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11:03
An Analog Macroscopic Technique for Studying Molecular Hydrodynamic Processes in Dense Gases and Liquids
Published on: December 4, 2017
Thermodynamic, diffusional, and structural anomalies in rigid-body water models.
Manish Agarwal1, Mohammad Parvez Alam, Charusita Chakravarty
1Department of Chemistry, Indian Institute of Technology-Delhi, New Delhi, India.
The Journal of Physical Chemistry. B
|May 11, 2011
Summary
This study maps anomalies in water models, finding TIP4P/2005 closely matches experimental maximum density temperatures. Different water models exhibit similar density anomaly ranges but vary in onset temperatures and phase diagrams.
Area of Science:
- Computational chemistry
- Physical chemistry
- Materials science
Background:
- Water exhibits anomalous behavior, including density, entropy, and diffusivity variations.
- Accurate modeling of these anomalies is crucial for understanding water's unique properties.
- Existing water models show discrepancies in reproducing experimental observations.
Purpose of the Study:
- To map the structural, density, entropy, and diffusivity anomalies of the TIP4P/2005 water model.
- To compare the anomalous behavior of TIP4P/2005 with other common water models (mTIP3P, TIP4P, TIP5P, SPC/E).
- To investigate the relationship between liquid-state anomalies and crystalline phase behavior in different water models.
Main Methods:
- Molecular dynamics simulations were used to explore a wide range of densities and temperatures.
- Analysis focused on identifying regions of anomalous behavior in density, entropy, and diffusivity.
- Comparison of phase diagrams and anomalous regions across various water models.
Main Results:
- The TIP4P/2005 model's locus of maximum density temperature (TMD) closely aligns with experimental data (250-275 K).
- All models studied showed anomalous behavior within density limits of 0.85-0.90 g cm⁻³ to 1.10-1.15 g cm⁻³.
- Onset temperatures for density anomalies varied significantly among models, from 202 K (mTIP3P) to 289 K (TIP5P).
- Structural anomaly regions were qualitatively similar across models, while crystalline phases showed greater model sensitivity than liquid anomalies.
Conclusions:
- The TIP4P/2005 model provides a good representation of water's density anomaly.
- Liquid-state anomalies occur at lower pressures than melting line slope changes.
- Understanding structure-entropy-diffusivity relationships is key for developing improved water models.
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