyzing hydrogen bond characteristics: strong along the bond, weak angularly.
• Correlating the proposed model with observed pressure and temperature dependencies.

Main Results:

• Water structure accurately represented as a mixture of two distinct, interpenetrating molecular species.
• Each species forms hydrogen bonds exclusively with the other species, not with itself.
• The model naturally explains the pressure and temperature dependence of water's structural and thermodynamic properties.

Conclusions:

• The two-species interpenetrating network model accurately describes water structure.
• This model provides a unified explanation for water's unique properties and spectroscopic findings.
• The model resolves the long-standing controversy regarding water's molecular arrangement.