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Water's two-critical-point scenario in the Ising paradigm.
Claudio A Cerdeiriña1, Jacobo Troncoso1, Diego González-Salgado1
1Departamento de Física Aplicada, Universidad de Vigo-Campus del Agua, Ourense 32004, Spain.
The Journal of Chemical Physics
|July 1, 2019
Summary
This study introduces a novel spin-1, three-state Ising model to explain water's unique thermodynamics, including its low-temperature icelike structures and hypothesized liquid-liquid transition. The model successfully describes experimental and simulation data for supercooled water.
Area of Science:
- Thermodynamics
- Statistical Mechanics
- Physical Chemistry
Background:
- Water exhibits unusual thermodynamic behavior, particularly at low temperatures.
- The existence of a liquid-liquid phase transition in water is hypothesized.
- Understanding water's low-temperature "icelike" structures is crucial.
Purpose of the Study:
- To develop a simplified model capturing the complex thermodynamics of fluid water.
- To investigate the relationship between local structures and water's phase transitions.
- To provide a theoretical framework for water's hypothesized liquid-liquid transition.
Main Methods:
- A spin-1, three-state Ising model was developed, incorporating vacant and singly occupied cells with two accessible volumes.
- The model utilizes two order parameters to describe phase transitions.
- Mean-field theory was applied to derive the equation of state.
Main Results:
- The model successfully characterizes local structures associated with low-density, low-energy, and low-entropy states.
- It reproduces key features of water's phase diagram, including the density maximum and deeply stretched states.
- The model accurately describes thermodynamic response functions for supercooled water, consistent with ST2 and TIP4P/2005 force fields.
Conclusions:
- The proposed spin-1 Ising model serves as a fundamental prototype for the "two-critical-point scenario" in water.
- The model offers a satisfactory explanation for water's unusual thermodynamics across various states.
- It provides insights into the microscopic origins of water's anomalous properties.
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