Thermodynamic Anomalies in Stretched Water

Area of Science:

• Physical Chemistry
• Computational Physics
• Materials Science

Background:

• Liquid water displays anomalous properties, particularly under extreme conditions like negative pressure.
• Understanding water's behavior is crucial for various scientific and technological applications.

Purpose of the Study:

• To investigate the anomalous behavior of liquid water at large negative pressures using molecular dynamics simulations.
• To explore the phenomenon of reentrant behavior in water under isochoric cooling.
• To examine the relationship between cavitation, tension, and spinodal properties in water.

Main Methods:

• Molecular dynamics simulations utilizing the TIP4P/2005 water model.
• Isochoric cooling protocols to achieve large negative pressures.
• Analysis of system behavior, including cavitation, rehomogenization, and density variations.

Main Results:

• Observed reentrant behavior in isochores without a pressure minimum, where water cavitates and then rehomogenizes.
• Finite size effects significantly influence the manifestation of reentrant behavior.
• Propensity toward cavitation does not always correlate with greater tension.
• Maximum spinodal density leads to maximum compressibility and minimum speed of sound, independent of a liquid-liquid critical point (LLCP).
• Widom line signatures extend to negative pressures but are only observable in the potential energy landscape.

Conclusions:

• Water under hydrophilic confinement may exhibit richer phase behavior than previously assumed.
• Current interpretations of water stretching experiments may need revision.
• The study provides insights into the fundamental properties of water under extreme conditions and the nature of the Widom line.