Entropy, diffusivity, and structural order in liquids with waterlike anomalies

Area of Science:

• Condensed Matter Physics
• Physical Chemistry
• Computational Materials Science

Background:

• Water exhibits unique liquid state anomalies, including density and viscosity variations with temperature.
• Understanding these anomalies is crucial for various fields, from materials science to geochemistry.
• Liquid silica and specific theoretical models (two-scale ramp potential) also display similar anomalous behaviors.

Purpose of the Study:

• To investigate the role of excess entropy in waterlike liquid state anomalies.
• To establish a method for distinguishing between different types of liquid anomalies.
• To provide a framework for diagnosing anomalous behavior in diverse liquid systems.

Main Methods:

• Calculating excess entropy as a function of density and temperature for liquid silica and a two-scale ramp potential.
• Employing a pair correlation approximation for accurate excess entropy evaluation.
• Analyzing orientational and translational order parameters to define anomalous regimes.

Main Results:

• A direct connection between excess entropy and observed density/diffusional anomalies was demonstrated.
• A method was developed to distinguish liquids with local anisotropy (e.g., silica) from those with isotropic interactions but multiple length scales.
• The relationship between macroscopic entropy and internal energy effectively categorizes different types of waterlike anomalies.

Conclusions:

• Excess entropy is a key indicator for understanding and classifying liquid state anomalies.
• The developed method, based on entropy-energy relationships and order parameters, can diagnose anomalous behavior in various liquids.
• This approach offers a convenient diagnostic tool for experimental and simulation data across diverse fluid systems.